Three-coordinate monoanions of rhodium(1–) and iridium(1–): Isolable examples of coordinatively-unsaturated metalate anions

Abstract

Metalate complexes – those that possess metal centers in formally negative oxidation states – are typically coordinatively and electronically saturated organometallic species. The reduced nature of the metal centers within these complexes is well understood to be responsible for their high reactivity as metal-based nucleophiles. While the chemistry of such complexes is extensive, there are very few examples where coordinative or electronic unsaturation accompanies highly-reduced d-orbital manifolds as a means to augment reactivity. Reported here is the isolation of the 16e–, d10 rhodium and iridium metalate anions, [M(CNArDipp2)3]–, where coordinative unsaturation is achieved through the use of encumbering m-terphenyl isocyanide ligands. Reactivity studies with electrophiles demonstrate that the Rh and Ir centers in these metalates retain significant nucleophilic character, which enables the formation of unusual metal/main-group-element species on account of low coordination numbers.