SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF ((ETA(5)-C(5)ME(4))(2)SIME(2))YCH(SIME(3))(2) - HYDROGENATION TO [((ETA(5)-C(5)ME(4))(2)SIME(2))Y](2)(MU(2)-H)(2) AND ITS FACILE LIGAND REDISTRIBUTION TO 5)ME(4))SIME(2)(ETA(5)-C(5)ME(4)))](2)(MU(2)-H)(2)

Syntheses of the new ansa yttrocene derivatives OpY(mu-Cl)(2)Li(OEt(2) )(2) (Op = {(eta(5)-C(5)Me(4))(2)SiMe(2)}), OpYCH(SiMe(3))(2) and [OpY ](2)(mu(2)-H)(2) are described. The structure of OpYCH(SiMe(3))(2) has been examined by single crystal X-ray diffraction methods. OpYCH(SiMe (3))(2) crystallizes in the monoclinic space group P2(1)/c (no. 14) wi th a = 10.441(2), b = 15.480(3), c = 19.644(4) Angstrom, beta = 105.28 (1)degrees and Z = 4. The bis(trimethylsilyl)methyl ligand is distorte d in the equatorial plane such that one of the methyl groups of the [C H(SiMe(3))(2)] bridges yttrium and a silicon in a 3-center, 2-electron bridging fashion. Hydrogenolysis of OpY-CH(SiMe(3))(2) results, initi ally, in the formation of the ansa yttrocene hydride dimer [OPY](2)(mu (2)-H)(2). This compound is unstable with respect to ligand redistribu tion affording the hydride- and Op-bridged ('flyover') hydride dimer ) Me(4))SiMe(2)(eta(5)-C(5)Me(4))}](2)(mu(2)-H)(2).