Organometallics 1996,14, 1278-1283
1278
Titanium Alkylidenes via Dineopentyl Complexes Johannes A. van Doorn and Harry van der Heijden" Koninklijke /Shell-Laboratorium, Amsterdam (Shell Research BV), P.O. Box 3003, 1003 AA Amsterdam, The Netherlands
A. Guy Orpen Department of Inorganic Chemistry, The University, Bristol B S 8 1 T S , United Kingdom Received September 29, 1994@
Mono(cyclopentadieny1)titanium neopentylidene complexes with bulky phosphinoalkoxide ancillary ligands were prepared via the corresponding dineopentyl complexes. The structure of 3b was determined by a n X-ray analysis. Crystal data: Ti(l?5-C5H5)(CHMe3)(PMe~CH2C(0)-CMe2-o-CsH4CMez),monoclinic, space group P2dc (No. 14), a = 10.728(3) b = 12.881(4) c = 18.553(6) p = 104.36(3)",2 = 4, No = 3419, R = 0.045. The titanium alkylidene readily reacts with ethene, initially forming a metallacycle, while subsequent reactions produce a stable ethene complex. Reaction of the alkylidene with CO to form ketene derivatives was briefly studied.
A,
A,
A,
Scheme 1"
Introduction Recently we reported a route to novel mononuclear titanium alkylidene complexes containing a bulky (pheny1phosphino)alkoxidel and a cyclopentadienyl ligand. The alkylidene complex was not isolated in a pure state due to a subsequent addition of a CH bond of one of the phenyl groups of the ligand across the double-bond system of the metal alkylidene,l forming the cyclometalated complex 4. The insertion reaction is reversible, but it complicates a study of reactions of the alkylidene with olefins. In order to avoid the orthometalation reaction, we have replaced the phenyl groups at the phosphorus atom with methyl groups. This allowed the isolation of well-defined neopentylidene species suitable for structural characterization and reactivity studies.
Results and Discussion The precursors of the (methy1phosphino)alkoxide ligands, the alcohols a and b,were prepared according to Lappert2 by addition of (CH3)2PCH2Li3to the appropriate ketone followed by hydrolysis. The dichlo-
rotitanium alkoxide complexes 1 were prepared by reaction between cyclopentadienyltitanium trichloride and (a)Li or (b)Li. The 31P NMR spectra of these products la or lb suggest that the phosphorus atom is Abstract published in Advance ACS Abstracts, February 1, 1995. (1) van Doorn, J. A, van der Heijden, H.; Orpen, A. G . Organometallics 1994,13, 4271. (2) Engelhardt, L. M.; Harrowfield, J.M.; Lappert, M. F.; MacKinnon, I. A.; Newton, B. H.; Raston, C. L.; Skeleton, B. W.; White, A. H. J . Chem. SOC.,Chem. Commun. 1986,846. (3) (a) Karsch, H. H.; Appelt, A. 2.Nuturforsch. 1983,38B, 1399. (b) Engelhardt, L.M.; Lacobsen, G . E.; Raston, C. L.; White, A. H. J. Chem. Soc., Chem. Commun. 1984,220. @
z'z+
z'z+
3
4
"Legend: a, R = Z = CH3; b, R = CH3, Z 1,2-phenylene.
+
2 =
only weakly bonded to the titanium atom. The signal is usually broad, and the chemical shift is strongly dependent on the solvent (see Experimental Section). This may indicate that a rapid exchange occurs between a bonded and a nonbonded situation. Reaction of the dichlorides 1 with neopentyllithium readily leads to the corresponding dineopentyl complexes, which are not stable at room temperature. The spectroscopic data for 2b are given in the Experimental Section together with the synthetic procedure for 3b. Both 2a and 2b form stable alkylidene complexes by expulsion of neopentane. They show characteristic resonances in the NMR spectra. The alkylidene hydrogen resonance is found around 12 ppm and is a doublet due to coupling to phosphorus. The alkylidene carbon atom resonance is found at ca. 280 ppm; the signal is a doublet due to coupling to phosphorus. The relatively low value of the lJ('H13C) coupling constant (approximately 95 Hz) may indicate an agostic interaction of the alkylidene hydrogen with the titanium atom. Compound 3a was obtained as a green oil which crystallized very slowly with difficulty from a concentrated pentane solution. In contrast, the alkylidene 3b readily forms dark green crystals which were suitable for an X-ray structure determination.
0276-733319512314-1278$09.0010 0 1995 American Chemical Society
Organometallics, Vol. 14, No. 3, 1995 1279
Titanium Alkylidenes via Dineopentyl Complexes
Table 2. Atomic Coordinates ( x lo4) and Equivalent Isotropic Displacement Parameters (Azx 103) for 3b atom
C141
Cllll
Cll8l
$
Figure 1. Molecular structure of 3b showing the full labeling scheme. Non-hydrogen atoms are represented as ellipsoids enclosing 30% probability density. Cyclopentadienyl, methylene, aryl, and methyl hydrogens have been omitted for clarity. Table 1. Selected Bond Lengths (A) and Bond Angles (deg) for 3b Ti-P Ti-C(22) Ti-C P-C(20) C(l)-C(2) C(2)-C(5) C(7)-C(15) C(8)-C(17) C(l0)-C(l1) C(13)-C(14) C(15)-C(19) C(23)-C(24)
2.534(1) 2.377(3) 2.373(3) 1.821(4) 1.516(4) 1.515(5) 1.577(4) 1.546(4) 1.384(5) 1.391(5) 1.538(4) 1.403(5)
P-Ti-0 0-Ti-C( 1) O-Ti-C(22) P-Ti-C(23) C( l)-Ti-C(23) P-Ti-C(24) C( l)-Ti-C(24) C(23)-Ti-C(24) O-Ti-C(25) C(22)-Ti-C(25) C(24)-Ti-C(25) O-Ti-C(26) C(22)-Ti-C(26) C(24)-Ti-C(26) Ti-P-C(6) C(6)-P-C(20) C(6)-P-C(21) Ti-0-C(7) C( l)-C(2)-c(3) C(3)-C(2)-C(4) C(3)-C(2)-C(5) P-C(6)-C(7) O-C(7)-C(8) O-C(7)-C(15) C(8)-C(7)-C( 15) C(7)-C(S)-C( 16) C(7)-C(S)-C( 17) C( 16)-C(8)-C(17) C(9)-C( 14)-c(15)
Ti-0 Ti-C(23) Ti-C(26) P-C(21) C(2)-C(3) C(6)-C(7) C(8)-C(9) C(9)-C(10) C(l1)-C(12) C(14)-C(15) C(22)-C(23) C(24)-C(25) 77.1(1) 107.2(1) 135.9(1) 107.6(1) 89.8(1) 86.5(1) 118.8(1) 33.8(1) 105.6(1) 57.2(1) 34.0(1) 106.8(1) 34.6(1) 57.0(1) 96.5(1) 105.5(2) 103.4(1) 138.3(2) 110.6(3) 107.9(3) 108.0(3) 112.2(2) 108.2(2) 108.7(2) 104.5(2) 112.3(2) 115.0(2) 107.7(3) 110.8(3)
1.869(2) 2.419(3) 2.341(3) 1.814(3) 1.533(7) 1.551(4) 1.523(4) 1.399(4) 1.373(5) 1.513(4) 1.415(5) 1.400(5)
Ti-C(1) Ti-C(24) P-C(6) 0-C(7) C(2)-C(4) C(7)-C(8) C(8)-C(16) C(9)-C(14) C(12)-C(13) C(15)-C(18) C(22)-C(26) C(25)-C(26)
P-Ti-C( 1) P-Ti-C(22) C( l)-Ti-C(22) 0-Ti-C(23) C(22)-Ti-C(23) 0-Ti-C(24) C(22)-Ti -C(24) P-Ti-C(25) C( l)-Ti-C(25) C(23)-Ti-C(25) P-Ti-C(26) C(l)-Ti-C(26) C(23)-Ti-C(26) C(25)-Ti-C(26) Ti-P-C(20) Ti-P-C(21) C(20)-P-C(21) Ti- C( 1)-C(2) C( l)-C(2)-c(4) C( 1)-c(2)-c(5) C(4)-C(2)-C(5) O-C(7)-C(6) C(6)-C(7)-C(8) C(6)-C(7)-C( 15) C(7)-C(8)-C(9) C(9)-C(8)-C( 16) C(9)-C(8)-C( 17) C(8)-C(9)-C(141 ci7j-c(15)-c(i4)
1.911(3) 2.409(4) 1.839(3) 1.415(3) 1.515(5) 1.599(4) 1.534(4) 1.390(4) 1.385(5) 1.542(4) 1.404(5) 1.403(5) 96.5(1) 141.2(1) 91.6(1) 161.8(1) 34.3(1) 132.31) 56.8(1) 100.2(1) 145.7(1) 56.6(1) 134.8(1) 123.1(1) 57.1(1) 34.6(1) 125.5(1) 122.6(1) 100.1(2) 158.7(2) 109.8(3) 112.2(3) 108.2(3) 107.3(2) 116.7(2) 111.2(2) 101.1(2) 109.7(2) 110.9(2) 112.4(2) 102.0i2j
X-ray Structure of 3b. The molecular structure of 3b is given in Figure 1. Pertinent bond distances and bond angles are given in Table 1. The molecule is monomeric, with a distorted three-legged piano-stool geometry around the metal center. The phosphinoalkoxide ligand is bidentate with a Ti-P distance of 2.534(1) A and a Ti-0 distance of 1.869(2)A (cf. average Ti-0 for terminal alkoxides of 1.847 A quoted in ref 4 and 1.787(2)A for the alkoxide in the metalated compound
X
764(1) 2092( 1) 2112(2) 1264(3) 1127(3) 2090(5) 1404(4) -211(4) 3564(3) 3270(3) 3120(3) 3584(3) 3409(3) 3849(3) 4462(3) 4665(3) 42 17(3) 4374(3) 1716(3) 3930(3) 5736(3) 4245(3) 1776(4) 2646(3) -1378(3) -1349(3) - 1092(3) -974(3) -1140(3)
Y
547(1) 643(1) -376(2) 1869(2) 2974(2) 3189(4) 3729(3) 3196(3) 7 0 ~ -703(2) - 1898(2) -2432(2) -3470(2) -3806(3) -3 130(3) -2 106(3) -1754(2) -697(2) -2197(2) -2241(3) -620(2) 204(2) -79(3) 1863(3) 769(3) 1232(3) 447(3) -495(3) -296(3)
Z
1340(1) 2674(1) 1347(1) 1036(2) 746(2) 275(3) 1392(2) 269(2) 2505(2) 1844(2) 2041(2) 1423(2) 1198(2) 597(2) 227(2) 452(2) 105l(2) 1419(2) 1988(2) 2814(2) 1939(2) 862(2) 3453(2) 3 130(2) 611(2) 1307(2) 1848(2) 1495(2) 733(2)
aEquivalent isotropic U , defined as one-third of the trace of the orthogonalized Uu tensor.
4.l The Ti-0-C angle in 3b is significantly smaller than that in the metalated complex 4, reflecting the larger ring size1 and probably an increased 0-Ti n-donation contribution in 4. The Ti-C double-bond distance is 1.911(3) 8, (cf. 2.120(4) 8, for the neopentyl ligand of 4. The Ti-C(l)-C(B) angle of 158.7(2)" together with the Ti-C(l)-H(l) angle of 85(3)O (Ti-H(1)= 2.05(5) A) suggests an a-agostic type distortion of the alkylidene, as is commonly found in do metal alkylidene~.~ The do complex 3b makes an interesting comparison with the related d2-metal three-legged piano-stool alkylidene complex CpV(CHCMe3)dmpe.6In the latter the alkylidene unit is rotated 90" with respect to the orientation relative to the Cp ligand and is much more distorted (angle V-C-C = 173.3(3Y,angle V-C-H = 65(3)"). Reactions of the Alkylidene. At room temperature alkylidene 3b reacts smoothly with ethylene to form the metallacyclobutane complex 5. This compound can be crystallized from pentane. The 'H NMR spectrum shows characteristic downfield shifts (6 3.8-2.9) for the a-protons, and one of the P-protons is strongly shifted upfield (6 -0.40). These characteristics are comparable with those of bis(cyclopentadienyl)titanacyclobutanes.7~8 (4) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, 0.;Watson, D. G.; Taylor, R. J . Chem. SOC.,Dalton Trans. 1989,S1. (5)(a)Demolliens, A.;Jean, Y . ;Eisenstein, 0. Organometallics 1986, 5,1457.(b) Nugent, W. A.; Mayer, J. M. Metal-Ligand Multiple Bonds; Wiley: New York, 1988;Chapter 5, and references cited therein. ( c ) Goddard, R. J.; Hoffman, R.; Jemmis, E. D. J . Am. Chem. SOC.1980, 102, 7667. (6)(a) Hessen, B.;Meetsma, A,; Teuben, J . H. J . Am. Chem. SOC. 1989,111,5977.(b) Hessen, B.; Buijink, J. K. F.; Meetsma, A.; Teuben, J. H.; Helgesson, G.;HBkansson, M.; Jagner, S.; Spek, A. L. Organometallics 1993,12, 2268. (7)(a) Howard. T. R.: Lee. J . B.: Grubbs. R. H. J . Am. Chem. SOC. 1980,102, 6876.'(b) Gilliom; L.R.'; Grubbs, R. H. J . Am. Chem. SOC. 1986,108,733.
1280 Organometallics, Vol. 14, No. 3, 1995
-
van Doom et al.
Silicon g r e a s e
H2
I ,
.a
Ill
.? 006
I
DDn,
"
,
hi -? ,
I
I
Figure 2. Selected resonances of the titanium ethene complex 8 together with the simulated spectrum. The data are given in the Experimental Section. Scheme Za \
0 \
3b
5
0
The phosphinoalkoxide ligand is drawn schematically.
The 31P resonance appears at -63.6 ppm, and this indicates that the phosphorus atom in this complex is not coordinated. These data are consistent with structure 5. When the reaction is performed at a higher temperature (60 "C) with an excess of ethene, the purple ethene complex 8 is obtained in addition to three olefins: propene (0.5 equiv), 3,3-dimethyl-l-butene (0.6 equiv), and 4,4-dimethyl-l-pentene (0.4 equiv) (GLC). The formation of these olefins suggests that the metallacyclobutane complex 5 reacts in two different ways. A P-H elimination leads to a hydrido alkyl complex which rearranges t o a 4,4-dimethylpentene complex by reductive elimination. Subsequently, the olefin is displaced by ethene, leading to the ethene complex 8. The other olefins, 3,3-dimethylbutene and propene, are the result of metathesis reactions. Metathesis of the metallacyclobutane 5 leads to 3,3dimethylbutene and a methylene complex. Reaction of this methylene compound with ethene leads t o a metallacycle which gives propene and the ethene complex 8 by a route similar t o that for the formation of 4,4dimethylpentene. The purple titanium ethylene adduct 8 was characterized by NMR spectroscopy. Figure 2 shows the ( 8 ) Anslyn, E. V.; Grubbs, R. H. J . Am. Chem. SOC.1987,109,4880.
hydrogen resonances of the ethene fragment. The structure of 8 was confirmed by an independent synthesis from lb and diethylmagnesium. The 31PNMR spectrum of 8 shows a sharp resonance at f17.7 ppm, suggesting that the phosphinoalkoxide is bidentate in this complex. The 13Cchemical shifis of the coordinated ethene and the C-H coupling constants (6(CH1H2)58.8, WCH) = 144 Hz, 6 (CH3H4)55.0, WCH) = 147 Hz) compare well with those in Cp*~Ti(q~-ethene).~ The resonances of the two ethene protons with the largest PH coupling constants appear at relatively high field. Both the lH and 13C chemical shifts and the IH-lH and lH-13C coupling constants are consistent with a carbon hybridization between an sp2 and an sp3 situation. A similar complex of 1-butene could be obtained as well. Reaction of titanium chloride lb with BuLi in hexane leads to a mixture of two isomeric 1-butene complexes (ratio 3:2). Exactly the same mixture of compounds was obtained from a reaction of lb with s-butyllithium; no 2-butene complex was formed. The 1-butene ligand can be readily replaced with ethene by adding ethene t o a solution of the butene complexes. Attempts to use the alkylidene complexes for catalytic olefin conversion were not very successful. Reaction of the alkylidene 3a with propene and 2-pentene at 60 "C gives the expected metathesis products. The turnover number, however, is very low ( 341) were retained for use in structure solution and refinement. An absorption correction was applied in the basis of 348 azimuthal scan data; maximum and minimum transmission coefficients were 0.788 and 0.692, respectively. Lorentz and polarization corrections were applied. The structure was solved by Patterson and Fourier methods. All non-hydrogen atoms were assigned anisotropic displacement parameters and all hydrogen atoms fixed isotropic displacement parameters. All non-hydrogen atoms and the hydrogen atom H(1) (which was located in a difference Fourier synthesis) were refined without positional constraints. All other hydrogen atoms were constrained to idealized geometries (C-H = 0.96 A, H-C-H = 109.5’). Full-matrix least-squares refinement of this model (265 parameters) converged to final residual indices given in Table 3. Weights, w ,were set equal to [a,2(Fo) gFO2]-’,where a,2(F0)is the variance in F, due to counting statistics a n d g = 0.0005 was chosen to minimize the variation in S as a function of IFoI. Final difference electron density maps showed no features outside the range +0.43 to -0.26 e A-3, the largest of these being close to the center of a P-C bond. All calculations were carried out on a Nicolet R3mN structure determination system using programs of the SHELXTL-PLUSpackage.lZ Complex neutral-atom scattering factors were taken from ref 13. Ligand b. A solution of butyllithium in hexane (1.6 M, 70 mmol) was added t o a stirred solution of trimethylphosphine
+
~
(18)Strohmeier, W.; Seifert, F. Chem. Ber. 1961,94, 2356. (19) Dryden, N. H.; Legzdins, P.; Trotter, J.;Yee, V. C. Orgunometallies 1991,10, 2857.
1282 Organometallics, Vol. 14,No. 3, 1995 (5.10 g, 67 mmol) and TMEDA (8.08 g, 69.5 mmol) in 50 mL of hexane, This solution was stirred overnight. The resulting mixture was cooled t o -78 "C, and solid 1,1,3,3-tetramethyl2-indanone (13.18 g, 70 mmol) was added. The mixture was allowed to reach room temperature. After 2 h the mixture was concentrated and 50 mL of water and 100 mL of diethyl ether was added, The organic layer was separated, washed twice with water, and dried on MgS04. After filtration the solvent was removed in vacuo. The resulting material was dried in vacuo at 80 "C. It was difficult to purify the product: yield ca. 90%;purity ca. 90%. It was used as such, and the resulting titanium complex was readily purified. The pure ligand can be obtained when the lithiated trimethylphosphine is isolated prior t o reaction with the indanone. A mixture of 5.77 g (29.1 mmol) of (CH3)zPCHzLiaTMEDAin 20 mL of pentane was slowly added to a solution of 1,1,3,3tetramethyl-2-indanone in 30 mL of pentane at 0 "C. The resulting mixture was stirred for 1 h at room temperature, and subsequently the product was extracted with 30 mL of water. A foam was formed. The water layer was separated and the organic materials were extracted two more times with water. The combined water layers were neutralized with HC1 until pH 7. The resulting alcohol was extracted with dichloromethane. After separation the dichloromethane layer was filtered over 1cm of silica. The solvent was removed in vacuo, leaving 6.41 g (83.1%)of the pure alcohol as a white solid. NMR (CDC13): 'H, CH3P 6 1.16 (2.5),CHzP 1.79 (3.21, CH3 1.31and 1.46, Ar 7.05-7.27, OH 1.59 (1.5); I3C, CH3P 6 16.4 (11.61, CHzP 36.7 (16.2), CH3 29.8 (1.6)and 23.8 (7.7),COH 87.5 (4.91, C(CH3)z 50.8, Ar 149.0 (1.11,127.2, 122.9; 31P, 6 -61.1. Titanium Dichloride Complex la. To a stirred mixture of 1.76 g (8 mmol) of (cyclopentadieny1)titaniumtrichloride and 60 mL of dichloromethane was added 1.8 g (8 mmol) of the lithium alkoxide derived from the alcohol a at 0 "C. The mixture was stirred for 16 h. The precipitate was removed by centrifugation, washed with dichloromethane, and centrifugated again. The combined dichloromethane layers were concentrated to ca. 3 mL. Then pentane was slowly added to induce crystallization of the product. The yellow material was filtered and dried in vacuo. Yield 2.7 g (67%). Anal. Calcd: C, 50.90;H, 7.79; C1, 17.67; P, 7.72; Ti, 11.93. Found: C, 50.77; H, 7.67; C1, 17.80; P, 7.95; Ti, 11.85. NMR (C6D6): 'H, CH3P 6 0.95 (6.7), CHzP 1.96 (10.0), t-BU 1.10, Cp 6.33 (2.0);31P,6 -1.8. NMR (CDzClz): 'H, CH3P 6 1.62 (8.8),CHzP 1.74 (10.81, t-BU 1.24, Cp 6.64 (2.2); 31P,6 +9.7. Titanium Dichloride Complex lb. A solution of butyllithium in hexane (19.7 mmol, 1.6 M) was added to a stirred solution of 5.2 g (ca. 19.7 mmol) of the alcohol b in 25 mL of hexane at 0 "C. The resulting mixture was concentrated to ca. 15 mL, and then 4.32 g (19.7 mmol) of (cyclopentadieny1)titanium trichloride was added at 0 "C. The mixture was stirred for another 16 h at room temperature. The precipitate was removed and washed four times with dichloromethane. The dichloromethane layers were combined and concentrated t o ca. 5 mL. Subsequently, pentane was added slowly to induce crystallization. The yellow material was filtered and dried in vacuo; yield 4.6 g (52%). Anal. Calcd: C, 56.40; H, 6.54; C1, 15.85; P, 6.93; Ti, 10.71. Found: C, 56.26; H, 6.48; C1, 16.11; P, 7.14; Ti, 10.45. NMR (CDzClz): 'H, CH3P 6 1.58 (4.31, CHzP 2.46 (8.51,CH3 1.34 and 1.60, Ar 7.2-7.4, Cp 6.44 (1.6); 31P,6 -17.2 (broadened). Alkylidene Complex 3a. This compound was prepared as described for 3b. The product was isolated as a green oil in ca. 90% yield. Crystals were obtained from a concentrated pentane solution at -40 "C. Anal. Calcd: C, 65.99; H, 10.32; Ti, 11.96. Found: c, 66.71; H, 10.15; Ti, 12.00. NMR (C6D6): 'H, CH-t-Bu 6 12.27 (3.81, C(CH3)3 1.22, Cp 6.11 (1.71, PMez 1.31 (6.4) and 0.71 (5.8),CHAHBP3.19 (10.4) and 2.40 (10.0), J(HAHB)= 16, t-Bu 0.97 and 1.44; 13C,neopentylidene, T i c 6 283.5 (11.4) [961, C(CH3)3 42.6, C(CH3)3 34.0 (3.6) [1241, Cp 106.7 [1711, alkoxide, PMez 23.2 (21.5) [1281 and 15.0 (9.1)
van Doorn et al. [127], CHzP 51.7 (22.0) [1251, CO 93.5 (4.51, C(CH3)347.2 (1.4) and 45.8 (2.31, CH3 30.8 [1261 and 30.1 [1251; 31P,6 0.53. Alkylidene Complex 3b. Solid neopentyllithium (585 mg, 7.5 mmol) was added to a stirred suspension of l b in pentane a t 0 "C. After the mixture was stirred for 2 h a t room temperature, the precipitate was removed by centrifugation. The liquid fraction was kept at room temperature for 24 h; then the solvent was removed, leaving a green solid, yield 90%. Crystals for the X-ray structure determination were prepared by recrystallization from a concentrated pentane solution at -40 "C. NMR of the intermediate dialkyl complex 2b: 'H (C6D6,20 "C), Cp 6 5.92, neopentyl, CH3 1.07, CHAHB,2.35 HBwas not observed due to overlap, J(HAHB)= 11Hz, phosphinoalkoxide, MezP 1.20, CHzP 2.01 (5), CH3 1.46 and 1.19, ArH, 5.9-7.2; I3C ([D&oluene, -30 "C), neopentyl, Tic 6 94.7 (3.2) [ l l l l , C(CH3)336.7, CH3 32.6 [125], Cp 110.8 [1721, alkoxide, PMez 16.2 (14) [125], CH2P 37.7 (17.9) [1251, CO 102.0 (8.61, C(CH312 51.1 (2.71, C(CH3)2 22.1 (7.8) [1251 and 29.8 [1261, Ar 126.2, 121.4, and 148.8; 31P(C6D6),6 -63.8. NMR of 3b: 'H (C6D6), 6 CH-t-Bu 11.92 (3.81, C(CH3)31.22, Cp 5.90 (1.7),PMez 1.23 (7.3)and 0.88 (6.21, CHAHBP3.41 (9.0) and 2.26 (8.7),J(HAHB)= 14.9, CH3 2.08, 1.28, 1.19, and 1.14; I3C ([D8]toluene),neopentylidene,Tic 278.1 (12.2) [951, C(CH3)3 45.8 (1.4), C(CH& 32.5 (3.2) [1241, Cp 105.1 [1691, alkoxide, PMez 19.9 (220) [127] and 13.7 (8.5) [1271, CHzP 44.7 (22.0) [125], CO 96.1 (5.81,C(CH3)2 52.8 (4.8) and 49.8, C(CH3)z 30.2 [125], 29.4 [125], 25.7 [1251, and 22.6 [1251,Ar, CH 125.9 [1551, 126.0 [155], 121.6 [155], and 121.5 [1551, C, 148.9 and 148.8; 31P([D&oluene), 6 1.03. Metallacycle 5. At room temperature 0.5 mL (ca. 0.04 mmol) of ethene gas was added to a solution of 80 mg (0.018 mmol) of alkylidene 3b in 3 mL of pentane. The resulting solution was cooled t o -40 "C. Orange crystals of the metallacycle were obtained (55 mg, 65% of theory). Anal. Calcd: C, 70.88; H, 9.13. Found: 70.66; H, 8.91. NMR: 11H, Ar 6 7.0-7.2, Cp 5.46, CH3 1.50, 1.42, 1.15, and 1.12, CH3P 0.93 (3.5) and 0.91 (3.8), PCH2 1.64 (4.61, t-Bu 1.04. The metallacyclobutaneresonances could be simulatedI5with the following data: Hi 6 3.09, H2 2.917, H3 1.738, H4 -0.400, H5 3.845, J(HIHz)= 9.05, J(H1H3)= 9.60, J(H'H4) = 12.5, J(H2H3)= 3.20, J(H2H4)= 10.50, J(H3H4)= 10.0, J(H3H5)= 12.0, J(H4H5) = 10.0, J(H5P)= 2.5; 31P 6 -63.6. Ethene Complex 8. To a mixture of the dichloride l b and C6D6 was added 1.3 equivalents of EtzMg-dioxane. The reaction was monitored by NMR. The resulting precipitate was removed by filtration, and the solvent was removed. The resulting purple solid ethene complex was identical with that derived from the reaction of the alkylidene 3b with ethene. NMR (C6D6): the 'H spectrum could be ~ i m u l a t e d with ' ~ the data H' 6 2.47, H2 2.01, H3 0.46, H4 0.15, CHAP3.36, CHBP 2.64, J(H1H2)= 10.9, J(H3H4)= 11.9, J(H1H3)= 5.2, J(H3P) = 3.1, J(H1H4)= 12.0, J(H4P)= 3.6, J(H'P) = 11.5, J(HAHB) = 14.7, J(H2H3)= 11.9, &HAP) = 8.4, J(H2H4)= 3.6, J(HBP) = 10.0; I3C, ethene, 6 58.8 (5) [144 tl, 55.0 [147, tl, Cp 107.6 [170, d], alkoxide, Ar 122.7 [155], one signal masked by benzene resonance, and 149.8, PMe, 15.1 (4) [128, ql and 12.2 (20) [129,q], CHzP 42.8 (19) [126, tl, CO 99.0 (81, C(CH3)z 53.5 (4) and 50.2, CH3 31.0 [126, ql, 30.6 [126, 91, 26.1 [126, 91, and 22.8 [126, q]; 31P,6 17.7. Ketene Complexes 9A and 9B. Carbon monoxide was bubbled through a green solution of the alkylidene 3b (ca. 80 mg, 0.02 mmol) in pentane. The red precipitate was filtered and dried in vacuo; yield ca. 80%. The product consists of two isomers, 9A and 9B Anal. Calcd: C, 68.35; H, 8.29; P, 6.53; Ti, 10.09. Found: C, 68.20; H, 8.20; P, 6.68; Ti, 10.25. NMR (CijDs) 9 A 'H, CH 6 4.19 (2.71, t-Bu 1.60, CHAHBP, HA2.58, HB2.12, J(HAHB)= 15, J(HAP)= 10, J(HBP)= 10.5, Cp 5.88 (2); I3C, CO 6 189.5 (4.8), C-t-Bu 89.4 (3.7), t-Bu, C 33.7 (2.81, CH3 32.0, Cp 110.2; 31P6 2.4. NMR (C6D6) 9B: '€3, CH 6 3.95 (1.81, t-Bu 1.59, CHAHBP, HA2.47, HB1.95, J(HAHB) = 15, J(HAP)= 10.2, J(HBP)= 10.2,
Organometallics, Vol. 14, No. 3, 1995 1283
Titanium Alkylidenes via Dineopentyl Complexes Cp 5.82 (2); 13C, 6 CO 196.9 (28.3),C-t-Bu 95.8 (2.4),t-Bu, C 33.2 (2.61, CH3 31.8, Cp 110.3; 31P6 -7.5. Bis(a1koxide) Complex 10. The mixture of ketene complexes 9A and 9B was dissolved in CsDs, and ethene was bubbled through the solution. The color changed from red to orange. NMR (CsDs): lH, 6 CH 4.19 (1.31, CHzCHz 3.41 (m) and 3.14 (m), t-Bu 1.33, Cp 5.97 (1.5),PCH3 1.03 (4.4) and 0.81 (3.9),PCH2 1.83 (8.9), CH3 1.50 and 1.46;13C,CO 6 164.6 (8.11, C-t-Bu 102.4, CHzC=C 48.0 (4.41, TiCH2 64.8 (10.61, t-Bu, C 31.5, CH3 31.6; 31P,6 -21.8.
Acknowledgment. We are indebted to Dr. B. Hessen for helpful discussions. Supplementary Material Available: Full tables of atomic coordinates, thermal parameters, and bond lengths and angles for 3b (3 pages). Ordering information is given on any current masthead page. OM940754K
