Closed-shell and open-shell square-planar iridium nitrido complexes

Coupling reactions of nitrogen atoms represent elementary steps to many important heterogeneously catalysed reactions, such as the Haber-Bosch process or the selective catalytic reduction of NO x to give N 2. For molecular nitrido (and related oxo) complexes, it is well established that the intrinsic reactivity, for example nucleophilicity or electrophilicity of the nitrido (or oxo) ligand, can be attributed to M-N (M-O) ground-state bonding. In recent years, nitrogen (oxygen)-centred radical reactivity was ascribed to the possible redox non-innocence of nitrido (oxo) ligands. However, unequivocal spectroscopic characterization of such transient nitridyl {M=N ̇} (or oxyl {M-O ̇}) complexes remained elusive. Here we describe the synthesis and characterization of the novel, closed-shell and open-shell square-planar iridium nitrido complexes [IrN(L t-Bu)] + and [IrN(L t-Bu)] (L t-Bu =N(CHCHP-t-Bu 2) 2). Spectroscopic characterization and quantum chemical calculations for [IrN(L t-Bu)] indicate a considerable nitridyl, {Ir=N ̇}, radical character. The clean formation of Ir I-N 2 complexes via binuclear coupling is rationalized in terms of nitrido redox non-innocence in [IrN(L t-Bu)]. © 2012 Macmillan Publishers Limited. All rights reserved.