Organometallics 1982, 1, 559-561
to give 38 (47%, 48 mg): mp 45 "C; IR 3040,2920, 1670,1590, 1460, 1370,1200,900,840 cm-'; NMR (CDClJ 6 3.70 (3 H, s), 4.35 (2 H, s), 7.9-8.3 (9 H, m); mass spectrum (m/e) calcd for C14H1402 274.099, obsd 274.100. The adduct 16 (100mg, 0.28 mmol) in dry tetrahydrofuran (5 mL) was treated with potassium hydride (35 mg) and the mixture heated at 60 "C for 12 h. Workup in the usual way gave 27 (70%, 78 mg purified by plate layer chromatography): IR (thin film) 3040,2940,2920,2850,1630,1460,1410,1330,1220,1210,1150, 840, 710 cm-'; NMR (CDC13) 6 3.9 (3 H, s), 7.05 (2 H, ABq., J = 14 Hz), 8.0-8.5 (9 H, b m); mass spectrum (m/e) calcd for Cl9Hl4O 258.104, obsd 258.104. Perilla Alcohol (Trimethylsily1)methyl Ether (40). Perilla alcohol (39) (1.8 g, 0.118 mmol) in dry THF (12 mL) and sodium hydride (370 mg) were heated a t reflux for 2 h. (Iodomethy1)trimethylsilane (3.2 g, 0.15 "01) wm added to the above mixture and the solution maintained at reflux for 15 h. The mixture was poured into saturated aqueous sodium bicarbonate (100mL) and the solution extracted with ether (2 X 30 mL), dried (MgSOJ, and evaporated to give an oil (2.86 g). Plate layer chromatography of this oil gave two products. 40 (0.86 g): IR (thin film) 3080, 2960,2920,1640,1250,1070,860,840cm-'; NMR (CDC13)6 0.1 (9 H, s), 1.0 (2 H, s), 1.8 (3 H, s), 2.0-2.2 (7 H, b m), 4.0 (2 H, t, J = 10 Hz), 4.7 (2 H, s), 5.7 (1 H, b 8); mass spectrum (m/e) calcd for C14H26Si0238.175, obsd 238.176. 41 (0.58 9): NMR (CD113) 6 3.3 (3 H, s, -0Me); mass spectrum (mle) calcd for CllHleO 166.136, obsd 166.136. The ratio of 40 to 41 is ca. 1:l (VPC) in a yield of 30% for each product.
((Trimethylsilyl)methoxy)tris(dimethylamino)phosphonium Trifluorosulfonate (42). To a solution of (trimethylsily1)methyl trifluoromethanesulfonate (519 mg, 2.2 "01) in dry THF (5 mL) was added HMPA (447 mg, 2.5 mmol). A colorless crystalline precipitate formed immediately. Filtration gave the salt 42 (660mg,69%): mp 150-152 OC; NMR (MeaO-dG)
559
6 3.88 (1H, s), 3.82 (1H, s), 2.68 (9 H, s), 2.54 (9 H, s), 0.09 (9 H, s). The salt did not give satisfactory mass spectrum or microanalytical data. 0-((Trimethylsily1)methyl)-m-cresol (43). m-Cresol(lO8 mg, 1mmol) in T H F (5 mL) was treated with NaH (26 mg) and the mixture stirred 4 h at 20 "C. The salt 42 (410 mg, 1 mmol) was added to the above solution and the mixture stirred for 48 h at 20 OC. Water (10 mL) was added to the above mixture and the solution extracted with ether (2 X 20 mL), dried (MgS04), and evaporated to give 43 (140 mg, 72%): IR (thin film) 2950, 1600,1490,1250,1154,860,840 cm-l; NMR (CDC13)6 7.30-6.80 (4 H, m), 3.53 (2 H, s), 2.70 (3 H, s), 0.1 (9 H, s). This compound did not give satisfactory mass spectrum (M+ - 15) or microanalytical data, although the above spectra, because of their simplicity, confirm the structure.
Acknowledgment. T h e National Science Foundation are gratefully thanked for their support of this work. Dr. Timothy Gallagher is thanked for experiments leading t o 42 a n d 43. Registry No. 6, 14704-14-4; 8, 73061-27-5; 9, 700-58-3; 10, 73061-29-7; 11,73061-28-6; 12,80434-53-3; 13 isomer 1, 80434-54-4; 13 isomer 2, 80434-66-8;14, 80434-55-5; 15, 80434-56-6; 16 isomer 1, 80434-57-7; 16 isomer 2,80434-58-8; 17,39750-93-1; 18, 2043-61-0;19, 5664-21-1; 20 isomer 1, 80434-59-9; 20 isomer 2, 80482-64-0; 21, 72590-63-7; 22,19096-89-0; 23,66051-09-0; (E)-24,80434-60-2; (2)-24, 80434-61-3;(E)-%, 80434-62-4; (2)-25,80447-42-3;26,80447-43-4; 27, 80434-63-5; 28, 73061-33-3; 29, 24759-97-5; 30, 63830-94-4; 31, 80434-64-6;32,73061-32-2;33, 80434-65-7;34,73061-34-4; 35 isomer 1,8043467-9;35 isomer 2,80434-68-0; 36, 73061-35-5;37,80441-10-7; 38, 80434-69-1; 39, 536-59-4; 40, 80434-70-4; 41, 80434-71-5; 42, 80434-73-7;43,80434-74-8; cyclohexanone,108-94-1;cycloheptanone, 502-42-1; myrtenal, 23727-16-4; L-menthone, 14073-97-3; l-pyrenecarboxaldehyde, 3029-19-4.
N
Communzcatzons Reductlon of Nitriles by a Binuclear Tantalum Hydrlde Complex. Structural Study of [(q5-C5Me,Et)TaC12](p-~'-IV, q2-C,N-NCHMe)( p-CI)( pH)[( q5-C,Me,Et)TaCl] Melvyn Rowen Churchlll, Harvey J. Wasserman, Patrlcla A. Belmonte, and Rlchard R. Schrock*t Departments of Chemistry, State University of New York Buffalo, New York 14210, and Massachusetts Institute of Technology Cambridge, Massachusetts 02 139 Received November 16, 198 1
Summary: [TaCp'CI,H], (Cp' = q5-C5Me,Et) reacts with acetonitrile to give Ta,Cp',CI,(HXNCHMe). A single-crystal X-ray structure shows that Ta,Cp',CI,(H)(NCHMe) has a structure related to that of Ta,Cp',CI,(H)(CHO) and Ta,Cp',CI,(H)(Me,PCH)(O) in which the three bridging positions between the two tantalum atoms are occupied by the nitrogen of the NCHMe ligand, a chloride, and a hydride. Addition of ethylene to Ta,Cp',CI,(H)(NCHMe) b
.
yields Cp'CI,TaCH,CH,CH,CH, and TaCp'CI,(NEt) by a proposed ethylene-induced formation of a C-H bond on one tantalum center. We have been exploring t h e reactions of [TaCp'Cl,H],' 0276-7333f 8212301-0559$01.25 f 0
(Cp' = q5-C5Me4Et) with reducible substrates in order t o probe t h e question concerning t h e role of more t h a n one metal in such reactions. For example, we have shown t h a t carbon monoxide is reduced to give a dimeric formyl hydride complex in which the formyl and hydride are trapped between t h e two metal centersa2p3 Here we show t h a t nitriles a r e also reduced t o give dimeric species whose structures are related t o that of t h e formyl hydride product. [TaCp'Cl2HI2 reacts rapidly with one a n d only one equivalent of acetonitrile at 25 "C t o give dimeric, orange-red T ~ , C P ' , C ~ ~ ( H ) ( N C H M ~The ) . ~ analogous react i o n b e t w e e n [TaCp'Cl,H], a n d C D & N gives Ta2Cp',C14(H)[NCH(CD3)],between [TaCp'Cl,D], a n d CH&N gives Ta2Cp'&l4(D)(NCDMe), a n d between [Ta'State University of New York. Massachusetts Institute of Technology.
*(1)Belmonte, P. A.; Schrock, R. R.; Day, C. V. J. Am. Chem. SOC.
1982,104, oo00.
(2) Belmonte, P.; Schrock, R. R.; Churchill, M. R.; Youngs, W. J. J. Am. Chem. SOC.1980,102, 2858. (3) (a) Churchill, M. R.; Wasserman, H. J. Inorg. Chem. 1982, 21, 226-230. (b) J. Chem. SOC.,Chem. Commun. 1981, 274-275. (4) Yield 78% from ether/pentane. Anal. Calcd for Ta2CuH&1,N C, 34.10; H, 4.65; N, 1.66. Found: C, 34.26; H, 4.81; N, 1.75. Mol wt ((&He): Calcd, 845; Found, 875. Pertinent 'H NMR data (ppm, C6D6): 6.62 (8, 1, TaHTa), 3.89 (4,1, J = 5.8 Hz, CHMeN),2.26 (d, 3, CHMeN). (5) Churchill, M. R.; Lashewycz, R. A.; Rotella, F. J. Inorg. Chem.
1977, 16, 265-271.
0 1982 American Chemical Society
560 Organometallics, Vol. 1, No. 3, 1982
Communications
c 37
Figure 1. Molecular structure H)(NCHMe). C5Me4Et)&14(
(ORTEP 11)
of Ta2(q5-
(v5-C5Me5)Cl2H]and CH3CN gives Ta2(q5-C5Me5),C1,(H)(NCHMe); the q5-C5Me5complex is significantly less soluble than the q5-C5Me4Etcomplex and therefore less convenient to handle. IR spectra of Ta2Cp’,C1,(H)(NCHMe) reveal peaks assignable to metal hydride modes at 1635 and 950 cm-l which shift to 1170 and 725 cm-’ in the IR spectrum of Ta2Cp’,C1,(D)(NCDMe). A resonance assigned to a hydride is found at 6.62 ppm in the ‘H NMR spectrum. The reaction between [TaCp’Cl,H], and propionitrile produced an analogous species. However, the initial product of the reaction between [TaCp’,Cl2HI2and benzonitrile decomposed readily to an unidentifiable brown oil. Ta2Cp’,C14(H)(NCHMe) crystallizes in the noncentrosymmetric orthorhombic space group Pbc2’ (No. 29) with a = 9.936 (2) A, b = 18.896 (5) A,c = 15.005 (3) A, V = 2817.4 (11)A3, and p(calcd) = 1.99 g for mol wt 844.95 and 2 = 4. Diffraction data were collected with a Syntex P21 automated four-circle diffractometer using a coupled O(crystal)-2O(counter) scan technique5 and graphitemonochromatized Mo KCYradiation. Intensities were corrected for absorption ( p = 85.7 cm-’), and the structure was solved by a combination of Patterson, differenceFourier, and full-matrix least-squares refinement techniques. All nonhydrogen atoms were located accurately, the bridging hydride ligand was located and refined, and all other hydrogen atoms were placed in idealized calculated positions based on C-H = 0.95 A6 and appropriate geometries. The final discrepancy indices are R, = 5.0% and RwF = 4.1% for all 4998 point group independent reflections with 3.5O C 20 C 50.0’ (none rejected). The molecular geometry is shown in Figure 1. The two tantalum atoms are inequivalent. Ta(1) is linked to an q5-C5Me4Etligand and to two terminal chloride ligands (Ta(l)-Cl(l) = 2.472 (3) A and Ta(l)-C1(2) = 2.398 (3) A), while Ta(2) is linked to an q5-C5Me4Etligand and a single terminal chloride ligand (Ta(2)-C1(3) = 2.389 (3) A). The two tantalum atoms are bridged by an +N,q2-C,NNCHMe ligand, a chloride ligand (C1(4)),and a hydride ligand (H(br)). Each of the bridges is asymmetric, with Ta(1)-N = 1.901 (8) 8, vs. Ta(2)-N = 2.059 (8) A, Ta(1)-C1(4) = 2.553 (3) A vs. Ta(2)-C1(4) = 2.617 (3) A, and Ta(1)-H(br) = 2.18 (9) A vs. Ta(2)-H(br) = 1.70 (9) A; the Ta(2)-C(1) bond length is 2.195 (10) A. Distances within the bridging NCHMe ligand are N-C(l) = 1.435 (12) A and C(l)-C(Z) = 1.491 (16) A, with L N - C ( ~ ) - C (=~ 120.4 ) (9)O. The Ta(l)-N€(l)-Ta(2) system is planar within the limits of experimental error, and the methyl carbon atom (C(2))
lies 1.22 (1)A from this plane, confirming the saturated (sp3) nature of C(1). The Ta(l)-Ta(2) distance is 2.979 (1)A. Atom Ta(1) has a rather precise “3,4,1”coordination environment, as is illustrated by the essentially equivalent Cp-Ta( 1)-L(equatorial)’ angles: Cp(1)-Ta(1)-Cl(1) = 106.4O, Cp(l)-Ta(l)-Cl(2) = 105.3O, Cp(l)-Ta(l)-C1(4) = 106.9O, and Cp(1)-Ta(1)-N = 109.1O; the Cp(1)-Ta(1)-H(br) angle is 176’. The coordination geometry about Ta(2) is necessarily rather distorted; within the framework of the “3,4,1” description, the NCHMe ligand spans two equatorial sites. Relevant angles are Cp(2)-Ta(2)-C1(3) = 108.1°, Cp(2)-Ta(2)-C(1) = 108.5O, Cp(2)-Ta(2)-N = 126.1°, and Cp(B)-Ta(B)-H(br) = 8 6 O ; the “axial” ligand angle is now Cp(2)-Ta(2)-C1(4) = 142.3O. The overall molecular geometry in this species bears a strong resemblance to that found previously in the related “formyl” and “disrupted formyl” complexes [TaCp’C1212(p-H)(P-CHO)~ and [TaCp’Cl,],(p-H) (p-CHPMe,) ( ~ - 0 ) ; ~ here N, C1(4), and H(br) make up the “trigonal core” of the molecule. Since C(1) is saturated, it cannot bind to Ta(1). Therefore Cl(4) fills in to complete the “closed” form observed in the formyl and disrupted formyl products. Ta,Cp’,Cl,(H)(NCHMe) reacts with ethylene (30 psi) in 12 h at 25 OC to give 1 equiv of , Cp’Cl2TaCH2CH,CH,CH2 and 1equivalent of an ethylimido complex, TaCp’Cl,(NEt),l’ by ‘H and 13C NMR. The analogous Ta2(q5-C5Me5),C14(H)(NCHMe) complex reacted with ethylene in pentane to give a 70% yield of , (q5-C5Me5)C1,TaCH2CH2CH2CH210 and a red oil (70% yield by weight) of what is believed to be Ta(q5-C5Me5)C12(NEt).Unfortunately, Ta(q5-C5Me5)C12(NEt) would not crystallize from pentane at -30 OC. 1-Hexene and styrene react with Ta2Cp’,C14(H)(NCHMe)faster than ethylene does to give high yields of TaCp’Cl,(NEt) by ‘H NMR. By analogy with the ethylene-induced reductive elimination of isobutane from Zr(q5-C5Me5),(H)(CH2CHMe2),12 we propose that formation of the ethylimido groups by migration of H(br) to C(l) is induced by addition of ethylene to Ta(2). Therefore Ta(2) most likely ends up in Cp’Cl2TaCH2CH2CHZCH2 and Ta(1) in TaCp’Cl,(NEt). These proposals are consistent with the Ta(B)-H(br) distance being shorter than the Ta(1)-H(br) distance and the Ta(1)-N distance shorter than the Ta(2)-N distance in the solid-state structure of Ta2Cp’,C14(H)(NCHMe). The reduction of acetonitrile by [TaCp’Cl,H], should be compared with its reduction by Re2(C0)6(Ph2PCH2PPh2)H2 to give Re2(CO)6(Ph2PCH2PPh,)(q2-NNCHMe)(H).13 Reduced acetonitrile ligands (MeC=NH and N=CHMe) have also been observed in the triiron carbonyl system14and trifluoroacetonitrile analogs in the 1
I
I
(7) The symbol “Cp” represents the centroid of the five-membered cyclopentadienyl ring. Cp(1) refers to the ring associated with Ta(1) and Cp(2) to that bound to Ta(2). (8) Churchill, M. R.; Youngs, W. J. Inorg. Chem. 1981,20,382-387. (9) By comparison with the NMR spectrum of known ($-C5Me6)C12TaCH2CH2CH2CH2.’0 (10) McLain, S. J.; Wood, C. D.; Schrock, R. R. J . Am. Chem. SOC. 1979,101,4558. (11) ‘H NMR (CDCI,, 60 MHz): 4.3 (a, J = 7 Hz, NCH7CHq),2.5 (a, J = 8 Hz, CsCH2CH3),2.15 ( 8 , C5CH3),2.1 (s, C&H3), 1.6 ppm (overlapping triplets, NCH7CHqand CRCHICHq). 13C NMR (CDCl,. 22.5 M€iz):-12&112 (ring &bon atoms); 53.4 (t,3 = 137 Hz, NCH2CHi),19.t5 (t,J = 128 HIz, CRCH,CHq),17.9 (a. J = 128 Hz, NCHXH,), 14.6 (a. J ” = 128 Hz, CsCH3j, If0 ppm (4,J-= 128 Hz, C&H3). (12) McAlister. D. R.: Erwin. D. K.: Bercaw. J. E. J. Am. Chem. SOC. 1978,100, 5966. (13) Mays, M. J.; Prest, D. W.; Raithby, P. R. J . Chem. SOC.,Chem. Commun. 1980, 171-173. ’
(6) Churchill, M. R. Inorg. Chem. 1973,12, 1213-1214.
Organometallics 1982,1, 561-562
561
triosmium carbonyl system.16 [TaCp’Cl2HI2 reduces acetonitrile especially easily simply because it also easily reduces carbon monoxide, a much more difficult feat.
Acknowledgment. We thank the National Science Foundation (Grant CHE 80-23448 to M.R.C.) and the Department of Energy (Contract No. ER-78-S-02-4949to R.R.S.) for supporting this research.
.
Registry No. [TaCp’Cl2HI2,74153-80-3;Ta,Cp’,Cl,(H)(NCHMe), 80514-61-0; Cp‘C12TaCH2CH2CH2,80502-36-9;TaCp’C12(NEt), 80502-37-0.
,C-LX
$22
3
x \ p I
i
C
Supplementary Material Available: Listings of anisotropic thermal parameters and positional parameters (and esd’s) and observed and calculated structure factors (XlO) for [Ta(C&fe4Et)Clz]z(H)(NCHMe) (31 pages). Ordering information is given on any current masthead page. (14)(a) Andrews, M.A.; Kaesz, H. D. J. Am. Chem. SOC.1979,101, 7238-7244 and references therein. (b) Andrew, M. A.; van Buskirk, G.; Knobler. C. B.: Kaesz. H. D. Ibid. 1979. 101. 7245-7254. (15)Adams,’ R. D.;’Katahira, L. W.;’Yang, J. J. Organomet. Chem. 1981,219, 85.
Evidence for Tilted Ground-State Structures and Fluxlonallty In CO,( CO),CCHR+ Robin 1. Edldln,’asb Jack R. Norton,+la*G and Kurt Mlslow Ib +
Departments of Chemlstry, Colorado State University Fort Collins, Colorado 80523, and Princeton University, Princeton, New Jersey 08544 Received January 13, 1981
Summary: The synthesis and variable-temperature NMR properties of Co,(CO),CCHCHMe,+ are described. At -65 OC the methyl groups are anisochronous, consistent with a tilted but not with an upright structure. Coalescence of the methyl signals at higher temperatures reflects enantiomerization of the cluster, presumably by disrotatory correlated rotation (gearing) about the Co3(CO)g-C and C-CHCHMe, axes. The barrier (AG*) to site exchange is 10.5 f 0.1 kcal mol-’ at -52 OC. The present findings corroborate theoretical predictions by Schilling and Hoffmann.
Among the many interesting properties of the Co3(C0),C cluster is ita ability to stabilize adjacent carbenium ion^.^^^ Schilling and Hoffmann4 have proposed, on the basis of theoretical considerations, that stabilization occurs in Co3(CO),CCH2+ as a result of the formation of tilted structures 2a or 3a rather than the upright structure of type la originally assumed2p5(Figure 1). We now report (1)(a) Colorado State University. (b) Princeton University. (c) Alfred P.Sloan Fellow. 1977-1981. (2)Seyferth,’D.; Williams, G. H.; Eschbach, C. S.; Nestle, M. D.; 1979,101,4867 and Merola, J. S.; Hallgren, J. E. J. Am. Chem. SOC. references therein. (3)Seyferth, D. Adu. Organomet. Chem. 1976,14,97and references therein. (4)(a) Schilling, B. E. R.; Hoffmann, R. J. Am. Chem. SOC.1978,100, 6274. (b) schilling, B. E. R.; Hoffmann, R. Ibid. 1979,101,3456. On p 3461 the structure labels 25 and 26 were accidentally transposed in the text below the drawings. The calculations predict that the 26 structures are local minima, with the 26 structures 88 saddle points (Hoffmann, R., private communication).
0276-7333/82/2301-0561$01.25/0
/y
&‘
9 I
3’
Figure 1. Schematic representation of CoS(CO)&CXY+ conformations. The Co&20), triangle is capped by a C-CXY+ fragment in upright (1) or tilted (2, 3) positions. The gearing 3 2’ is shown by the curved arrows. motion in 2
--
NMR evidence for C O ~ ( C O ) ~ C H C H M which ~ ~ +unambiguously excludes the upright structure and which permits an analysis of the dynamic stereochemistry in this system. In la the C3 axis of Co3(CO)9and the C2axis of C-CH2+ are collinear, leading to a sixfold rotation barrier about the common axis. In the tilted structures, the two axes subtend an angle, and the extended Huckel calculations of Schilling and Hoffmann4indicate two stationary pointa on the potential energy hypersurface. In one (2a, C,)the C+ bends toward a Co atom and the u plane bisecta the HC-H angle, whereas in the other (3a, C,) the CH, group bends toward the Co-Co bond center and lies in the u plane. According to Schilling and Hoffmann: 2a is the ground state, and degenerate isomerization (topomerization) occurs by way of the saddle point 3a. When X # Y, 2 becomes chiral(2b), and the topomerization described above becomes an enantiomerization (2b F? 2’b) by way of achiral transition states 3b or 3’b. On the other hand, l b is expected to be achiral (the approximately sixfold barrier ensures that any chiral conformation has a negligible lifetime on the NMR timescale). Under conditions of slow enantiomerization, a probe testing for chirality therefore allows a distinction between l b and 2b. The isopropyl group in the derivative with X = H and Y = i-Pr is such a probe: in l b and 3b (or 3’b), the methyls are enantiotopic on the NMR timescale and hence isochronous, whereas in 2b they are diastereotopic and therefore anisochronous (barring accidental isochrony). The unsaturated (alky1idyne)tricobalt complex 4,6 required as a precursor to C O ~ ( C O ) ~ C C H C H M was ~ ~pre+, pared in 14% yield (after extensive purification) by the treatment of l,l,l-trichloro-3-methyl-2-butene (5)’ with C O ~ ( C Oin ) ~the usual method for the preparation of Co3(CO),CR complexes.* The required trichloromethyl compound 5 was obtained by careful dehydrobromination (6)., of l , l ,1-trichloro-3-bromo-3-methylbutane (6)(a) Seyferth, D.; Williams, G. H.; Hallgren, J. E. J. Am. Chem. Soc. 1973,95,266. (b) Seyferth, D.; Williams, G. H.; Trdicante, D. D. Ibid. 1974,96,604.(c) Seyferth, D.; Williams, G. H.; Wehman, A. T.; Nestle, M. 0. Ibid. 1975,97,2107. (6)‘H NMR of 4 (CD2Cl2):6 1.87 (8, 3 H), 1.83 ( 8 , 3 H), 7.53 (m, 1 H). Anal. Calcd for C1,H7C%08: C, 33.90;H, 1.42. Found C, 34.08;H, 1.41. (7)Nesmeyanov, A. N.; Freidlina, R. Kh.; Zakharkin, L. I.; Belyavekii, A. B. Zh. Obshch. Khim. 1956,26,1070.‘H NMR of 6 (CCl,): 6 1.85 (m, 3 H), 2.10 (m, 3 H), 6.25 (m, 1 H). (8) (a) Seyferth, D.; Hallgren, J. E.; Hung, P. L. K. J. Organomet. Chem. 1973,50,265.(b) Seyferth, D.; Eschbach, C. D.; Williams, G. H.; Hung, P. L. K. Ibid. 1977,134,67.
0 1982 American Chemical Society
