RELATIVE RATES OF HYDROSILYLATION OF REPRESENTATIVE ALKENES AND ALKYNES BY CP-ASTERISK-2YME-CENTER-DOT-THF AND [(CP2YME)-Y-TMS](2)

Reactivity in the hydrosilylation of alkenes and alkynes catalyzed by the organoyttrium catalysts Cp-2YMe . THF and [(Cp2YMe)-Y-TMS](2) is generally determined by the steric environment of the substrate. Alkyn es and conjugated alkenes show an increased reaction rate because of e lectronic effects; the magnitude of this increase is highly substrate dependent. The electron rich pyrrole system is particularly reactive, especially with the sterically open [(Cp2YMe)-Y-TMS](2) precatalyst. F or nonconjugated substrates, Cp-2YMe . THF is generally a more select ive catalyst than [(Cp2YMe)-Y-TMS](2).