EARLY METAL CARBORANE CHEMISTRY - GENERATION AND REACTIVITY OF (C(5)ME(5))(ETA(5)-C2B9H11)TIME

The methane elimination reaction of Cp()TiMe(3) (Cp(*) = C(5)Me(5)) a nd C2B9H13 yields the thermally sensitive titanacarborane (Cp())(eta( 5)-C2B9H11)TiMe (4), which has been characterized by H-1, C-13, and B- 11 NMR spectroscopy. Complex 4 decomposes at 23 degrees C to the fulve ne complex (eta(6)-C(5)Me(4)CH(2))(eta(5)-C2B9H11)Ti (5, 30% isolated) and forms labile adducts with PMe(3) and THF. Complex 4 inserts CH3CN , yielding (Cp())(eta(5)-C2B9H11)Ti(N=CMe(2))(MeCN) (7), which loses MeCN upon recrystallization from toluene to afford (Cp())(eta(5)-C2B9 H11)(Ti(N=CMe(2)) (8). X-ray diffraction analyses establish that 7 and 8 adopt monomeric bent metallocene structures with eta(5)-C2B9H11 lig ands. Data for 7: space group P (1) over bar, a = 9.588(6) Angstrom, b = 9.940(4) Angstrom, c = 13.034(5) Angstrom, alpha = 96.69(3)degrees, beta = 97.13(4)degrees, gamma = 96.70(4)degrees, V = 1213(1) Angstrom (3), Z = 2, R = 0.081, R(w) = 0.091. Data for 8: space group C2/c, a = 23.058(7) Angstrom, b = 13.042(6) Angstrom, c = 15.411(6) Angstrom, b eta = 118.66(3)degrees, V = 4179(3) Angstrom(3), Z = 8, R = 0.088, R(w ) = 0.088. Complex 4 also inserts 2-butyne, yielding (Cp())(eta(5)-C2 B9H11)Ti(CMe=CMe(2)) (9). The reaction of 4 with ethylene yields prope ne and (Cp())(eta(5)-C2B9H11)TiEt (10), which adopts a beta-agostic s tructure. The B-11 NMR spectra of 4-10 are similar and indicate that a ll of these compounds have bent metallocene structures analogous to th ose established crystallographically for 7 and 8. Complex 10 catalyzes the slow dimerization of ethylene to 1-butene; this contrasts with th e ethylene polymerization catalysis observed for the analogous d(0) me tallocenes Cp(2)()ScR and Cp(2)(*)Ti(R)(+).