Comparison of the Reactivities and Selectivities of Group 9 [Cp*M^III ] Catalysts in C-H Functionalization Reactions

Pentamethylcyclopentadienyl (Cp*)-based Group 9 metal (Co, Rh, or Ir) catalysts have emerged as powerful tools for C-H functionalization reactions. Whilst a diverse range of organic transformations have been developed by using [Cp*M^III ] catalysts, they have often exhibited orthogonal reactivities and varied selectivities that depended on the choice of the central metal atom. An understanding of the physicochemical properties of the metals, as well as of their reaction mechanisms, has led to significant expansion of the synthetic scope of C-H functionalization reactions. This Focus Review summarizes and discusses the comparative catalytic reactivities and selectivities of the [Cp*M^III ] catalysts, with an emphasis on metal-dependent pathway-switching by considering the mechanistic rationale.