Coupling of terminal iridium nitrido complexes

Abstract

The oxidative coupling of nitride ligands (N3−) to dinitrogen and its microscopic reverse, N2-splitting to nitrides, are important elementary steps in chemical transformations, such as selective ammonia oxidation or nitrogen fixation. Here an experimental and computational evaluation is provided for the homo- and heterocoupling of our previously reported iridium(IV) and iridium(V) nitrides [IrN(PNP)]n (n = 0, +1; PNP = N(CHCHPtBu2)2). All three formal coupling products [(PNP)IrN2Ir(PNP)]n (n = 0–+2) were structurally characterized. While the three coupling reactions are all thermodynamically feasible, homocoupling of [IrN(PNP)]+ is kinetically hindered. The contributing parameters to relative coupling rates are discussed providing qualitative guidelines for the stability of electron rich transition metal nitrides.