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In this study, two [PCP] pincer silylene cobalt(I) complexes [((Ph2POCH2)2CH)Co(PMe3)(SiCl((NtBu)2CAr))] (Ar = Ph (2) and 4-MePh (3)) were synthesized through the substitution reaction of the [PCP] pincer cobalt(I) complex [((Ph2POCH2)2CH)Co(PMe3)2] (1) with silylene ligands: SiCl((NtBu)2CAr) (Ar = Ph (L1) and 4-MePh (L2)). The reaction of complex 2 with CO afforded the carbonyl silylene cobalt(I) complex [((Ph2POCH2)2CH)Co(CO)(SiCl((NtBu)2CPh))] (4), while complex 2 reacted with CH3I to give rise to cobalt(II) iodide [((Ph2POCH2)2CH)Co(I)(PMe3)] (6). With a catalyst loading of 2 mol%, complex 6 displayed efficient catalytic activity for hydrosilylation of alkenes by using Ph2SiH2 as the hydrogen source under mild conditions. The molecular structures of complexes 2, 3, 4 and 6 were determined by single crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Five [PSiP]-pincer iron hydrides 1–5, [(2-Ph2PC6H4)2HSiFe(H)(PMe3)2 (1), (2-Ph2PC6H4)2MeSiFe(H)(PMe3)2 (2), (2-Ph2PC6H4)2PhSiFe(H)(PMe3)2 (3), (2-(iPr)2PC6H4)2HSiFe(H)(PMe3) (4), and (2-(iPr)2PC6H4)2MeSiFe(H)(PMe3)2 (5)], were used as catalysts to study the effects of pyridine N-oxide and the electronic properties of [PSiP]-ligands on the catalytic hydrosilylation of carbonyl compounds. It was proved for the first time that this catalytic process could be promoted with pyridine N-oxide as the initiator at 30 °C because the addition of pyridine N-oxide is beneficial for the formation of an unsaturated hydrido iron complex, which is the key intermediate in the catalytic mechanism. Complex 4 as the best catalyst shows excellent catalytic performance. Among the five complexes, complex 3 was new and the molecular structure of complex 3 was determined by single crystal X-ray diffraction. A proposed mechanism was discussed. [ABSTRACT FROM AUTHOR]