Synthesis of silyl cobalt hydrides and their catalytic activity on hydrosilylation of alkenes.

Two silyl [P,Si]‐chelate cobalt hydrides, [(o‐Si(Ph)2‐(PiPr2)C6H4)Co(H)(PMe3)2] (1) and [(o‐Si(Ph)2‐(PPh2)C6H4)Co(H)(PMe3)2] (2), were prepared through the chelate‐assisted Si–H activation of bidentate preligand, o‐HSi(Ph)2‐(PiPr2)C6H4 (L1) and o‐HSi(Ph)2‐(PPh2)C6H4 (L2) by [Co(PMe3)4] or [Co(Me)(PMe3)4], respectively. Both cobalt(II) hydrides 1 and 2 can efficiently catalyze hydrosilylation of olefins, and the catalytic effect of complex 1 is better than that of complex 2. The Markovnikov products were formed from aryl alkenes, whereas the anti‐Markovnikov products were produced from aliphatic alkenes. In the mechanism study, a silyl cobalt(II) intermediate, [(o‐Si(Ph)2‐(PiPr2)C6H4)Co(SiHPh2)(PMe3)2], as the real catalyst is proposed and supported by in situ infrared (IR) study. The molecular structure of complex 1 was determined by single crystal X‐ray diffraction analysis. [ABSTRACT FROM AUTHOR]