Heterobimetallic catalysis is an approach to catalysis that employs two different metals to promote a chemical reaction. Included in this definition are cases (Scheme 1) where: 1) each metal activates a different substrate (synergistic catalysis, used interchangeably with the terms "cooperative" and "dual" catalysis.), 2) both metals interact with the same substrate, and 3) only one metal directly interacts with the substrate(s), while the second metal interacts with the first.