THEORETICAL-STUDY OF CP2TI(H)(SIH3) AND CP2TISIH2 AND THEIR POSSIBLE ROLE IN THE POLYMERIZATION OF PRIMARY ORGANOSILANES

The two reactions Cp2Ti(H)(SiH3) → Cp2Ti═SiH2 + H2 and Cp2Ti═SiH2 + SiH4 → Cp2Ti(H)SiH2SiH3 have been modeled with use of density functional theory and the HFS-LCAO program system by Baerends et al. Both kinetic and thermodynamic features of these reactions were studied, and the results of the computations indicate that the first reaction can proceed with a moderate activation barrier of ca. 60 kJ mol-1 and an enthalpy of ca. 40 kJ mol-1. The second reaction is found to be exothermic (ca. -48 kJ mol-1) with an activation barrier of ca. 12 kJ mol-1. The previously proposed mechanism for the titanocene-catalyzed dehydrocoupling of organosilanes is evaluated in terms of these calculations, and it is concluded that the α-hydride elimination–silane addition route is viable. The structural and thermodynamic parameters for each of the important reaction intermediates are also calculated. © 1990, American Chemical Society. All rights reserved.