Synthesis of heptamethylindenyl rhodium(III) complexes: molecular structures of [(η 5 -C 9 Me 7...

Synthesis of heptamethylindenyl rhodium(lll) complexes: molecular structures of [ ( q 5 - ~ g ~ e , ) ~ h ~ ~ ( p - ~ ~ ) ] 2 and [ ( q 5 - ~ g ~ e , ) ~ h ( ~ ~ e 2 ~ h ) ~ ~ 2 ]

Ashok K. Kakkar, Graham Stringer, Nicholas J. Taylor, and Todd B. Marder

Abstract: The synthesis of a series of permethylindenyl (Ind*) rhodium(II1) complexes, [ ( r 15 -~9Me7)~h~1(p - CI)],, [ ( r 1 5 - ~ , ~ e 7 ) ~ h ~ ~ 1 , ] (L = PMe,, PMe,Ph, PPh,), and [(r15-C9Me7)Rh(PMe3)2Cl]+CI-, is reported. The structure of [ ( r15 -~ ,~e7 )~h~1(p -C l ) ] , (4) was determined, confirming the dimeric nature of the compound. Ruby red crystals of 4 are monoclinic, space group C2/c, with four molecules per unit cell of dimensions a = 18.598(5), b = 10.520(3), c = 17.376(3) A and P = 115.10(2)". The indenyl rings exhibit minimal distortion from perfect r15 coordination to the Rh centres. A single crystal X-ray structure determination of [ ( ~ l ~ - C,Me,)Rh(PMe,Ph)CI,] (6) indicates a more distorted ~l~-coordination of the indenyl ligand, with the auxiliary ligand having the greatest trans influence, namely, the PMe2Ph group, being trans to the indenyl ring junction C-C bond. Yellow prismatic crystals of 6 are orthorhombic, space group P2,2,2,, with four molecules per unit cell of dimensions a = 8.819(1), b = 15.303(3), c = 17.296(3) A. Key words: rhodium, indenyl, permethylindenyl, heptamethylindenyl, phosphine complex, X-ray structure.

RCsumC : On a effectuC la synth5se d'une strie de complexes permithylindCnyl(Ind*) rhodium(III), [($- C,Me7)RhCI(p-C1)]2, [(r15-~,~e7)RhLC12] (L = PMe,, PMe,Ph et PPh,), et [(r15-~9~e7)~h(~~e3),~1]+~1-. On a determine la structure du composC [ ( r 1 5 - ~ , ~ e 7 ) ~ h ~ ~ ( p - ~ ~ ) l , (4) et confirm6 la nature dim5re du composC. Les cristaux rubis du composC 4 sont monocliniques, groupe d'espace C2/c, avec quatre molCcules par motif de dimensions a = 18,598(5), b = 10,520(3) et c = 17,376(3) A et P = 115,10(2)". Les cycles indtnyles prisentent une distorsion minimale par rapport B une coordination r15 parfaite avec les centres Rh. Une dttermination de structure du [(r15-~,Me7)Rh(~Me,Ph)C1,] (6) indique, dans ce cas, qu'il existe une coordination r15 plus dCformCe du coordinat indCnyle avec le coordinat auxiliaire ayant la plus grande influence trans, le groupe PMezPh se trouvant trans par rapport B la liaison C-C de la jonction avec le cycle indinyle. Les cristaux jaunes, prismatiques, du composi 6 sont orthorhombiques, groupe d'espace P2,2,2,, avec quatre molCcules par motif de dimensions a = 8,819(1), b = 15,303(3) et c = 17,296(3) A. Mots cl6s : rhodium, indCnyle, permCthylindCnyle, heptamCthylindCnyl, complexe de phosphine, structure par diffraction des rayons X.

[Traduit par la rCdaction]

Introduction been prepared via mono-Cp* halide, Cp*MX,, precursors.3 In contrast, there are few reports (3-10) of metal 'c~m~lexes con-

he stron ly electron-donating pentameth~lc~clo~entadien~l taining the heptamethylindenyl ligand ([q5-C,M~,]-, Ind*). 5 ligand ([q -C5Me51-, Cp*) has received considerable attention This may, in part, be due to the lack of experimental details for in organometallic chemistry, and many useful reagents have the synthesis of the ligand in the original communication (3).

Received September 2, 1994.

This paper is dedicated to Professor William A.G. Graham on the occasion of his 65th birthday.

A.K. Kakkar,' G. Stringer, N.J. Taylor, and T.B. ~ a r d e r . ' Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada.

I Present address: Department of Chemistry, McGill University, Montreal, QC H3A 2K6. Author to whom correspondence may be addressed. Telephone: (5 19) 888-4582. Fax: (5 19) 746-0435. E-mail: [email protected]

We recently reported detailed preparative procedures for the synthesis of heptamethylindene, Ind*H, on both the 10 g (9) and 90 g (8) scales. Ind*H is reported to have a pK, of 27.4 in DMSO compared with values of 20.1 for indene, 26.1 for Cp*H, and 18.0 for cyclopentadiene (1 1). Thus, Ind* should have donor properties similar to, or even stronger than Cp", while maintaining the unusually high stoichiometric reactivity (12-14) and catalytic activity (15-17) associated with indenyl metal complexes. For example, kinetic studies (5, 10) on the

For a general review of Cp-type metal halide complexes see ref. 1. For original reports of the synthesis of [ C ~ * R ~ C I ( ~ - C I ) ] , and related studies see, for example, ref. 2.

Can. J . Chem. 73: 981-988 (1995). Printed in Canada 1 Imprimi au Canada

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Can. J. Chem. Vol. 73, 1995

substitution of CO by PR3 in a series of indenyl ring substi- tuted [ ( q 5 - ~ 9 ~ 7 - I , ~ e I , ) ~ h ( ~ 0 ) , 1 complexes indicate that the second-order rate constant for i ( 1 5 - ~ 9 ~ e 7 ) ~ h ( ~ ~ ) 2 ] (1) is ca. 150 X smaller than that for [(q -C9H,)Rh(CO:~,] (2) but ca. lo7 larger than that for [ ( q 5 - ~ p * ) ~ h ( ~ ~ ) , ] (3). The values of vco for complexes 1 and 3 are similar, and the average nonbonding d-orbital ionization energy (18) for 1 (7.93 eV) is slightly lower than that for 3 (8.12 eV). Interestingly, in the case of the sandwich complexes [(q5-L),M] (L = Cp*, Ind*; M = Fe, Cr, Co) PES and electrochemical studies (8) show that the Ind* ligand is a stronger donor than Cp* for M = Fe and Cr, but for M = Co, the first ionization energy was higher for the Ind* compound. It is also worth noting that X-ray crystallographic studies on [(q5-L),F~] (L = Ind, Ind*) (7), and [(q5- L ) R ~ ( ~ ~ - ~ , ~ - c o D ) ] (L = Ind, Ind*) (6b) showed no signifi- cant changes in the structural parameters describing metal - indenyl ring bonding upon permethylation.

As part of our continuing study of indenyl complexes, we have begun to examine the synthesis of Ind* complexes that can serve as basic starting materials for subsequent organometallic chemistry. We report herein the synthesis and structure of [ ( q 5 - ~ n d * ) ~ h ~ 1 ( p - ~ 1 ) ] 2 and its reactions with monodentate phosphine ligands.

Results and discussion

Preparation of [(q5-~9~e7)~h~l(p-~1~~]2(4) Complex 4 was prepared (Scheme 1) by adaptation of the procedure outlined (2d, e ) for the synthesis of [Cp*RhCl(p-Cl)], (2). Heptamethylindene and RhCl3.xH,O were heated in refluxing methanol for 24-48 h. Evaporation of the solvent and extraction into toluene gave the dark red compound 4, which was characterized by elemental analysis, NMR spectroscopy, and by single crystal X-ray diffraction. The solid state structure of 4 is shown in Fig. 1. A summary of the crystallographic data and parameters for data collection is presented in Table 1, and selected bond distances and angles are given in Table 2, together with those reported for [Cp*RhCl(p-Cl)], (2h). The final atomic coordinates for 4 are given in Table 3. The molecular structure of 4 indicates that the molecule exists as a dimer in the solid state, sitting on a centre of inversion, with two bridging chloride ligands, comparable to [Cp*RhCl(p-Cl)],. There are, however, differences in the lengths of the metalkhloride bonds in the two compounds. In [Cp*RhCl(p-Cl)],, the R h - C l distances are 2.465(1), 2.452(1), and 2.397(1) A for the two bridging and one terminal chloride, respectively, whereas the comparable distances for 4 are 2.394(1), 2.499(1), and 2.381(1) A, respectively. Thus, there is considerably more asymmetry in the bridging system of the Ind* compound. These bond lengths result in nonbonding Rh..Rhl distances of 3.1791(6) A for [Cp*RhCl(p-Cl)], and 3.612(1) A for 4. The yields of 4 were somewhat variable. Occasionally, the preparation of 4 yielded a toluene-insoluble orange-brown solid. It was found, however, that this material reacts with phosphines to yield the same products as does 4.

Reaction of [ ( q 5 - ~ 9 ~ e 7 ) ~ h ~ 1 ( p - ~ 1 ) ] 2 (4) with phosphines: preparation of [ ( q 5 - ~ , M e 7 ) ~ h ~ ~ 1 2 ] (L = PMe, (5), PMe2Ph (6), PPh, (7)

As is the case for the Cp* analogue (1,2), the bridging Rh-Cl

Fig. 1. The ORTEP diagram of the molecular structure of 4. Hydrogen atoms have been omitted for clarity.

CI1 Clla

bonds in complex 4 are easily cleaved by tertiary phosphines (Scheme 1) to form monomeric [ q 5 - ~ n d * ) ~ h ( ~ ~ 3 ) ~ 1 2 ] complexes in quantitative yields. These complexes were characterized by elemental analysis, 'H, I3c ( 'H ) , 3 1 ~ ( 'H) NMR spectroscopy for 5-7, and by a single crystal X-ray structure determination for 6. The solid state structure of 6 is shown in Fig. 2. A summary of the crystallographic data and parameters for data collection are presented in Table 1, and final atomic coordinates and selected bond lengths and angles for 6 are given in Tables 4 and 5.

It is well documented (6, 7, 19-23) that all [(q-inde- ny1)ML ] complexes show some degree of slipfold distortion

5" from q towards q 3 coordination in the ground state. Struc- tural characterization of many indenyl complexes indicates that the metal to carbon distances M-C,, M-C,, M-C3 are shorter than those to the bridgehead carbons (M-C,,, M- C,,). The degree of distortion in the solid state in these complexes has been discussed (6, 7, 19, 21) in terms of three parameters: (i) slip parameter (A), which we define as the difference in the average metal to carbon distances of C3,,,, and CIS, (A = d( (M-C,,,,) - (M-CI,3))); (ii) hinge angle (HA), which is the angle between normals to the least-squares planes defined by [CI, C,, C3] and [C,, C3, C3,, C,,]; and (iii) fold angle (FA), which is the angle between normals to least- square planes defined by [C,, C,, C3] and [C3,, C4, C5, C6, C,, C,,]. The values for these parameters range (6b, 7, 21) from 0.030 A (A), 2.5" (HA), 4.4" (FA) for "true" q5 complexes to 0.8 A (A), 28" (FA) for "true" q3 complexes, with intermedi- ate values of 0.11 - 0.42 A (A), 7-14" (HA), 6-13" (FA) observed for "distorted" complexes in which there is clearly some degree of bonding of the metal to C3,,,,. Other geometric parameters have also been used (20,22) to describe the distortions in indenyl and carboranyl complexes. The critical feature is the soft potential surface for distortions of the indenyl ring system that involve folding of the rings and changes in C - C bond lengths.

The values for the slipfold parameters for 4 are A = 0.087(5) A; FA = 5.0°, HA = 4.6". These values imply that

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Scheme 1.

Heptarnethylindene, Ind'H

'Y3

Table 1. X-ray crystal data for compounds [ ( q 5 - c , ~ e 7 ) ~ h c 1 ( ~ - Cl)], (4) and [Ind*Rh(PMe,Ph)Cl,] (6).

Table 2. A comparison of selected bond distances and angles for [ ( q 5 - ~ 9 ~ e 7 ) ~ h ~ 1 ( k - ~ 1 ) ] 2 , 4, and [Cp*RhCl(p-Cl], (2h).

4 Formula C32H42C1,R h2 FW 774.3 Crystal system Monoclinic a (A) 18.598(5) b (A) 10.520(3) c (A) 17.376(3) P ("1 115.10(2) v (A3) 3078.6(13) z 4

~ c a ~ c (g cm-)) 1.670 Space group C21c Crystal dimensions (mm) 0.1 10(110, TTO) x

0.070(1iO, 1iO) x 0. I 40(20 1, 201)

Temperature (K) 180 Radiation MoKa P (cm-l) 1 4.40 Data collection method 0

Max. 29 50.0 Scan speed (O m i d ) 2.44-19.53 Scan width (O). 1.50 No. of independent reflections 2733 No. of observed reflectionsa 21 13 Range for h 0-22 Range for k 0-12 Range for I -20-1 8 Final No 0.023 F(000) 1568 R ( % ) b 2.87 R, 2.78 In the last A-map

the highest peak (elA3) 0.62 the deepest hole (elA3) -0.40

G O F ~ 1.75

6 C24H32PC12Rh

525.34, Orthorhornbic

8.819(1), 15.303(3) 17.296(3) -

2360.7(8) 4

1.478

200 MoKa 10.15 0

60.0 2.93-29.3

1.20 3879 3546 0-12 0-2 1 0-24 0.150 1080 2.27 2.47

Rh ..... Rh' Rh-C1( 1 ) Rh-Cl(2) Rh-Cl(2A) Rh-C(1) Rh-C(2) Rh-C(3) Rh-C(3A) Rh-C(7A) Rh-Cl(2)-Rh' Cl(2)-Rh-Cl(2A)

there is very little distortion in this complex. In contrast, the values for the sl ipfold parameters for 6 are A = 0.154(3) A; FA = 8.8", HA = 7.2", which indicates a distorted 715 coordination of rhodium to the indenyl ring. Hence, the distortions observed in the d 8 - [ ( r l - ~ 9 ~ 7 ) ~ h ~ , ] complexes also persist for the d 6 - [ ( r l - ~ ~ 7 ) ~ h ~ 2 ~ ' ] systems. Similar findings were reported for d6-[(rl-~9~7)~r{~(~6~5)3)(H)][BF,] for which A = 0.185(8) A (20).

It has been shown (20, 22) that the indenyl ligand exhibits a conformational (i.e., rotational) preference in [(715-c9R7!- ML,L'] complexes. The arrangement about the metal centre 1s such that the ligand with the greatest trans influence prefers a position trans to the ring junction carbons. For example, in [(q-C,H,)Ir{P(C,H~),),(H):I[BF,] the hydride ligand, which has a greater trans influence than [P(C6H5)3], is trans to the C3a-7a bond in the solid state (20). A similar arrangement of ligands is observed in a number of other complexes, including a series of [ ( T 5 - ~ 9 ~ 7 ) ~ ~ ( q S - ~ 2 ~ 2 ~ 9 ~ 9 ) ] complexes (22), in which a cisoid arrangement of indenyl and carboranyl ligands is preferred. The consequence of having a ligand with a greater trans influence trans to C3,C7, is a reduction in the bonding between the metal and C3a,7a, which is reflected in increased M-C distances to C3a,7a. A more detailed examina- tion of the structure shown in Fig. 2 indicates that the PPhMe, ligand (which has a higher trans influence than chloride) is trans to the six-membered ring.

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Table 3. Atomic coordinates (xlOJ) and equivalent isotropic displacement coefficients (A2 x 1000) for [(q5-C,Me,)RhCl(p-CI)l2, (4).

Table 4. Atomic coordinates (xloJ) and equivalent isotropic displacement coefficients (A' x 1000) for [Ind*Rh(PMe,Ph)Cl,], (6)

"Equivalent isotropic U defined as one third of the trace of the orthogonalized U, tensor.

Fig. 2. The ORTEP diagram of the molecular structure of 6. Hydrogen atoms have been omitted for clarity.

The ring C-C distances in 4 and 6 are shown in Fig. 3. It is clear that the average C4-C,, C6-C, distances (1.3737) A) is shorter than the C,-C6 distance (1.442(7) A) in 4 by 0.067 A. The difference between these two distances is less in 6, at 0.041 A (1.387(5) A and 1.428(5) A for average (C4-C,, C6-C,) and C,--C6 distance, respectively), than in 4. From these data it can be inferred that there is a more localized diene-like structure for the six-membered ring in 4 than in 6. This trend is consistent with the slipfold parameters described above, and comparable to the trends observed in -q5 and -q3 bis(indeny1) metal complexes (7).

Formation of [ ( q 5 - ~ , ~ e , ) ~ h ( ~ ~ e , ) 2 ~ 1 ] [ ~ ~ - ] (8) Treatment of 4 with 4 equivalents of PMe3 results in the initial formation of an orange solution from which 8 precipitated in a quantitative yield. It was characterized by 'H, ' 3 ~ ( 1 ~ ) , and 3 1 ~ ( ' ~ 1, NMR spectroscopy, and by elemental analysis,

" Equivalent isotropic U defined as one third of the trace of the orthogonalized Uii tensor.

which indicate that 8 should be formulated as [(-q5- CgMe7)Rh(PMe3),C1][C1-1. The 3 1 ~ ( 'H J and I3c( ]HI NMR spectra showed obvious disparities from those for 5-7. The chemical shift of the phosphines in 8 is downfield by -18 ppm from that in 5-7. Carbons 1, 2, 3, 3a, and 7a also exhibit a downfield shift in the I3c NMR spectrum of 8. The value of J,,, in 8 is 7 Hz smaller than in 5, presumably reflecting the opposing effects of better donor ligands vs. increasing positive charge at rhodium, with the latter being more important.

Conclusion

In conclusion, we have prepared and structurally characterized heptamethylindenyl ([C9Me7-], Ind*) analogues of [Cp*RhCl(p-Cl)], and [Cp*Rh(PR,)CI,]. These complexes are important starting materials in light of the enhanced reactivity of indenyl metal complexes compared with their Cp counterparts.

Experimental section

General procedures All reactions were carried out under a nitrogen atmosphere in a glove. box, except for the synthesis of 4, which employed

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Table 5. Selected bond distances and angles for [Ind*Rh(PMe,Ph)Cl,], (6).

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standard Schlenk techniques. THF was dried and distilled from Na-benzophenone, and all deuterated solvents were freeze-pumpthaw degassed and distilled on a vacuum line. RhC13.3H,0 was obtained from Johnson Matthey Ltd., and the phosphineligands were obtained from Strem Chemicals and used as received. Heptamethylindene was prepared according to the published procedure (8a, 9). 'H, 13c( 'HI , and ,'P{ 'H) NMR spectra were recorded on Bruker AC200 or AM250 spectrometers. 'H and chemical shifts are reported in ppm relative to external TMS and referenced to CDC1, residual proton and carbon resonances, respectively; coupling constants are in Hz. Multiplicities are reported as (br) broad, (s) singlet, (d) doublet, (t) triplet, and (m) multiplet. chemical shifts are reported relative to the external standard H3P04.

Preparation of [ ( q 5 - ~ 9 ~ e 7 ) ~ h ~ 1 ( p - ~ 1 ) ] 2 (4) A mixture of heptamethylindene (C9Me,H, 260 mg, 1.2 mmol) and RhC1,-3H20 (250 mg, 0.95 mmol) in methanol (15 mL) and water (0.5 mL) was refluxed for 48 h. After removing the volatiles in vacuo, the dark red solid was washed with hexane (to remove excess heptamethylindene), and then extracted into toluene. On cooling to -40°C, compound 4 (276 mg, 67% yield) was obtained as a dark red solid. A single, dark ruby, polyhedral crystal suitable for X-ray diffraction was grown by slow evaporation of a CHC1, solution, which also produced analytically pure material. 'H NMR (CDCl,, 250 MHz), 6: 1.56 (s, 6H, CH3), 1.95 (s, 12H, CH,), 2.04 (s, 12H, CH,), 2.52 (s, 12H, CH,). ' 3 ~ { ' ~ ] NMR (CDCI,, 63 MHz), 6: 10.2, 13.3, 17.7, 18.4(s,CH3),81.0(brd,C,,,),95.1 (d,JRh-,=7Hz,C2), 102.5 (d, JRh, = 9 Hz, C3a,7a), 130.4, 143.5 (s, C4-,). Anal. calcd. for C3,H4,Rh2C14: C 49.64, H 5.47; found: C 49.78, H 5.53.

Preparation of [ ( q 5 - ~ , ~ e 7 ) ~ h ( P ~ e 3 ) ~ 1 2 ] (5) Compound 4 (32 mg, 0.04 mmol) was reacted with PMe, (9 FL, 0.08 mmol) in THF (10 mL) for 24 h. The solvent was removed in vacuo and the solid obtained was recrystallized from a THF-hexane mixture at -40°C. Complex 6 (38 mg, 99% yield) was obtained as an orange solid. 3 1 ~ ( ' ~ ] ~ ~ ~ (CDCl,, 81 MHz), 6: 26.7 (d, JRh-, = 145 Hz). 'H NMR (CDCl,, 200 MHz), 6: 1.58 (d, J,,= 12.5 Hz, 9H, PMe,), 1.92 (s, 9H, CH,), 2.16 (s, 6H, CH,), 2.53 (s, 6H, CH,). i 3 C { ' ~ ] NMR (CDCl,, 50 MHz), 6: 10.2 (s, 1 CH,), 13.3 (s, 2 CH,), 15.4 (d, J,, = 37 Hz, PMe,), 17.5 (br s, 4 CH,), 82.1 (d, JRh-, = 8 Hz, C,,,), 105.3 (s, C2), 11 1.2 (d, JRh-, = 3 Hz, C3a,7a), 130.2, 140.1 (s, C4-,). Anal. calcd. for C19H3,RhCl,P: C 49.27, H 6.53; found: C 49.37, H 6.89.

Preparation of [ ( q 5 - ~ 9 ~ e 7 ) ~ h ( ~ ~ e 2 ~ h ) ~ 1 2 ] (6) Compound 4 (35 mg, 0.05 mmol) was reacted with PPhMe, (13 pL, 0.09 mmol) in THF (10 mL) for 24 h. Following work- up as for 5, complex 6 (47 mg, 99% yield) was obtained as an orange solid. A single, pale yellow, prismatic crystal suitable for X-ray diffraction was grown by slow evaporation of a THF solution under N2 in a glove box. Recrystallization of the material from CH,Cl,-Et 0 results in the incorporation of CH,Cl, into the complex. "P{'H) NMR (CDCI,, 81 MHz); 6 28.6 (d, JRh-, = 149 Hz). 'H NMR (CDCl,, 200 MHz), 6: 1.32 (dd, Jp-, = 5.4 Hz, JRh-, = 1.7 HZ, 3H, CH,), 1.72 (s, 6H, CH,), 1.88 (dd, J,, = 13 Hz, JRh-, = 0.8 HZ, 6H, PPhMe,), 2.21 (d, Jp-, = 2 Hz, 6H, CH,), 2.56 (s, 6H, CH,), 7.46 (m, 3H,

PPhMe,), 7.95 (m, 2H, PPhMe,). ' 3 ~ ( ' ~ ) NMR (CDCl,, 50 MHz), 6: 8.7(s, 1 CH,), 13.0(s,2CH3), 14.4(d, Jp-,=39Hz, PPhMe,), 17.5 (br s, 4 CH,), 82.4 (d, J = 8 Hz, C,,,), 104.6 (s, C,), 111.0(s, C,,,,), 128.2 (d, Jp-, = lOHz, PPhMe,), 131.0 (d, Jpz = 10 Hz, PPhMe,), 131.2 (s, PPhMe,), 133.7 (s, PPhMe,), 130.2, 140.4 (s, C4-,). Anal. calcd. for (C,,H,,Rh- Cl,P),CH,Cl,: C 53.29, H 5.99; found: C 53.34, H 6.10.

Preparation of [ ( q 5 - ~ 9 ~ e 7 ) ~ h ( ~ ~ h 3 ) ~ 1 2 ] (7) Compound 4 (35 mg, 0.05 mmol) was reacted with PPh, (24 mg, 0.09 mmol) in THF (10 mL) for 24 h. Following work-up as for 5, complex 7 (58 mg, 99% yield) was obtained as an orange solid. 3 1 ~ ( ' ~ ] NMR (CDCl,, 81 MHz), 6: 40.7 (d, JRh-, = 157 Hz). 'H NMR (CDCI,, 200 MHz), 6: 1.24(dd, Jp-H = 4.6 HZ, JRh-, = 1.4 HZ, 3H, CH3), 1.60(~, 6H, CH3), 2.17 (t, J,, = JRh-, = 1.4 Hz, 6H, CH,), 2.56 (s, 6H, CH,), 7.25 (br s, 9H, P(C,H,),), 7.69 (m, 6H, P(C6H5),). ',c{'H) NMR (CDCl,, 50 MHz), 6: 9.22 (s, 1 CH,), 13.0 (s, 2 CH,), 17.8 (s, 2 CH,), 18.0 (s, 2 CH,), 84.7 (d, J = 8 Hz, C,,,), 105.6 (d, J = 7 Hz, C,), 109.8 (s, C,,,), 127.8 (v br s, P(C6H5),), 134.8 (d, Jp, = 9 HZ, P(C6H5),), 130.8, 141.4 (s, C,-,). Anal. calcd. for C3,H3,RhC1,P: C 62.88, H 5.59; found: C 62.89, H 5.49.

Preparation of [(q5-~,~e7)~h(P~e3)&l]+[~1-] (8) Compound 4 (35 mg, 0.05 mmol) was reacted with PMe, (21 pL, 0.2 mmol) in THF (10 mL) for 48 h. The resulting precip- itate was collected by filtration and dried in vacuo. Complex 8 (49 mg, 99% yield) was obtained as a yellow solid. 3 ' ~ { ' ~ ] NMR CDCl,, 81 MHz), 6: 8.7 (d, JRh-P = 138 Hz). 'H NMR (CDCl,, 200 MHz), 6: 1.58 (t, J= 5.7 Hz, 18H, PMe,), 2.10 (t, JP-, = 2 HZ, 9H, CH,), 2.12 (s, 6H, CH,), 2.49 (s, 6H, CH,). ' 3 C ( ' ~ ] NMR (CDCI,, 50 MHz), 6: 11.1 (s, 1 CH,), 13.9 (s, 2 CH,), 16.3 (m, 2 PMe,), 17.2 (s, 4 CH,), 88.9 (s, C,,,), 113.4 (s, C,), 116.4 (s, C,,,), 129.2, 141.4 (s, IT,-,). Anal. calcd. for C22H39RhCl,P,: C 49.00, H 7.29; found: C 49.12, H 7.40.

A summary of the crystal data for compounds 4 and 6 is given in Table 1. The data were collected on a Nicolet- Siemens R3mlV diffractometer equipped with graphite- monochromated Mo Ka radiation and a Nicolet LT2 low-temperature device. Accurate unit-cell parameters were derived from 25 general reflections well distributed in reciprocal space. Background measurements were made at the beginning and end of each scan for a total time equal to half the scan time. Crystal stability was monitored by measuring two standard reflections every 100 data; only statistical fluctuations (22%) were observed. Data were corrected for Lorentz and polarization effects and absorption (for 4, face indexed analyt- ical, transmission factors 0.8558-0.9 186; for 6, $-scan, semi- empirical ). The structures were solved by Patterson and Fou- rier techniques, and refined by full-matrix least-squares meth- ods using Siemens SHELXTL PLUS software (24), the function minimized being ~ w ( ~ F , I - I F , I ) ~ . Difference Fourier synthesis provided the location of all hydrogen atoms, which were included in the refinement with isotropic thermal parameters. A total of 194 and 382 parameters were refined for 4 and 6, respectively, with data:parameter ratios of 10.9: 1 and 9.3: 1. During the final cycles of refinement, a weighting scheme of the form w-' = a 2 ( ~ ) was included. Refinement of the inverse enantiomorph of 6 gave significantly higher R values, R = 2.55, R, = 2.79%. Scattering factors used, including the anom-

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Fig. 3. The C-C bond lengths (A) in Ind* rings of 4 and 6.

alous dispersion corrections for rhodium, were taken from the International Tables, Vol. 4 (25). Details of the crystal structure determination including complete tables of coordinates, bond distances and angles, and anisotropic thermal parameters have been deposited.4

Acknowledgments

We thank the Natural Sciences and Engineering Research Council of Canada and Imperial Oil Ltd. for support, Johnson Matthey Ltd. for a loan of rhodium chloride, and Professor William D. Jones (University of Rochester) for helpful discus- sions.

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A complete set of data may be purchased from: The Depository of Unpublished Data, Document Delivery, CISTI, National Research Council Canada, Ottawa, Canada ON K1A OS2.

Tables of bond lengths and angles and atomic coordinates have also been deposited with the Cambridge Crystallographic Data Centre, and can be obtained on request from The Director, Cambridge Crystallographic Data Centre, University Chemical Laboratory, 12 Union Road, Cambridge, CB2 lEZ, U.K.

Structure factor amplitudes are no longer being deposited and may be obtained directly from the author.

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Synthesis of heptamethylindenyl rhodium(III) complexes: molecular structures of [(η 5 -C 9 Me 7...

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