1975 1683

Formation of Substituted Cyclohexadienyl Tricarbonylmanganese Com- plexes by Nucleophilic Addition Reactions of Functionally Substituted (3 - Arene)tricarbonylmanganese Cations By Peter 1. Pauson and John A. Segal, Department of Pure and App!ied Chemistry, University of Strathclyde,

Cyclohexadienyl and 6-exo-methyl- or -phenyl-cyclohexadienyl complexes bearing halogeno-, al koxy-, or dialkyl- amino-substituents in the 1 - or 2-positions are obtained by reaction of lithium tetrahydridoaluminate or methyl- or phenyl-lithium with the appropriately substituted (?-arene)tricaibonylmanganese salt. Directive effects in these nucleophilic additions are compared with those observed for arene complexes of iron and chromium.

Glasgow G1 1XL

PREPARATION of the first (3-arene)tricarbonylmanganese cations, (I), bearing functional substituents was reported in an earlier paper.l Amino- and alkoxy-substituted arene complexes of this type are readily formed from the chloro-compounds (I ; X = Cl) with amines or alkoxides, relatively weak nucleophiles whose addition to un- substituted ring positions is presumably readily revers- ible and hence ineffective. But, by analogy with the

+ MY LI)

tested previously in this type of complex and the present result (Table 1) clearly shows that it is significantly greater than that of methoxy. From the reaction of LiAlH, with the NIV-dimeth~-l-P-toluidine complex (I ; R = Me, X = Nhle,) we isolated sufficient of the product of ortho attack for identification, but nzeta attack yielding (111; R = ilfe, S = NMe,, Y = H) accounted for >95?/, of the total product. As in the previous studies

Y Y

+

behaviour of (3-arene) (3-cyclopentadieny1)iron cations, [(XH,C,R)Fe(C,H,)]+, addition would be expected to predominate over substitution even when X is a good leaving group provided that the nucleophile adds irreversibly. A brief study of reactions with lithium tetrahydridoaluminate and with methyl- and phenyl- lithium was undertaken to confirm this and to ascertain whether directive effects were similar to those found in our more extensive work in the iron series.2 Our con- clusions in that case, that directive effects are relatively weak so that, for example, the toluene complex suffered attack at o-, m-, and $-positions in an approximately statistical ratio and that inductive effects are relatively important, seem to apply similarly in the present series. Indeed selectivity is even lower. Thus chlorobenzene and 9-chlorotoluene complexes yielded the 1- and 2- substituted cyclohexadienyl complexes (I1 and 111, respectively; R = H or Me) in ca. 2 : 1 ratio [4 : 1 for the corresponding Fe(C,H,) derivatives] in harmony with the inductive effect predominating over the mesorneric effect for halogen atoms, while the reverse was true and approximately inverse proportions were obtained when methoxy-groups (X) exert the chief directing influence.

The effect of the dimethylamino-group had not been

there was little attack para to a halogen or methosy- group and the products, though probably detected in trace amounts, were not isolated pure and hence not identified unambiguously.

Determination of the ratio of ortho : rneta attack in the p-tolyl series was facilitated by the clearly separated 1H n.ni.r. signals of methyl groups attached to the 1- and 2-positions of such cyclohexadienyl complexes (c j . Table 2). Although slightly smaller than in the iron series, this separation is in the same direction and, like that of the protons directly attached to the ring, i t reflects the increasing s character in the series C1@) i C2(41< C3. The same trends have also been noted very recently in a series of dicarbonylnitrosyl(~-polymeth~~l- cyclohexadieny1)chromium c ~ m p l e x e s . ~ Assignments based on this pattern fully confirm structures deduced from the inultiplicities (and coupling constants) of the other lH n.m.r. signals. Where assignments had been possible, previously recorded data for the cyclohexa- dienyliron series agree well with our data for analogous manganese complexes. The order of elution on chroma- tography was also that previously noted2 in the iron series, cyclohexadienyl complexes with polar sub - stituents a t C2 moving faster than their C1 isomers.

I. U. Khand, P. L. Pauson, and W. E. Watts, J . Chevz. SOC.

N. G. Connelly and R. L. Kelly, J.C.S. Daltoz!, 1974, 2334. P. L. Pauson and J. A. Segal, J.C.S. Dalton, 1975, preceding (C), 1968, 2257, 2261 ; 1969, 116, 2024.

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J.C.S. Dalton The lower selectivity which we observe for nucleo-

philic attack on cations of the manganese series, (I), compared to those of the (7-arene) (7-cyclopentadieny1)- iron type may be seen as a reflection of the greater reactivity of the f0nner.l Conversely, the less reactive

phile used, this result appears to reflect a significant increase in selectivity compared to the two cationic complexes.

Finally we note that sodium tetrahydridoborate reacted with (I; R = H, X = C1) in an apparently much more

TABLE 1

Directive effects as ratio of products of meta to 0rth.o attack, (111) : (11) Salt (I) Nucleophile LiAlH, MeLi PhLi Li AlH, LiAlH, Ratio 31 : 69 26 : 74 * 39: 61 * 63 : 37 07 : 3

* The low yields obtained probably make these values less reliable than those for hydride attack.

R = Me, X = C1 R = Me, X = Cl R = Me, X = C1 R = H, X = OMe R = Me, X = NMe,

TABLE 2

Comples (11; R = X =

Y = H) (11; R = Me, x = c1,

Y = H) (111; R = Me,

X = c1,

lH S.ii1.r. data (2) a

H3 H? H4 H' HS endo-H exo-H Me Other Solvent 4.12(tt) 5.21 (t *) 5.21 (t *) 7.11 (t b, 7.11 (t b, ca. 7.36 8.98 CDCl,

(m) (br, d) 4.48 (dd) 5.00 (dd) 6.91 (m) 6.98 (m) ? 7.38 (m) ? 8.15 (s) CS,

4.09 (dd) 5.60 6.93 (m) 7.34 he 7.64c 8.46 (s) (br, d)

Y = H) (11; R = Y = 4.20 (dd) 4.73 (dd)

Me, X = Cl) (111; R = Y =

Me, X = C1)

x = c1, Y = Ph)

x = c1, Y = Ph)

x = c1, (br, dd)

X = c1, (br, dd)

(br, dd)

3.85 (dd)

(11; R = Me, 4.24 (dd) 4.60 (dd)

(111; R = Me, 3.90 (dd)

(11; R = HI 4.08 (dt) 4.48

Y = Ph) (111; R = HI 3.78

Y = Ph) 3.90

(11; R = Y = H, 4.43 (dt) 4.90 X = Br) (br, d)

X = OMe) (br, d)

= H , X = (br, dd) OMe)

(11; R = Y=H, 4.60 (dt)

(111; R = Y 4.28

6.17

5.08 (dd)

4.89 (t b,

4.81 (t &)

5.00 (t *)

5.42 (br, t)

(br, t) 5.26

5.25 (t b,

6.42 (dd) 6.91 (d, q) 8.16 (s)

8.38 (s)

8.13 (s)

6.42 (br) 7.18 (br14)

6.23 (dd) ? 5.75 (dd) ?

8.39 (s) 6.01 ca. 6.23d (br, d)

6.06 5.72 (dd) (distorted

dt) 6.00 ? 6.06 ? 6.36 (t b,

6.14 d ? 6.16 ? 6.53 (t b,

6.97 6.97 1.44 (m) - 7.15 (m) 7.07 7.37e

(4

7.28 7.28 7.28 7.82 \ J v (br, m) ?

(4

exo-Me (CDJ ZCO

exo-Me (CDJ ,co Ph ca. (CD,) 2CO

9.41 (d)

9.46 (d)

2.90 (m)

2.90 (m)

2.87 (m)

2.90 (m)

2.98 (m)

Ph ca. (CD3) Zco

Ph ca. (CD3) ZCo

Ph ta. (CD,) 2CO

Ph ca. CD,OD

cs,

OMe 6.67 (s) CS,

OMe 6.62 (s) CS,

(11; R = Me, 4.87 (dd) 7.18 (d) ? ca. 7.4 ? 6.81 ca. 7.43 8.15 (s) NMe,7.34 (s) CS,

(111; R = Me, 4.86 (dd) 5.58 7.72 (m) ? ca. 7.45 7.45 8.48 (s) NMe, 7.34 (s) CS,

(111; R = H, 4.75 (m) 5.00 (t) ca. 6.87 6.58 6.22 (t) NEt, 6.87, (CD3),C0

X = NMe,, (dd) ? (d) ? IT = H)

c---y----' (4 X = NMe,, (br, d)

X = NEt,, (br, t) 8.92 ( t ) ; Y = Ph)

Additional splitting. [J(AB) 12 Hz].

Y = H)

P h ca. 3.1

* Uncertain assignments are marked ' ? '. d Obscured by other peak.

Approximate centres corresponding to distorted AB quartet

tricarbonyl(q-ch1orobenzene)chromium adds the I-cyano- complex fashion than LiAlH,, so that competing 1-methylethyl anion ortho and meta to chlorine in the nucleophilic substitution and ring-metal cleavage lead ratio ca. 5 : 2 with no detectable (<2%) para attack as to the principal products, the unsubstituted cyclo- shown in a study published after the present work was

hindrance to ortho addition of the rather bulky nucleo- concluded. As there is likely to be significant steric 4 M. F. Semmelhack and H. T. Hall, J . Amey. Chenz. Sot.,

1974, ofj, 7092.

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1975

hexadienyl complex (11; R = X = Y = H) and the cluster [Mn,H (CO),,(B,H,)] .5

EXPERIMENTAL

All reactions were carried out under an atmosphere of dry oxygen-free nitrogen. 1.r. spectra were recorded on a Perkin-Elmer 257 grating instrument and were calibrated against deuterium chloride. lH N.m.r. spectra were obtained in sealed tubes on a Perkin-Elmer R 1 4 spectro- meter at 100 MHz. Mass spectra were recorded on an A.E.l . MS9 spectrometer. 1.r. and analytical data are collected in Table 3.

Reduction of (7-Arene)tricarbonylmanganese Hexafluoro-

Complex (11; R = Me, X = C1, Y = H) (111; R = Me, X = C1, Y = H) (11; R = Me, X = C1, Y = Ph) (111; R = Me, X = C1, Y = Ph) (11; R = H, X = C1, Y = Ph) (111; R = H, X = C1, Y = Ph) (11; R = Y = H, X = OMe) (111; R = Y = H, X = OMe) (111; R = Me, X = NMe,, Y = H) (11; R = Me, X = NMe,, Y = H) (111; R = H, X = NEt,, Y = Ph)

1.r. (cm-1)

v(C0) 2024 1957 1 2026 1956 1 2026 1959 1 2026 1966 1 2025 1958 1 2016 1959 1 2014 1938 1 2018 1944 1 2007 1928 1

1994 1 2009 1933 1

a In cyclohexane solution. From the mass

mixture (0.45 g) after chromatography on alumina was separated on silica plates with 6% diethyl ether-light petroleum giving two bands. Extraction of the silica, followed by sublimation at room temperature and 0.01 mmHg gave yellow crystals of tricarbonyl( 1--5-~~-2-methoxy- cyclohexadienyl)manganese, (111; R = H, X = OMe) (upper band) , and, as an oil, tricarbonyZ( 1-5-~-l-mefhoxycyclo- hexudienyl)manganese, (I1 ; R = H, X = OMe) (lower band).

(c) NN-Dimethyl-p-toluidine complex, (I; R = Me, X = NMe,). Reaction of the manganese cation (1.00 g) with LiAlH, (70 mg) as above gave the crude product (0.54 g, 82%). Chromatography on neutral alumina with 7% diethyl ether-light petroleum gave tricarbonyZ(l-6-r)-2- d~methylamino-5-methylcyclohexadienyl)manganese, (I11 ;

TABLE 3

and analytical data

943 945 947 947 948 961 927 936 918 911 921

M b

265.9544 (265.9542) 265.9544 (266.9642) 341.9835 (341.9865) 341.9835 (341.9856) 327.9700 (327.9699) 327.9689 (327.9699) 247.9853 (247.9882) 247.9877 (247.9882) 276.0348 (276.0356) 27 5.03 23 ( 2 76.0366) 365.0805 (365.0824)

Analyses A (%)

Found Calc. r- & C H N C H N

I -7

46.4 3.0 45.1 3.0 46.1 3.06 46.1 3.0 56.6 3.65 56.1 3.5 66.9 3.6 56.1 3.6

64.8 3.1 54.9 3.1 66.0 3.1 64.8 3.1 48.4 3.5 48.4 3.7 48.4 3.65 48.4 3.7 52.6 5.0 4.9 62.4 5.1 5.1 62.35 4.9 4.8 52.4 6.1 5.1 62.9 6.35 3.6 62.6 5.5 3.8

spectrum ; calculated values are given in parentheses.

phosphates, (I), with Lithium Tetrahydridoa1ztminate.-(a) Complex ( I ; R = Me, X = Cl). Lithium tetra- hydridoaluminate (60 mg) was added to a stirred suspension of complex (I; R = Me, X = C1) (1.00 g) in dry tetrahydrofuran (thf) (30 cm3) a t room temperature. The solid slowly dissolved giving an orange- yellow solution. Water (1 cm3) was added to destroy the excess of hydride and then the solvent was evaporated. The residue was extracted with light petroleum and the extracts were dried (R'gSO,) , filtered through Kieselguhr, and evaporated to give the crude product (0.553 g , 85%). This material was chromatographed on neutral alumina with light petroleum (b.p. 40-60 "C) as eluant. A portion (0.120 g) of the purified isomeric mixture (0.485 g) thus obtained was chromatographed on a preparative t .l.c. plate (20 x 40 mm) of fluorescent silica (Merck PF 254) using 37; diethyl ether-light petroleum. Two bands separated and were collected and washed with diethyl ether. The resulting solutions were evaporated and the residues sublimed a t 5 x mmHg.* The upper band gave tvicarbonyl( 1-5-~-2-chloro-5-methyZcyclohexadienyl)- manganese, (111; R = Me, X = C1) (26 mg), and the lower band gave tvicarbonyl( 1-5-3- 1-chloro-4-methylcyclohexa- dienyZ)nznnganese, (11; R = Me, X = C1) (55 mg). Further purification was effected by crystallization from pentane at

A similar The isomer

H. D. Kaesz, W. Fellmann, G. R. Wilkes, and L. F. Dahl,

-78 "C. (b) Anisole complex, ( I ; R = H, X = OMe).

* 1 mmHg z 13.6 x 9.8 Pa. reaction gave the crude product (0.50 g, 7976).

J . Amer. Chenz. SOL, 1965, 87, 2753.

K = Me, X = NMe,) (0.505 g), which was recrystallized from pentane a t -78 "C. Changing the eluant to 25% diethyl ether-light petroleum gave tricarbonyl( 1-5-7-1- dimethylami~to-4-methylcyclohexadienyl)maizganese (I1 ; R = Me, X = NMe,) (18 mg), which was recrystallized from benzene-n-heptane.

Reduction of Complex (I; R = H, X = C1) with Excess of Sodium Tetrahydridoborate.-Sodium tetrahydridoborate (0.25 g) was added over a period of 20 min to complex (I ; R = H, X = C1) (1.00 g) in 1,2-dimethoxyethane (30 cm3). The initial pale yellow solution rapidly became red. After 2 h water (100 cm3) was added and the aqueous solution was ex- tracted first with hexane (3 x 50 cm3) and then with diethyl ether (3 x 30 cm3). The yellow hexane extracts were dried (MgSO,) and evaporated to give crude tricarbonyl( 1-5-7- cyclohexadieny1)manganese (0.15 g) which was purified by chromatography on alumina and was identified by its i.r. and lH n.m.r. spectra. The red diethyl ether extracts were dried and evaporated to give a red crystalline material (0.08 g) which was identified as the cluster [Mn,H(CO),,- (B,H,)] by its i.r. and mass spectra [Found: m / e 473.8372. Calc. for C,,H,B,Mn,O,,' : (P') 473.83681. Successive loss of all 10 carbonyl groups (except P - CO) was observed without H loss, together with H and B losses after P - 6CO.

Reactions of Complexes (I) with 0rganoZithiums.-(a) (I; R = H, X = Cl) with phenyl-lithium. Phenyl-lithium (1.5 cm3 of a 2 . 1 5 ~ diethyl ether solution) was added to a stirred suspension of the complex (1.00 g) in thf (30 cm3) cooled to - 50 "C. After 5 min, dilute HPF, solution (1 cm3) was added and the mixture was allowed to warm to room temperature giving a clear orange solution. The solvent

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1686 J.C.S. Dalton was then evaporated and the yellow partly solid residue was extracted with benzene (2 x 20 cm3). The benzene extracts were dried (MgSO,) , filtered through Kieselguhr, and evaporated to give a pale oil which began to crystallize on standing. A portion (0.500 g ) of this crude product was chromatographed on two preparative t.1.c. plates using 4% diethyl ether-light petroleum as eluant. Two bands separated which were isolated as above. The upper band, after sublimation (60 "C, 0.01 mmHg), gave tricarb- onyl( 1-5-q-2-chZor0-6-exo-phenylcyclohexadienyl) manganese, (111; R = H, X = C1, Y = Ph) (0.172 g), and the lower band (70 "C, 0.0 1 mmHg) gave tricarbonyZ( 1-5-q- 1-chloro- 6-exo-phenylcyclohexadienyl)manganese, (I1 ; R = H, X = C1, Y = Ph) (0.141 g). Further purification was effected by crystallization from pentane a t -78 "C.

(b) Others. The reactions of phenyl- and methyl-lithium with (I; R = Me, X = C1) were carried o u t similarly but the products were obtained in lower yields, the crude products being contaminated with much hydrocarbon material. The reaction of phenyl-lithium with (I; R = H, X = NEt,) was carried out similarly and the tricarbonyl( 1-5-3-2-diethyl- amino-6-exo-~henylcyclohexadienyZ)manganese (I11 ; R = H, X = NEt,, Y = Ph), so formed was isolated by crystal- lization of the crude product from benzene-heptane.

We thank the S.R.C. for the award of a research fellow- ship (to J. A. s.), Dr. P. Bladon and his staff for spectra, and Mr. F. Daubney and his staff for microanalyses.

[6/146 Received, 22nd January, 19753

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