A platinum(ii) metallonitrene with a triplet ground state

Metallonitrenes (M–N) are complexes with a subvalent atomic nitrogen ligand that have been proposed as key reactive intermediates in nitrogen atom transfer reactions. However, in contrast to the common classes of nitride complexes (M≡N) and organic nitrenes (R–N), structurally and spectroscopically well defined ‘authentic’ metallonitrenes with a monovalent atomic nitrogen ligand remain elusive. Here we report that the photolysis of a platinum(ii) pincer azide complex enabled the crystallographic, spectroscopic, magnetic and computational characterization of a metallonitrene that is best described as a singly bonded atomic nitrogen diradical ligand bound to platinum(ii). The photoproduct exhibits selective C–H, B–H and B–C nitrogen atom insertion reactivity. Despite the subvalent metallonitrene character, mechanistic analysis for aldehyde C–H amidation shows nucleophilic reactivity of the N-diradical ligand. Ambiphilic reactivity of the metallonitrene is indicated by reactions with CO and PMe3 to form isocyanate and phosphoraneiminato platinum(ii) complexes, respectively. Transient metallonitrenes (M–N) have been proposed as key intermediates in nitrogen atom transfer reactions, but well-defined examples have remained elusive. Now, a platinum complex with an atomic nitrogen ligand, best described as a subvalent nitrogen diradical singly bonded to a platinum(ii) ion (Pt–N), has been isolated and shows ambiphilic reactivity.