Organometallic intermediates in the group 4 metallocene-catalyzed dehydrocoupling of organosilanes. 2. Variations in the intermediates of dimethyltitanocene reactions with several silanes

As previously described, organosilanes react with dimethyltitanocene (DMT) to give three reduced titanium intermediates, Cp 2 Ti(μ-SiRR′H)(μ-H)TiCp 2 , 1 , [Cp 2 Ti(μ-SiRR′H)] 2 , 2 , and [Cp 2 Ti(H)] 2 (μ-H), 3. When R = Me and R′ = n-Bu, the DMT is quantitatively converted to 1 , which is persistent at room temperature. When R′ = H, DMT is initially converted quantitatively to 1 , which then rapidly declines to give an equilibrium mixture of 1 , 2 , and 3 , with 2 as the dominant species. When R = Ph and R′ = Ph or Me, 1 is again produced quantitatively, but it rapidly declines to produce an unidentified paramagnetic product, rather than 2 or 3 . It is believed that 2 is unstable with respect to dissociation in these cases due to the steric bulk of the substituents.