PyridineN-oxide promoted hydrosilylation of carbonyl compounds catalyzed by [PSiP]-pincer iron hydrides

Five [PSiP]-pincer iron hydrides1-5, [(2-Ph2PC6H4)(2)HSiFe(H)(PMe3)(2)(1), (2-Ph2PC6H4)(2)MeSiFe(H)(PMe3)(2)(2), (2-Ph2PC6H4)(2)PhSiFe(H)(PMe3)(2)(3), (2-(iPr)(2)PC6H4)(2)HSiFe(H)(PMe3) (4), and (2-(iPr)(2)PC6H4)(2)MeSiFe(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 degrees C because the addition of pyridineN-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.