Transition metal mediated C-X coupling reactions form an integral part of chemistry today due to their immense utility in synthesis of previously unaccessible substrates. Most of the transition metal based coupling reactions, however, use expensive metals, most commonly palladium and less frequently iridium and rhodium. In this light, coupling reactions using cheap and abundant base metals presents an interesting frontier. Cobalt is an alluring alternative due to the availability of a Co(III)/Co(I) couple analogous to that of Pd(0)/Pd(II) for coupling reactions. The mechanism for cobalt based coupling reactions is still largely unestablished even though a few instances of catalytic activity by cobalt complexes have been reported recently. We intend to bridge this gap by studying the various steps involved in a typical catalytic cycle such as oxidative addition, reductive elimination for a Co(III)/Co(I) couple. In this report, we focus our efforts on investigating the reductive elimination of carbon- carbon and carbon-heteroatom bonds from a cobalt(III) complex with pincer ligands as the ancillary ligands. The results with a variety of pincer ligands such as (PoCoP), PCP, PNP and PSiP will be highlighted to illustrate the effects of changing the central donor atoms on the kinetics. The effect of varying the bulk of the phosphine side arms will also be discussed to elucidate the role sterics might play in these transformations. The nature of C-X bond eliminations to be studied include C-C (sp2, sp3), C-S and C-N bonds. We believe that these studies will broaden our understanding of Cobalt based catalysis and help design new Co catalysts for coupling reactions.

Studies on the reductive elimination of C-X ( X = C, N, S) bonds from a Co(III) center and its applications in catalysis

249th National Meeting (2015)

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