Co6H8((PPr3)-Pr-i)(6): A Cobalt Octahedron with Face-Capping Hydrides

摘要

A square-planar Co-4 amide cluster, Co-4{N(SiMe3)(2)}(4) (2), and an octahedral Co-6 hydride cluster, Co6H8((PPr3)-Pr-i)(6) (4), were obtained from metathesis-type amide to hydride exchange reactions of a Co-II amide complex with pinacolborane (HBpin) in the absence/presence of (PPr3)-Pr-i. The crystal structure of 4 revealed face-capping hydrides on each triangular [Co-3] face, while the formal (Co2Co4I)-Co-II oxidation state of 4 indicated a reduction of the cobalt centers during the assembly process. Cluster 4 catalyzes the hydrosilylation of 2-cyclohexen-1-one favoring the conjugate reduction. Generation of the catalytically reactive Co cluster species was indicated by a trapping experiment with a chiral chelating agent.