The Organic Chemistry of Nickel || π-Cyclopentadienyl Nickel Complexes

CHAPTER VIII

π-Cyclopentadienyl Nickel Complexes

The chemistry of the 7r-cyclopentadienylnickel complexes has been studied in great detail. The theoretician and spectroscopist have been attracted by the symmetry of the 77-C5H5 group; the preparative organometallic chemist by its stabilizing influence; and the industrial chemist by its potential value in fuel oil additives and as a ligand in catalysis. The parent compound, bis(7r-cyclopentadienyl)nickel (nickelocene), is second only to nickel tetracarbonyl in being the most thoroughly investigated organonickel complex and is the starting point for the preparation of most of the mono-7r-cyclopentadienyl-nickel complexes.

In this chapter we discuss those compounds in which the ττ-cyclopentadienyl group is the only organic group bonded to the nickel and have devoted sepa-rate sections to the preparation, structure, and reactions of nickelocene, the 7r-cyclopentadienylnickel carbonyl complexes, the 7r-C5H5NiX(Lig) com-plexes, the τΓ-cyclopentadienylnickel cluster compounds, and 7r-C5H5NiNO. These are followed by a section devoted to the related nickel carborane com-plexes. The known complexes are arranged in tables at the end of each section.

There is more than a passing resemblance between the chemistry of com-pounds containing the 7r-C5H5Ni and the 7r-C3H5Ni systems. This is mainly due to the ability of the two groups to stabilize the two favored electronic configurations adopted by nickel in its organometallic complexes : the 77--C5H5 group stabilizing the 18 electron configuration [e.g., 7r-C5H5NiNO] and the 77--C3H5 group the 16 electron configuration [e.g., 4

(7r-C3H5)2Ni]. Some authors (1-3) have even suggested that the 7r-C5H5 group is perhaps better regarded as a 7r-h3-C5H5 system (1) than as a 77-h5-C5H5 system (2).

420

/. Bis-TT-Cyclopentadienylnickel {nickelocene) All

M M 1 2

For nickelocene itself there seems to be no really convincing reason for its formulation as 7r-h3-C5H5Ni-7r-h5-C5H5, even supposing a rapid conversion between various isomers, while the strict C5v symmetry observed in the gas phase for 7r-C5H5NiNO rules out a 7r-h3-C5H5 arrangement here. In other cases the situation is not so clear [e.g., (7r-indenyl)2Ni, page 432] and a τΓ-allyl structure must be seriously considered. In a few cases, e.g. 7r-C5H5NiGeCl3[P(C6H5)3] (Fig. VIII-9) and (7r-C5H5Ni)27r-C6H8 (Fig. VI-16), the x-ray data could be interpreted in terms of a 7r-h3-C5H5 arrangement; however, caution is necessary since in addition to inequality in the C—C bond lengths strict planarity of the ring is not normally observed (see Appendix, Table A-6).

I. Bis-77-Cyclopentadienylnickel (nickelocene)

A. Preparation

The metallocenes and related compounds were considered for some time as antiknock additives and received considerable attention from industrial chemists. Most of the methods which have been used to prepare nickelocene are analogous to those for ferrocene and can conveniently be divided into three: (1) direct reaction between metallic nickel and cyclopentadiene; (2) reaction of a main-group metal cyclopentadienide with a nickel salt; and (3) deprotonation of cyclopentadiene by an inorganic base in the presence of a nickel salt.

The reaction between nickel oxalate and cyclopentadiene at 450° probably involves metallic nickel (4-6) and is reminiscent of a similar reaction used to prepare nickel tetracarbonyl (7).

By far the most extensively studied method used to prepare nickelocene is the reaction between the cyclopentadienide anion and a nickel salt. Many of the possible combinations of the reaction of a cyclopentadienide of the alkali metals, thallium or magnesium, with the halides, acetylacetonate, hexammine chloride, tetrapyridine chloride, or thiocyanate of nickel have been reported (8-32, 43). The reactions involving the alkali metal cyclopentadienide are preferably conducted in polar solvents, e.g., THF or ethylene glycol (8-21, 43, 44). The use of thallium cyclopentadienide is recommended because of its high stability and insensitivity to water, which allows it to be used in reactions with hydrated nickel salts (22, 25). The cyclopentadienide magnesium reagent

< $ >

422 VIII. TT-Cyclopentadienyl Nickel Complexes

is prepared by reacting ethyl magnesium bromide with cyclopentadiene (26-32).

T1C1 + KOH + C5H6 ► T1C5H5 + H20 + KC1

2TIC5H5 + NiCl2-6H20 ► (7r-C5H5)2Ni + 2T1C1 + 6H20

Probably the most convenient laboratory method for preparing nickelocene is the deprotonation of cyclopentadiene by an inorganic base in the presence of the nickel salt, and reactions involving potassium hydroxide and diethyl-amine have been reported (33-38). The reaction with potassium hydroxide in DMSO does not require the use of an anhydrous nickel salt (37), although the yield is lower than that using anhydrous nickel bromide and diethylamine (38).

NiCl2-6H20 4- 2C5H6 + 10KOH ► Or-C5H5)2Ni + 2KC1 + 8KOHH20

NiBr2 + 2C5H6 + 2(C2H5)2NH ► Or-C6He)aNi + 2[(C2H5)2NH2]Br

Nickelocene is also formed in the direct reaction between nickel chloride vapor (prepared at 850°) and cyclopentadiene at 250° (39), and is the main product of the reaction between cyclopentadiene and nickel tetracarbonyl at 300° (at 70° 7r-cyclopentadienylnickel-77--cyclopentenyl is formed) (26, 40, 41)· This last reaction may involve metallic nickel, or, alternatively, dispropor-tionation of the 7r-cyclopentenyl complex to nickelocene and the unstable bis(7T-cyclopentenyl)nickel which decomposes. A related observation is the formation of a mixture of nickelocene and 7r-C5H5NÍ7r-C5H7 on reacting nickel bromide with the Grignard reagent prepared from 3-chlorocyclo-pentene (42).

B. Physical Properties

Nickelocene is a dark green volatile solid which may be sublimed at 50° and 0.1 mm Hg and which is soluble in most organic solvents. The solid is not particularly air-sensitive, but solutions must be handled in an inert atmos-phere. It is probably more toxic than is normally supposed and tests with rats and hamsters have shown that it readily induces cancer (46).

Thermodynamic data and some of the physical properties are shown in Table VIII-1.

1. STRUCTURE

The crystal structure of nickelocene has not been investigated in detail but it is reported to be isostructural with ferrocene and the Ni—C distance has been estimated to be approximately 2.2 Â (17, 47, 59, 60). The cell constants are a = 5.88, b = 7.86, c = 10.68; ß = 121.2; Z = 2; space group P2Jc.

Two determinations have been made of the structure in the gas phase by

/. Bis^-Cyclopentadienylnickel (nickelocene) 423

TABLE VIII-1

PHYSICAL AND THERMODYNAMIC DATA FOR NICKELOCENE

Color mp(°C) Density (g/cm3) Dipole moment Magnetic susceptibility (μβί{) Vapor pressure (s)

Heat of sublimation (ΔΗ298) Heat of formation AH0

f298(s) AH°f298(g)

Free energy of formation AG0f298(g)

Entropy /S°298(s) S°298(g)

Dark green 173-174 1.47 0 ± 0.33 D (benzene) 2.89 ± 0.15 BM 399.0 = 14.85 mm,/?353.i5 = 1.1 mm,

Rlnp = -2028.3 /Γ- 101ηΓ + 116.070 17.3 ± 0.3 kcal/mole 62.8 ± 0.5 kcal/mole 80.1 ± 2 kcal/mole 105.31 kcal/mole 56.3 cal deg"1 mole- 1

92.21 cal deg- 1 mole- 1

17,47 48,49 17, 26, 50-53 54

54 54,79 55,56 55,56 54 54

electron diffraction (61-63). Both research groups agree that the molecule has the familiar ferrocene-like sandwich structure in which the metal-carbon distance is about 0.1 Â greater than that found for the iron compound. However large discrepancies are found in the molecular parameters and in the detailed interpretation of the radial distribution curve. The more recent determination appears to be more reliable and is discussed here.

£H

ÇH

Nickelocene (63) Ferrocene (64)

Ni—C 2.196(4) C—C 1.430(15) C—H 1.08(1)

Fe—C 2.064(3) C—C 1.440(2) C—H 1.10(1)

ZC5—H 0.28 ± 1.45 ZC5—H 5 ± 2.5

Fig. VIII-1. Molecular parameters for nickelocene and ferrocene.

424 VIII. π-Cyclopentadienyl Nickel Complexes

The principal molecular parameters, assuming a symmetric sandwich structuref with freely rotating rings, are shown in Fig. VIII-1, and compared to those obtained, by electron diffraction, for ferrocene. There is no evidence to indicate that the hydrogen atoms lie out of the plane formed by the ring (this is in contrast to ref. 62 in which it is suggested that the hydrogen atoms are deflected by 5° toward the nickel atom). The rings are apparently free to rotate and the electron diffraction determination allows no decision to be made as to whether the rings are eclipsed or staggered in the equilibrium conformation. The difference in the M-ring distance in ferrocene and nickelo-cene is consistent with the theoretical picture of the bonding in these systems in which the additional electrons present in nickelocene occupy antibonding orbitals. This is probably the reason why attempts to estimate the covalent radii of nickel using the Ni—C distance in 7r-C5H5Ni complexes give anomalous results (65, 66).

2. MAGNETIC SUSCEPTIBILITY Nickelocene is paramagnetic (17, 26, 50-53, 67-69, 361). The magnetic

susceptibility varies with the temperature. Above 70°K the Curie-Weiss law is applicable and a magnetic moment of 2.89 ±0.15 BM is obtained, corre-sponding to two unpaired electrons; below 70°K the Curie-Weiss law is no longer applicable, indicating that there is a large zero field splitting of the spin levels which in turn accounts for the absence of a measurable ESR spectrum. The measured curve extrapolated to 0°K can be fitted with the parameters g]{ = 2.0023, g± = 2.06 and the zero-field splitting parameter D = +25.6. The large value for this last parameter indicates that the orbitals containing the two unpaired electrons have mainly metal character, i.e., elu

2* or elg2*

symmetry (51, 69). An attempt has been made to use the para-hydrogen conversion to estimate

the number of unpaired electrons in the paramagnetic metallocenes : for both, nickelocene and cobaltocene, the values obtained are significantly higher than those found using the magnetic balance (70, 71).

3. MASS SPECTRAL INVESTIGATIONS

The mass spectra of the metallocenes all have the molecular ion as the base peak. Other intense peaks observed for nickelocene are (C5H5)Ni+ and Ni + . In addition fragmentation of the ring occurs to give (C3H3)Ni+ (72, 73). At low ionizing energy, low temperature and relatively high pressure (2 x 10~5mmHg) ion-molecule reactions occur to give bimetallic species including (C5H5)3Ni2

+ and (CsHs^NiaCgHg"1" for which "tripledecker" sandwich structures have been proposed (74; see also Section I-E). The re-

t The "best fit," however, is obtained for a model containing a slightly asymmetrically placed nickel atom.

/ . Bis-TT-Cyclopentadienylnickel (nickelocene) 425

ported ionization and appearance potentials vary over a small range (72, 73, 75, 76, 81, 342, 369); representative values are (C5H5)2Ni+, 7.16(10) eV; (C5H5)Ni+, 12.59(10)eV; Ni + , 13.65(20) eV (73). The methane chemical ionization spectrum of nickelocene has also been reported: the spectrum is similar to that obtained using conventional techniques and also contains fragments due to bimetallic species (341).

Several attempts (72, 73, 75, 342) have been made, using the mass spectro-metric data, to calculate the ionic bond dissociation energy Dl9 for the process

(π-05Η5)2Νί+ ► (7T-C5H5)Ni+ + C5H5

and D2 for the process (7r-C5H5)Ni+ ► Ni+ + C5H5

The most reliable results give values of 6.5(±0.5) eV and 4.8(±0.5) eV for Dx and D2, respectively (342), which are considerably higher than those obtained by thermochemical calculation (26, 75).f The value of Dx for ferro-cene obtained by both methods is approximately 1 eV greater than that for nickelocene indicating the greater bond strength between the metal and the ring in the former molecule. Valence state calculations using atomic spectral data are in qualitative agreement with these results (80).

4. INFRARED AND RAMAN SPECTRA

The infrared spectrum (26, 56, 82-84, 86, 330) and the Raman spectrum (330) of nickelocene have been published. The spectra closely resemble those of ferrocene (331) and by analogy an almost complete assignment of the vibrational frequencies is possible (330). The infrared active fundamental frequencies and their assignments are shown below.

C—H stretch asymm. C—C stretch asymm. ring breath 3108, 3096 1423 1109

C—H bend (||) C—H bend (J_) asymm. ring tilt ring M bend 1002 802 838 355

Based upon the estimated force constants for the metal ring symmetric and asymmetric stretching frequencies, the heat of formation and other thermodynamic parameters have been calculated for ferrocene, ruthenocene, and nickelocene. The order of thermodynamic stability is found to be Ru > Fe > Ni (55, 56, 83).

t There is some disagreement concerning the value for Aür/298Ni(g) : values of 81.0 ± kcal/mole (77) or 102.8 kcal/mole (78) having been used by different authors.

426 VIH. π-Cyclopentadienyl Nickel Complexes

5. ELECTRONIC SPECTRUM

Nickelocene has three strong absorptions in the 43,000 to 28,000 cm"1

region and a detailed analysis of the absorption curve below 28,000 cm"1

shows the presence, with some certainty, of a further three absorptions as well as two of very low intensity (17, 26, 69, 88-91). The spectrum has been inter-preted on the basis of an axial sandwich ligand field of D^h symmetry and a brave attempt (Table VIII-2) has been made to identify the transitions and use them to order the d orbital energies. The experimentally determined order is *ig > alg > e2g.

TABLE VIII-2

ELECTRONIC SPECTRUM OF NICKELOCENE IN HEPTANE"

Vmaxicm - 1 ) emax(mol"1cm~11) Assignment

36,000(sh) 32,700 29,700(sh) 23,450(sh) 19,150(sh) 16,900(sh) 14,380 11,700

8,100 11,200 7,250

26 5

23 62 1.0

Intraligand transition (N -> V or N -Intramolecular CT transition (C5H5 -4/7 <*- 3d transition Normal d<—d transition Intercombination d<- d transition Normal d<- d transition Normal d<- d transition Intercombination d<— d transition

Q) -3d)

a From Ref. 89.

6. NUCLEAR MAGNETIC RESONANCE

Large chemical shifts are observed in the NMR spectra of the paramagnetic metallocenes as a result of hyperfine coupling between the unpaired electron spin and the nuclear spin (Table VIII-3). The value of these contact shifts for vanadium and chromium are opposite in sign to the values for manganese, cobalt, and nickel (43, 92-98, 103, 104). The origin of this phenomenon is a challenge to the various bonding theories and has been discussed at length.

TABLE VIII-3

N M R CONTACT SHIFTS (ppm) FOR NICKELOCENE0

Nucleus (TT-CSHWSNÍ (TT-CsEUCHa^Ni

3C

+ 254.8

- 1 3 0 0

+ 253.8 (ring) -200 .5 (CH3) - 1 1 3 8 (ring) + 503 (CH3)

α From Refs. 43, 96, 100, and 105 (wrt ferrocene).

/. BiS'TT-Cyclopentadienylnickel {nickelocene) All

Nickelocene (and cobaltocene) differ from the other paramagnetic metallocenes in that the unpaired electrons occupy antibonding orbitals (probably an elg orbital of π symmetry) and there appears to be general agreement that the contact shift arises by a direct transfer of positive spin density from the metal to the ring carbon atoms which, on transfer to the proton, changes sign (43,92,95,103). The result is a deshielding of the protons and a shift to higher field. The expected positive spin density on the carbon atom has been confirmed by the 13C NMR spectrum of nickelocene (Table VIII-3). It can be shown theoretically that, assuming ττ-delocalization, the methyl contact shift in the Ι,Γ-dimethyl metallocenes should have approxi-mately the same value as the ring proton chemical shift but be opposite in sign: this is observed for Ι,Γ-dimethylnickelocene and the theory is further supported by 13C contact shift measurements. The ratio of the 13C to *H shifts for Ι,Γ-dimethylnickelocene ( — 2.5) is close to that predicted ( — 2) theoretically assuming a 7r-delocalization mechanism to be operative (100, 105).

It is more difficult to explain the origin of the negative spin density on the ring carbon atoms (or the positive spin density on the protons) of the other paramagnetic metallocenes (V and Cr) and it has been suggested that this is the result of either a direct transfer of spin density between the metal and the ring protons through space (95, 96, 99) or, alternatively of an exchange inter-action between the filled elg or e2g orbitals (which have predominantly ligand character) and the unpaired electron of the metal (which is predomi-nantly in an alg or e2g orbital) (43, 92, 94).

The effect of temperature upon the proton NMR spectrum of nickelocene and Ι,Γ-dimethylnickelocene has been investigated: the contact shift varies with the temperature—increasing temperature being accompanied by broadening of the signals (99, 101, 102, 106). Extrapolation of the second moment to zero external field shows that the cyclopentadienyl rings are rotating even at 77°K.

7. MISCELLANEOUS

The x-ray K spectra of a number of metallocenes have been measured and that for nickelocene shows a high energy absorption at around 20 eV and a shoulder at approximately 10 eV. An attempt to interpret these absorptions as s->p transitions has been criticized (60, 107-109). Based upon this tech-nique, a method has been developed by which the electronic distribution within a molecule may be determined. When applied to nickelocene the charge on the metal is calculated to be +0.65 and that on the rings —0.32 (111, 112). However, caution is called for since an x-ray photoelectron spectrum indi-cates that the rings have a small positive charge (115, 370): the Cl s bonding energy for the cyclopentadienyl group (284.9 ± 0.3 eV) increases on complex-ing to nickel (285.6 ± 0.3 eV). However, the validity of this deduction is


questionable, it having been shown that Koopman's theorem is not valid for metallocenes (377).

A high resolution He(I) photoelectron spectrum of nickelocene has a band at 6.4 eV and broad bands at 8.2-10.9, 12-15, and 17-18 eV. The first band is attributed to ionization of one of the unpaired electrons, while the remaining three bands are common to metallocenes in general and are believed to be associated with the rings (344).

A multiwire proportional counter method has been applied to measurements of the L and K radiation arising from orbital electron capture for 56Ni and 57Ni using gaseous nickelocene. The value of the L/K capture ratio is 0.115 ± 0.006 for 56Ni and 0.100 ± 0.006 for 57Ni. The same technique has also been applied to other metallocenes (44, 110).

Analysis of the radioactive products formed by neutron activation of nickelocene show that about two thirds of the activity is retained while one third is converted to nickel ions (113). y-Irradiation of nickelocene in bromo-benzene is reported to cause decomposition to nickel bromide (114), while in methylpentene it acts as an electron scavenger (351).

C. Electronic Structure and Bonding

Theoreticians have been attempting to describe the electronic structure of the metallocenes for the last two decades. Ferrocene has received the greatest attention and it is generally assumed that only slight modification is needed to apply the same model to the other metallocenes.

The five molecular orbitals for the cyclopentadienyl group are shown in Fig. VIII-2a. A linear combination of two such sets of molecular orbitals (assuming D5d symmetry) gives a set of ten new molecular orbitals having symmetry Alg(l), A2u(l), Elg{2\ Elu(2), E2g(2), and E2u(2). This is illustrated in Fig. VIII-2b for the Alg and A2u molecular orbitals. The metal orbitals can also be classified in the D5d point group (see below) and a correlation diagram can be constructed if the various energy levels and overlap integrals are determined or estimated.

Group classification

Alg

A2u 2Elg

2Elu

2E2g 2E2u

Ring orbitals

ag

σ« 2lTg

2πη

2hg

2hu

Metal orbitals

45, 3É/22

^Ρζ

3dxe, 3dy!¡

4Ρχ, *Py 3¿/*2-3/2, 3tfk —

Space prohibits a detailed discussion of the early molecular orbital models (52, 71, 92, 116-139, 144), and the reader is referred to references 87, 109,

/. Bis-TT-Cyclopentadienylnickel (nickelocene) 429

(a) (b)

Fig. VIII-2. HMO's for the C5H5 and (C5H5)2 groups.

and 110 where they are critically reviewed. The more recent publications in which nickelocene is specifically discussed are to be found in references 43, 69, 91, 94, 140-143, 156, and 354. The main development in the molecular orbital treatment is the introduction of all the valence electrons of both the metal and the ligands into the calculations; in addition an electron gas model has been discussed (142, 143).

The various physical data for nickelocene, which we have discussed in the preceding sections, as well as the thermodynamic instability in comparison to ferrocene, indicate that the two unpaired electrons occupy an antibond-ing orbital. The large zero-field splitting observed for nickelocene suggests that this orbital is mainly of metal character and the more recent semi-empirical MO calculations agree upon the e*g orbital. Most of the MO calculations assign the highest filled orbitals in ferrocene alg and e2g symmetry with the energy difference between these two levels being much less than that between alg and e?g. The more recent calculations suggest that the order of the orbitals is efg > alg > e2g with all three orbitals having mainly d orbital character. A partial molecular orbital diagram for nickelocene is shown in Fig. VIII-3. It is interesting that most of the characteristics of this diagram were predicted by one of the earliest qualitative descriptions (117).

It would probably be little more than a coincidence if the results of the MO calculations agreed quantitatively with the physical data but they do satis-factorily explain the origin and magnitude of the paramagnetism and the NMR spectra, while a recent (141) calculated value for the ionization potential (6.874 eV assuming Koopman's theorem to be valid; see Ref. 377) compares


- 4 έ - β ι ; " " " / " ' / / ■r y !

eifern / î | i l e*9

Fig. VIII-3. A partial MO diagram for nickelocene.

well with the value obtained from the mass spectrum (7.1 eV) and photo-electron spectrum (6.4 eV). All the recent calculations show a small positive charge on the nickel atom which is also indicated by the x-ray K spectra. However, caution is necessary since the molecular core binding energies as determined by x-ray photoelectron spectroscopy suggest a small positive charge on the rings (115).

D. Ring Substituted Nickelocene Derivatives and Related Complexes (Table VIII-4)

Nickelocene, having two unpaired electrons occupying antibonding orbitals, is easily oxidized and hence there is no equivalent in its chemistry to the aromatic substitution reactions exhibited by ferrocene; reactions of nickelocene with organic reagents generally resulting in displacement of one or both of the rings and being frequently accompanied by a ligand exchange reaction. However, a number of ring substituted derivatives are known (Table VIII-4), and these have, in general, been synthesized from substituted cyclopentadiene derivatives by methods similar to those used to prepare the parent compound. [The dimethylcyclopentadienylsilyl derivative has been claimed in a patent without details (145) while the trimethylsilyl derivative has not been obtained pure (146).]

Reactions in which dimethylfulvene is either hydrogenated or treated with phenyllithium in the presence of a nickel salt produce the di-dimethylbenzyl and di-isopropyl (3) derivatives (20).

Ring exchange reactions have been observed on reaction of nickelocene

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with LiC5D5 (346) or LiC5H4CH(CeH5)N(CH3)2 (147) and in the reaction of (7T-C5D5)2Ni with chromocene or manganocene (346).

^ < + Nipy4Cl2 i ^ü i^ Ni

3

Deuteration of the cyclopentadienyl rings is said to occur at an appreciable rate at room temperature if nickelocene is treated with DN(C2H5)2 in the presence of catalytic amounts of lithium amide. The acidity of nickelocene has been estimated from the results and a pKa value of 21.5 was found (149,150,352). No deuteration occurs on reacting nickelocene with deuterated acids (151). Although solid nickelocene acts as a catalyst for H2—D2 ex-change it is not itself deuterated in the process (152, 153). Under pressure (26 atm) hydrogénation occurs to give 7r-C5H5Ni-7r-C5H7 (154).

The NMR spectra of the substituted nickelocene complexes have already been discussed in connection with the spectrum of nickelocene itself. The infrared spectra of the metallocenes contain two highly characteristic ab-sorptions around 1100 and 1000 cm"1 and the absence of one or both of these in the spectra of the substituted metallocenes is used as a guide in determining the degree of substitution (87). The data for the substituted nickelocene complexes is limited but it does conform to the general pattern (16).

Bis(tricyclo(3.0.1.2)decadienyl)nickel (4) can exist in three isomeric forms which differ in the arrangement of the fused rings. Separation of these isomers has not been possible but the presence of at least two of them is indicated by the NMR spectrum (146). Two isomers of the analogous iron complex have been isolated (148).

4

Bis-7r-indenyl nickel occupies an anomalous position in that it, instead of the expected green, is a red brown solid, has a magnetic moment (1.73 or 2.12 BM) (71, 155) more consistent with one than two unpaired electrons, has a dipole moment of 1.05 ± 0.1 D in benzene (that for the bis-7r-indenyl complexes of the other transition metals is zero) and has an NMR spectrum typical for a diamagnetic species, viz. τ 3.07(t, IH), 3.48(s, 4H), and 4.85(d, 2H)

'O

/. Bis-TT-Cyclopentadienylnickel (nickelocene) 433

in d-toluol (28, 29, 71, 123, 146, 155). The infrared spectrum, however, is very similar to that of the other bis-7r-indenyl metal complexes.

Although not able to explain all the physical data the formulation as a bis(7r-h3-C9H7)Ni complex (5) (146) is more satisfactory than the bis(7r-h5-C9H7)Ni structure (6) originally proposed. The simplicity of the NMR spectrum and its invariance with temperature would seem to eliminate unsymmetrical structures (e.g., 7) as well as valence tautomerism between different structures.

The reaction between dilithium pentalenide and nickelocene or NiCl2.-monoglyme produces bispentalenylnickel (348). The structure is not known

NiCl2 · monoglyme + Li2 -2LÍC1

with certainty and besides 8, a bis-(h3,h5-pentalenyl) arrangement as well as a structure related to bis(pentadienylnickel) (see Chapter VI, Fig. VI-5) are possible.

E. The Nickelocinium Cation, Dication, and Related Complexes

The unpaired electrons present in nickelocene may be removed stepwise to give the d7-monocation and the dedication. The dication, which is formally, electronically equivalent to the stable (7r-C5H5)2Fe and (77-C5H5)2Co + , is very much less stable than nickelocene itself (see below) and, although no adequate explanation for this fact has been given, it has been suggested that it may be a result of a reduction in the overlap between the ring orbitals and the orbitals of the formally four-valent nickel atom (26).

The most elegant method for producing the cationic species is electro-


chemical oxidation (26, 27, 30, 159, 160). By working in acetonitrile at —40°, the reversible formation of both the orange-yellow monocation, (7r-C5H5)2Ni + , and the dication, (7r-C5H5)2Ni2 + , have been demonstrated. The reversible voltammogram with the reduction peak potentials is shown below.

The monocation can also be generated by chemical oxidation of nickelo-cene with halogens, nitric acid, oxygen, eerie salts, etc. (17, 26, 30, 36, 161, 166) and it may be precipitated by the addition of suitable anions [e.g., V , B(C6H5)4-, Cr(SCN)4(NH3)2-].

-0.09 V

+ 0.77 V ( 7 T - C 5 H 5 ) 2 Ni2 ++ e~ ^ ( ^ - C 5 H

5 ) 2N i +

+ 1.2 -hl.0 + 0 . 8 + 0 . 6 + 0 . 4 + 0 . 2 0 . 0 - 0 . 2 - 0 . 4

Volts vs saturated calomel electrode

Fig. VIII-4. Cyclic voltammogram of the (7r-C5H5)2Ni system in acetonitrile at — 40° (159).

The dication decomposes in acetonitrile at temperatures above 0°C and as yet no simple salt has been isolated. Its presence is, however, suspected in the 1:2 adduct formed between nickelocene and p-chloranil and related compounds, viz., (C5H5)2Ni2 + (/?-C6CU02)2

2-, (153, 162, 163), and a Mössbauer study of the nickelocene-SnCl4 system (which produces a black-precipitate) indicates that a redox reaction occurs in which the intermediate nickelocinium dication (7r-C5H5)2Ni2 + SnCl4

2 " is suspected. However, this reaction is not understood in detail (165). In addition, the reaction between nickelocene and picric acid in the absence of air is said to give a dipicrate which might also contain the dication (164). The same reaction in the presence of air produces a black monopicrate (26).

The presence of one unpaired electron in the nickelocinium monocation has been confirmed by magnetic moment determinations [/xeff =1.75 + 0.1 BM (17, 26)]. The 1H NMR contact shifts for the nickelocinium cation and two derivatives have been determined : the presence of two signals for the ring protons in the substituted cation (Table VIII-5) is in contrast to the result for the corresponding uncharged complexes (see Table VIII-3) and is attributed to Jahn Teller distortion in the d7-monocation (161).

/. Bis-n-Cyclopentadienylnickel (nickelocene) 435

TABLE VIII-5 1H-CONTACT SfflFTS FOR THE NlCKELOCINIUM CATION

(ppm rel to ferrocene)

Compound Ring Substituent (7r-C5H5)2Ni+ +105 — (77-CH3C5H4)2Ni + +153, +90.5 -30.0 (Wer/-C4H9C5H4)2Ni + +128, +92.0 -2 .5

Bimetallic fragments, e.g., (C5H5)3NÍ2 + , (C5H5)2NÍ2C3H3 + , observed in the mass spectrum of nickelocene are thought to have "triple-decker" sandwich structures (74, 341), the triscyclopentadienyl-dinickel cation (9) has been prepared by conventional chemical means and the structure verified spectro-scopically (229, 263) (see Table VIII-4).

BF4- + C5H5R

9 (R = H,CH3, tert-CiH9)

F. Reactions of Nickelocene in Which Both Cyclopentadienyl Rings are Displaced

One of the standard methods used to prepare Lig4Ni complexes is the re-action of nickelocene with excess ligand and as such has already been dis-cussed in Chapter III.

The reduction of solutions of nickelocene with hydrogen, which produces metallic nickel and cyclopentadiene has been recommended as a method for depositing nickel onto powder surfaces (345).

Pyrolysis of nickelocene at 950° and 0.08 mm Hg produces, in addition to the cyclopentadienyl and nickel cyclopentadienyl radicals, 9,10-dihydrofulva-lene (10) as an unstable liquid which, in dilute solution, rearranges at room temperature to give 1,5-dihydrofulvalene (11) (75, 167, 169).

(..c.„.,,Ni *. Q ^ _^ Q _ Q 10 11

Alkylation of the cyclopentadienyl ring occurs on reaction of nickelocene with triphenylmethylchloride to give a mixture of 2- and 3-triphenylmethyl-cyclopentadiene (57, 166). A related reaction of nickelocene with CC14 in the

2(77-C5H4R)2Ni + HBF4


presence of P(C6H5)3 has been shown to give trichloromethylcyclopentadiene in addition to ^C5H5NiCl[P(C6H5)3] (367).

C(C6H5)3

>NiC.2 +f \ + f \ Or-C5H5)2Ni + 2(C6H5)3CC1 C(C6H5)3

An analogous reaction involving ferrocene results in formation of trityl ferrocene. Both reactions are suggested to occur by a similar mechanism involving oxidation of the metal complex followed by reaction of the trityl radical with the ring either directly or via the metal atom. The difference

(W-CeHe)aNi + C(C6H5)3 +

( T - C 5 H 5 ) 2 N Í + + -C(C6H5)3 ; " ^-C5H5)2Ni+—C(C6H5)3

-C5H5Ni7r-C5H4C(C6H5)3 < // ^C5H5Ni+—j- V ^ / C(C6H5)3

12

77-C5H5Ni+ + C5H5C(C6H5)3

between the behavior of nickelocene and ferrocene is probably attributable to the instability of the ionic species 12, which, in the nickel case, decomposes before deprotonation can occur. Similar species have also been postulated to be intermediates in the catalytic formation of polymethylene by reaction of nickelocene with diazomethane'(168).

The reaction of oxygen atoms with nickelocene has been compared with that of oxygen atoms with cyclopentadiene; at least nine hydrocarbons are produced (e.g., acetylene, aliene, cyclopentadiene) and of these vinylacetylene and propyne are observed only in the reaction involving nickelocene (85).

G. Reactions of Nickelocene in Which One of the Cyclopentadienyl Rings is Displaced

Practically all of the mono-7r-cyclopentadienylnickel complexes may be prepared by displacing one of the rings from nickelocene. Many of the prod-ucts of these reactions, in as much that they contain a second organic group, have been discussed in preceding chapters, and here we are only concerned with reactions which lead to products in which the ττ-cyclopentadienyl group is the only organic ligand (CO being an exception). The 1,3-addition of an alkyne molecule to produce the σ-norbornyl system 13 and the displacement

77. π-Cyclopentadienylnickel Carbonyl and Isonitrile Complexes 437

of one of the rings by an azobenzene molecule giving 14 are discussed in Chapter IV, the reaction with an alkyne to give the binuclear complex 15 is discussed in Chapter V and the 1,2-addition of an olefin molecule or the re-action with allyl metal reagents which give ττ-allyl systems (e.g., 16) are to be found in Chapter VI.

7T-C5H5Ni

7r-C5H5Ni

13

RCEEECR / \

7r-C5H5Ni—NÍ7r-C5H5

15

77-C5H5NÍ

For the sake of compactness we have created sections treating each class of compound separately (e.g., 7r-C5H5NiX(Lig) compounds), and within these sections we discuss the chemistry of the individual complexes.

II. 77-Cyclopentadienylnickel Carbonyl and Isonitrile Complexes (Table VIII-6)

A. Preparation and Structural Considerations The dimeric carbonyl complex (7r-C5H5NiCO)2 (17) is most conveniently

prepared by reacting nickelocene with nickel tetracarbonyl in benzene (170-173). The same complex is formed in the reaction of sodium cyclo-

(7r-C5H5)2Ni + Ni(CO)4 (7r-C5H5NiCO)2 + 2CO

17

pentadienide with nickel tetracarbonyl in the presence of the halides of nickel, mercury, or copper (174, 175).

The kinetics of the reverse reaction [i.e., treatment of 17 with CO to give Ni(CO)4] have been studied and the mechanism is discussed on page 48. Assuming microscopic reversibility the reverse of this mechanism should apply to the preparation of 17, and it does seem plausible that the first step is the generation of a Ni(CO)3 species which attacks the nickelocene to form an intermediate (one possibility is 18, which has not, however, been isolated) which then rearranges to 17 with loss of CO (353).


:<=>: OC CO \ / W

18 (7r-C5H5NiCO)2 is a diamagnetic, purple-red solid and its infrared

spectrum indicates that only bridging carbonyl groups are present. Two structures are possible differing in the eis or trans arrangement of the π-cyclopentadienyl groups. An, as yet unpublished, structural determination indicates that the eis arrangement (19) exists in the solid state (Ni—Ni = 2.36 Â) and this arrangement is also adopted in the complex (7r-C5H5Ni)2-C6H5C:CC6H5 (15) formed by reacting the dimer with diphenylacetylene (180,181). The infrared spectrum in solution is also interpreted in terms of the eis arrangement (182, 183). The zero dipole moment, however, is in conflict with this suggestion but the value may well be coincidental (170). The dia-magnetism requires the presence of a nickel-nickel bond which, from the geometry of the molecule may be assumed to be of the bent variety.

Mixed metal complexes related to 17 can be prepared by reacting nickelo-cene with other metal carbonyls. The reaction with iron pentacarbonyl or triiron dodecacarbonyl leads to the nickel-iron system 20 (176, 177) while the product of the reaction with diphenylphosphine iron tetracarbonyl (21) is the bridging phosphide 22. The latter compound is also produced by reacting the alkyne complex 15 (R = C6H5) with 7r-C5H5NiCl[P(C6H5)3] or 7r-C5H5-Nil(CO) in diethylamine (185-187). A ruthenium compound analogous to 20 is believed to be formed in the reaction with Ru3(CO)i2 but proved too un-

o C CO

(7r-C5H5)2Ni + Fe(CO)5 ► 7r-C5H5Ni- F e ^ + 2CO Ν 0 Χ TT-CSHS

O 20

//. π-Cyclopentadienylnickel Carbonyl and Isonitrile Complexes 439

O c

(ir-CeHe)aNi + HP(C6H5)2Fe(CO)4 "C 5 H 6) 7r-C5H5Ni^-^Fe(CO)3 21 p

(CeH5)2 22

stable to isolate (178, 179). A brief mention has also been made in a patent of a compound of unknown structure, having the composition (7r-C5H5)3-NiCr(CO)3, formed by reacting nickelocene with [77--C5H5Cr(CO)3]2 (188).

By analogy with reactions involving the transfer of a tetraphenylcyclo-butadiene molecule, it has been suggested that 20 is formed through an inter-mediate 23 having a bridging cyclopentadienyl group (184). (The reverse reaction—transfer of 7r-C5H5 from iron to nickel—occurs during the prepara-tion of [^-C5H5NÍ7r-C4(C6H5)4]+ and is discussed in Chapter VII.)

O O

7T-C5H5NÍ;' \Fe—CO

/ *co

23

The infrared spectrum of 20 suggests that only one isomer is present in solution but does not enable it to be identified with certainty (183).

Related complexes (e.g., 24 and 25) have been prepared by reacting 7r-C5H5NiX(Lig) complexes with the sodium salt of the ττ-cyclopentadienyl-iron dicarbonyl anion or cobalt tetracarbonyl anion whereby, in both cases, ligand transfer from the nickel occurs (332, 347, 360).

O / C \ 7"C 5 H 5

^C5H5NiCl[P(C6H5)3] + [7r-C5H5Fe(CO)2]Na ^ ^ i > „.QHsNi- Fe^ Cy P(C6H5)3 O

24

O

7r-C5H5NiCl[P(CeH5)3] + [Co(CO)4]Na — ^ * (n-CsH^m^—^Co—CO g P(C6H5)3

25

The isonitrile group has similar ligand properties to the carbonyl group and complexes analogous to the ττ-cyclopentadienylnickel carbonyl dimer 17


have been prepared by similar methods. The reaction between nickelocene and tetrakisphenylisonitrile nickel produces the dimeric complex 26 which has bridging isonitrile groups. Nickelocene also reacts directly with isonitriles,

C6H5

N II

c (TT-CSHS^NÍ + Ni(CNC6H5)4 ► π -CeHeNi -—Νΐπ-0 5 Η 5 + 2CNC6H5

C II

N C6H5

26

the nature of the product being dependent upon the substituent. terí-Butyl isonitrile reacts to give the tetrakis-ligand complex and the dimer analogous to 26 while cyclohexylisonitrile only forms the dimer. Infrared studies of the cyclohexylisonitrile complex show that, in solution, it is in equilibrium with a nonbridging species 27 (192-195). This has, however, been contested (371).

cyclo-CeHu N

/ C N cyclo-CeH^NC yTT-C5H5

77-C5H5NÍ NÍ77-C5H5 , Ni—Ni C TT-CSHS CNcK/o-QHn

N L1

cyclo-CeHu

The structure of the bridging methylisonitrile complex has been determined (Fig. VIII-5). The dihedral angle between the two Ni—C—Ni planes is 121°.

H3C

2.143(5)

1.41 (1) 1.905(4)/Χΐ.8β9(4) 2.104(4)/ \ 2 201 (5) y< \

I Λ \2.2υπ»^Ί 2.322(l)^Ni

\1.44(1)

.19(1)

2.086(5){ /l .39(l) X^7 6-5Vi.893(4)

1.20(1) N

1 4 5 ( l K C H 3

Fig. VIII-5. Structure of (Tr-CsHsNiCNCHg^ (329). a = 6.999, b = 22.07, c = 9.130; β = 93.43; Z = 4; space group P21/c; R = 3.7%.

TA

BL

E

VII

I-6

TT

-CY

CL

OP

EN

TA

DIE

NY

LN

ICK

EL

CA

RB

ON

YL

0 A

ND

ISO

NIT

RIL

E C

OM

PL

EX

ES

Co

mp

lex

Co

lor

(mp

) T

C5

H5

Sp

ectr

al

da

taa

Ref

.

(7r-

C5H

5N

iCO

) 2

(17

)

7r-

C5H

5N

i(C

O) 2

Fe(

CO

)7r-

C5H

5 (2

0)

7r-

C5

H5

Ni(

CO

) 2F

eP(C

6H

5)3

^-C

5H

5

(24)

7r-

C5H

5N

i(C

O) 2

FeP

(C6H

5)2

-C

Ha-

TT

-CoH

o

7r-

C5H

5N

i(C

O) 2

FeP

(CH

3) 2

-

CeH

ö-T

r-C

öHs

1r-

C5H

5N

i(C

O) 2

FeP

(CH

3)3

-^-C

5H

5

7r-

C5H

5N

i(C

O) 2

FeP

(OC

6H

5V

-C5

H5

7r-

C5H

5N

i(C

O) 2

Co

(CO

) 2-

P^

c/o-

CeH

iOaC

eHB

7r

-C5H

5Ni(

CO

) 2C

o(C

O) 2

P(C

6H5)

3

(25)

7r

-C5H

5Ni(

CO

) 2C

o(C

O) 2

-P

(C6H

4-/>

-F) 3

7r-C

5H5N

iCO

[P(C

6H5)

2]F

e(C

O)3

(2

2)

(7r-

C5H

5NiC

NC

H3)

2

(7r-

C5H

5NiC

NC

6H5)

2 (2

6)

(7r-

C5H

5NiC

NC

H2C

6H5)

2

(TT

-CsH

sNiC

N-c

^c/

o-C

eHni

a (2

7)

Red

-vio

let

(136

d)

Dar

k b

row

n

(132

d)

4.70

4.69

, 5.

08 (

c)

Bla

ck-b

row

n 4

.91(

s)

(140

-150

d)

— (1

74-1

75)

— (1

40-1

50d

) —

(170

d)

—

Bro

wn

Bro

wn

Bro

wn

Bro

wn

(1

50-1

52)

Red

-bro

wn

(1

55-1

56d

)

5.5

4(d

,/1

.2)

4.90

(s)

5.5

1(d

,/1

.8)(

c)

4,79

(s) f

4.68

(d,

/1.8

) (c

) 4.

72(e

),

8.43

(d

,

8.74

(d

,

8.88

(d

, 5

.45

(d,/

1.8

)(c)

4

.84

,2.7

5 (c

)

4.58

(c)

r

2.2

-2.

v co1

854(

s),

1896

(w)

(a)

μ =

0-0

.38

D

v co2

004(

s),

1825

(s),

18

55(w

) (a

) v c

o180

5(w

), 1

760(

s) (

c)

CH

3/

8.4)

v c

o180

2(w

), 1

750(

s) (

c)

CH

3,

/ 9.

6)

vcol

800(

w),

173

5(s)

(c)

CH

3,

/ 9.

6)

v col8

00(w

), 1

753(

s) (

c)

v co18

20(w

),17

68(s

)(c)

v

co s

ee R

ef.

veo

see

Ref

.

vco

see

Ref

.

8 (C

6H

5)

v co20

35,

19

90

, 1

96

8,

1840

(d

)

v c:N

1785

VC

:N21

40 (

e)

v c:N

1880

, 18

40

49,

170-

175,

18

2,

183,

18

9-19

1 17

6,

177,

18

2,

183,

3

32

332

332

332

332

332

347

347

347

185,

18

7

329

193,

1

94

195

192

a [(7

r-C

5H5)

Ni]

3(C

O) 2

an

d r

elat

ed c

lust

er c

omp

oun

ds

are

to b

e fo

un

d in

Tab

le V

III-

7.

b Sol

ven

t: (

a)

hep

tan

e; (

b)

nujo

l m

ull

; (c

) C

DC

1 3;

(d)

hex

ene;

(e)

ben

zen

e.

442 VIH. ΤΓ-Cyclopentadienyl Nickel Complexes

The cyclopentadienyl rings are planar, adopt a partially staggered relation-ship to each other and are tilted away from the bridging methyl isonitrile group to give a dihedral angle, between the two ring planes, of 43.7°.

B. Reactions

Both (77-C5H5NiCO)2 and (7r-C5H5Ni)3(CO)2 form 1:1 and 1:2 adducts with aluminum alkyls. Although no details have been published it may be assumed that the structures of the adducts resemble that established by x-ray methods for [^-C5H5Fe(CO)2]22Al(C2H5)3 in which the aluminum alkyl is coordinated to the oxygen atoms of the bridging carbonyl groups and is, in this case, associated with a shift in the CO stretching frequency of 125 cm"1 to lower frequency (336, 337$ 372).

The nickel-nickel bond in (77--C5H5NiCO)2 (17) can be cleaved chemically by reaction with potassium in THF (196), magnesium amalgam (157), or electrolytically (197-199). Attempts to prepare the anion by reacting sodium cyclopentadienyl with nickel carbonyl produce only the dimer, while the product of the reaction of the dimer with sodium amalgam in methanol is (7r-C5H5Ni)3(CO)2 (170).

The nucleophilicity of (7r-C5H5NiCO)~ has been compared with that of other organometallic anions by generating the anion electrochemically and comparing the relative rate of reaction with alkyl halides (199). In monoglyme the following nucleophilic series results:

[7r-C5H5Fe(CO)2]- > [77-C5H5Ru(CO)2]- > [7r-C5H5NiCO] " > ](CO)5Re]-

> [7r-C5H5W(CO)3]- > [(CO)5Mn]- > [7r-C5H5Mo(CO)3]-

> [7r-C5H5Cr(CO)3]- > [(CO)4Co]-

The use of the anion as a nucleophilic reagent is confined to the preparation of the few nickel-alkyl complexes discussed in Chapter IV (Section XII-A2). The reaction of the anion with main group metal halides to prepare com-plexes containing a metal-nickel bond has not apparently been successfully carried out. [The compounds 7r-C2H5C5H4Ni(CO)-Pb(CH3)2Br and 7r-CH3COC5H4Ni(CO)Pb(C6H4-0-CH3)l2 have been reported without any details in a patent (200), and were presumably prepared by reacting the appropriate anions. On reaction of these complexes with hydrogen halide cleavage of the organolead group is said to occur.]

Oxidative cleavage of the Ni—Ni bond occurs readily, and has been re-

(7r-C5H5NiCO)2 + RX ► 7T-C5H5NiR(CO) + 77-C5H5NiX(CO)

28

ported in the reaction with iodine (28, R = I; 170, 203) perfluoroalkyl halides (28, R = RF; 196), organosulfonyl chloride (R = CF3S02, 205)

77. π-Cyclopentadienylnickel Car bony I and Isonitrile Complexes 443

trichlorosilane (28, R = SiCl3, 206), tin and germanium tetrahalides (R = GeX3 or SnX3, 202), bis(triethylgermyl)mercury (28, R = (C2H5)3Ge, 203), cyclopentadienyltrimethylstannane and hexamethyldistannane (28, R = Sn(CH3)3, 201, 207, 7r-C5H5Fe(CO)2MX3(M = Sn, Ge; X = Cl, Br) (365) and [(CH3)3Sn]20 and [(CH3)3Sn]3N (373). The products, being of the 7r-C5H5NiX(Lig) type, are included in Table VIII-8.

A related reaction is the insertion of tin(II) chloride and -bromide into the nickel-nickel bond to give 29 (202, 208, 209). The kinetics of this reaction

(7r-C5H5NiCO)2 + SnX2 ► ^C 5 H 5 Ni(CO)—SnX 2 —NÍ(CO)T7-C 5 H 5

17 29

have been studied [for SnBr2 in THF AH* = 19.4 ± 0.2 kcal/mole, AS* = -8.8 ± 0.4 eu: for SnCl2 in THF Am = 22.5 ± 0.2 kcal/mole, AS* = —4.0 ± 0.2 eu (209)] and a bimolecular mechanism involving direct attack of the tin(II) halide on the nickel dimer has been proposed. An analogous germanium complex is formed in the reaction of 17 with GeCl4 but this is believed to arise by reaction of the monosubstituted product (30) with further

TT-CsHsNiGeCWCO) + (7r-C5H5NiCO)2 ►

30 (7r-C5H5NiCO)2GeCl2 + 7r-C5H5NiCl(CO)

dimer (202). A similar insertion reaction has been observed for the nickel-iron system 20 (332).

O

7r-C5H5Ni——Fe + SnCl2 ► ^C5H5Ni(CO)—SnCl2—Fe(CO)27r-C5H5

C 7r-C5H5 O 20

Carbon monoxide, phosphines, and arsines react with 17 to give a bis-ligand nickel dicarbonyl complex and nickelocene. The application of this

(7r-C5H5NiCO)2 + 2Lig ► (7T-C5H5)2Ni + Lig2Ni(CO)2

17

reaction to prepare bisligand nickel dicarbonyl complexes has been discussed in Chapter II.

14CO exchanges very rapidly with 17. The reaction is first order in both dimer and CO and has been estimated to occur about 70 times faster than the reaction of 17 with CO to give Ni(CO)4 (210).

Tetrasubstituted bisphosphines and bisarsines [e.g., (C6H5)2P—P(C6H5)2] react with the carbonyl dimer eliminating carbon monoxide and forming the bridging phosphide (or arsenide) (31). Compounds of this type have also been isolated from the reaction of diphenylphosphine nickel tricarbonyl with


7r-C5H5NiI(CO) (187) and from the reaction of nickelocene with bistri-fluoromethylphosphine (215) (see Table VIII-10). Electrochemical reduction of 31 (R = C6H5) is reported to give a stable radical anion of unknown struc-ture, the ESR spectrum of which consists of a single line 10 G in width (214).

R2 P

(7r-C5H5NiCO)2 + PR2—PR2 ► 7r-C5H5Ni Niw-C6He + 2CO χ ρ κ

R2

31

The crystal structure of the diphenylphosphide 31, (R = C6H5) has been determined (Fig. VIII-6). The nickel and phosphorus atoms are coplanar with a nonbonding nickel-nickel separation of 3.36 Â. The cyclopentadienyl rings are neither symmetrically bonded to the nickel nor are the C—C bond distances within the ring uniform. The structure should be compared with that of [(CO)2NiP(C6H5)2]2 in which the nickel and phosphorus atoms are also coplanar but in which the presence of a Ni—Ni bond (2.51 Â) closes the Ni—P—Ni angle to 70° and opens the P—Ni—P angle to 110° (see Chapter

C Ö H Ö

Fig. VIII-6. Structure of [^C5H5NiP(C6H5)2]2 (212). a = 9.46(2); b = 10.83(2); c = 16.78(3); y = 122.28' ± 10'; Z = 2; space group P2x\n\ R = 13.9%.

Bistrifluoromethyldithietene reacts with the ττ-cyclopentadienylnickel carbonyl dimer to give the black, paramagnetic (jieff = 1.67 BM) complex 7r-C5H5Ni[S2C2(CF3)2]. Electrochemical reduction converts this compound into a colorless diamagnetic anion whose chemistry has received no further attention; reduction with hydrazine produces [Ni(S2C2(CF3)2]2~ (197, 216— 218).

III. 77-Cyclopentadienylnickel Cluster Compounds (Table VIII-7)

An interesting series of cluster compounds have been isolated from the reaction of (7r-C5H5NiCO)2 (17) with various metal carbonyl complexes.

///. π-Cyclopentadienylnickel Cluster Compounds 445

Heating 17 above 130° or treating it with sodium amalgam produces the parent compound (77-C5H5Ni)3(CO)2 (32) (170, 173, 190, 226, 227). Other members of the family, viz. (77-C5H5Ni)27r-C5H5Co(CO)2 (33), (7r-C5H5Ni)2-Fe(CO)5 (34), and [(7r-C5H5Ni)2Mn(CO)5] - (35) are formed by reacting 17 with 7T-C5H5Co(CO)2, Fe2(CO)9 or [Mn(CO)5]~, respectively. Yet a further example, (7r-C5H5Ni)3S2 (36), is formed by reacting the dimer 17 with sulfur. The structures of 32, 33, and 36 have been established by x-ray structural methods, while those proposed for 34 and 35 are based upon NMR, infrared, and mass spectral evidence (Table VIII-7). The relevant structural data for 32, 33, and 36 is shown on page 446.

Both the metal atoms and the cyclopentadienyl rings in the nickel-cobalt complex 33 are disordered. The only significant alteration in the structure of the cluster upon replacement of a nickel atom by a cobalt atom is an in-crease in the Ni—M distance by 0.03 Â. The infrared spectra of the Fe—Ni and Mn—Ni complexes 34 and 35 differ in solution from that in the solid state suggesting that isomers are present.

A qualitative MO picture of the bonding in these cluster compounds has been developed and explains the magnetism and variation of the metal-metal bonds lengths both simply and elegantly (219). We consider first (7r-C5H5Ni)3S2 (36): In this complex 9 valence orbitals are available for each nickel atom, of these 5 are used in localized coordination with the 2 sulfur atoms and the cyclopentadienyl group. The remaining four orbitals per nickel atom are combined in a system having D3h symmetry to give 6 bonding and 6 antibonding orbitals. The 23 valence electrons present in the complex (15 from the three 7r-cyclopentadienyl groups and 8 from the two S atoms) fill these orbitals and place an unpaired electron in the highest antibonding orbital. This is obviously an energetically unfavorable situation and the resulting Ni—Ni bond is fairly weak and hence long. In the analogous complex (7r-C5H5Ni)3(CO)2 there are only 19 valence electrons (15 from the three 7r-cyclopentadienyl groups and 4 from the two CO molecules), and hence the number of antibonding electrons has decreased by 4 and the Ni—Ni bonds increases in strength and decreases in length. Replacing a nickel atom by a cobalt atom removes one more valence electron and one obtains the diamagnetic complex 33 with, as expected, a slight decrease (0.03 Â) in the Ni—M bond length. An early description of the bonding in (7r-C5H5Ni)3-(CO)2 based upon the ESR spectrum suggested that the unpaired electron occupies a bonding orbital of a2 symmetry; however, the observed g values can be equally well understood if the electron were to occupy an antibonding orbital of the same symmetry (223, 224).

A stable anion is formed on electrolysis of 32. The structure is not known but the suggestion has been made that cleavage of a Ni—Ni bond occurs to give a compound having a linear structure: viz., (7r-C5H5)NiCO—Ni-

STR

UC

TU

RA

L D

AT

A F

OR

TH

E (7

7-C

5H5N

O2M

X2

CO

MPO

UN

DS0

Com

poun

d M

X

N

i—M

(Â

):

Ni—

X(Â

):

Ni—

C (r

ing)

(Â)

¿Ni—

X—

Ni

Mis

e.

Ref

.

32

Ni-7

r-C

5H5

CO

2.

39(1

) 1.

93(2

) 2.1

2

77°

C—

O 1

.19(

3)

222

36

N

i-TT-

CsH

s S

2.

801(

5)

2.17

2(6)

2.1

3

80.3

219

33

CO

-TT-

CSH

S C

O

2.35

8(2)

1.

933(

10)

2.10

5(av

g)

75.1

C

—O

1.1

83(1

3)

58,2

20,2

21

0 32

a =

9.2

6(5)

; b =

10.

70(6

); Z

= 2

; sp

ace

grou

p P

6 3/m

. 36

a =

9.5

95(6

); b

= 9

.923

(6);

Z =

4;

spac

e gr

oup

P6 3

/m;

k =

10.

2%.

33 a

= 9

.158

(3);

c =

10.

739(

4); Z

= 1

; sp

ace

grou

p 2

mm

(id

eal)

; R

= 4

.6%

.

III. π-Cyclopentadienylnickel Cluster Compounds 447

(7r-C5H5NiC07r-C5H5) (198, 228). As yet no chemical reactions involving this species have been reported. A study of the mass spectrum of 32 shows that other cluster compounds, e.g., (^C5H5)4NÍ4(CO)n

+, are formed in the spectrometer (191).

Fig. VIII-7. Structure of teri-C4H9N[Ni-77-C5H5]3 (230, 231). a ~ 28.4; b c ~ 15.28 Â; ß = 100°30'; Ζ = 8; space group C2/c.

9.16;

Related cluster compounds are obtained by reacting nickelocene or the carbonyl dimer 17 with 7V-terí-butylsulfurdiimide [(teri-C4H9N)2S] and from the reaction of nickelocene with benzylmagnesium chloride or /?-methyl-benzylmagnesium chloride at room temperature. The first reaction produces a black, sulfur-free paramagnetic (/xeff = 1.68 BM) complex which has been shown by a partial x-ray analysis (Fig. VIII-7) to contain the nitrene, N-tert-C4H9 (230, 231, see also 366). By analogy with the structurally related Co3(CO)9X (X = S, Se) molecules it has been suggested that the unpaired electron in this molecule occupies an antibonding orbital (232). The product of the reaction between nickelocene and the benzyl Grignard reagent probably has structure 37. A byproduct of this reaction is 38 which is produced by alkylation of one of the cyclopentadienyl rings and may also be formed directly by reacting 37 with the Grignard reagent (233). This is apparently the only

<oH4>-{o> <^Nft->~(5> Ni Ni

R

37 38


example to have been observed of ring substitution in a 7r-cyclopentadienyl-nickel system. [Similar behavior has been recently reported during the reac-tion of 7T-C5H5NiNO with organolithium compounds; in addition to the nitrene complexes (7r-C5H5Ni)3NR, ring substituted products are produced (366).]

The products of thfe reaction between the alkyne complexes, (7r-C5H5Ni)2RC;CR' and iron pentacarbonyl, e.g., (7r-C5H5Ni)2Fe(CO)3-C6H5C:CH, probably also contain metal atom clusters although their structures are not known with certainty (177). Further details are found in Chapter V (Section V-C).

A second nickel-cobalt system has been isolated by reacting the carbonyl dimer with Co2(CO)8. The resulting dark green complex (7r-C5H5)Ni-[Co3(CO)9] probably has structure 39 which is related to that of Co4(CO)12 (179).

(CO)2Co

2(7r-C5H5Ni)3S2

36

;co(co)2

(CO)2

39

-► (7r-C5H5NiS)4Ni + (7r-C5H5)2Ni 40

The sulfur containing cluster 36 disproportionates slowly in solution to give 40 whose structure has also been determined by an x-ray analysis (Figure VIII-8). In 40 two (7r-C5H5NiS)2 fragments are joined together by a

\ 2.493

Fig. VIII-8. Structure of [77-C5H5NiS]4Ni, 40 (225). a = 7.870(5); b = 12.704(7); c = 11.661(7); ß = 99.52; Z = 2; space group P2x\c\ R = 6.7%.

TA

BL

E

VII

I-7

ΤΓ

-CY

CL

OP

EN

TA

DIE

NY

LN

ICK

EL

C

LU

ST

ER

C

OM

PO

UN

DS

Com

pou

nd

M

32

NÍ-

TT

-CS

HS

36 N

i-7r

-C5H

5

33 C

o-7r

-C5H

5

34 F

e(C

O) 3

35 [

Mn

(CO

) 3]~

X

1

CO

s CO

CO

CO

Col

or (

mp

) Sp

ectr

al d

ata0

Ref

.

(7r-

C5H

5N

i)2

MX

2 C

OM

PO

UN

DS

Dar

k gr

een

v co17

29;

μθπ

1.7

9 B

M;

(~2

00

d)

(7r-

C5H

5Ni)

3N-^

r/-C

4H9

(Tr-

CsH

sNO

aCC

eHs

(37

, R =

C

6H

5)

(7r-

C5H

5NÍ)

3C-C

6H4-

p-C

H3

(7r.

C5H

5Ni)

27r-

C6H

5CH

2C5H

4NiC

C6H

5

(7r-

C5H

5Ni)

27r-

/7-C

H3C

6H4C

H2C

5H4-

NiC

CH

2C6H

4-/>

-CH

3

7r-C

5H5N

i[C

o 3(C

O) 9

] (3

9)

(7r-

C5H

5Ni)

4S4N

i (4

0)

—

/Lieff

1.7

BM

D

ark

gree

n v c

o17

23;

τ5.0

0 (C

o-C

5H

5),

5.2

3 (N

i-C

5H

5)

(180

d)

Dar

k gr

een

v co20

40(s

), 1

980(

s, b

r), 1

942(

s, s

h),

177

7(w

, sh

),

1730

(m)

(b)

Bla

ck

v co1

964(

s),

1890

(s),

185

3(s)

, 16

71(m

) (b

) [N

(CH

3) 4

+]

MIS

CE

LL

AN

EO

US

7T

-C5H

5N

i C

LU

ST

ER

C

OM

PO

UN

DS

Bla

ck

/¿off

1.68

BM

(1

80d

) B

lack

r5

.13(

s) (

C),

3.2

0,

2.6

5 (C

eH5)

(158

-160

d)

Bla

ck

r4.9

(s),

7.7

(S,

CH

3),

3.2

, 2.6

(C

6H

5)

(169

-171

d)

(38)

B

lack

r5

.0,

4.85

(s),

6.7

(br,

CH

2),

2.3

0, 2

.9 (

C6H

5)

(181

-183

d)

—

r5.0

5(s)

, 4.

9(s)

, 7.

6(d

, C

H3),

6.7

(br,

CH

2),

3.

2, 2

.55

(C6H

5)

Dar

k gr

een

v co2

082(

s) (

a),

204

3(vs

), 2

025(

s),

2012

(m),

185

0(s)

B

lack

(1

35d

)

49,

17

0,

17

3,

189,

19

0,

222,

22

6,

227

219

220,

221

179

179

230,

231

233

233

233

233

179

225

α Sol

ven

t: (

a)

hep

tan

e; (

b)

Nu

jol

mu

ll;

(c)

CS«


central square planar zerovalent nickel atom. In order to attain an inert gas configuration nickel-nickel bonds must be postulated.

IV. 7r-C5H5NiX(Lig) and Related Complexesf (Table VIII-8 and VIII-9)

Disproportionation of nickelocene with bisphosphine nickel dihalide produces the π-cyclopentadienyl ligand nickel halide complex 41 (234, 235, 249). This reaction has, in the case where R = C6H5 and X = Cl, been shown to be reversible if carried out in acetonitrile (250). A related reaction is that

(7r-C5H5)2Ni + (R3P)2NiX2 ► 277-C5H5NiX(PR3)

41

of bistriphenylphosphine nickel dichloride with C5H5T1 or (C5H5)2Hg (248). The same complex 41 (R = C6H5) has been isolated from the reaction of

nickelocene with triphenylphosphine and hydrogen halide (or directly with triphenylphosphonium halide) (236, 238), and also by reacting equimolar quantities of nickelocene and ligand with allylbromide (237), carbon tetra-chloride (238, 258, 367), or iodine (238). Triethylphosphonium halide is reported to react similarly (236, 254).

(7r-C5H5)2Ni + (C6H5)3PH + X - ► 7T-C5H5NiX[P(C6H5)3] + C5H6

Two different mechanisms have been proposed for these reactions: the reaction with the hydrogen halide is suggested to involve an intermediate ionic complex 42 which then reacts further with the ligand (236), while the reaction in CC14 is suggested to involve an intermediate σ-cyclopentadienyl complex 43 which is then cleaved by the halocarbon—a reaction common to many nickel alkyl complexes (238, see also 367).

Ni + X - Ni

42 43

Other reactions which lead to 41 are those of the carbonyl complex 44 (X = I) with a ligand (196, 235, 239), and cleavage of the appropriate nickel-alkyl complex 45 with halogen (235, 238).

Lie Y 7T-C5H5NiX(CO) - — + Tr-CeHeNiX(Lig) «f^— 7r-C5H5NiR(Lig)

Λ Λ - K .X 44 41 45

t The 7r-C5H5NiR(Lig) complexes where R = alkyl or aryl have been discussed in Chapter IV.

IV. n-C5H5NiX(Lig) and Related Complexes 451

Individual 7r-C5H5NiX(Lig) complexes have also been prepared by the insertion of S02 into the Ni—CH3 bond to give an Ni—S02CH3 complex (249), insertion of phenylacetylene into the NiS—H bond to give a Ni—SC-(C6H5):CH2 complex (251) and insertion of CS2 into the NiS—R bond to give NiSC(:S)SR complexes (333). Insertion of C6H5NC5 into an Ni—SC2H5 bond giving an Ni—SC(:NC6H5)SC2H5 system has also been reported (362).

The monoligand complex 41 reacts with a further ligand molecule to form the π-cyclopentadienylnickel bisligand cation (46). This type of compound has

7r-C5H5NiX(Lig) + Lig , [7r-C5H5NiLig2] + X -

41 46

also been prepared by reacting nickelocene with excess ligand and chloroform or an allyl halide: presumably an σ-cyclopentadienyl derivative similar to 43 is formed which is cleaved by the halocarbon to give 41 (241, 340). Members of this class are also the product of reactions involving the cationic tris-7r-cyclopentadienyl dinickel complexes (e.g., 47) and Lewis bases (57, 158, 229).

[(7r-CH3C5H4)3Ni2]+BF4- + 2P(OC6H5)3 ►

47 7r-C5H4CH3Ni[P(OCeH5)3]2 + BF 4 - + (7r-C5H4CH3)2Ni

The preparation of the ionic bis-ligand complexes is not confined to reac-tions of 41 with phosphines, and similar complexes have been isolated incor-porating isonitriles. The type of product in this case being dependent upon the nature of both ligand and X in the starting complex. The reaction of 41 (Lig = P(C6H5)3 or P(C2H5)3, X = I) with an isonitrile gives the mixed ionic complex 48; the same compound where X is Br or Cl reacts with displace-ment of the cyclopentadienyl group to give the dimer 49, while reaction of 41 Lig = P(OC6H5)3 or As(C6H5)3, X = Br or I, results in displacement of both of the original ligand molecules to give the ionic bisisonitrile complex 50, (246, 247).

^ C N R 7r-C5H5Ni

teri-C4H9NCx X ^Lig X - N i — — N i

Lig J L i g ^ X CN-teri-C4H9

48 49

CNR" π-ΟδΗδΝί^

N C N R J

X"

50

The stability of the ionic bis-ligand complexes is dependent upon both ligand and X. Reformation of 41 by loss of a ligand molecule can be brought about in some cases by dissociation in solution or vacuum sublimation, while in other cases the expected product of anion exchange reaction rearranges


immediately to the monoligand complex (240, 241, 245, 251, 252, 333-335). This last type of reaction has been used to prepare the cyano complex 52 in which only one of the phosphorus atoms is bonded to the nickel. The

(CeH5)2

P

77-C5H5NiN ^CHa

»■ CN

Cl" + NaCN = ^ > TT-CsHsNi^ XP(C6H5)2CH2P(C6H5)2

(C6H5)2

51 52

complexes analogous to 51 formed by l,2-bis(diphenylphosphine)-ethane, -propane, and -butane react differently with sodium cyanide giving instead the binuclear complexes 7r-C5H5NiCN[P(C6H5)2(CH2)nP(C6H5)2]NiCN-^ C5H5 {n = 2, 3, 4) (334).

The azide complex [46, X = N3, Lig = P(C4H9)3] reacts with carbon disulfide in an unusual way. The nickel thiatriazole complex 53 is formed which, on heating, rearranges to the isonitrile complex 77--C5H5Ni-NCS[P(C4H9)3] With benzoyl chloride 53 reacts to produce 4-benzoyl-l,2,3,4-thiatriazoline-5-thione (54) (253).

P(C4H9)3

7r-C5H5Ni[P(C4H9)3]2 + N3- + CS2

Ρ(°4Ηθ)3> 7T-C5H5Ni^ CeH5COC1> r\ c N

53

77-C5H5NiCl[P(C4H9)3] + N = N

I COQHs

54

The reaction of 41 (X = Cl) with triphenylphosphine and excess SnCl2 produces the ionic complex 7r-C5H5Ni[P(C6H5)3]2

+ SnCl3- (243, 244, 251). In the absence of phosphine, insertion of SnCl2 into the Ni—Cl bond occurs to give the mixed metal complex 55 (243, 244, 255, 368). A number of other

7r-C5H5NiCl[P(C6H5)3] + SnCl2 ► Tr-CsHsNiSnClatPCQHs^]

55

compounds containing metal-metal bonds have been synthesized from 41 and these are included in Table VIII-8. The nickel-magnesium compound 56 is believed to be formed when 41 [X = Br, Lig = P(C6H5)3] is treated with

TA

BL

E

VII

I-8

7r-

C5H

5N

iX(L

ig)

CO

MPL

EXES

Lig

and

CO

P(O

C6H

5)3

P(C

6H5)

3

P(C

6H5)

2CÍÍ

3

P^g

Hs^

CH

^PiC

eHs^

P(C

6H5)

2(C

H2)

2P(C

6H5)

2b

X

I S02C

F3

I S02C

H3

Cl

Br

I SC6F

5

SCF 3

Cl Br

CN

CN

Col

or (

mp)

Vio

let-

blac

k (d

>0

) —

(d

> -

10

) D

ark

brow

n-re

d (1

32-1

33d)

D

ark

gree

n (1

95d)

D

ark

red

(141

)

Dar

k re

d (1

25d)

D

ark

red

(140

-141

)

Purp

le

(126

) O

rang

e-ye

llow

(4

15d)

M

aroo

n (1

12-1

14)

Dar

k br

own-

red

(118

-120

) G

reen

(1

40)

Gre

en

(123

) (2

C6H

6)

r(C

5H5)

4.77

(a)

5.09

(a)

5.04

(a)

4.95

(a)

5.1

5.08

(a)

4.86

(b)

4.86

1 Sp

ectr

al d

ataa

v co2

040

(s) (

f),

v SO

2124

0 (s

)

T7.5

7 (C

H3)

, 2.5

0 (C

6H5)

T2.

43

(C6H

5)

T2.2

-2.6

(C

6H5)

r2.2

-2.6

8 (C

6H5)

Si9 F

131

.7 (g

), 1

66.6

, 164

.3

δι9ρ

+ 2

7.7

(s, C

F3, w

rt C

CI3

F)

τ2.4

4 (C

6H5)

, 8.

06 (

d, C

H3, /

10)

T6.

70 (

d,

CH

2P

, /P

H 1

0),

δ 3ι Ρ

-

52.2

[N

i-Pr

el.

to P

(C6H

5)3]

; +

7.7

(P

CH

2)

T7.1

3 (b

r, P

-CH

2)

Ref

.

170,

204

205

235

249

234-

236,

23

8,

248,

24

9 23

6, 2

37

196,

236

, 23

8,

239

258

262

249

235

334

334

(con

tin

ued

)

http://r2.2-2.68

TAB

LE V

III-

8 (c

ontin

ued)

Liga

nd

X

Col

or (

mp)

r(

C5H

5)

Spec

tral

data

a Re

f.

P(C

6H5)

2(C

H2)

3P(C

6H5)

2b C

N

P(C

6H5)

2(C

H2)

4P(C

6H5)

2d C

N

P(C

2H5)

3

P(C

4H9)

3

Cl

Br

I

Gre

en

(162

) G

reen

(1

90.5

)

Mar

oon

(59)

S0

2CH

3 G

reen

(7

7.5-

78)

Cl

Dar

k br

own

(59-

59.5

) C

N

Gre

en

(94-

95)

NC

S R

ed-b

row

n (9

9-10

0)

NC

O

Red

(6

6-67

) SC

6H5

Gre

en

(51-

52)

SC6H

4-/?-

CH3

Gre

en

(49-

50)

SC6H

4-/?-

Cl

Gre

en

(63-

64)

SC6H

4-/7-

COCH

3 B

row

n (7

9-80

) SC

6H4-

/?-N

0 2

Bro

wn

(113

-114

) SC

(C6H

5):C

H2

Gre

en

(55-

56)

SCH

2C6H

5 B

row

n (3

8-39

)

4.91

T

6.9-

8.16

(C

H2)

4.82

T7

.61,

8.1

0 (C

H2)

4.94

(a)

4.88

(a)

4.80

(a)

4.76

(a)

T7.1

7 (C

H3)

; 8.4

0, 9

.03

(C4H

9)

4.92

(a)

T7.8

-9.3

(C

4H9)

4.80

(a)

T7.8

-9.3

(C

4H9)

4.94

T7

.8-9

.3 (

C3H

9)

4.80

(c)

rl.9

0-2.

13, 2

.70-

3.15

4.98

(a

) T

2.84

(d,

/

7.5)

, 3.

44

(d),

7.90

(s,

CH

3)

4.91

(a)

T2.

61 (d

, / 8

.0),

3.29

(d)

4.85

(a

) T

2.57

(d,

/

9.5)

, 2.

65

(d),

7.69

(s, C

H3)

4.

81

(a)

T2.

38 (

d, /

10),

2.

52

(d)

334

334

236,

254

23

6, 2

54

236,

239

, 25

4 24

9

235,

245

, 25

3 v c

; N21

25

240,

245

VC:N

2070

, V

C:S

820

240,

25

3

vc: N

2250

24

0

251,

335

335

335

335

335

4.65

T3

.35

(:C

H2)

, 8.2

-9.3

,2.7

-2.9

25

1

4.84

(c)

T6.7

(CH

2), 8

.3-9

.3, 2

.35-

3.10

25

1, 3

35

http://t6.9-8.16

^C5H5NiX(Lig) and Related Complexes P(

C*H

9) 3

SCH

2C0 2

H

SCO

CH

3

SC4H

9 0C

3H.7

0C2H

.5

SCH

3 SH

S—(C

H2) 2

—Sb

S—(C

H2) 4

—Sb

S—(C

H2) 6

—Sb

SC(:

S)SC

2H5

SC(:S

)SC

H2-

CeH

5 SC

(:S)S

(CH

2) 2-

SC(:S

)Sb

SC(:S

)S(C

H2) 4

-SC

(:S)S

b

SC(:S

)S(C

H2) 6

-SC

(:S)S

b

S0 2

CeH

5

S02C

eH4-/

?-C

H3

Brow

n (7

7-79

) Br

own

(67-

68)

Gre

en-b

row

n oi

l G

reen

(4

1)

Gre

en

(53-

54)

Gre

en-b

row

n oi

l R

ed-b

row

n (5

1-52

) R

ed-b

row

n (7

0-71

) G

reen

(1

01-1

02)

Gre

en

(85-

87)

Red

-bro

wn

(85.

5-86

.5)

Red

-bro

wn

(76.

5-77

.5)

Red

-bro

wn

(88.

8-89

.0)

Red

-bro

wn

(82.

0-83

.0)

Red

-bro

wn

(80.

5-81

.0)

Gre

en

(116

.5-1

17.5

) G

reen

(9

7.0-

97.5

)

4.74

(c)

4.86

(c)

4.82

(c)

4.82

(c)

4.82

(c)

4.85

(c)

4.86

(c)

4.75

(c)

4.77

(c)

4.77

(c)

4.86

(a)

4.85

(a)

4.84

(a)

4.87

(a)

4.87

(a)

5.18

r7.9

7 (S

, SC

H2)

T7.

55 (

S, C

CH

3)

r7.8

5 (t

, S—

CH

2, /

5.5)

r7

.85

(t, S

—C

H2,

/ 5.

5)

r7.8

5 (q

, S—

CH

2, /

6.0)

T8.

20 (

S, S

—C

H3)

T4

.7 (S

H),

7.7-

9.3

(C4H

9)

r7.5

0 (S

, SC

H2)

T7.

80 (

t, S

—C

H2)

, 8.

05 (

SC—

CH

2) T

7.85

(t,

S—

CH

2)

r7.0

0 (q

, SC

H2)

8.3-

9.3

T5.

72 (

S, S

CH

2) 8

.2-9

.2

6.82

(s, S

CH

2), 8

.3-9

.2

T6.

99 (

t, S

CH

2) 8

.2-9

.2

r7.1

0(t,

SCH

2) 8.

3-9.

2

T8.

1-9.

2, 2

.5-2

.8

v SH25

00-2

700

v c

"c:

vc:

vc:

vc: :s

l003

sl01

5

sl01

5

s101

0

s995

335

335

335

335

335

335

240,

335

252

252

252

333

333

333

333

333

251

251

(con

tinue

d)

TAB

LE V

III-

8 {c

ontin

ued)

as

Li

gand

X

C

olor

(m

p)

r(C

5H5)

Sp

ectra

l dat

a0 Re

f.

As(

C6H

5)3

Sb(C

6H5)

3

CO

P(C

6H5)

3 C

O

P(C

6H5)

3 P

(C2H

5) 2

C6H

5 P(

C2H

5)3

P(C

3H7)

3 P(

C4H

9)3

As(

C6H

5)3

CO

P(C

6H5)

3 CO

P(C

6H5)

3

iV-th

iatri

azol

e

Br

I I SiC

l 3 Si

Cl 3

GeC

l 3

GeC

l 3-C

6H6

GeC

l 3 G

eCl 3

GeC

l 3 G

eCl 3

GeC

l 3-i

C6H

6 G

eBr 3

GeB

r 3.¿

C6H

6 G

el3

Ge(

C2H

5)3

SnC

l 3

SnC

l 3

SnC

l 3-i

C6H

6

Bro

wn

(80.

5-81

.5d)

D

ark

red-

viol

et

(109

-1lO

d)

Dar

k re

d-vi

olet

(1

18-1

19d)

D

ark

red-

viol

et

(101

-102

d)

— (

38-4

0)

Dar

k br

own

Dar

k gr

een

(73-

75)

Dar

k gr

een

Dar

k gr

een

Dar

k gr

een

Dar

k gr

een

Dar

k gr

een

Dar

k gr

een

Dar

k gr

een

(100

-102

) G

old

Dar

k gr

een

(120

-125

) O

rang

e liq

. (b

p 79

.8/0

.2 m

m)

Gre

en

4.18

(b)

(42-

43)

Yel

low

(1

35d)

G

old

4.86

(b)

4.25

(b)

4.77

(b)

4.70

(b)

5.02

(c)

4.98

(c)

4.97

(c)

4.68

(b)

4.

27 (b

)

4.79

(b)

4.38

(b)

v co2

062

v co2

075(

s)

2076

(s)

4.74

T8

.93

(br,

C2H

5)

4.66

(b)

r2.5

1(C

6H5)

4.66

(b)

v co2

072(

s)

2074

(s)

v co2

063(

s)

v co20

72(s

)

253

235

235

235

206

255

202

255

255

255

255

255

255

202

255

202

203

202, 206

244

255

1 3 r>

^ c* 1"

S

S-̂ 3 *-*

^

Ci

( ¿ s ^ *̂

X

<X>

to

IV. TT-C5H5NiX(Lig) and Related Complexes 457

TAB

LE V

III-

9 [7

7--C

5H5N

iLig

2]+ X

"

CO

MPL

EXES

Liga

nd

P(C

6H5)

3

P(C

6H5)

2CH

2P(C

6H5)

2 P(

C6H

5)2(

CH

2)2P

(C6H

5)2

P(C

6H5)

2(C

H2)

3P(C

6H5)

2 P(

C6H

5)2(

CH

2)4P

(C6H

5)2

P(C

4H9)

3

X

F C10

4

B(C

6H5)

4

SnC

l 3-C

H2C

l 2 Sn

Cl 3-

(CH

3)2C

O

Cl

Cl

Cl

Cl

Cl

Br

I NC

O

NC

S

Col

or (

mp)

Yel

low

Pa

le g

reen

(1

97d)

Y

ello

w

(139

) G

olde

n Y

ello

w-g

reen

—

—

—

—

Y

ello

w-g

reen

(8

5-87

d)

Yel

low

-gre

en

(97-

99d)

Y

ello

w-g

reen

(9

5-97

d)

Yel

low

-gre

en

(57-

58d)

G

reen

(6

8-70

d)

T(C

5H

5)

4.55

(d)

4.72

(b)

4.

72 (

b)

4.95

(a)

4.90

(a)

4.85

(a)

4.93

(a)

4.84

(a)

Spec

tral d

ataa

T2.52

(C6H

5)

T4.68

(f),

2.59

(C

6H5)

T7

.83 (d

), 2.

59 (

C6H

5)

T7.7

-9.2

(C4H

9)

T7.

6-9.

2 (C

4H9)

Ref.

254

242

242

243,

244

^c

ol70

5 24

3, 2

44

334

334

334

334

241

241

241

v c=N

2140

,216

0 24

0

VC=N

2060

24

0

P(C

H3)

2C6H

5

P(C

6H5)

3(C

N-t

erí-

C4H

9)

P(C

eH5)

3(C

N-c

Kto

-CeH

ii)

P(C

2H5)

3(C

N-t

erí-

C4H

9)

CN

-ter

t-C

4H9

N3 cio 4

C10

3

N0

3

N0

2

B(C

6H5)

4

I B(C

6H5)

4

I B(C

6H5)

4

I Br

I B(C

6H5)

4

Yel

low

-gre

en

(77-

79)

Gre

en

(113

-115

d)

Gre

en

(117

-118

d)

Yel

low

-gre

en

(164

-165

d)

Gre

en

(85-

87d)

O

rang

e (1

29-1

30)

Gre

en

(137

-139

d)

Pal

e gr

een

(161

-162

d)

— (

138-

141d

) —

(98

-101

) —

(11

7-11

9)

— (

118-

119)

G

reen

(1

24)

— (

145-

149)

4.71

(a)

4.47

(e)

4.45

(e)

4.46

(e)

4.75

(a)

4.81

4.58

4.18

T7.

2-9.

3 (C

4H9)

T8.

0-9.

15 (

C4H

9)

τδ.0

-9.2

(C

4H9)

r8.0

-9.1

5 (C

4H9)

T9.

5-9.

4 (C

4H9)

T2.

86,

3.30

(m

), 6.

98 (

t, P

—C

H2

8.78

(t,

P—

CH

3;

T8

.96

(CH

3),

2.4

8-:

(C

6H5)

T8.

40

(CH

3)

,/ll

H

z),

, / 9

.0 H

z)

Z.58

VN

3

"c=

»Ό=

vc=

vc

=

^C

=

v c=

"c

-

v c=

2001

= N21

63

=N

2208

=N

2189

= N21

93

= N21

72

= N21

90

=N21

92

= N21

93

240

240

240

240

240

340

246,

247

246,

247

246,

247

24

6, 2

47

246,

247

24

6, 2

47

246,

247

246

a Sol

vent

: (a

), C

S 2;

(b),

CD

C1 3

; (c)

, C

6D6;

(d)

, ace

tone

; (e

), (C

D3)

2CO

; (f

), C

H2C

1 2.

http://t8.0-9.15

http://r8.0-9.15


magnesium turnings (256). This complex reacts with methyl p-toluene sul-fonate to give a mixture of the compounds 41 (X = CH3) and (X = C6H5)

7r-C5H5NiBr[P(C6H5)3] + Mg ► 7r-C5H5NiMgBr[P(C6H5)3]

56 and [7r-C5H5NiP(C6H5)2]2. A nickel silicon complex 57 has been obtained by reacting 41 with trichlorosilane (255). The reaction between 41 and

7r-C5H5NiCl[P(C6H5)3] + HS1CI3 ► ^C5H5NiSiCl3[P(C6H5)3] + [HC1]

57

organometal reagents (e.g., alkyl lithium) is the standard method used to prepare ττ-cyclopentadienylnickel alkyls and aryls. This type of reaction can also be used to form metal-metal bonds and a series of ττ-cyclopentadienyl-nickel-germanium, -tin, -lead, -selenium, and -tellurium complexes have been prepared in this way (255, 360, 363, 368). The crystal structure of the german-ium trichloride complex has been determined (Fig. VIII-9). The nickel german-

Tr-CsHsNiXfPiQHs^] + CsGeCl3 ► ^C5H5NiGeCl3[P(C6H5)3] + CsX

ium bond is 0.36 Â shorter than the sum of the covalent radii, an effect which may be due to significant dn-dn bonding between the two metal atoms. Distortion of the cyclopentadienyl ring shows itself in the nonplanarity of the ring and in the differences in the C—C bond lengths.

Fig. VIII-9. Structure of w-CeH6NiGeCl3[P(CeHe)3]. iC 6 H 6 (255). a = 15.080; b = 11.889; c = 29.113; ß = 93.38°; Z = 8; space group C2/c; R = 5%.

As part of an attempt to rationalize the 31P NMR spectra of transition metal-phosphine complexes the spectra of a series of 7r-C5H5NiX[P(C6H5)3] complexes [X = halogen, alkyl, Sn(C6H5)3 and Pb(C6H3)3] have been studied. It is indicative of the complexity of the problem that no correlation is obtained between the 31P chemical shift and the electronegativity of X. Although a fair linear correlation is obtained with the high, energy "d-d" transition

V. Nickelocene with Phosphorus and Sulfur Compounds 461

observed in the electronic spectra of the nickel-alkyl, -tin, and -lead com-plexes, even this is not observed for the halogen compounds (257, see also 359).

The C—H out of plane bonding vibration and the proton chemical shift for the 7r-C5H5 group in the mercaptide complexes 77--C5H5NiSR[P(C4H9)3] and 7r-C5H5NiSC6H4-/?-X[P(C4H9)3] have been correlated with the Taft σ*- constant of the group R and the Hammett σ constant of the substituent X: satisfactory linear correlations are obtained in all cases (although the varia-tion in the spectral parameters is rather small) and it is concluded that "the inductive effect of the R groups and the overall polar effect of the X groups are transmitted through the sulfur-nickel bond to influence the 77-electron density in the 77-C5H5 ring" (335).

V. Reaction of Nickelocene with Phosphorus and Sulfur Compounds

The reaction of nickelocene with donor ligands is one of the standard methods used to prepare Lig4Ni complexes and, as such, has been discussed in Chapter III. Related reactions with isonitriles have been discussed in Section II-A and here we need only mention various reactions which failed to give the expected tetrakisligand nickel compound and which are perhaps relevant to the mechanism of this reaction. Phosphine (PH3) was reported, without details (in 1968), to form a bisphosphine adduct (7r-C5H5)2Ni(PH3)2 (259) while the reaction with four equivalents of P(C4H9)2C6H5 gives a dark blue paramagnetic complex (μβΐΐ = 1.76 BM) 7r-C5H5Ni[P(C4H9)2C6H5]2 (it is possible to prepare the corresponding tetrakisligand nickel complex of dibutylphenyl phosphine by other routes) (260). The absence of absorp-tions typical for the 7r-cyclopentadienyl group in the infrared spectrum of this compound would seem to rule out a sandwich structure. The reaction with bistrifluoromethylphosphine also fails to give a tetrakisligand complex, instead the bridging phosphide complex 58 results (215). Reactions leading to other examples of this class of compound are discussed in Section II-B and they are listed in Table VIII-10.

(Cr3)2 P

(7r-C5H5)2Ni + 4(CF3)2PH ► 77-C5H5Nix ^NÍTT-CSHS + 2

(CF3)2 H ' P ( C F*>*

58

Mercaptans also react with nickelocene with transfer of a proton to one of the rings to produce the dimeric nickel mercaptide 60 (Table VIII-10) (204, 261, 357). The kinetics of the reaction have been studied and it has been shown to be first-order in both nickelocene and mercaptan. The rate constants are essentially independent of the solvent or the mercaptan and in the case


of thiophenol values for AH* and Δ£* of 12.7 kcal/mol and — 26 eu. in cyclo-hexane are obtained. The values for cyclohexanethiol in the same solvent are 11.7 kcal/mol and — 34 eu. The results are interpreted in terms of a mechanism involving a σ-cyclopentadienyl intermediate (59) which reacts further to give a monomeric 7r-cyclopentadienylnickel thiol which then dimerizes (261).

Ni + RSH

-RSH

-C5He ^ ^ * < 0 > < > 4 § > Ni

I S R

N V N i -R

60

The reaction of nickelocene with C6F5SH produces a polymeric material formulated as (7r-C5H5NiSC6F5)n (258). The ττ-cyclopentadienylnickel mer-captides may also be prepared by reacting the mercaptan with 7r-C5H5NiI(CO) in the presence of a base (204), by irradiating nickelocene and bis-(trifluoro-methyl)disulfide (261) or by reacting nickelocene with (CH3)2A1SC6H5 (328). Both τΓ-cyclopentadienyl groups are displaced on reaction with Na2S2C2(CN)2 ; the product, [Ni(S2C2(CN)2)2]2", is also formed on reacting (7r-C5H5NiCO)2

with the same salt (264, 265). The mercaptides (60) can exist as isomers differing in the conformation of

the substituents (syn or anti) on the sulfur atoms. The methyl mercaptide (60, R = CH3) is reported to be an equilibrium mixture of two isomers, although no details have been published, and they do not appear to have been separated (266). The fluorine NMR spectrum of the trifluoromethyl derivative (60, R = CF3) exhibits only one absorption for the CF3 group indicating that in this compound the substituents are mutually syn (262) [similar isomerism in the (7T-allyl-NiMR)2 system has been discussed in Chapter VI, Section IV-B]. Cleavage of the bridging mercaptide by reaction with triphenylphos-phine has been reported for the CF3 and C6F5 complexes.

(7r-C5H5NiSCF3)2 + 2P(C6H5)3 277-C5H5NiSCF3[P(C6H5)3]

Electrochemical reduction of 60 (R = CH3) gives an unstable radical anion (197, 214).

The methyl and ethyl derivatives (but not phenyl) react with carbon di-sulphide. NMR evidence indicates that an unstable insertion product 61 is formed which readily loses CS2 to regenerate the starting material (267).

S

7r -C 5 H 5 Ni C — S R

V 61

V. Nickelocene with Phosphorus and Sulfur Compounds 463

TA

BL

E V

III-

10

A.

(7r-

C5H

5N

iSR

)2

CO

MPL

EX

ES

R

CF

3a

CeH

5

\^Q

iri4-

p-K^

ri3

C6H

4-/?-

Cl

C10

H7

Col

or (m

p)

Purp

le-b

lack

(3

90-3

96d)

B

lack

(1

25)

Dar

k br

own

(127

-129

) B

lack

(1

64)

Bla

ck

(198

)

Ref

.

262

204,

261

, 32

8 26

1

261

261

268,

R

CH

2C

6H

5

CH

3

C2H

5b

cycl

o-C

6llii

Col

or (

mp)

Bla

ck

(149

-150

) B

lack

(1

18)

Bla

ck

(78)

B

lack

(1

52-1

54)

Ref

.

261

204,

268

204,

267

261

B.

(ir-

CsH

5N

iPR

2) 2

C

OM

PLE

XE

S

PR

2 C

olor

(m

p)

TC

5H

5 Sp

ectr

al d

ata0

Ref

.

P(C

6H5)

2

P(C

H3)

2

P(C

F 3) 2

As(

CH

3)2

Dar

k br

own

(264

^265

d)

Red

-bro

wn

(217

-220

d)

Bla

ck

(297

-299

) B

lack

(2

40d)

5.16

(t,

/ HP 0

.6)

(a)

5.13

(s) (

b)

4.54

5.10

(8) (

b)

r2.2

, 2.7

5 (C

6H5)

r8.6

7(t,

CH

3;/

HP

6.6)

Si9 P

53.

4 (d

, /P

F 6

6)

r8.7

9(s,

CH

3)

187,

211,

212

211

215

211

■ 8 1

9P +

27.

2 (w

rt C

C1 3

F).

b r5.

6 (S

, C

5H5)

; 8.

7, 7

.8 (C

H2C

H3)

. c (

a), C

DC

1 3; (

b),

CS

2.


VI. ΤΓ-Cyclopentadienylnickel Nitrosyl

77-Cyclopentadienylnickel nitrosyl is the simplest mono-7r-cyclopentadienyl metal complex and, as such, is of interest to both theoreticians and spectros-copists. Soon after its discovery it was patented as a fuel oil additive (277-279) but has not, apparently, been used as such on a large scale, one of the reasons probably being its toxicity which is said to be at least as high as that of nickel tetracarbonyl (293).

The simplest method of preparation is treatment of nickelocene with nitric oxide (269-273, 300); it is also formed in a similar reaction with

(^-C5H5)2Ni + NO ► 77-C5H5NiNO + [C5H5]

(77-C5H5NiCO)2 (274-276, 280-282) or the bis-77-cyclopentadienylnickel alkyne complexes (283), as well as in the reaction of nickelocene with tri-fluoromethylnitrosyl (299). Ring-substituted derivatives, e.g., 77--CH3C5H4-NiNO, ττ-indenyl-NiNO (284), and T T - C 6 H 5 C ( C H 3 ) 2 C 5 H 4 N Í N O (20) have been prepared by similar methods. A carborane analog, 77-1,7-B9CHP(CH3)NiNO, has been prepared by reacting [1,7-B9H9CHPCH3]-with nitric oxide and nickel chloride (285).

7T-C5H5NiNO is a stable, diamagnetic red liquid (mp — 41°, bp ca. 6O73O mm) which may be distilled at atmospheric pressure without serious decomposition. The chemistry has been relatively neglected and appears to be limited to the following five observations; in contrast to Co(CO)3NO and Fe(CO)2(NO)2 it does not undergo appreciable nitrosyl exchange (286); electrolytic reduction causes decomposition to give nickelocene as one of the products, presumably through the formation of an anion radical (288); the Ni—NO bond is cleaved preferentially in the mass spectrometer (the ionization potential is 8.50 eV) (287); gas phase ion molecule reactions with olefins (e.g., cyclohexene) occur in the mass spectrometer to give 77--cyclo-pentadienyl nickel olefin species (355); and reaction with organolithium compounds produce polynuclear nitrene complexes, e.g. (77--C5H5Ni)3NR (366).

The structure has been determined by analysis of the microwave spectra of five isotopic species (e.g., 77--C5H5

60Ni15N16O). The molecule has strict C5v symmetry which requires that the Ni—N—O system is linear, and the following interatomic distances have been calculated (289-291):

Ni—C 2.11(1) C—C 1.43(1)

Ni—N 1.626(5) N—O 1.165(5)

C—H 1.09 (assumed)

These bond distances agree reasonably with an early electron diffraction study which, however, indicated that the Ni—N—O system might be bent (ZNi—N—O - 160°) (292).

VI. π-Cyclopentadienylnickel Nitrosyl 465

The Ni—N distance is much shorter than that found for nitrosyl com-pounds involving other transition metals, e.g., (CO)4MnNO,Mn—N = 1.80 Â (297), but similar results have been obtained for other nickel nitrosyl com-plexes, e.g., [(C6H5)3P]2Ni(NO)N3, Ni—N 1.69 Â (298), and indicate con-siderable double bond character. The decrease in the Ni—C distance by 0.09 Â in comparison with nickelocene is further evidence that the extra two electrons in the latter compound occupy antibonding orbitals.

The fundamental modes for the C5v system are 6 Ax (infrared and Raman active), 1 A2 (inactive), 7 Ελ (infrared and Raman active), and 6 E2 (Raman active). Both Raman and infrared spectra have been analyzed (294-296, 343, 364). A recent assignment made with the aid of 7r-C5D5NiNO and 7r-C5H5-Ni15NO is shown for the liquid in Table VIII-11. A detailed analysis of the infrared and Raman spectra of 7r-CH3C5H4NiNO has also been published (284).

TABLE VIII-11

FUNDAMENTAL VIBRATIONAL MODES FOR 7 T - C 5 H 5 N Í N O (LIQ.)°

Species

Ax

E2

Type

VO—H

*>N—0

Ring breath o.p. Bc—H vm—N vr i n & — N i

»Ό-Η

»Ό-C

o .p . Bc—H

O.p. δ 0 _ Η

i .p. Bring

O.p. 3 r I n g

Kern *)

3115 1809 1112 799 649 322

3098 1343 1102 964 840 565

Species

E,

A2

Type

VC—H

*O-c i.p. Sc—H O.p. 8C—H

ÔNi—N—O

Ring tilt Brin« Ni—N

I.p. 8C—H

Kern-1)

3105 1425 1054 1005 484 290 92

1240b

a From Ref. 343. b By comparison with the spectrum of 7r-CH3C5H4NiNO (284, 294) and observed

in the solid state (343).

Both qualitative and quantitative attempts have been made to describe the bonding in 7r-C5H5NiNO (301, 350). The energy of the valence orbitals and their approximate description as determined by an ab initio SCF-MO calculation is given in Table VIII-12. The resulting charge distribution places a formal charge of +0.8 on the nickel, —0.8 on the cyclopentadienyl ring, and leaves the NO group uncharged. The 7r-C5H5—Ni bond is suggested to be of an ionic nature in which one electron is transferred from the metal to the ring. The bond between the nickel and the nitrosyl group is mainly of the 7r-acceptor type.


T A B L E VI I I -12

V A L E N C E M O L E C U L A R O R B I T A L S O F ( 7 r - C 5 H 5 ) N i ( N O ) d

Orbital energy (au) Approx. description

Set -0 .3464 lex -0 .4959 4e2 -0 .5580

15flx -0 .5607 3e2 -0 .5805

14fli -0 .6013 6e1 -0 .6180

13«! -0 .7643 2e2 -0 .7760 5*i -0 .8154

12«! -0 .8331 4e1 -1 .0228

11«! -1 .0389 10û! -1 .2719

a From Ref. 350.

77-C5H5

3d 3d 3d a-C5H5

TT-CsHs a-C5H5

a-C5H5

a-C5H5

7Γ-ΝΟ σ-ΝΟ a-C5H5

σ-ΝΟ CT-CÖHÖ

Infrared evidence indicates that an ion-pair, 7r-C5H5Ni+NO~, is produced on photolysis of 77--C5H5NiNO in an argon matrix at 20°K (356).

VII. Nickel-Carborane Complexes (Table VIII-13)

The first transition metal complexes of the polyhedral carboranes were reported in 1965 and since this time the investigation of these compounds has established itself as a specialized, independent area of research. The carborane ligand in these systems is ττ-bonded to the metal atom and many have structures resembling those of the metallocenes. The compounds of nickel have been thoroughly investigated but do, however, only represent a part of the complete picture for which the reader is referred to recent review articles (325-327). The known complexes of nickel are brought together in Table VIII-13 in which the complexes are arranged according to the ligand.

A. Complexes Formed by the 2?9C2//ii Dianion and Related Species

The earliest reported complexes of nickel involve the [(3)-l,2-B9C2H11]2~ and [(3)-l,7-B9C2H11]2~ systems. These ionic species are formed on treating 1,2-B10C2H12 or 1,7-B10C2H12 with a strong base whereby the boron atom adjacent to the carbon atoms (being most electron-deficient) is extracted, i.e., B4 or B6 in the 1,2-system and B2 or B3 in the 1,7-system. The resulting dianions are believed to have structures 62 and 63.

TA

BL

E V

III-

13

NIC

KEL

-CA

RB

OR

AN

E CO

MPL

EXES

Com

plex

C

olor

(m

p)

Ora

nge

(2

65d

) Y

ello

w-b

row

n

(>3

00

) B

lack

P

ale

bro

wn

B

row

n-g

reen

O

ran

ge

Ora

nge

-bro

wn

(2

50d

) D

eep

red

O

ran

ge-b

row

n

(250

d)

Red

-bro

wn

R

ed

(190

d)

Red

(1

90d

) D

eep

red

B

lack

Y

ello

w

Red

-ora

nge

Bro

wn

—

(164

.5-1

65)

Yel

low

G

old

en

Dar

k b

row

n

Ora

nge

Ph

ysic

al D

ata

0

μ6Λ

β ±

0.

05 D

(cyc

loh

exan

e)

^ef

fl.7

6 B

M

/Lt ef

f2.9

0 B

M

/xef

fl.9

9 B

M

Dia

mag

net

ic τ

6.96

(b

r, C

—H

), 8

.35

(s,

CH

3)

(a)

Pef

fl.7

2 B

M

Dia

mag

net

ic r

6.51

(b

r, C

—H

), 2

.65

(m,

/*ef

f 1.

73

BM

Si9F

-2

.94

, -3

.98

pp

m (

c) (

rel.

C6F

6)

δΐΒ

, -2

.81

, -4

.00

pp

m (

c) (

rel.

/χ7.

65 ±

0.

01 D

(ben

zen

e);

τ7.9

9 3

8.72

(s,

CH

3)

(a)

ME

3 140

±

10°

T8.

07,

8.6

2(s

, C

H3)

(a)

C6F

6)

, 80

.06,

C6H

5)

(b)

8.41

,

Ref

.

30

6-3

08

307,

308

308

315

303

303

303

303

305

305

303

303

302,

303

303

303

303

303,

338

303,

338

(l,2

-B9C

2H11

) 2N

i

[(l,2

-B9C

2H11

) 2N

i]-N

(CH

3)4+

Rb +

[(1,

2-B

9C2H

11) 2

Ni]2 -

[N(C

2H5)

4]22 +

(U-B

gCsH

n^N

JTT-

CsH

s [l,

2-B

9H9C

HC

(CH

3)] 2

Ni

{[l,2

-B9H

9CH

C(C

H3)

] 2N

i}-C

s+

[l,2-

B9H

9CH

C(C

6H5)

] 2N

i {[

(l,2-

B9H

9CH

C(C

6H5)

] 2N

i}-N

(CH

3)4 +

Rb +

[1,2

-B9H

9CH

C(C

6H4-

m-F

)]2N

i

[1,2

-B9H

9CH

C(C

6H4-/

?-F)

] 2Ni

{[l,2

-B9H

9C2(

CH

3)2]

2Ni}

-N(C

H3)

4 +

K+

H2

0 {[

l,2-B

9H9C

2(C

H3)

2]2N

i}2 -

[(3)

,(4)'-

l,2-B

9H9C

2(C

H3)

2]2N

i

{[(3

),(4)

/ -l,2-

B9H

9C2(

CH

3)2]

2Ni}

-N(C

H3)

4 +

d-TM

PEA

4

[(4)

-l,2-

B9H

9C2(

CH

3)2]

2Ni

{[(4

)-l,2

-B9H

9C2(

CH

3)2]

2Ni}

-N(C

H3)

4 +

{[l,2

-B9H

9C(C

H2)

3C] 2

Ni}

-N(C

2H5)

4 +

[(3)

,(4)'-

l,2-B

9H9C

(CH

2)3C

] 2N

i

(Con

tinue

d)

TAB

LE V

III-

13 (

cont

inue

d)

Com

plex

C

olor

(m

p)

Phys

ical

Dat

a0 Re

f.

[(4)-l

,2-B

9H9C

(CH

2)3C

] 2N

i (l,

7-B

9C2H

11) 2

Ni

[(l,7

-B9C

2H11

) 2N

i]-N

(CH

3)4 +

[(1,

7-B

9C2H

11) 2

Ni]2 -

CH

3N(C

2H4)

3NC

H32 +

1,7-

B9H

9C2(

CH

3)2N

i(CO

D)

[l,7-

B9H

9CH

PCH

3]2N

i l,7

-B9H

9CH

PCH

3Ni^

C3(

C6H

5)3

l,7-B

9H9C

HPC

H3N

Í7r-

C3H

5

1,7-

B9H

9C

HP

CH

3N

ÍTT

-CH

2C

(CH

3)C

H2

l,7-B

9H9C

HPC

H3N

iNO

{[(B

10H

10C

H) 2

]Ni}

2 -Cs 2

2 + [N

(CH

3)4]

22 +

[N(C

H3)

3H] 2

2 +

[(B

10H

10C

OH

) 2N

i]2 - [N

(CH

3)4]

22 +

(B10

H10

CN

H3)

2Ni

[(B

10H

10C

NH

2)2N

i]2 -C

s 2 +

(B10

H10

CN

H2C

3H7)

2Ni

[B10

H10

CN

H(C

H3)

2]2N

i [B

10H

10C

NH

(CH

3)C

3H7]

2Ni

[(B

10H

12) 2

Ni]

2 -[N

(CH

3)4]

22 +

«-B

18H

20N

i[P(C

6H5)

3]2

H-B

18H

20N

iP(C

6H5)

2C2H

4P(C

6H5)

2

Yel

low

O

rang

e O

live

gree

n (>

300)

R

ed

Bro

wn

(207

-210

d)

—

Red

(2

02-2

03)

Red

(1

20-1

21)

Red (1

23-1

24)

Red

(1

12-1

13)

Ora

nge

Ora

nge

Ora

nge

—

Ora

nge

—

Ora

nge

—

Dar

k or

ange

O

rang

e-re

d (1

80d)

R

ed

Purp

le

/¿effl

.74 B

M

r4.3

6(m

, HC

:), 7

.4 (m

, CH

2), 7

.20

(s, C

H3)

NM

R s

pect

rum

, see

Tab

le V

I-6 (

page

368

)

NM

R s

pect

rum

, see

Tab

le V

I-6 (

page

368

)

v N01

842

i-B1e

Hie

CN

Ha-^

c/ö-

CeH

i 1Ni[P

(CeH

6)2-

C2H

4P(C

6H5)

2]

303,

338

30

8 30

8

308,

309

45

321

285

285

285

285

317,

318

32

0 32

0 32

0 31

7 31

8 31

8 31

9 31

7 31

9 32

2, 3

23

324

324

349

a Sol

vent

: (a)

, ben

zene

; (b)

, C2C

1 4; (

c), C

H2C

1 2.

VIL Nickel-Carborane Complexes 469

62 63

Fig. VIII-10. Postulated structures for [(3)-l,2-B9CaHu]2- (62) and [(3)-l,7-B ^ H Ü ] 2 - (63).

These dianions (62 and 63) react readily with transition metal salts to give complexes having the composition [M(B9C2H11)2]ri~. The chemistry of these complexes is characterized by the ease with which they undergo one-electron transfer reactions to give species in which the metal atom has & formal oxida-tion state of + 2, +3, and +4.

Nickel acetylacetonate or chloride react with the dianion 62 to give, after air oxidation, the nickel (3+) anion 65 which on treatment with ferric salts is oxidized to the neutral nickel (4 + ) complex 64. The nickel (2 + ) dianion 66 can be prepared chemically by reduction of 65 with base. These redox proc-esses can be demonstrated more elegantly electrochemically and two revers-ible one-electron processes are normally observed (307, 308, 315, 316). In

NiîU-BgCaHn) , , + ^ ^ [NiÛ-BgCaHxOa]- ^ = ± [NP + O^-BgCaHâ]2-

64 65 66

addition a reversible reduction at the relatively high negative potential of —2.10 V has been observed, corresponding to an as yet unidentified species containing a formal nickel (1+) atom (316). The neutral complex (64) has also been isolated in low yield from the reaction of the corresponding cobalt (3+) complex with nickel chloride in the presence of air: the main products from this reaction have not been identified but it is suggested that a mixed cobalt-nickel complex may be formed, viz. [(l,2-B9C2H11)CoB8H10C2-NiíU-BsAHn)]"- (306).

A mixed ττ-cyclopentadienyl, carborane complex (68), with a formal nickel (3+) atom, may be prepared by reacting NiBr2. monoglyme with a mixture of sodium cyclopentadienide and B9C2HnNa2. This molecule also undergoes two reversible redox processes. The cation 67 decomposes at room tempera-ture in acetonitrile and has not been isolated (315).

+ 0.46 V [TT-CsHsNiÛ-BgCsHur k

TT-CsHsNi^l^-BgCaHn ~ a 5 2 V ^ [w-CeHeNP + l^-BgCaHu]-

68


3 \ \ / ' \ '^K

B—p- C C—C 1.601(2) Â ! C—B 1.732(3) Â

Ni 1.710(3) A B—B 1.843(3) Â

p ; r 1.832(3) Λ

2.120 (2) B < ^ \ ' JJ^C 2.077(2)

2.105 (2)

2.086 (2) ! 2.065 (2)

Ni—C 2.146(5) A Ni—B 2.10(2) A C—C 1.59(1) A C—B 1.72(1) A B—B 1.77(1) A

CB\ ;B

(b)

Fig. VIII-11. Idealized structures of the [(3)-l,2-B9C2Hn)2Ni]n- complexes: (a) (l,2-B9C2H11)2Ni, 64 (310); (b) [(l,2-B9C2H11)2Ni]N(CH3)4, 65 (314); (c) [(1,2-B9C2H1]L)2Ni] [N(C2H5)4]2, 66 (311).

The structure of the biscarborane complexes 64, 65, and 66 have been investigated by x-ray crystallography, and are shown in idealized form in Fig. VIII-11.

The neutral complex 64 (a = 13.371; b = 10.398; c = 13.556; ß = 119.16; Z = 4; space group Pl^c, R = 3.5%) is diamagnetic and in the crystal the carborane rings adopt a staggered conformation in which the


carbon atoms of the two ligands are on the same side of the molecule (Fig. VIII-11a). The carborane ligands are slightly distorted and the facial planes are tilted by 6°, thereby increasing the interligand carbon distance. Two enanti-omorphic rotational isomers are present in the molecule. The monoanion 65 is paramagnetic with one unpaired electron (/xeff = 1.76 BM) and is iso-morphous with the corresponding cobalt (3+) compound. The carborane groups adopt a symmetrical staggered arrangement with the carbon atoms of the two ligands on opposite sides of the molecule (Fig. VIII-llb). The nickel (2 + ) dianion 66 is isomorphous with [Cu(l,2-B9C2H11)2]2~, in which mole-cule the carborane groups are asymmetrically bonded to the metal (Fig. VIII-llc), the metal atom being closer to the boron atoms than to the carbon atoms (311, 312). Comparison with a bis(7r-allyl)nickel system is misleading since this molecule is diamagnetic in contrast to the biscarborane nickel com-plex which is paramagnetic (μβίΐ = 2.90 BM); the asymmetry here is probably associated with the high electron density in the system and the inherent asymmetry of the ligand. This latter suggestion finds support in the more or less symmetrical structure observed for the analogous complex containing the more symmetrical [1,7-B9C2H11]2~ ligand (Fig. VIII-12). A qualitative attempt has been made to describe the metal-ligand orbital interactions in these systems (311, 313) and a detailed study of the UV spectrum of 66 has been published (339).

Ni(l,2-B9C2H11)2 reacts with halide ions and sulfur-containing donor compounds [e.g. (C2H5)2S] to form diamagnetic 1:1 charge transfer com-plexes. Related systems are also formed by condensed aromatic compounds as well as iV,iV-dimethylaniline (303). A preliminary report of the structure of the pyrene adduct indicates that the aromatic molecule is situated sym-metrically and perpendicularly to the carborane-Ni-carborane"axis (304).

The C—H protons in the neutral complex 64 are acidic and may be deuter-ated by treatment with basic D 2 0 . The product [(l,2-B9H9C2D2)2Ni]~ may then be oxidized with ferric chloride to the neutral complex. Monosubstituted carborane complexes, e.g. [l,2-B9H9CHC(CH3)]2Ni, may be similarly deu-terated. Thermal rearrangement of 64 has been observed in the vapor phase at 360°-400° and a cyclic voltammogram of the product shows the presence of three compounds, each of which exhibits two reversible one-electron processes (303). The identity of these products is not known with certainty but they probably correspond to the A, B, and C isomers observed in the Ni[(B9H9C2(CH3)2]2 system discussed on page 473.

The [(l,7-B9C2H11)2Ni]n" complexes analogous to 64, 65, and 66 have also been isolated and are apparently somewhat less stable (308). The structure of [(lJ-BgCaHn^Ni]2- has been determined (a = 16.95; b = 24.52, c = 11.63; Z = 8; space group Fdd2; R = 10.5%) and an idealized representation is shown in Fig. VIII-12. The carborane molecules, in contrast to the result


2.11 (3)

2.12 (2) C < \ / , \ / ">B 2.18 (J)

2.14(2) j 2.39(2)

Ni

Fig. VIII-12. Idealized structure of [(l^-BsCsHuJaNilCHgNÍQH^aNCHg (309).

obtained for 66 (Fig. VIII-lie), are essentially symmetrically bonded to the nickel atom. However, the facial atoms of the ligand are nonplanar, the carbon atoms being bent away from the nickel while the bond distances in the ligand vary from a C—B distance of 1.55 Â to a B—B distance of 1.95 Â. Figure VIII-12 is misleading in that the molecule actually adopts a non-centrosymmetric rotamer form (309).

Complexes suggested to contain the 1,7-B9H9C2(CH3)3 group (e.g., 69) are produced in the reaction between 1,8-B9H9C2(CH3)2 and bis(cycloocta-diene)nickel or cyclooctadiene nickel bistriethylphosphine. In both cases substitution of a COD molecule occurs (45).

c c

Λ Λ \ c = c /

,CH3 C — = C CH3

X y

+ Ni(COD)2 -COD

CH3


Both mono- and disubstitution of the C—H protons in the parent [B9H9C2H2]2" systems is possible and biscarborane nickel complexes have been isolated from the reaction of nickel salts with [1,2-B9H9CHCCH3]2~,

[1,2-B9H9C2(CH3)2]2-, [1,2-B9H9C(CH2)2C]2-, [1,2-B9H9CHCC6H5]2-, and [1,2-B9H9CHCC6H4F]2- (303, 305, 338). The structure of the [(1,2-B9H9-CHCR)2Ni]n" complexes is assumed to be analogous to 64, 65, and 66 with the difference that optical isomers are possible arising from the enantiomeric C-substituted ligand. The observation of two fluorine resonances in the spec-trum of both the meta- and/?ara-FC6H4 substituted system is cited as evidence for such isomers (305).

The chemistry of the {Ni[B9H9C2(CH3)2]2}n- and {Ni[B9H9C(CH2)3C]2}n-systems has been studied in detail, and a most interesting rearrangement within the carborane ligand is observed : three series of complexes, A, B, and C, may be isolated and their preparation and interrelationship are summarized for the B9H9C2(CH3)2 system in the equations below (303, 338).

Ni(acac)2 + 2[B9H9C2(CH3)2]2-

Series A : {Ni2 + [B9H9C2(CH3)2]2}2 " , {Ni3 + [B9H9C2(CH3)2]2} yellow deep red

/ 2 0 0 o

Series B : {Ni2 + [B9H9C2(CH3)2]2}2 " , -1.02 V

{Ni3 + [B9H9C2(CH3)2]2}- w Ni4 + [B9H9C2(CH3)2]2 u + 0.15V brown red-orange

Series C : {Ni2 + [B9H9C2(CH3)2]}22 -

-1 .19V

100°

{Ni3 + [B9H9C2(CH3)2]}2 - , Ni4 + [B9H9C2(CH3)2]2 u -0.10V „

golden yellow

The series A isomers are assumed to have structures related to 65 and 66 and the nickel (3 + ) complex has been shown to be isomorphous with the analogous cobalt (3 + ) complex which has the expected symmetrical structure related to 65 (Fig. VIII-13a). The series B isomers are formed by a thermal rearrangement of the series A isomers and are thought to contain one (3)-l,2-B9H9C2(CH3)2 ligand and one (4)-l,2-B9H9C2(CH3)2 ligand (Fig.


VIII-13b). This suggestion explains the observation of four methyl absorptions in the NMR spectrum of the neutral series B complex. The rearrangement is assumed to pass through a sterically unfavorable intermediate in which the substituents on the two rings are mutually cisoid. The structure of the neutral series B isomer has been confirmed by an x-ray structural determination of the racemic B isomer [(3)(4)Hl,2-B9H9C2(CH3)2]2Ni {a = 13.489 (10); b = 20.223 (12); c = 7.626 (6); ß = 93.62 (5); Z = 4; space group P2Jn, R = 8.64%.) The nickel atom in this complex is essentially symmetrically bonded to the two carborane molecules which are, however, tilted at 14°5Γ with respect to each other, thereby increasing the interligand C—C distance (Fig. VIII-13b): this distortion has been attributed to steric repulsion between the methyl groups (302). The series C isomers are obtained by thermal rearrangement of the series B isomers and the observation of only two ab-sorptions for the methyl groups in the NMR spectrum of the neutral complex is most easily explained by assuming that both ligands adopt the (4)-l,2-B9H9C2(CH3)2 configuration (Fig. VIII-13c). Several of the{[B9C9C2(CH3)2]2-Ni}n_ complexes can exist as optical isomers and it has been possible to resolve the series-B monoanion by fractional recrystallization of the d-N,N,N-trimethy\, a-phenyl, ethyl ammonium salt, which has then been used to prepare other optically active members of both series B and C (303).

GO (b) (c)

Fig. VIII-13. Structures of the Ni[B9H9C2(CH3)2]2n" complexes: (a) Ni + 3-[ B 9 H 9 C 2 ( C H 3 ) 2 ] 2 - ; (b) N i + 4 [ B 9 H 9 C 2 ( C H 3 ) 2 ] 2 (series B ) ; (c) N i + 4 [ B 9 H 9 C 2 ( C H 3 ) 2 ] 2

(series C, meso-form).


The rearrangement of the carborane molecule in these transformations does not apparently occur in the absence of the transition metal. Two pos-sible mechanisms involving successive 1,2-shifts or successive 1,7-shifts can be considered. The facile isomerization observed for the complexes involving the bridging 1,2-trimethylene carborane (e.g., 70), however, makes the 1,7-rearrangement improbable.

H2C

70 (Series B)

B. Miscellaneous Complexes

Bis(carborane)nickel complexes have also been isolated from reactions involving the [B10C10CR]3- ion (e.g., 71) and the [1,7-B9H9CHPCH]2- ion (317-321). Mixed complexes containing one B9H9CHPCH3 ligand and a

H

H / . ^ C — H

/ H

Ni

-¿s,

Β 72


77-allyl, TT-methylallyl, π-triphenylcyclopropenyl or NO molecule may also be prepared (285). The NMR spectrum of the ττ-allyl group in TT-C3H5NÍ-(B9H9CHPCH3) (72) shows that each proton is magnetically unique; a result of the asymmetry of the carborane molecule.

Related compounds have been isolated from the reaction of the B10H13~ ion with the appropriate metal halide (322). The reaction with bistriphenyl-phosphine nickel dichloride causes displacement of the phosphine molecules and formation of [Ni(B10H12)2]2~, the structure of which has been established by x-ray crystallography (Fig. VIII-14), (a = 7.34(1); b = 11.97(2); c = 15.73(2); ß = 93.8; Z = 2; Space group Pljc; R = 9.6%).

Fig. VIII-14. Structure of [(BioH12)2Ni][N(CH3)4]2 (323).

The complex can be regarded as the boron equivalent of a bis(butadiene) nickel system, and a semitheoretical HMO treatment has been developed for the molecule which indicates that the metal-ligand bond is primarily realized through interaction with the nickel 4s orbital.

The related «-B18H202~ ion, 73 also reacts with bisphosphine nickel di-

chloride complexes without, however, displacing the phosphine molecules. The product, (B18H20)NiLig2 [where Lig = P(C6H3)3 or P(C6H5)2], has been suggested to contain a nickel atom ττ-bonded to the B5 face of the B n -carborane fragment (324,375). The alternative possibility of bonding through the B4 face of the B10 carborane is perhaps electronically more attractive.

An interesting mixed metal species, viz. 7r-C5H5NiB7CH8Co7r-C5H5, has been obtained by reduction of [7r-C5H5CoB7CH8] " with sodium naphthalide in the presence of sodium cyclopentadienide and nickel bromide (376). A

References 477

complex having the composition [(B10C2H12)2Ni]2+ has recently been re-ported (374). Preliminary x-ray data on a related cobalt compound suggest that the carborane is bonded asymmetrically to the nickel.

References

1. M. J. Bennett, M. R. Churchill, M. Gerloch, and R. Mason, Nature {London) 201, 1318 (1964).

2. M. R. Churchill and R. Mason, Advan. Organometal. Chem. 5, 93 (1967). 3. C. A. Tolman, Chem, Soc. Rev. 1, 337 (1972). 4. R. Riemschneider (Ethyl Corp.), U.S. Patent 3,064,020 (1962); Chem. Abstr. 58,

11403 (1963). 5. R. Riemschneider and D. Helm, Z. Natur forsch. B 14, 811 (1959). 6. R. Riemschneider and D. Helm, Z. Naturforsch. B 16, 234 (1961). 7. K. Mayer and J. P. Wibaut, Rec. Trav. Chim. Pays-Bas 56, 356 (1937). 8. H. Cordes (BASF), German Patent 1,206,897 (1965); Chem. Abstr. 64, 8240 (1966). 9. H. Cordes and S. Schreiner (BASF), German Patent 1,223,839 (1966); Chem. Abstr.

66, 2642 (1967). 10. California Research Corp., British Patent 768,345 (1957); Chem. Abstr. 51, 15593

(1957). 11. H. Shapiro, E. G. deWitt, and J. E. Brown (Ethyl Corp.), U.S. Patent 3,306,917

(1967); Chem. Abstr. 67, 73689 (1967). 12. C. L. Hobbs (E. I. du Pont), British Patent 733,129 (1955); Chem. Abstr. 50, 7146

(1956). 13. R. Ross, East German Patent 51,312 (1966); Chem. Abstr. 66, 95206 (1967). 14. M. A. Lynch and J. C. Brantley (Union Carbide), British Patent 785,760 (1957);

Chem. Abstr. 52, 11126 (1958). 15. L. T. Reynolds and G. Wilkinson, / . Inorg. Nucl. Chem. 9, 86 (1959). 16. A. N. Nesmeyanov, E. V. Leonava, N. S. Kochetkova, S. M. Butyugin, and I. S.

Meisner, Bull. Acad. Sei. USSR, p. 89 (1971). 17. E. O. Fischer and R. Jira, Z. Naturforsch. B 8, 217 (1953). 18. E. O. Fischer and H. Grubert, Z. Anorg. Allg. Chem. 286, 237 (1957). 19. J. F. Cordes, Chem. Ber. 95, 3084 (1962). 20. G. R. Knox, J. D. Munro, P. L. Pauson, G. H. Smith, and W. E. Watts, / . Chem.

Soc, London p. 4619 (1961).


21. C. L. Hobbs (E. I. du Pont), U.S. Patent 3,092,647 (1963); Chem. Abstr. 59, 11568 (1963).

22. E. K. von Gustorf and G. O. Schenk (Studiengesellschaft Kohle m.b.H.), French Patent 1,343,770 (1963); Chem. Abstr. 60, 8062 (1964).

23. A. N. Nesmeyanov, R. B. Materikova, and N. S. Kochetkova, Bull. Acad. Sei. USSR,p. 1211 (1963).

24. A. N. Nesmeyanov, R. B. Materikova, N. S. Kochetkova, and R. V. Luk'yanova, Bull. Acad. Sei. USSR p. 896 (1969).

25. C. C. Hunt and J. R. Doyle, Inorg. Nucl. Chem. Lett. 2, 283 (1966). 26. G. Wilkinson, P. L. Pauson, and F. A. Cotton, / . Amer. Chem. Soc. 76,1970 (1954). 27. J. Tirouflet, E. Laviron, R. Dabard, and J. Komenda, Bull. Chem. Soc. Fr. p. 857

(1963). 28. E. O. Fischer, D. Seus, and R. Jira, Z. Naturforsch. B 8, 692 (1953). 29. H. P. Fritz, F. H. Köhler, and K. E. Schwarzhans, / . Organometal. Chem. 19, 449

(1969). 30. G. Wilkinson, P. L. Pauson, J. M. Birmingham, and F. A. Cotton, / . Amer. Chem.

Soc. 75, 1011 (1953). 31. A. F. Reid and P. C. Wailes (CSIRO), Australian Patent 290,355 (1969); Chem.

Abstr. 72, 132939 (1970). 32. J. Cunningham (E. I. du Pont), U.S. Patent 2,680,785 (1954). 33. E. L. Morehouse (Union Carbide), British Patent 797,151 (1958); Chem. Abstr. 53,

4297 (1959). 34. E. L. Morehouse (Union Carbide), U.S. Patent 3,071,605 (1963); Chem. Abstr. 58,

12602 (1963). 35. H. Watanabe, I. Motoyama, and K. Hata, Bull. Chem. Soc. Jap. 38, 853 (1965). 36. G. Wilkinson, F. A. Cotton, and J. M. Birmingham, / . Inorg. Nucl. Chem. 2, 95

(1956). 37. W. L. Jolly and D. J. Chazan, Inorg. Syn. 11, 122 (1968). 38. R. B. King, " Organometallic Syntheses," Vol. 1, p. 71. Academic Press, New York,

1965. 39. D. C. Freedman and T. L. Thomas (Union Carbide), U.S. Patent 3,032,569 (1962);

Chem. Abstr. 57, 13807 (1962). 40. E. O. Fischer and H. Werner, Chem. Ber. 92, 1423 (1959). 41. V. F. Hnizda (Ethyl Corp.), German Patent 1,159,949 (1964); Chem. Abstr. 60,

12056 (1964). 42. W. Keim, Ph.D. Dissertation, Technische Hochschule Aachen, 1963. 43. M. F. Rettig and R. S. Drago, / . Amer. Chem. Soc. 91, 1361 (1969). 44. G. Winter, K. Hohmuth, R. Ross, H. Kästner, and J. Schintlmeister, Z. Phys.

Chem. {Frankfurt am Main) 234, 305 (1967). 45. J. L. Spencer, M. Green, and F. G. A. Stone, Chem. Commun, p. 1178 (1972). 46. A. Fürst and M. C. Schlauder, Froc. West. Pharmacol. Soc. 14, 68 (1971). 47. W. Pfab and E. O. Fischer, Z. Anorg. Allg. Chem. 274, 316 (1953). 48. W. Strohmeier and D. von Höbe, Z. Elektrochem. 64, 945 (1960). 49. E. O. Fischer and S. Schreiner, Chem. Ber. 92, 938 (1959). 50. H. Leipfinger, Z. Naturforsch. B 13, 53 (1958). 51. R. Prins, J. D. W. van Voorst, and C. J. Schinkel, Chem. Phys. Lett. 1, 54 (1967). 52. R. E. Robertson and H. M. McConnell, / . Phys. Chem. 64, 70 (1960). 53. T. Englemann, Z. Naturforsch. B 8, 775 (1953). 54. A. G. Turnbull, Aust. J. Chem. 20, 2757 (1967). 55. A. G. Turnbull, Aust. J. Chem. 20, 2059 (1967).

References 479

56. E. R. Lippincott and R. D. Nelson, / . Amer. Chem. Soc. 77, 4990 (1955). 57. A. Salzer and H. Werner, Chinda 25, 410 (1971). 58. P. D. Frisch and L. F. Dahl, / . Amer. Chem. Soc. 94, 5082 (1972). 59. E. Weiss and E. O. Fischer, Z. Anorg. Allg. Chem. 284, 69 (1956). 60. E. O. Fischer, Rec. Trav. Chim. Pays-Bas 75, 629 (1956). 61. I. A. Ronova and N. V. Alekseev, / . Struct. Chem. (USSR) 7, 821 (1966). 62. I. A. Ronova, D. A. Bochvar, A. L. Christjakov, Y. T. Struchkov, and N. V. Alek-

seev, / . Organometal. Chem. 18, 337 (1969). 63. L. Hedberg and K. Hedberg, / . Chem. Phys. 53, 1228 (1970). 64. A. Haaland and J. E. Nilsson, Acta Chem. Scand. 22, 2653 (1968). 65. V. G. Andrianov, B. P. Biryukov, and Y. T. Struchkov, / . Struct. Chem. (USSR)

10, 1014 (1969). 66. M. J. Bennett and R. Mason, Nature (London) 205, 760 (1965). 67. M. Nussbaum and J. Voitländer, Z. Naturforsch. A 20, 1411 (1965). 68. M. Nussbaum and J. Voitländer, Z. Naturforsch. A 20, 1417 (1965). 69. R. Prins and J. D. W. van Voorst, / . Chem. Phys. 49, 4665 (1968). 70. G. M. Schwab, E. O. Fischer, and J. Voitländer, Naturwissenschaften 41, 228 (1954). 71. G. M. Schwab and J. Voitländer, Z. Phys. Chem. (Frankfurt am Main) [N.S.] 3, 341

(1955). 72. L. Friedman, A. P. Irsa, and G. Wilkinson, / . Amer. Chem. Soc. 77, 3689 (1955). 73. J. Müller and L. d'Or, / . Organometal. Chem. 10, 313 (1967). 74. E. Schumacher and R. Taubenest, Helv. Chim. Acta 47, 1525 (1964). 75. P. Schissel, D. J. McAdoo, E. Hedaya, and D. W. McNeil, / . Chem. Phys. 49, 5061

(1968). 76. S. Pignataro and F. P. Lossing, / . Organometal. Chem. 10, 531 (1967). 77. A. N. Nesmeyanov, "Vapour Pressure of the Chemical Elements." Elsevier,

Amsterdam, 1963. 78. R. Hultgren, R. L. Orr, P. D. Anderson, and K. Kelly, "Supplement to Selected

Values of Thermodynamic Properties of Metals and Alloys," Department of Mineral Technology, University of California, Berkeley, 1966.

79. H. S. Hull, A. F. Reid, and A. G. Turnbull, Inorg. Chem. 6, 805 (1967). 80. O. P. Charkin and M. E. Dyatkina, Bull. Acad. Sei. USSR p. 2502 (1969). 81. S. Pignataro and F. P. Lossing, / . Organometal. Chem. 11, 571 (1968). 82. H. P. Fritz, Chem. Ber. 92, 780 (1959). 83. H. P. Fritz and R. Schneider, Chem. Ber. 93, 1171 (1960). 84. J. Brunvoll, S. J. Cyvin, and L. Schäfer, Acta Chem. Scand. 24, 3427 (1970). 85. S. Koda and T. Hikita, Chem. Lett. p. 353 (1972). 86. H. P. Fritz, Advan. Organometal. Chem. 1, 239 (1964). 87. M. Rosenblum, " Chemistry of the Iron Group Metallocenes." Wiley, New York,

1965. 88. D. R. Scott and R. S. Becker, / . Chem. Phys. 35, 516 (1961). 89. I. Pavlik, V. Cerny, and E. Maxova, Collect. Czech. Chem. Commun. 35, 3045

(1970). 90. T. S. Piper and R. L. Carlin, / . Chem. Phys. 33, 1208 (1960). 91. D. R. Scott and F. A. Matsen, / . Phys. Chem. 72, 16 (1968). 92. D. A. Levy and L. E. Orgel, Mol. Phys. 3, 583 (1960). 93. M. F. Rettig and R. S. Drago, Chem. Commun, p. 891 (1966). 94. M. F. Rettig and R. S. Drago, / . Amer. Chem. Soc. 91. 3432 (1969). 95. H. J. Keller and K. E. Schwarzhans, Angew. Chem. 82, 227 (1970). 96. H. P. Fritz, H. J. Keller, and K. E. Schwarzhans, Z. Naturforsch. B 23, 298 (1967).

480 VIIL TT-Cyclopentadienyl Nickel Complexes

97. H. P. Fritz, H. J. Keller, and K. E. Schwarzhans, Z. Naturforsch. B 21, 809 (1966). 98. H. P. Fritz, H. J. Keller, and K. E. Schwarzhans, / . Organometal. Chem. 7, 105

(1967). 99. H. P. Fritz, H. J. Keller, and K. E. Schwarzhans, Z. Naturforsch. B 22, 891 (1967).

100. P. K. Burkert, H. P. Fritz, F. H. Köhler, and H. Rupp, / . Organometal. Chem. 24, C59 (1970).

101. H. Nakajima, / . Phys. Soc. Jap. 20, 1725 (1965). 102. C. H. Holm and J. A. Ibers, / . Chem. Phys. 26, 1753 (1957). 103. H. M. McConnell and C. H. Holm, / . Chem. Phys. 28, 749 (1958). 104. H. M. McConnell and C. H. Holm, / . Chem. Phys. 27, 314 (1957). 105. S. E. Anderson and N. A. Matwiyoff, Chem. Phys. Lett. 13, 150 (1972). 106. H. Nakajima, Proc. Colloq. Ampere {At. Mol. Etud. Radio Elec.) 13, 259 (1969). 107. E. Kauer, Z. Phys. Chem. {Frankfurt am Main) [N.S.] 6, 105 (1956). 108. E. O. Fischer, G. Joos, and E. Vogg, Z. Phys. Chem. {Frankfurt am Main) [N.S.]

18, 80 (1958). 109. G. Wilkinson and F. A. Cotton, Progr. Inorg. Chem. 1, 1 (1959). 110. R. B. Moler and R. W. Fink, Phys. Rev. 131, 821 (1963). 111. E. E. Vainshtein and Y. F. Kopelev, Zh. Struct. Khin. 3, 448 (1962). 112. S. S. Batsanov and I. A. Ovsyanikova, Proc. Acad. Sei. USSR 165, 839 (1965). 113. O. H. Wheeler and M. L. McClin, Radiochim. Acta 7, 181 (1967). 114. E. K. von Gustorf, M. J. Jun, H. Koller, and G. O. Schenk, "Industrial Uses of

Large Radiation Sources," Vol. II, p. 73 (1963). 115. D. T. Clark and D. B. Adams, Chem. Commun, p. 740 (1971). 116. J. D. Dunitz and L. E. Orgel, Nature {London) 171, 121 (1953). 117. J. D. Dunitz and L. E. Orgel, / . Chem. Phys. 23, 954 (1955). 118. H. H. Jaffé, / . Chem. Phys. 21, 156 (1953). 119. W. Moffitt, / . Amer. Chem. Soc. 76, 3386 (1954). 120. M. Yamazaki, / . Chem. Phys. 24, 1260 (1956). 121. E. Ruch, Rec. Trav. Chim. Pays-Bas 75, 638 (1956). 122. E. Ruch and E. O. Fischer, Z. Naturforsch. B 7, 676 (1952). 123. E. Ruch, Z. Phys. Chem. {Frankfurt am Main) [N.S.] 6, 356 (1956). 124. E. Ruch, Z. Elektrochem. 61, 913 (1957). 125. J. Voitländer, Z. Phys. Chem. {Frankfurt am Main) [N.S.] 6, 371 (1956). 126. A. D. Liehr and C. J. Ballhausen, Acta Chem. Scand. 11, 207 (1957). 127. J. P. Dahl and C. J. Ballhausen, Kgl. Dan. Vidensk. Selsk., Mat.-Fys. Medd. 33,

5 (1961). 128. C. J. Ballhausen, "Introduction to Ligand Field Theory." McGraw-Hill, New

York, 1962. 129. D. A. Brown, / . Chem. Soc, London p. 690 (1961). 130. I. E. M. Shustorovich and M. E. Dyatkina, Zh. Neorg. Khim. 3, 2721 (1958). 131. M. E. Dyatkina, Izv. Akad. Nauk SSSR, Otd. Khim. Nauk p. 1025 (1959). 132. E. M. Shustorovich and M. E. Dyatkina, Dokl. Akad. Nauk SSSR 128,1234 (1959). 133. E. M. Shustorovich and M. E. Dyatkina, Dokl. Akad. Nauk SSSR 133, 141 (1960). 134. E. M. Shustorovich and M. E. Dyatkina, Zh. Strukt. Khim. 1, 109 (1960). 135. E. M. Shustorovich and M. E. Dyatkina, Dokl. Akad. Nauk SSSR 131, 113 (1960). 136. E. M. Shustorovich and M. E. Dyatkina, Zh. Neorg. Khim. 6, 1247 (1961). 137. J. W. Linnett, Trans. Faraday Soc. 52, 904 (1956). 138. F. A. Matsen, / . Amer. Chem. Soc. 81, 2023 (1959). 139. R. D. Fischer, Theor. Chim. Acta 1, 418 (1963). 140. J. H. Schachtschneider, R. Prins, and P. Ros, Inorg. Chim. Acta 1, 462 (1967).

References 481

141. A. T. Armstrong, D. G. Carroll, and S. P. McGlynn, / . Chem. Phys. 47,1104 (1967). 142. D. A. Bochvar and A. L. Chistyakov, / . Struct. Chem. (USSR) 9, 206 (1968). 143. D. A. Bochvar, A. V. Tutkevich, and A. L. Chistyakov, / . Struct. Chem. (USSR)

11, 310 (1970). 144. D. A. Brown, / . Inorg. Nucl. Chem. 10, 39 (1959). 145. A. H. Rosenberg and M. D. Rausch, U.S. Patent 3,060,215 (1962); Chem. Abstr.

58, 6865 (1963). 146. F. H. Köhler, Ph.D. Dissertation, Technische Hochschule München, 1970. 147. Y. A. Ustynyuk, unpublished results (1968); quoted by A. Z. Rubezhov and S. P.

Gubin, Advan. Organometal. Chem. 10, 402 (1972), and by E. G. Perevalova and T. V. Nikitina, Organometal React. 4, p. 334 (1972).

148. T. J. Katz and J. J. Mrowca, / . Amer. Chem. Soc. 89, 1105 (1967). 149. E. V. Bykova and V. N. Selkina, Bull. Acad. Sei USSR p. 1575 (1967). 150. D. N. Kursanov, E. N. Bykova, and V. N. Setkina, Proc. Acad. Sei. USSR 184, 6

(1969). 151. V. N. Setkina and D. N. Kursanov, Usp. Khim. 37, 1729 (1968). 152. P. Jiru and K. Kuchynka, Z. Phys. Chem. (Frankfurt am Main) [N.S.] 25,286 (1960). 153. M. Ichikawa, M. Soma, T. Onishi, and K. Tamaru, Trans. Faraday Soc. 63, 2528

(1967). 154. K. W. Barnett, F. D. Mango, and C. A. Reilly, / . Amer. Chem. Soc. 91, 3387 (1969). 155. E. O. Fischer and H. Leipfinger, Z. Naturforsch. B 10, 353 (1955). 156. C. J. Ballhausen and H. G. Gray, Coord. Chem. Amer. Chem. Soc. Monogr. 168

3 (1971). 157. G. B. McVicker and R. S. Matyas, Chem. Commun, p. 972 (1972). 158. A. Salzer and H. Werner, Syn. Inorg. Metal. Org. Chem. 2, 249 (1972). 159. R. J. Wilson, L. F. Warren, and M. F. Hawthorne,/. Amer. Chem. Soc. 91,758 (1969). 160. S. P. Gubin, S. A. Smirnova, and L. I. Denisovich, / . Organometal. Chem. 30, 257

(1971). 161. H. P. Fritz and F. H. Köhler, Z. Anorg. Allg. Chem. 385, 22 (1971). 162. J. C. Goan, E. Berg, and H. E. Podall, / . Org. Chem. 29, 975 (1964). 163. H. Watanabe, I. Motoyoma, and K. Hata, Bull. Chem. Soc. Jap. 39, 850 (1966). 164. B. Hetnarski, Z. Grabowski, and W. Kutkiewicz, Rocz. Chem. 43, 1589 (1969). 165. T. G. Golenko, K. L. Makovetskii, V. A. Libina, A. N. Karasev, E. I. Tinyakova,

and B. A. Dolgoplosk, Bull. Acad. Sei. USSR p. 2147 (1968). 166. H. Werner, G. Mattmann, A. Salzer, and T. Winkler, / . Organometal. Chem. 25,

461 (1970). 167. E. Hedaya, D. W. McNeil, P. Schissel, and D. J. McAdoo, / . Amer. Chem. Soc. 90,

5284 (1968). 168. H. Werner and J. H. Richards, / . Amer. Chem. Soc. 90, 4976 (1968). 169. A. G. Harrison, L. R. Honnen, H. J. Dauben, and F. F. Lossing, / . Amer. Chem.

Soc. 82, 5593 (1960). 170. E. O. Fischer and C. Palm, Chem. Ber. 91, 1725 (1958). 171. J. F. Tilney-Bassett, / . Chem. Soc, London p. 577 (1961). 172. R. B. King, " Organometallic Syntheses," Vol. 1, p. 119. Academic Press, New York,

1965. 173. E. O. Fischer and C. Palm (BASF), German Patent 1,060,399 (1954); Chem. Abstr.

55, 8431 (1961). 174. H. Cordes (BASF), German Patent 1,060,397 (1959); Chem. Abstr. 55, 8341 (1961). 175. H. Cordes and W. Jäckl (BASF), German Patent 1,131,214 (1962); Chem. Abstr.

57, 15157 (1962).

482 VIH. ττ-Cyclopentadienyl Nickel Complexes

176. J. F. Tilney-Bassett, Proc Chem. Soc, London p. 419 (1960). 177. J. F. Tilney-Bassett, / . Chem. Soc, London p. 4784 (1963). 178. T. Blackmore, J. D. Cotton, M. I. Bruce, and F. G. A. Stone, / . Chem. Soc, A

p. 2931 (1968). 179. A. T. T. Hsieh and J. Knight, / . Organometal. Chem. 26, 125 (1971). 180. J. P. Nice and O. S. Mills, quoted in réf. 181. 181. O. S. Mills and B. W. Shaw, / . Organometal. Chem. 11, 595 (1968). 182. P. McArdle and A. R. Manning, / . Chem. Soc, A p. 2133 (1970). 183. P. McArdle and A. R. Manning, / . Chem. Soc, A p. 717 (1971). 184. P. M. Maitlis, A. Efraty, and M. L. Games, / . Amer. Chem. Soc. 87, 719 (1965). 185. K. Yasufuku and H. Yamazaki, Bull. Chem. Soc. Jap. 43, 1588 (1970). 186. K. Yasufuku and H. Yamazaki, Bull. Chem. Soc. Jap. 42, 3049 (1969). 187. K. Yasufuku and H. Yamazaki, / . Organometal. Chem. 28, 415 (1971). 188. T. Kondo and A. Miyake (Toyo-Rayan Co. Ltd.), Japanese Patent 69-32,773

(1969); Chem. Abstr. 72, 67114 (1970). 189. E. O. Fischer, G. Joos, and W. Meer, Z. Naturforsch, B 13, 456 (1958). 190. E. O. Fischer, / . Inorg. Nucl. Chem. 8, 268 (1958). 191. E. Schumacher and R. Taubenest, Helv. Chim. Acta 49, 1447 (1966). 192. Y. Yamamoto and N. Hagihara, Bull. Chem. Soc Jap. 39, 1084 (1966). 193. K. K. Joshi, O. S. Mills, P. L. Pauson, B. W. Shaw, and W. H. Stubbs, Chem.

Commun, p. 181 (1965). 194. P. L. Pauson and W. H. Stubbs, Angew. Chem. 74, 466 (1962). 195. Y. Yamamoto and N. Hagihara, Mem. Inst. Sei. Ind. Res., Osaka Univ. 27, 109

(1970). 196. D. W. McBride, E. Dudek, and F. G. A. Stone, / . Chem. Soc, London p. 1752

(1964). 197. R. E. Dessy, F. E. Stary, R. B. King, and M. Waldorp, / . Amer. Chem. Soc 88,

471 (1966). 198. R. E. Dessy, P. M. Weissman, and R. L. Pohl, / . Amer. Chem. Soc. 88, 5117 (1966). 199. R. E. Dessy, R. L. Pohl, and R. B. King, / . Amer. Chem. Soc. 88, 5121 (1966). 200. R. D. Gorisch (Ethyl Corp.), U.S. Patent 3,069,449 (1962); Chem. Abstr. 58, 10241

(1963). 201. E. W. Abel, S. A. Keppie, M. F. Lappert, and S. Moorhouse,/. Organometal. Chem.

22, C31 (1970). 202. R. C. Edmondson, E. Eisner, M. J. Newlands, and L. K. Thompson, / . Organo-

metal. Chem. 35, 119 (1972). 203. E. N. Gladyshev, V. I. Ermolaev, Y. A. Sorokin, O. A. Kruglaya, N. S. Vyazankin,

and G. A. Razuvaev, Proc Acad. Sei. USSR 179, 350 (1968). 204. W. K. Schropp, / . Inorg. Nucl. Chem. 24, 1688 (1962). 205. E. Lindner, G. Vitzthum, and H. Weber, Z. Anorg. Allg. Chem. 373, 122 (1970). 206. W. Jetz and W. A. G. Graham, / . Amer. Chem. Soc 89, 2773 (1967). 207. E. W. Abel and S. Moorhouse, / . Organometal. Chem. 24, 687 (1970). 208. D. J. Patmore and W. A. G. Graham, Inorg. Chem. 5, 1405 (1966). 209. P. F. Barrett and R. C. Clancy, Can. J. Chem. 49, 2627 (1971). 210. A. Wojcicki and F. Basólo, / . Inorg. Nucl. Chem. 17, 77 (1961). 211. R. G. Hayter, Inorg. Chem. 2, 1031 (1963). 212. J. M. Coleman and L. F. Dahl, / . Amer. Chem. Soc. 89, 542 (1967). 213. J. A. J. Jarvis, R. H. B. Mais, G. P. Owston, and D. T. Thompson, / . Chem. Soc, A

p. 1867 (1970). 214. R. E. Dessy, R. Kornmann, C. Smith, and R. Haytor, / . Amer. Chem. Soc. 90,

2001 (1968).

References 483

215. R. C. Dobbie, M. Green, and F. G. A. Stone, / . Chem. Soc, A p. 1881 (1969). 216. R. B. King, / . Amer. Chem. Soc. 85, 1587 (1963). 217. R. B. King and M. B. Bisnette, Inorg. Chem. 6, 469 (1967). 218. R. B. King (E. I. du Pont), U.S. Patent 3,361,777 (1968); Chem. Abstr. 68, 106510

(1968). 219. H. Vahrenkamp, V. A. Uchtman, and L. F. Dahl, / . Amer. Chem. Soc. 90, 3272

(1968). 220. V. A. Uchtman and L. F. Dahl, / . Amer. Chem. Soc. 91, 3763 (1969). 221. V. A. Uchtman, Ph.D. Dissertation, University of Wisconsin, Madison, 1968. 222. A. A. Hock and O. S. Mills, Advan. Chem. Coord. Compounds, Proc. 6th ICCC1961

p. 640 (1961). 223. H. C. Longuet-Higgins and A. J. Stone, / . Mol. Phys. 5, 417 (1960). 224. C. E. Strouse and L. F. Dahl, Discuss. Faraday Soc. 47, 93 (1969). 225. H. Vahrenkamp and L. F. Dahl, Angew. Chem. 81, 152 (1969). 226. G. G. Petukhov, V. I. Ermolaev, and R. V. Kaplina, Tr. Khim. Khim. Tekhnol.

p. 160 (1969). 227. G. G. Petukhov, V. I. Ermolaev, and R. V. Kaplina, Zh. Obshch. Khim. 38, 465

(1968). 228. R. B. King, Progr. Inorg. Chem. 15, 287 (1972). 229. A. Salzer and H. Werner, Angew. Chem. 84, 949 (1972). 230. S. Otsuka, A. Nakamura, and T. Yoshida, Inorg. Chem. 7, 261 (1968). 231. S. Otsuka, A. Nakamura, and T. Yoshida, Justus Liebigs Ann. Chem. 719, 54

(1968). 232. C. E. Strouse and L. F. Dahl, / . Amer. Chem. Soc. 93, 6032 (1971). 233. T. I. Voyevodskaya, I. M. Pribytkova, and Y. A. Ustynyuk, / . Organometal. Chem.

37, 187 (1972). 234. G. E. Schroll (Phillips Petroleum), U.S. Patent 3,054,815 (1962); Chem. Abstr. 58,

1491 (1963). 235. H. Yamazaki, T. Nishido, Y. Matsumoto, S. Sumida, and H. Hagihara,/. Organo-

metal. Chem. 6, 86 (1966). 236. M. van den Akker and F. Jellinek, Rev. Trav. Chim. Pays-Bas 86, 897 (1967). 237. P. L. Maxfield (Phillips Petroleum), U.S. Patent 3,476,769 (1969); Chem. Abstr.

72, 43880 (1970). 238. Y. A. Ustynyuk, T. I. Voevodskaya, N. A. Zharikova, and N. A. Ustynyuk, Proc.

Acad. Sei. USSR 181, 640 (1968). 239. W. K. Schropp, / . Inorg. Nucl. Chem. 24, 1690 (1962). 240. M. Sato, F. Sato, and T. Yoshida, / . Organometal. Chem. 31, 415 (1971). 241. M. Sato, F. Sato, and T. Yoshida, / . Organometal. Chem. 27, 273 (1971). 242. P. M. Treichel and R. L. Shubkin, Inorg. Chim. Acta 2, 485 (1968). 243. P. A. McArdle and A. R. Manning, Chem. Commun, p. 417 (1967). 244. M. van den Akker and F. Jellinek, / . Organometal. Chem. 10, P37 (1967). 245. M. Sato, F. Sato, and T. Yoshida, / . Organometal. Chem. 26, C49 (1971). 246. Y. Yamamoto, H. Yamazaki, and N. Hagihara, Mem. Inst. Sei. Ind. Res., Osaka

Univ. 26, 167 (1969). 247. Y. Yamamoto, H. Yamazaki, and N. Hagihara, / . Organometal. Chem. 18, 189

(1969). 248. R. J. Cross and R. Wardle, / . Organometal. Chem. 23, C4 (1970). 249. M. D. Rausch, Y. F. Chang, and H. B. Gordon, Inorg. Chem. 8, 1355 (1969). 250. S. A. Smirnova, private communication, quoted in ref. 147, p. 402. 251. M. Sato, F. Sato, N. Takemoto, and K. Iida, / . Organometal. Chem. 34, 205 (1972). 252. F. Sato, T. Yoshida, and M. Sato, / . Organometal. Chem. 37, 381 (1972).


253. F. Sato, M. Etoh, and M. Sato, / . OrganometaL Chem. 37, C51 (1972). 254. M. van den Akker and F. Jellinek, Abstr., Int. Symp. OrganometaL Chem., 3rd,

1967 p. 32 (1967). 255. F. Glockling, A. McGregor, M. L. Schneider, and H. M. M. Shearer, / . Inorg.

Nucl. Chem. 32, 3101 (1970). 256. H. Felkin and P. J. Knowles, / . OrganometaL Chem. 37, C14 (1972). 257. J. Thomson, D. Groves, and M. C. Baird, / . Magn. Resonance 5, 281 (1971). 258. J. Cooke, M. Green, and F. G. A. Stone, / . Chem. Soc, A p. 170 (1968). 259. F. Klanberg and E. L. Muetterties, / . Amer. Chem. Soc. 90, 3296 (1968). 260. E. Uhlig and H. Walther, Z. Chem. 11, 23 (1971). 261. P. C. Eligen and C. D. Gregory, Inorg. Chem. 10, 980 (1971). 262. J. L. Davidson and D. W. A. Sharp, / . Chem. Soc., Dalton Trans, p. 107 (1972). 263. H. Werner and A. Salzer, Syn. Inorg. Metal. Org. Chem. 2, 239 (1972). 264. J. Locke and J. A. McCleverty, Inorg. Chem. 5, 1157 (1966). 265. T. A. James and J. A. McCleverty, / . Chem. Soc., A p. 3318 (1970). 266. M. Ahmad, R. Bruce, and G. Knox, Z. Naturforsch. B 21, 289 (1966). 267. P. Bladon, R. Bruce, and G. R. Knox, Chem. Commun, p. 557 (1965). 268. F. J. Preston and R. I. Reed, Chem. Commun, p. 51 (1966). 269. E. O. Fischer, O. Beckert, W. Hafner, and H. O. Stahl, Z. Naturforsch. B 10, 598

(1955). 270. T. S. Piper, F. A. Cotton, and G. Wilkinson, / . Inorg. Nucl. Chem. 1, 165 (1955). 271. W. R. Axtell, J. B. Bingeman, and A. P. Giraitis (Ethyl Corp.), U.S. Patent

3,067,227 (1962); Chem. Abstr. 58, 10242 (1963). 272. J. E. Brown, E. G. de Witt, and H. Shapiro (Ethyl Corp.), U.S. Patent 3,185,718

(1965); Chem. Abstr. 63, 8407 (1965). 273. J. E. Brown, H. Shapiro, and E. G. de Witt (Ethyl Corp.), U.S. Patent 3,110,577

(1963); Chem. Abstr. 60, 6688 (1964). 274. International Nickel Co., British Patent 882,747 (1960); Chem. Abstr. 56, 15548

(1962). 275. R. D. Feltham, J. F. Anzenberger, and J. T. Carriel (International Nickel Co.),

U.S. Patent 3,088,959 (1963); Chem. Abstr. 59, 10128 (1963). 276. J. E. Brown, E. G. de Witt, and H. Shapiro (Ethyl Corp.), U.S. Patent 3,086,034

(1963); Chem. Abstr. 59, 8791 (1963). 277. J. E. Brown, H. Shapiro, and E. G. de Witt (Ethyl Corp.), U.S. Patent 3,110,577

(1963); Chem. Abstr. 60, 6688 (1964). 278. J. E. Brown, H. Shapiro, and E. G. de Witt (Ethyl Corp.), U.S. Patent 3,006, 742

(1958); Chem. Abstr. 56, 6250 (1962). 279. E. L. Niedsielski (E. I. du Pont), U.S. Patent 3,353,938 (1967); Chem. Abstr. 68,

61470 (1968). 280. T. H. Coffield and K. G. Ihrman (Ethyl Corp.), U.S. Patent 3,086,035 (1963);

Chem. Abstr. 59, 8792 (1963). 281. T. H. Coffield and K. G. Ihrman (Ethyl Corp.), U.S. Patent 3,086,036 (1963);

Chem. Abstr. 59, 8791 (1963). 282. T. H. Coffield and K. G. Ihrman (Ethyl Corp.), U.S. Patent 3,086,037 (1963);

Chem. Abstr. 59, 8791 (1963). 283. M. Dubeck (Ethyl Corp.), U.S. Patent 3,088,963 (1963); Chem. Abstr. 59, 10126

(1963). 284. R. T. Bailey, Spectrochim. Acta, Part A 25, 1127 (1969). 285. P. S. Welcker and L. J. Todd, Inorg. Chem. 9, 286 (1970). 286. F. A. Palocsay and J. V. Rund, Inorg. Chem. 8, 696 (1969).

References 485

287. A. Foffani, S. Pignataro, G. Distefano, and G. Innorta, / . Organometal. Chem. 7, 473 (1967).

288. G. Paliani, Z. Naturforsch. B 25, 786 (1970). 289. A. P. Cox and A. H. Brittain, Trans. Faraday Soc. 66, 557 (1970). 290. A. P. Cox, L. F. Thomas, and J. Sheridan, Nature {London) 181, 1157 (1958). 291. A. P. Cox, A. H. Brittain, and M. J. Whittle, / . Mol. Spectrosc. 35, 49 (1970). 292. A. F. Berndt, Ph.D. Dissertation, California Institute of Technology, Pasadena,

1957. 293. R. B. King, " Organometallic Syntheses," Vol. 1, p. 171. Academic Press, New York,

1965. 294. R. D. Feltham and W. G. Fateley, Spectrochim. Acta 20, 1081 (1964). 295. I. J. Hyams and E. R. Lippincott, Nature {London) 214, 267 (1967). 296. A. Foffani, A. Poletti, and R. Cataliotti, Spectrochim. Acta, Part A 24, 1437 (1968). 297. B. A. Frenz, J. H. Enemark, and J. A. Ibers, Inorg. Chem. 8, 1288 (1969). 298. J. H. Enemark, Inorg. Chem. 10, 1952 (1971). 299. M. Green, R. B. L. Osborn, A. J. Rest, and F. G. A. Stone, / . Chem. Soc, A

p. 2525 (1968). 300. R. B. King, "Organometallic Syntheses," Vol. 1, p. 169. Academic Press, New

York, 1965. 301. L. E. Orgel, / . Inorg. Nucl. Chem. 2, 315 (1956). 302. M. R. Churchill and K. Gold, / . Amer. Chem. Soc. 92, 1180 (1970). 303. L. F. Warren and M. F. Hawthorne, / . Amer. Chem. Soc. 92, 1157 (1970). 304. R. M. Wing, private communication, quoted in ref. 303. 305. R. G. Adler and M. F. Hawthorne, / . Amer. Chem. Soc. 92, 6174 (1970). 306. J. N. Francis and M. F. Hawthorne, / . Amer. Chem. Soc. 90, 1663 (1968). 307. L. F. Warren and M. F. Hawthorne, / . Amer. Chem. Soc. 89, 470 (1967). 308. M. F. Hawthorne, D. C. Young, T. D. Andrews, D. V. Howe, R. L. Pilling, A. D.

Pitts, M. Reintjes, L. F. Warren, and P. A. Wegner, / . Amer. Chem. Soc. 90, 879 (1968).

309. R. M. Wing, / . Amer. Chem. Soc. 92, 1187 (1970). 310. D. St. Clair, A. Zalkin, and D. H. Templeton, / . Amer. Chem. Soc. 92,1173 (1970). 311. R. M. Wing, / . Amer. Chem. Soc. 90, 4828 (1968). 312. R. M. Wing, / . Amer. Chem. Soc. 89, 5599 (1967). 313. L. F. Warren and M. F. Hawthorne, / . Amer. Chem. Soc. 90, 4823 (1968). 314. F. V. Hansen, R. G. Hazell, C. Hyatt, and G. D. Stucky, Acta Chem. Scand. 27,

1210 (1973). 315. R. J. Wilson, L. F. Warren, and M. F. Hawthorne,/. Amer. Chem. Soc. 91,758 (1969). 316. W. E. Geiger and D. E. Smith, Chem. Commun, p. 8 (1971). 317. W. H. Knoth, / . Amer. Chem. Soc. 89, 3342 (1967). 318. W. H. Knoth, J. L. Little, and L. J. Todd, Inorg. Syn. 11, 41 (1968). 319. D. E. Hyatt, J. L. Little, J. T. Moran, F. R. Scholer, and L. J. Todd, / . Amer. Chem.

Soc. 89, 3342 (1967). 320. W. H. Knoth (E. I. du Pont), U.S. Patent 3,409,650 (1968); Chem. Abstr. 70,

116235 (1969). 321. L. J. Todd, I. C. Paul, J. L. Little, P. S. Welcker, and C. R. Peterson, / . Amer.

Chem. Soc. 90, 4489 (1968). 322. F. Klanberg, P. A. Wegner, G. W. Parshall, and E. L. Muetterties, Inorg. Chem. 7,

2072 (1968). 323. L. J. Guggenberger, / . Amer. Chem. Soc. 94, 114 (1972). 324. R. L. Sneath, J. L. Little, R. Burke, and L. J. Todd, Chem. Commun, p. 693 (1970).


325. L. J. Todd, Advan. Organometal. Chem. 8, 87 (1970). 326. M. F. Hawthorne, Accounts Chem. Res. 1, 281 (1968). 327. R. N. Grimes, " Carboranes," Chapter 9. Academic Press, New York, 1970. 328. T. Hirabayashi and Y. Ishii, / . Organometal. Chem. 39, C85 (1972). 329. R. D. Adams, F. A. Cotton, and G. A. Rusholme, / . Coord. Chem. 1, 275 (1971). 330. J. Brunvoll, S. J. Cyvin, J. D. Ewbank, and L. Schäfer, Acta Chem. Scand. 26, 2161

(1972). 331. L. Schäfer, J. Brunvoll, and S. J. Cyvin, / . Mol. Struct. 11, 459 (1972). 332. K. Yasufuku and H. Yamazaki, / . Organometal. Chem. 38, 367 (1972). 333. F. Sato, K. Iida, and M. Sato, / . Organometal. Chem. 39, 197 (1972). 334. F. Sato, T. Uemura, and M. Sato, / . Organometal. Chem. 39, C25 (1972). 335. M. Sato and T. Yoshida, / . Organometal. Chem. 39, 389 (1972). 336. D. F. Shriver and A. Alich, Coord. Chem. Rev. 8, 15 (1972); D. F. Shriver, Chem.

Brit. 8, 419 (1972). 337. N. J. Nelson, N. E. Kime, and D. F. Shriver, / . Amer. Chem. Soc. 91, 5173 (1969). 338. T. E. Paxson, M. K. Kaloustian, G. M. Tom, R. J. Wiersema, and M. F. Haw-

thorne, / . Amer. Chem. Soc. 94, 4882 (1972). 339. I. Pavlik, E. Maxora, and E. Vecernikova, Z. Chem. 12, 26 (1972). 340. R. L. Bennett, M. I. Bruce, and F. G. A. Stone, / . Organometal. Chem. 38, 325

(1972). 341. D. F. Hunt, J. W. Russell, and R. L. Torian, / . Organometal. Chem. 43, 175 (1972). 342. G. D. Flesch, G. A. Junk, and H. J. Svec, / . Chem. Soc, Dalton Trans, p. 1102

(1972). 343. G. Paliani, R. Cataliotti, A. Poletti, and A. Foffani, / . Chem. Soc. Dalton Trans.

p. 1741 (1972). 344. J. W. Rabalais, L. O. Werme, T. Bergmark, L. Karlsson, M. Hussain, and K.

Siegbahn, / . Chem. Phys. 57, 1185 (1972). 345. C. M. Pleass and D. G. Schimmer, / . Catal. 24, 424 (1972). 346. M. E. Switzer and M. F. Rettig, Chem. Commun, p. 687 (1972). 347. A. R. Manning, / . Organometal. Chem. 40, C73 (1972). 348. T. J. Katz and N. Acton, / . Amer. Chem. Soc. 94, 3281 (1972). 349. J. J. Todd, Pure Appl. Chem. 30, 587 (1972). 350. I. H. Hillier and V. R. Saunders, Mol. Phys. 23, 449 (1972). 351. A. C. Ling, / . Inorg. Nucl. Chem. 34, 2978 (1972). 352. B. V. Bykova, V. N. Setkina, and D. N. Kursanov, Bull. Acad. Sei. USSR p. 1600

(1972). 353. P. C. Eligen, Inorg. Chem. 10, 232 (1971). 354. K. D. Warren, / . Phys. Chem. 77, 1681 (1973). 355. J. Müller and W. Goll, Chem. Ber. 106, 1129 (1973). 356. O. Crichton and A. J. Rest, Chem. Commun, p. 407 (1973). 357. T. Takiguchi, M. Abe, M. Abe, and H. Suzuki, Nippon KagakuZasship. 1066 (1973). 358. V. Harder and H. Werner, Helv. Chim. Acta 56, 1620 (1973). 359. J. Thomson and M. C. Baird, Can. J. Chem. 51, 1179 (1973). 360. J. Thomson and M. C. Baird, Inorg. Chim. Acta 7, 105 (1973). 361. M. Tanimoto, Y. Yqkozawa, and H. Nakajima, Phys. Letters 42A, 517 (1973). 362. F. Sato and M. Sato, / . Organometal. Chem. 46, C63 (1972). 363. M. Sato and T. Yoshida, / . Organometal. Chem. 51, 231 (1973). 364. A. Poletti, R. Cataliotti, and G. Paliani, Spectrochim. Acta 29A, 277 (1973). 365. L. K. Thompson, E. Eisner, and M. J. Newlands, / . Organometal. Chem. 56, 327

(1973). · 366. J. Müller, H. Dorner, and F. H. Köhler, Chem. Ber. 106, 1122 (1973).

Reviews 487

367. C. Moberg and M. Nilsson, / . OrganometaL Chem. 49, 243 (1973). 368. F. Glockling and A. McGregor, / . Inorg. Nucl. Chem. 35, 1481 (1973). 369. G. M. Begun and R. N. Compton, / . Chem. Phys. 58, 2271 (1973). 370. M. Barber, J. A. Connor, L. M. R. Derrick, M. B. Hall, and I. H. Hillier, / . Chem.

Soc. Faraday Trans. II, p. 559 (1973). 371. R. D. Adams and F. A. Cotton, Synth. Inorg. Metal. Org. Chem. 2, 277 (1972). 372. A. Alich, N. J. Nelson, D. Strope, and D. F. Shriver, Inorg. Chem. 11, 2976 (1972). 373. E. W. Abel and M. O. Dunster, / . OrganometaL Chem. 49, 435 (1973). 374. D. F. Dustin, G. B. Dunks, and M. F. Hawthorne, / . Amer. Chem. Soc. 95, 1109

(1973). 375. R. L. Sneath and L. J. Todd, Inorg. Chem. 12, 44 (1973). 376. C. G. Salentine and M. F. Hawthorne, Chem. Commun, p. 560 (1973). 377. M. M. Coutière, J. Demuynck, and V. Veillard, Theoret. Chim. Acta 27, 281 (1972).

Reviews

Important review articles on transition metal rr-cyclopentadienyl complexes are listed below. K. W. Barnett and D. W. Slocum, Cyclopentadienyl complexes of chromium, molyb-

denum, and tungsten. / . OrganometaL Chem. 44, 1 (1972). R. E. Bozak, Photochemistry of the metallocenes. Acivan. Photochem. 8, 227 (1971). D. E. Bublitz and K. E. Rinehart, Synthesis of substituted ferrocenes and other π-

cyclopentadienyl transition metal compounds. OrganometaL React. 17, 1 (1969). M. Cais and M. S. Lupin, Mass spectra of metallocenes and related compounds. Advan.

OrganometaL Chem. 8, 211 (1970). M. R. Churchill, Transition metal complexes of azulene and related ligands. Progr.

Inorg. Chem. 11, 53 (1970). G. Davidson, Vibrational spectra of π-bonded organo-transition metal complexes.

OrganometaL Chem. Revs. 8A, 303 (1972). R. N. Grimes, Carborane-transition metal ττ-complexes. " Carboranes," Chapter 9.

Academic Press, New York, 1970. M. F. Hawthorne, Recent developments in the chemistry of polyhedral complexes

derived from metals and carboranes. Pure Appl. Chem. 29, 547 (1972). M. F. Hawthorne, New routes to and reactions of polyhedral transition metal carborane

species. Pure Appl. Chem. 33, 475 (1972). M. F. Hawthorne and G. B. Dunks, Metallocarboranes that exhibit novel chemical

features. Science 178, 462 (1972). H. J. Keller and K. E. Schwarzhans, Magnetische Resonanz paramagnetischer Komplex-

verbindungen. Angew. Chem. 82, 227 (1970). R. C. Kerber and D. J. Ehntholt, Transition metal complexes of fulvenes. Synthesis

p. 449 (1970). R. B. King, Transition metal cluster compounds. Progr. Inorg. Chem. 15, 287 (1972). E. V. Leonova and N. S. Kochetkova, Chemical reactions of cobaltocene and nickelocene.

Usp. Khim. 42, 615 (1973). E. G. Perevalova and T. V. Nikitina, Reactions of bis(^cyclopentadienyl) transition

metal compounds. OrganometaL React. 4, 163 (1972). R. L. Pruett, Cyclopentadienyl and arene metal carbonyls. Prep. Inorg. React. 2, 187

(1965). M. Rosenblum, "Chemistry of the Iron Group Metallocenes: Ferrocene, Ruthenocene,

Osmocene," Part I. Wiley, New York, 1965.


A. Z. Rubezhov and S. P. Gubin, Ligand substitution in transition metal π-complexes. Advan. Organometal. Chem. 10, 347 (1972).

K. Schlögl, Stereochemistry of metallocenes. Top. Stereochem. 1, 39 (1967). D. W. Slocum and C. R. Ernst, Electronic effects in metallocenes and certain related

systems. Advan. Organometal Chem. 10, 79 (1972). R. Snaith and K. Wade, Carboranes and metallocarboranes. MPT Int. Rev. Sei., Inorg.

Chem. Ser. 1 1, 139 (1972). L. J. Todd, Transition metal carborane complexes. Advan. Organometal. Chem. 8, 87

(1970). L. J. Todd, Recent developments in the study of carboranes. Pure Appl. Chem. 30, 587

(1972). H. Werner, Ringliganden-Verdrängungsreaktionen von Aromaten-Metall-Kom-

plexen. Fortschr. Chem. Forsch. 28, 141 (1972).

The Organic Chemistry of Nickel || π-Cyclopentadienyl Nickel Complexes

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