Bimetallic cooperation across the periodic table

Organometallic chemistry and its applications in homogeneous catalysis have been dominated by mononuclear transition-metal complexes. The catalytic performance and physico-chemical properties of these mononuclear complexes can be rationally tuned by ligand modification, which has also led to the discovery of new reactions. There is a growing body of evidence implicating the participation of two metals in catalytic processes originally believed to follow monometallic mechanisms. Moreover, the deliberate preparation of bimetallic structures has proven popular because these preorganized structures have many tunable features, such as metal–metal bond order and polarity. These structures can exhibit metal–metal complementarity and allow for multisite activation — reactivity unattainable with truly mononuclear species. This Perspective summarizes the features that are exclusive to bimetallic systems and their roles in substrate activation. Bimetallic complexes are fertile territory for investigating metal–metal cooperativity. This Perspective highlights how complexes with two proximal metals have tunable features of relevance to bond activation, catalysis and unprecedented reactivity.