Synthesis of silyl cobalt hydrides and their catalytic activity on hydrosilylation of alkenes
Haiquan Yang, Guoliang Chang, Xiaoyan Li, Hongjian Sun, Olaf Fuhr, Dieter Fenske
Abstract
Two silyl [P,Si]‐chelate cobalt hydrides, [( o‐ Si(Ph) 2 ‐(P i Pr 2 )C 6 H 4 )Co(H)(PMe 3 ) 2 ] ( 1 ) and [( o ‐Si(Ph) 2 ‐(PPh 2 )C 6 H 4 )Co(H)(PMe 3 ) 2 ] ( 2 ), were prepared through the chelate‐assisted Si–H activation of bidentate preligand, o ‐HSi(Ph) 2 ‐(P i Pr 2 )C 6 H 4 ( L1 ) and o ‐HSi(Ph) 2 ‐(PPh 2 )C 6 H 4 ( L2 ) by [Co(PMe 3 ) 4 ] or [Co(Me)(PMe 3 ) 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 ‐(P i Pr 2 )C 6 H 4 )Co(SiHPh 2 )(PMe 3 ) 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.