Metal-catalyzed nucleophilic carbon-heteroatom (C-X) bond formation: the role of M-X intermediates

Many important reactions that lead to carbon-heteroatom bond formation involve attack of anionic heteroatom nucleophiles, such as hydroxides, alkoxides, amides, thiolates and phosphides, at carbon. Related catalytic transformations are mediated by late transition metal complexes of these groups, which remain nucleophilic on metal coordination as a result of repulsive filled-filled interactions between the heteroatom lone pairs and metal d-orbitals and/or of polarization of the bonds M delta+-X delta-. This Perspective presents examples of catalytic nucleophilic C-X bond formation in both biological and synthetic systems and describes how changes in the metal, ancillary ligands and X groups may be used to tune nucleophilic reactivity.