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A square-planar Co4 amide cluster, Co4{N(SiMe3)2}4 ( 2), and an octahedral Co6 hydride cluster, Co6H8(P iPr3)6 ( 4), were obtained from metathesis-type amide to hydride exchange reactions of a CoII amide complex with pinacolborane (HBpin) in the absence/presence of P iPr3. The crystal structure of 4 revealed face-capping hydrides on each triangular [Co3] face, while the formal CoII2CoI4 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. [ABSTRACT FROM AUTHOR]