Synthesis, X-ray Structure, and Dynamic NMR Investigation of

Jul 1, 1995 - URA 403 CNRS, ENSCP, 11 rue P. et M. Curie, 75231 Paris Ckdex 05, France, ... chimie des mdtaux de transition, URA 419 CNRS, Universitt!...
0 downloads 0 Views 861KB Size
Download PDF
Organometallics 1995, 14,3802-3809

3802

Synthesis, X-ray Structure, and Dynamic NMR Investigation of Secondary Cymantrenyl- and Ferrocenylcarbenium Ions Stabilized by Heterobimetallic Cobalt-Molybdenum Clusters: [(MoCo(CO)&p) (p-Mn(CO)~C~CHC=CCH~)]+BFC and [(MoCO(CO)&p) (p-FcCHC=CCH3)IfBF4Mikhael A. Kondratenko,t>$Marie-Noelle Rager,' Jacqueline Vaissermann,s and Michel Gruselle"77 URA 403 CNRS, ENSCP, 11 rue P. et M . Curie, 75231 Paris Ckdex 05,France, Laboratoire de chimie des mdtaux de transition, U R A 419 CNRS, Universitt! P.et M . Curie, 4 place Jussieu, 75252 Paris Cddex 05,France, and Laboratory for Organometallic Stereochemistry, INEOS, 28 Vavilov Street, 11 7813 Moscow, Russian Federation Received February 10, 1995@

A solution-phase variable-temperature lH NMR investigation was performed on [(MoCo(CO)5Cp)@-Mn(CO)&pCHC=CCH3)]+BF4- (4), [(MoCo(CO)&p)@-FcCHC~CCH3)l+BF4-(5b),and [(MoCo(C ~ ) & ~ ) ( , M - F C C H C W ( C H ~ ) ~ C H ~ (5c). ) I + BThe F ~ NMR spectra were temperature dependent for 4 and for 5b,c. The fluxional process could be ascribed to simple rotation around the C+-cluster bond, In addition the X-ray structure of the complexes 4 and 5b were determined. In all cases it appears that the molybdenum plays a major role in the stabilization of the positive charge.

Introduction We have previously described the synthesis1 and structure2 of the stabilized carbenium ion [(MozCpz(CO)~)(P-FCCHC=C(CH~)~CH~)I+BF~(5a), where the

(4) h4L#Zo(CO),, n=O, M'Ln=Mn(CO), (5a) W=MoCp(CO),, n=2, MLn=FeCp (5b) &=Co(CO),, n=O, M'Ln=FeCp (5c) ML#2o(CO),, n=4, M'Ln=FeCp

carbon atom bearing the positive charge is simultaneously adjacent to a ferrocenyl group and an acetylenic [Mogl cluster. Our NMR results, together with molecular structure data, have shown the competition between the ferrocenyl group and the dimolybdenum acetylenic cluster toward stabilization of the adjacent carbenium center. While the dimetallic cluster is the main contributor to the stabilization and is the center of the fluxional behavior of the molecules, the ferrocenyl group also seems to participate with its n-electronic system located on the substituted ring. In this case, we demonstrated that in acetone-d6 solution, the cation 5a is fluxional even at room temperature. Cooling the * To whom correspondence should be addressed. URA 403 CNRS.

INEOS. URA 419 CNRS. @Abstractpublished in Advance ACS Abstracts, July 1, 1995. (1)Troitskaya, L. L.; Sokolov, V. I.; Bakhmutov, V. I.; Reutov, 0. A.; Gruselle, M.; Cordier, C.; Jaouen, G. J . Organomet. Chem. 1989, 364, 195. (2)Cordier, C.; Gruselle, M.; Vaissermann, J.; Troitskaya, L. L.; Bakhmutov, V. I.; Sokolov, V. I.; Jaouen, G. Organometallics 1992, 11, 3826. t

+

solution t o 248 K leads t o the observation of two diastereomers equilibrating slowly on the NMR time scale. Two possible processes were invoked to explain these results as follows. (1)A diastereomerization process of high activation energy was invoked, attributed to the following. (i) A suprafacial migration of the carbenium group occurs from one molybdenum t o the other. In this mechanism the configuration of the carbenium ion is unchanged while the configuration of the cluster is inverted. (ii)A simple rotation occurs around the C+-cluster bond. In this case the configuration of the cluster does not change but the carbenium center is inverted. (2) An enantiomerization process was invoked (called antarafacial migration of the carbenium center) perhaps lower in activation energy than the diastereomerization processes, in which the configuration of the cluster and that of the carbenium center are simultaneously changed. The stereochemical consequences of these mechanisms are shown in Figure 1. In recent years, a number of tri- and dimetallic cluster cations have been synthesized and their variabletemperature NMR spectra have been i n ~ e s t i g a t e d . ~ - ~ The mechanistic proposals described above are very useful for understanding the dynamic processes observed for these carbenium ions, but the mechanism which is actually operative has not been delineated. In one case,6simple rotation was demonstrated in the solid state for a tertiary homobinuclear [Moa1 cation. The major difficulty in this differentiation is the local symmetry of the [Moz] acetylenic cluster. (3) Edidin, R. T.; Norton, J. R.; Mislow, K. Organometallics 1982,

1 , 561.

(4) Padmanabhan, S.;Nicholas, K. M. J . Organonet. Chem. 1983,

268, C23.

0276-7333/95/2314-3802$09.0~/~ 0 1995 American Chemical Society

Carbenium Ions Stabilized by Clusters

Organometallics, Vol. 14,No. 8, 1995 3803

Enantiomerization occurring by antarafacial migration

M,=Co(C0)J'R3 or MoCp(CO), M?=CdCO), Figure 2. Determination of the configuration for a bimetallic acetylenic cluster.

Diastereomerization occurring by suprafacial migration or by rotation around the Cluster-C' bond Figure 1. Upon the building of a heterobinuclear complex by substitution of one of the ligands7 or by substitution of one metallic vertex by another metal,E,9an intrinsically chiral cluster is obtained, as shown in Figure 2. In these cases it is not possible t o observe an enantiomerization process, unless the cluster itself can isomerize. Nicholasl0 has reported an example of a carbenium ion stabilized by a chiral acetylenic cluster [Co~(C0)5PR31; in this case it was demonstrated that the formation of the cation starting from diastereomeric alcohols is diastereoselective and controlled by kinetic factors. The ratio between anti and syn isomers depends on the nature of the substituents at the carbenium center and in the acetylenic position. The carbenium ion is preferentially stabilized by the phosphine-substituted cobalt vertex. For secondary cations, the initial [antilsyn] ratio is in favor of the anti isomer. For carbenium substituents such as methyl or phenyl, the cation initially ( 5 ) (a) Sokolov, V. I.; Barinov, V. I.; Reutov, 0. A. Isu. Akad. Nauk SSR Ser. Khim. 1982,1992.(b) Meyer, A.;McCabe, D. J.; Curtis, D. Organometallics 1987, 6, 1491. (c) Barinov, V. I.; Reutov, 0. A.; Polyanov, A. V.; Yanovsky, A. I.; Struchkov, Yu.T.; Sokolov, V. I. J . Organomet. Chem. 1991, 418, C24. (d) Cordier, C.;Gruselle, M.; Jaouen, G.; Bakhmutov, V. I.; Galakhov, M. V.; Troitskaya, L. L.; Sokolov Organometallics 1991,10, 2303.(e) El Amouri, H.; Vaissermann, J.; Besace, Y.; Vollhardt, K. P. C.; Ball, G. E. Organometallics 1993,12,605.(0 El Amouri, H.; Besace, Y.; Vaissermann, J.; Jaouen, G.; McGlinchey, M. J. Organometallics 1994,13,4426. (g) El Hafa, H.; Cordier, C.; Gruselle, M.; Besace, Y.; McGlinchey, M. J.; Jaouen, G . Organometallics 1994,13, 5149. (6)Galakhov, M. V.; Bakhmutov, V. I.; Barinov, V. I. Magn. Reson. Chem. 1991,9,2972. (7)(a)Bradley, D. H.; Khan, M. A.; Nicholas, K. M. Organometallics 1989,8, 554.(b) D'Agostino, M. F.; Frampton, C. S.; McGlinchey, M. J. Organometallics 1990,9,2972. ( c ) Dunn, J. A,; Pauson, P. L. J . Organomet. Chem. 1991,419, 383. (d) Verdaguer, X.;Moyano, A.; Pericas, M. A.; Riera, A,; Bernardes, V.; Greene, A. E.; Alvarez, A. A.; Piniella, J. F. J . Am. Chem. Soc. 1994,116, 2153. (8)(a) McGlinchey, M. J.; Mlekuz, M.; Bougeard, P.; Sayer, B. G.; Marinetti, A,; Saillard, J. Y.; Jaouen, G. Can. J . Chem. 1983,61,1319 and references cited. (b)D'Agostino, M. F.; Frampton, C. S.;McGlinchey, M. J. J . Organomet. Chem. 1990,394,145. (9)Gruselle, M.; El Hafa, H.; Nikolski, M.; Jaouen, G.; Vaissermann, J.; Li, L.; Mc Glinchey, M. J. Organometallics 1993,12, 4917. (10)Bradley, D. H.; Khan, M. A.; Nicholas, K. M. OrganometaElics 1992,11, 2598.

formed isomerizes slowly to give a 1:l [antilsyn]mixture. For larger substituents such as isopropyl or tert-butyl, the anti isomer is predominant and does not isomerize (Figure 3). McGlinchepb has established the diastereoselective formation of a binuclear [W-Col stabilized secondary cation in solution, starting from diastereomerically pure secondary alcohol. No isomerization was observed from the mixture of initially formed cations, as shown in Scheme 1. For dicobalt hexacarbonyl propargylic secondary cations, Schreiberll has determined the synlanti isomer ratios by integration of the corresponding resonances in the lH NMR spectra. Structural assignments were based on NOE experiments. The results show that the syn isomer is in all cases the major isomer. The ratio synlanti depends on the bulkiness of the carbenium and alkynyl substituents (Figure 4). The equilibration between syn and anti isomers occurs even a t low temperature and is dependent on the R1 and RZ substituents for a secondary cation. These results are suggestive of thermodynamic control in the syn:anti ratio, while those obtained by NicholaslO result initially from kinetic control. In our own experimentsg in the field of heterobimetallic [Mo-Col clusters, we have prepared some stabilized cations and we have determined their structures. In all cases the carbenium center interacts with the molybdenum atom rather than cobalt as shown in Figure 5, and we do not observe isomerization of the cluster core. On the basis of these earlier results we report here on the fluxional processes observed for carbenium ions 4 and 5b,c, which possess a chiral cluster in the a position.

Results and Discussion Synthesis of 4 and 5b,c. The carbenium ions 4 and 5b,c were obtained as depicted in Scheme 2. Starting from either of the pure diastereomeric alcohols of [q2,q2(l-cymantrenyl-2-butyn-l-ol)(CoMoCp(C0)5)3 (3a or 3b), we obtain at room temperature the same lH and 13C NMR spectra in CHzClz solution attributed to [(MoCo(CO)5Cp&-Mn(C0)3CpCHC~CHdl+BF4(4). The situation is the same for [(MoCo(CO)sCp)@-FcCHC=CCH3)]+BF4- (5b) and [(MoCo(CO)&p)@-FcCHC=C(CH2)4CH3)lfBF4- (5c). The cations 4 and 5b,c were completely identified by spectroscopictechniques (NMR, IR) and by elemental analysis. (11)Schreiber, S. L.;Klimas, M. T.; Sammakia, T. J. J . Am. Chem. SOC.1987,109,5749.

Kondratenko et al.

3804 Organometallics, Vol. 14, No. 8, 1995

H-&

................... ,Cu(Co~2PPh,

RI CdC0)3

R1 R2 Initial ratio antihyn 8:I

H CH3 CH3 CH3 H tBu

7: I >20:1

Figure 3. Diastereoselective formation of stabilized [Co-CoPPhs] carbenium ions from a pure diastereomeric alcohol. Scheme 1 H

H .,-)'

These two diastereomeric cations formed in a 2/1 ratio do not isomerize in solution

Catiori syn

RI=H RI=Me RI=SiMe, RI=SiMe, RI=SiMe,

195:5

Figure 4. Synlanti diastereoselective formation of [ C O ~ ] stabilized carbenium ions as a function of R1 apd R2. Figure 5. View of the [(2-propynylbornyl)Mo(CO)~CpCo[~2,~3-(l-cymantrenyl-2-butyn-l-ylium)(Coz(CO)s)l(CO)3]+cation. BF4 ( 6 ) was obtained from [Cod complexed alcohol (2) in ether solution by the action of H B F a t 2 0 . A greenlS*clusterS*, which conforms with an anti configuration brown solid precipitates. After being washed several using the Nicholas's formalism. In each case the times with ether, the powder was dissolved in CDzClz carbenium center leans toward the molybdenum vertex. and its NMR spectrum was recorded. Surprisingly the The distances between Cf and Mo are 2.66(1) and product formed was identified as an ethoxy complex (7) 2.726(4)A for 4 and 5b,respectively. For 4 the distance resulting from an attack of the ether oxygen on the is similar compared to other secondary carbenium ions carbenium center (Scheme 3). stabilized by homo4Mozl acetylenic clusters;12a for Description of the Structures. The X-ray crystal example the C+-Mo distance was 2.63 A for 5a.2 For structures were performed using single crystals of 4 and 5b the result is close t o those found for a tertiary 5b obtained by the diffusion technique (Et20-CH~C12). cation.12b"he molybdenum-cobalt, cobalt-carbon, and Crystal data, atomic coordinates, and selected intermolybdenum-carbon distances within the tetrahedral atomic distances are reported in Tables 1-3 and 4-6, cluster are 2.715, 1.95 (average), 2.15 (average) A and respectively, for 4 and 5b. CAMERON views are shown (12)(a) Gruselle, M.; Cordier, C.; Salmain, M.; El h o u r i , H.; in Figure 6. The CAMERON views presented in Figure Guerin, C.; Vaissermann, J.; Jaouen, G. Organometallics 1990,9,2993. 6 reveal that the two structures are very similar. The (b) Le Berre-Cosquer, N.; Kergoat, R.; L'haridon, P. Organometallics relative configurations of the two chiral elements are 1992, 11, 721.

Carbenium Ions Stabilized by Clusters Scheme 2. Synthetic Pathway to the Carbenium Ions 4 and 5b,c CH3CCMgBr+ JMn(CO),JC,H,CHO

1

[Mn(CO), JC,H,CH(OH)CCCH,

1

coz~co), IIMn(CO)31C5H4CH(OH)CCCH, IICO~(CO)~I I NaMoCp(CO),

I

[IMn(CO),JC,H4CH(OH)CCCH3IICOMO(CO)~I I

1

HBF4

[ [ Mn(CO),]C5H,CHCCCH,IICoM~(CO),I IBF,

Scheme 3. Reaction of the Carbenium Ion 6 with Diethyl Ether

Organometallics, Vol. 14, No. 8, 1995 3805 Table 2. Selected Interatomic Distances (A) and Bond Angles (deg) for [C22HlsOsMnCoMol(BFd Mo(l)-Co(l) Mo(l)-C(3) Mo(l)-C(12) Mo(l)-C(14) Mo(l)-C(16) Mo(l)-C(17) Co(l)-C(2) Co(l)-c(18) Co(1)-C( 19) Co(l)-C(20) Mn(l)-C(21) Mn( 1)-C(23) Mn( 1)-C(25) Mn(l)-C(26) Mn(l)-C(27) Mn(l)-C(28) C(1)-C(2) C(3)-C(4) C(16)-Mo(l)-C(17)

2.715(2) 2.11(1) 2.28(1) 2.34(1) 2.03(1) 2.01(1) 1.88(1) 1.80(1) 1.75(2) 1.85(2) 2.14(1) 2.13( 1) 2.13( 1) 1.78(1) 1.79(2) 1.77(1) 1.39(1) 1.50(2) 82.3(5)

Mo(l)-C(2) Mo(l)-C(ll) Mo(l)-C(13) Mo(l)-C(15) 0(16)-C(16) 0(17)-C(17) CO(l)-C(3) 0(18)-C(18) 0(19)-C(19) 0(20)-C(20) Mn(l)-C(22) Mn(1)- C(24)

2.22(1) 2.31(1) 2.28(1) 2.36(1) 1.11(1) 1.14(1) 1.98(1) 1.14(2) 1.16(2) 1.10(2) 2.12(1) 2.14(1)

0(26)-C(26) 0(27)-C(27) 0(28)-C(28) C(2)-C(3) C(l)-C(21)

1.15(2) 1.15(2) 1.14(1) 1.36(1) 1.45(1)

Mo(l)-C(16)-0(16) Mo(l)-C(17)-0(17) 102.3(7) CO(l)-C(l8)-0(18) 103.3(7) CO(l)-C(19)-0(19) 98.1(7) C0(l)-C(20)-0(20) 91.8(8) Mn(l)-C(26)-0(26) 91.6(7) Mn(l)-C(27)-0(27) 90.9(6) Mn(l)-C(28)-0(28) 127.4(11) C(l)-C(2)-C(3) 133.8(12)

177.1(12) 175.1(11) 179.3(13) 176.6(16) 175.9(17) 178.3(17) 179.8(16) 178.0(13) 133.4(11)

C(18)-Co(l)-C(19) C(18)-C0(l)-C(20) C(19)-C0(l)-C(20) C(26)-Mn(l)-C(27) Table 1. Crystal Data for [C~~HI~O~M~COMO](BF~) C(26)-Mn(l)-C(28) C(27)-Mn(l)-C(28) (4) C(2)-C(l)-C(21) fw 701.95 C(2)-C(3)-C(4) a (A) 8.998(4) b (A) 9.975(4) Table 3. Fractional Parameters for c (A, 14.916(5) [CzzHiaOeMnCoMol(BF~) a (deg) 82.09(3) p (deg) 77.82(3) atom xla Yfb ZIC U(eq) (A? 78.1393) 0.1425(1) 0.19118(9) 0.15726(7) 0.0370 ; l # 1274(12) 0.0512 0.2728(2) 0.1834(2) 0.3153(1) z 2 0.4889(2) -0.2502(2) 0.3563(1) 0.0417 cryst system teclinic -0.111(1) 0.030(1) 0.0803 0.1372(8) P1 space group -0.144(1) 0.4327(9) 0.0739 16.49 0.1646(7) linear abs coeff ,u (em-') 0.503(1) 0.316(1) 0.0876 0.2509(8) density e (g cm3) 1.82 0.160(2) 0.218(2) 0.5142(9) 0.1175 diffractometer CAD4 Enraf-Nonius -0.007(2) 0.552(1) 0.1016 Mo Ka (A = 0.710 69 A) 0.31 1(1) radiation -0.521(1) 0.665(2) 0.1076 0.4069(9) scan type w12e -0.349(2) 0.195(2) 0.1086 0.4160(9) 0.8 0.345 tn e scan range (deg) 0.0789 -0.162(1) 0.469(1) 0.5369(6) e limits (deg) 1-28 -0.031(1) 0.249(1) 0.2617(7) 0.0448 temp of measmnt room temp 0.173( 1) 0.092( 1) -11, 11; -13, 13; 0, 19 0.2965(7) 0.0449 octants collcd 0.030(1) 0.169(1) 0.2959(8) 0.0458 6369 no. of data collcd -0.128(2) 0.158(1) 0.0642 6138 0.3518(9) no. of unique data collcd 0.396(1) 0.152( 1) 0.0575 0.0811(8) no. of unique data 3084, (FJ2 > 3u(FJ2 0.308(2) 0.087(1) 0.0601 0.039(1) used for refinement 0.202(2) 0.181(2) 0.0627 0.0017(9) R(int) 1.47 0.310(1) 0.0623 0.226(2) 0.0149(9) 0.0629 R = IllFot - IFclIElFol 0.344(2) 0.293(1) 0.0642(9) 0.0554 0.0699, w = 1.0 Rw = Z~(lFol- IFc1)2E~Fo2 -0.020(2) 0.084(1) 0.0590 0.1457(9) DIFABS (min = 0.578, abs coir -0.036(1) 0.349(1) 0.1595(8) 0.0499 max = 1.545 0.379(2) 0.300(1) 0.0605 0.2753(9) extinction param ( x 10-6) no 0.243(2) 0.0765 0.172(2) 0.435(1) 3.29 goodness of fit s 0.068(2) 0.450(2) 0.0741 0.311(1) 343 no. of variables -0.091(1) 0.0425 0.412(1) 0.2550(7) Aemln(elA3) -0.93 -0.215(1) 0.484(2) 0.2132(8) 0.0543 Aemax(elA3) 1.84 -0.245(1) 0.638(2) 0.2245(9) 0.0609 2.715, 1.94 (average), and 2.16 A (average) for 4 and -0.146(1) 0.665( 1) 0.2745(9) 0.0597 5b, respectively. These values lie within the normal 0.523( 1) -0.050(1) 0.2952(9) 0.0527 range for [Co-Mol clusters13 of this type. Finally we 0.0771 -0.414(2) 0.596(2) 0.388( 1) 0.0707 -0.310(2) 0.393(1) 0.310(2) note that all the CO ligands are terminally bound. 0.0547 0.4663(8) 0.474(2) -0.196( 1) NMR Spectra. The lH and 13CNMR spectra of the 0.0931 0.686(2) 0.080(3) 0.194(4) starting complexed diastereomeric alcohols 3a and 3b 0.1183 0.625(1) 0.058(1) 0.099(1) are consistent with the presence of two chiral elements 0.1479 0.606(1) 0.113(1) 0.306(2) 0.2023 0.788(2) 0.123(2) 0.135(3) in the molecules. For the homobinuclear [Cozl complex 0.3042 0.742(4) O.OOl(2) 0.268(3) 2, the spectra are consistent with the presence of one

+

chiral element. (13)Bailey, W. I., Jr.; Chisholm, M. H.; Cotton, F. A.; Rankin, L. A. J.Am. Chem. SOC.1978,100, 5764.

Protonation of 2 in CDzClz solution with HBFdEt20 leads to the observation of a new IH NMR spectrum attributable to the carbenium ion 6 on the following

Kondratenko et al.

3006 Organometallics, Vol. 14, No. 8, 1995

Table 6. Fractional Parameters for [CMHI~O~F~COMOI(BF~)

Table 4. Crystal Data for [C~Hl,306FeCoMoI (BFd (5b)

z

683.9 8.386(2) 10.272(3) 15.657(3) 94.35(2) 103.76(2) 102.74(2) 1266 z triclinic

atom Mo(1) Co(1) Fe(1) O(16)

n

cryst system space group linear abs coeff p (cm-l) density 4 (g cm3) diffractometer radiation scan type scan range (deg) -9 limits (deg) temp of measmnt octants collcd no. of data collcd no. of unique data collcd no. of unique data used for refinement R(int) R = XI I F o I - F e l I E I F o I R w = ZW(l F o l - IF1)*EwFo2 abs corr extinction param ( x 10-6) goodness of fits no. of variables A e m i n (e1A3) A e m a x (elA3)

Pi 17.5 1.79 Philips PW 1100 Mo Ka (A = 0.710 69 A) w129 1.1 0.345 tn 0 2-25 room temp -9, 9; -12, 12; 0, 18 4620 4416 3634, (F,J2> ~ U ( F , ) ~

+

1.42 0.0306 0.0322, w = 1.0 DIFABS (min = 0.86, max = 1.15) 34 0.57 390 -0.57 1.00

Table 5. Selected Interatomic Distances (A)and Angles (deg) for [C~H~e0sFeCoMol(BF4) Mo(l)-Co(l) Mo(1)-c(3) Mo(l)-C(12) Mo(l)-C(14) Mo(l)-C(16) Mo(l)-C(17) Co(l)-C(2)

c0(l)-c(18) Co(l)-C(19) C0(l)-C(20) Fe(l)-C(21) Fe(l)-C(23) Fe(l)-C(25) Fe(l)-C(27) Fe(l)-C(29)

2.7150(7) 2.125(4) 2.315(5) 2.363(5) 2.020(5) 2.021(5) 1.912(4) 1.812(5) 1.832(5) 1.785(6) 2.032(4) 2.059(5) 2.034(4) 2.024(7) 2.031(6)

Mo(l)-C(2) Mo(l)-C(11) Mo(l)-C(13) Mo(l)-C(15) 0(16)-C(16) 0(17)-C(17) co(l)-c(3) 0(18)-C(18) 0(19)-C(19) 0(20)-C(20) Fe(l)-C(22) Fe(l)-C(24) Fe(l)-C(26) Fe(l)-C(28) Fe(l)-C(30)

2.229(4) 2.287(5) 2.353(5) 2.318(5) 1.128(6) 1.130(5) 1.982(4) 1.133(6) 1.119(6) 1.125(6) 2.033(5) 2.056(5) 2.040(7) 2.022(6) 2.027(6)

C(16)-Mo(l)-C(17)

84.3(2) Mo(l)-C(16)-0(16)

177.6(4)

C(l8)-C0(l)-C(20) C(19)-C0( 1)-C(20) C(2)-C(l)-C(21) C(4)-C(3)-C(2)

101.9(3) CO(l)-C(19)-0(19) 100.6(2) C0(l)-C(20)-0(20) 125.6(4) C(3)-C(2)-C(l) 134.3(4)

175.6(5) 175.8(5) 140.2(4)

basis: disappearance of the hydroxyl proton, HI shifts from 5.49 to 7.50 ppm, HcP shifis from respectively 5.00-4.76 and 4.74-4.71 ppm to 5.52 and 5.13 ppm, H3 shifts from 2.64t o 3.03 ppm. These downfield shifts are suggestive of charge delocalization onto the [ C O ~ ] cluster and the cymantrene moieties. For carbenium ions 4 and 5b,c, all the lH NMR signals are shifted downfield compared to the starting alcohols. At room temperature, for example, the CpMo signals are shifted from 5.46-5.45 t o 5.67 ppm, 4.86-4.92 to 5.47 ppm, and 4.89-4.86 t o 5.43 ppm, respectively, for 4 and 5b,c. At room temperature the lH NMR spectrum for 4

O(17) O(18) O(19) O(20) C(1) C(2) C(3) C(4) C(11) C(12) C(13) C(14) (215) C(16) C(17) C(18) C(19) C(20) C(21) C(22) C(23) C(24) C(25) C(26) C(27) C(28) C(29) C(30) B(1) F(1) F(2) F(3) F(4)

xla

0.10411(5) 0.14402(8) 0.43883(8) -0.1670(5) -0.1967(5) 0.4995(5) -0.0513(6) 0.1483(8) 0.2131(6) 0.1227(5) -0.0310(5) -0.2085(7) 0.2931(7) 0.1849(7) 0.2099(7) 0.3362(6) 0.3875(6) -0.0692(6) -0.0854(6) 0.3621(7) 0.0282(6) 0.1420(8) 0.3875(6) 0.4874(7) 0.6414(7) 0.6410(6) 0.4856(6) 0.293(1) 0.448(1) 0.473(1) 0.331(1) 0.2190(9) 0.807(1) 0.745(1) 0.8999(9) 0.6858(7) 0.9144(6)

Yfb 0.75113(3) 0.63024(6) 1.12168(6) 0.9115(4) 0.4998(3) 0.6289(5) 0.3508(4) 0.6433(6) 0.9411(4) 0.8109(4) 0.7253(4) 0.7068(7) 0.9018(5) 0.8142(6) 0.6842(5) 0.6907(5) 0.8251(5) 0.8556(5) 0.5881(4) 0.6295(5) 0.4555(5) 0.6339(6) 0.9969(4) 1.1279(5) 1.1536(5) 1.0427(5) 0.9457(5) 1.0892(8) 1.170(1) 1.2839(8) 1.2752(9) 1.153(1) 0.7053(7) 0.757(1) 0.8187(6) 0.6387(4) 0.6346(4)

zlc

0.84852(2) 0.69733(4) 0.65976(4) 0.8691(3) 0.8377(3) 0.7754(3) 0.6881(3) 0.5130(3) 0.7489(3) 0.7166(3) 0.7127(3) 0.6562(4) 0.9621(3) 1.007(3) 0.9869(3) 0.9405(3) 0.9252(3) 0.8602(3) 0.8433(3) 0.7473(3) 0.6935(3) 0.5833(4) 0.7497(3) 0.7937(3) 0.7698(3) 0.7106(3) 0.6976(3) 0.5320(5) 0.5378(5) 0.5946(7) 0.6255(6) 0.5871(6) 0.0931(6) 0.0250(7) 0.1459(7) 0.1258(4) 0.0817(4)

u(eq) (A2) 0.0276 0.0342 0.0356 0.0587 0.0534 0.0659 0.0663 0.0903 0.0347 0.0314 0.0331 0.0492 0.0456 0.0479 0.0458 0.0436 0.0440 0.0436 0.0370 0.0459 0.0439 0.0573 0.0349 0.0437 0.0485 0.0433 0.0382 0.0780 0.0725 0.0721 0.0790 0.0720 0.0611 0.1982 0.1607 0.1078 0.0977

indicates a fluxional process in the intermediate exchange regime. All the signals are broadened. The situation is not as clear for 5b and 5c but in these cases the HIsignal is slightly broadened. The spectra of the carbenium ions 4 and 5b,c in CDzClz are temperature dependent, and this is best illustrated from the behavior of HI and H4 (Figure 7). The evolution observed for the other protons is reported in Table 7. It is clear that the evolution of the spectra, for these protons, from one signal to two signals, different in intensity, reveals the formation of two distinct diastereomers in the ratio 90110 and 9515, respectively, for 4 and 5b. Protons HIin the less populated diastereomers of 4 and 5b have resonances shown to be hardly shifted toward higher field that can be well compared in Table 8 with the data reported for the related [(MozCpz(CO)e)It seems HCCCH(CHs)I+secondary carbenium to be obvious that the diastereomeric chemical shift differences in tables 7 and 8 observed for protons bound t o the carbenium centers are caused by the different relative orientations of HI and the metal-metal bonds which have been correctly deduced for cation [(MozCpz(C0)4)HCCCH(CH3)]+from the solution and solid NMR data.14 In addition it has been found that the less populated diastereomer of this cation exists only in solution whereas the structure of the more populated diastereomer corresponds to the solid state structure.14 Thus these data allow us t o propose that the more populated diastereomers of 4 and 5 b have the configurations found in the solid state. (14)Galakhov, M. V.; Bakhmutov, V. I.; Barinov, I. V.; Reutov, 0. A. J. Organomet. Chem. 1991, 421, 65.

Carbenium Ions Stabilized by Clusters

Organometallics, Vol. 14,No. 8,1995 3807

12.0 f 1 kcal-mol-l, respectively, for 4 and 5b. This result is close to that found for the diastereomerization process in the case of a secondary stabilized [Mozl carbenium ion.2 These results show that the rotation around the C+A G * 2 5 3 ~=

cluster bond is not as high in energy as postulated previously16and can explain the isomerization processes observed even at room temperature for secondary stabilized [Mz]carbenium ions.

Conclusion

P (4)

Our NMR results and molecular structure data show the major role of the molybdenum atom in the stabilization of its adjacent carbenium center concurrently bonded t o cobalt, iron, or manganese metallic atoms. In one case the fluxional process observed in the NMR spectra can be clearly attributed to a simple rotation around the C+-cluster bond. It seems that the isomerization of carbenium ions stabilized by homo- or heterobimetallic clusters is the consequence of two elementary processes which are (1)the rotation around the C+cluster bond and (2) the antarafacial migration of the carbenium center from one metallic atom to the other and that the C+-cluster rotation can occur a t lower energy.

Experimental Section All reactions were carried out under a n inert atmosphere using standard Schlenk techniques. Solvents were distilled before use, Et20 and THF from Na-benzophenone and CHZClz from CaHz. The NMR spectra (6) were recorded in solution on Bruker AM250 and AC200 spectrometers, and IR on a Bomem IR-FT. Analyses were provided by “le service regional de microanalyse de l’Universite Pierre et Marie Curie, Paris”. X-ray Data for 4 and 5b. X-ray-quality crystals of the carbenium ion 4 and 5b were obtained by the diffusion technique (Et20-CHZClz). Intensity data were collected a t room temperature on a n Enraf-Nonius CAD4 diffractometer for compound 4 and on a Philips PW 1100 diffractometer for 5b using Mo Ka radiation. Accurate cell dimensions and orientation matrices were obtained from least-squares refinements of the setting angles of 25 well-defined reflections. No decay in the intensities of two standard reflections was observed during the course of data collection. The usual corrections for Lorentz and polarization effects were applied. Computations were performed by using the PC version of CRYSTALS.17 Scattering factors and corrections for anomalous dispersion were taken from ref 18. The structures were resolved by direct methods SHELXSlg and refined by least squares with anisotropic thermal parameters for all nonhydrogen atoms. For compound 4 hydrogen atoms were introduced as fixed contributors in theoretical positions and their coordinates were recalculated after each refinement. For compound 5b hydrogen atoms were located on a Fourier (15)Martin, M. L.; Martin, G. J.; Delpuech, J. J. Practical NMR Spectroscopy (Dynamic NMR Experiments); Heyden and Son: London,

Figure 6. CAMERON view for 4 a n d 6b. In the case of the carbenium ions 4 and 5b, the formation of two diastereomers equilibrating slowly on the N M R time scale is clearly a consequence of a slowing down of the rotational process around the (?-cluster bond. The energy associated with this process is calculated15 as hG*zs3~= 13.3 f 1 kcalmol-’ and

1981. (16) (a) Schilling, B. E. R.; Hoffmann, R. J.Am. Chem. SOC.1978, 100,6274. (b)Schilling, B. E. R.; Hoffmann, R. J . Am. Chem. SOC.1979, 101, 5764. ( c ) Girard, L.; Lock, P. E.; El h o u r i , H.; McGlinchey, M. J. J . Organomet. Chem. 1994, 478, 189. (17) Watkin, D. J.;Carruthers, J. R.; Betteridge, P. W. Crystals User Guide; Chemical Crystallography Laboratory; University of Oxford: Oxford, U.K., 1988. (18)International Tables for X-ray Crystallography; Kynoch Press: Birmingham, U.K., 1974; Vol. IV. (19) Sheldrick, G . M. SHELXS-86Program for Crystal Structure Solution, University of Gottingen, 1986.

Organometallics, Vol. 14,No. 8, 1995

3808

, - - ( . , . , , , . , . , . 0 2

0.0

7.0

7.6

PPY

7.4

Kondratenko et al.

r-7

1.2

.

I

7.0

PPY

t

2.0

.

r

-

-

0.6

r

v

0.4

,

8.2 PPU

,

I

8.0

,

I

7.0

.

r----r--

7.0

PPn

2.0

Figure 7. Sections of the variable-temperature 250 MHz 'H NMR spectra of 4 a n d 5b, showing t h e peaks of H1 a n d H4. Table 7. Comparative 'H NMR Chemical Shifts (ppm) for 4 and 5b at Two Temperatures temp for 5b

temp for 4 293 K

233 K

Hi

8.00

Mo(C~H~)

5.66

Mn(C5Hd

5.95 5.04 4.97

8.08 (5) major 7.08 (s) minor 5.54 (s) major 5.87 (s) minor 5.92 (m) major 5.27 (m) major 5.07 (m) major 4.93 (m) major

-CH3

2.92

2.92 (s) major 3.13 (s) minor

Table 8. lH NMR Data for the Proton at C1 R1 CH3 CH3 CH3 CH3 H H

R2 CH3 H CH3 H CH3 H

R3 H CH3 H CH3 H CH3

M1 Co Co Co Co Mo Mo

M2 Mo Mo Mo Mo

Mo Mo

6,ppm 8.02 7.08 8.66 7.75 6.36 5.80

temp,K 233" 238 193" 193" 187b 187b

This work. Reference 14. difference map, and their coordinates were refined with an overall refinable isotropic thermal parameter. l-Cymantreny1-2-butyn-l-o1(1). The Grignard reagent was prepared from 1.45 g (13.25 mmol) of EtBr and 0.19 g (7.95 mmol) of Mg in 30 mL of EtzO. After the Grignard reagent was cooled to -40 "C, a solution of 1.24 g (5.3 mmol) of cymantrenyl aldehyde in 20 mL of ether was added dropwise, and the reaction was stirred for 2 h a t this temperature. The solution was hydrolyzed at room temperature and the ethereal layer separated. After removal of the solvent in vacuum the residue was chromatographed on a silica gel column, using EtsO/pentane (1/1)a s eluent. A 0.99 gamount of 2 was recovered in 68% yield. 'H NMR (CDC13): 5.09 ('H, dd, J = 6-2 Hz, H1); 5.01 (2H, dd, J = 14-2 Hz, Cp); 4.63 (2H, m, Cp); 2.48 ( l H , d, J = 6 Hz, OH); 1.88 (3H, d, J = 2 Hz, H4). I3C NMR (CDC13): 224.5 (CO); 104.8 ((21');84.3-83.5-81.2-80.7 (CY, 3', 4', 5'); 82.7

HI

295 K 8.69 (s), 1H

Mo(C5H5)

5.47 (l),5H

Fe(C5H4-)

5.02 (t),1H 4.99 (dd), 2H 4.86 (t),1H

Fe(CsH5) -CH3

4.42 (s), 5H 2.92 (SI, 3H

193 K 8.64 (s), major 7.74 (s), minor 5.32 (s), major 5.71 (s), minor 4.88 (t),major 4.91 (dd),major 4.73 (t),major 4.33 (s), major 2.80 (61, major 3.10 (s), minor

(C2,3); 58.8 (Cl); 3.3 (C4). IR (cm-I): 1935,2022. Anal. Calcd for ClzH904Mn: C, 52.94; H, 3.31. Found: C, 53.33; H, 3.42. [q2,q2-(1-cymantrenyl-2-butyn-l-ol)(Co~(CO)~)l (2). To 0.33 g (1.21 mmol) of 1in 10 mL of Et20 was added 0.41 g of Co2(CO)s (1.22 mmol). After the solvent was removed, the crude red oil was chromatographed on silica plates using pentane-Et20 (3/1) a s eluent. A 0.47 g amount of 2 was recovered in 70% yield. 'H NMR (CDC13): 5.49 ( l H , d, J = 3 Hz, H l ) ; 5.00 ( l H , dd, J = 2.6-1.0 Hz, Cp); 4.76 ( I H , dd, J = 2.6-1 Hz, Cp); 4.744.71 (2H, t, J = 2.6 Hz, Cp); 2.64 (3H, s, H4); 2.24 ( l H , d, J = 3 Hz, OH). I3C NMR (CDC13): 224.2-199.2 (CO); 109.1 (Cl'); 99.9-92.5 (C2,3); 80.2 (C2', 3', 4', 5'); 68.6 (Cl);20.8 (C4). IR (cm-I): 1934,2022, 2053,2093. Anal. Calcd for ClsHgOgCozMn: C, 38.64; H, 1.79. Found: C, 39.48; H, 1.86.

[~2,~2-(l-cymantrenyl-2-butyn-l-ol)(CoMoCp(CO)~)l (3a,b). To a solution of 0.33 g (0.59 mmol) of 2 in 20 mL of THF was added a solution of NaMoCp(CO)3 prepared a s follows: 0.290 g of Mo&p~(C0)6(0.59 mmol) in 10 mL of THF was added to an amalgam (0.015 g of Na (1.15 mmol) with 2.3 g of Hg). The reaction is complete after 1 h a t reflux. The solvent was removed, and the resulting red-brown oil was chromatographed on silica plates using EtzO-pentane (1/3) as eluent. Two products were separated, 0.18 g of the more polar (3a) and 0.20 g of the less polar compound (3b)in 95% yield. 'H NMR (CDC13) (3a)5.46 (5H, s, Cp-Mo); 5.20 ( l H , d, J = 3 Hz, H l ) ; 4.91 (lH, m, Cp-Mn); 4.73 ( l H , m, Cp-Mn), 4.68

Carbenium Ions Stabilized by Clusters

Organometallics, Vol. 14, No. 8, 1995 3809

1.45 (4H, m); 0.96 (3H, t, J = 6.2 Hz). I3C NMR (CDzClz) (2H, m, Cp-Mn); 2.66 (3H, s, H4); 1.90 ( l H , d, J = 3 Hz, OH). (5b): 221.9; 214.2; 200.6; 139.6; 95.27; 77.6; 77.2; 73.5; 72.4; 'H NMR (CDC13) (3b): 5.45 (5H, S, Cp-Mo); 5.44 ( l H , d, J = 23.5. NMR (5c): 221.7; 215.2; 201.1; 135.3; 110.6; 108.7; 3 Hz, H l ) , 4.91 ( l H , m, Cp-Mn), 4.68 (3H, m, Cp-Mn), 2.70 98.1; 78.3; 77.8; 76.5; 75.9; 71.9; 66.3; 37.2; 33.4; 31.9; 23.0; (3H, S, H4); 2.03 ( l H , d, J = 3 Hz, OH). NMR (CDC13) 14.5. IR (cm-l) (5b): 1931, 1989,2045,2055,2083. IR (cm-') (3a): 225.9-224.7-223.4 (CO); 206.0 (CO broad); 110.6 (Cl'); (5c): 1931, 2044, 2055, 2082. Anal. Calcd for C24H18BF40597.9-91.4 (C2,3); 90.0 (Cp-Mol; 82.3-80.7-80.5 (Cp-Mn); CoMoFe (5b): C, 42.00; H, 2.72. Found: C, 42.26; H, 2.63. 65.7 (Cl); 20.3 ((24). NMR (CDC13) (3b): 226.0-224.2Calcd for 5c: C, 46.70; H, 3.62. Found: C, 45.63; H, 3.48. 221.2 (CO); 204.0 (CO broad); 109.3 ((21'); 98.5-91.6 (C2,3); [q2,qs-( l-cymantrenyl-2-butyn-l-ylium)(Co~(CO)~)l89.8 (Cp-Mol; 81.9-80.8-80.5-79.9 (Cp-Mn); 71.8 (Cl);25.5 BF4 (6). This compound was obtained in situ in the NMR (C4). IR cm-' (3a): 1934, 1981, 1997, 2021, 2048. IR cm-' probe using a solution of 2 in CDzClz with 2 drops of HBFJ (3b): 1935, 1980, 1998, 2020, 2048. Anal. Calcd for c17Et20 complex. H140eCoMoMn: C, 41.77; H, 2.22. Found: C, 41.81; H, 2.22. [q2,qs-(l-cymantrenyl-2-butyn-l-ylium)(CoMoCp(CO)~)l- 'H NMR (CDZClz): 7.50 ( l H , s, H l ) ; 5.52 (2H, m, Cp-Mn); 5.13 (2H, m, Cp-Mn); 3.03 (3H, s, H4). BF4 (4). To a solution of 0.09 g (0.142 mmol) of 3a or 3b in [q2,q2-(1-cymantrenyl-2-butyn-1-ethoxy)(Co~(CO)~)l (7). EtzO was added 0.1 mL of H B F D t 2 0 complex. The ochre lH NMR (CDCl3): 5.04 ( l H , m); 4.99 ( l H , s); 4.74 (lH,m), 4.72 precipitate formed was washed six times using Et20 and dried ( l H , m); 4.65 ( l H , m); 3.82 (2H, dq, J = 7.2-1.2 Hz); 1.29 (3H, under vacuum leading to 0.081 g (81%yield) of 4. J = 7.2 Hz). IR (cm-l): 1933, 2021, 2051, 2090. 'H NMR (CDzCl2, 297 K) 8.00 ( l H , broad, H l ) ; 5.95 (2H, NMR Experiments. Variable-temperature NMR spectra broad, MnCp); 5.67 (5H, broad, MoCp); 5.04 ( l H , broad, were recorded on a Bruker AM250 spectrometer, using meMnCp); 4.97 ( l H , sharp, MnCp); 2.92 (3H, broad, H4). I3C thylene chloride-dz as solvent. Chemical shifts are reported NMR (acetone-ds, 297 K): 224.6-220.6-218.8 (CO sharp); in ppm relative to TMS from the central peak of deuterio 200.0 (CO broad); 121.0-115.7 (broad); 96.0 (broad); 91.0methylene chloride (5.3 ppm for 'H and 54 ppm for I3C). 91.0 (sharp); 85.0 (broad); 23 (sharp). IR (cm-l): 1953, 2029, spectra were acquired at 250.133 MHz and carbon 2045, 2061, 2092. Anal. Calcd for C ~ ~ H ~ ~ B F ~ O ~ C C, O M O MProton ~: spectra at 62.896 MHz with a 5 mm dual frequency lWI3C 37.61; H, 1.85. Found: C, 37.92; H, 1.99. [q2,q3( l-ferrocenyl-2-butyn-l-ylium)(CoMoCp(CO)~~l-probehead. 'H spectra were obtained in 32 scans in 32 K data BF4 (5b) and [q2,qS-(1-ferrocenyl-2-octyn-l-ylium)(Co-points over a 3.5 kHz spectra width (4.7 s acquisition time). Temperatures quoted in Figure 7 are known with an accuracy M o C ~ ( C O ) ~ ) ] B(5c). F ~ The dicobalt-complexed alcohol preof 2 K. cursors of 5b and 5c were prepared according t o previous work.' 5b,c. The mixed [Co-Mol alcohols were prepared starting Acknowledgment. We thank the CNRS (France)for from [Cozl complexed alcohol; vide supra. The carbenium ion financial support and Dr. H. El h o u r i for helpful was obtained quantitatively as a violet powder by addition of discussion. HBFfitz0 to an ethereal solution of the starting alcohol and crystallized in Et20/CH2ClZ mixture using the diffusion techSupporting Information Available: Tables of bond nique. distances and angles, hydrogen parameters, and anisotropic 'H NMR (CDzClZ) (5b): 8.69 ( l H , s); 5.47 (5H, 5); 5.03 ( l H , thermal parameters for 4 and 5b (10 pages). Ordering t, J = 3 Hz); 5.01 (2H, m); 4.82 ( l H , dd, J = 1-3 Hz); 4.42 information is given on any current masthead page. : ( l H , s); 5.43 (5H, s); 2.92 (3H, s). 'H NMR (CDzClz) ( 5 ~ ) 8.66 OM950114X (5H, s); 4.97 (3H, m); 4.92 ( l H , m); 2.96 (2H, m); 1.72 (2H, m);