CRYSTAL-STRUCTURES AND CONFORMATIONAL-ANALYSIS OF COMPLEXES OF THE TYPE CP2TI(SIHRR')PME3 (R, R' = H, ME, PH) - RELATIONSHIPS BETWEEN CALCULATED MOLECULAR-STRUCTURES AND OBSERVED SOLID-STATE STRUCTURES

In an effort to understand the effects of steric factors on catalytic silane dehydrocoupling reactions, the X-ray crystal structures of the catalyst model compounds Cp2Ti(SiH2Ph)PMe3 [a = 8.548(2) angstrom, b = 9.098(2) angstrom, c = 12.786(2) angstrom, beta = 101.48(2)degrees; monoclinic, P2(1); 2 molecules per unit cell] and Cp2Ti(SiHMePh)PMe3 [a = 9.076(3) angstrom, b = 12.078(4) angstrom, c = 18.299(5); orthorhombic, P2(1)2(1)2(1); 4 molecules per unit cell] were determined and compared to those of similar compounds from the literature. The conformational energy profiles for silyl ligand rotation in these two compounds and in Cp2Ti(SiHPh2)PMe3, obtained utilizing molecular mechanics calculations, suggest that the conformations, and apparently distorted Ti-Si-C(ipso) angles, exhibited in the solid state by all three compounds are determined by intramolecular steric factors.