Interpnictogen cations: exploring new vistas in coordination chemistry.

Pnictine derivatives can behave as both 2e(-) donors (Lewis bases) and 2e(-) acceptors (Lewis acids). As prototypical ligands in the coordination chemistry of transition metals, amines and phosphines also form complexes with p-block Lewis acids, including a variety of pnictogen-centered acceptors. The inherent Lewis acidity of pnictogen centers can be enhanced by the introduction of a cationic charge, and this feature has been exploited in recent years in the development of compounds resulting from coordinate Pn-Pn and Pn-Pn' interactions. These compounds offer the unusual opportunity for homoatomic coordinate bonding and the development of complexes that possess a lone pair of electrons at the acceptor center. This Review presents new directions in the systematic extension of coordination chemistry from the transition series into the p-block.