Stabilizing Doubly Deprotonated Diazomethane: Isolable Complexes with CN 2 2- and CN 2 - Radical Ligands.

Transition metal complexes with a doubly deprotonated diazomethane (CNN 2- ) ligand have been proposed as fleeting intermediates in nitrogen transfer reactions. However, in contrast to isoelectronic azide (N 3 - ), well-defined examples are unknown. We here report the synthesis and characterization of isolable complexes with terminal and bridging CNN 2- ligands, stabilized by platinum(II) pincer fragments. Bonding within the allenic dimetallanitrilimine core (Pt-N═N═C-Pt) was probed by oxidation of the bridging ligand. Enhanced reactivity toward [3 + 2]-cycloaddition with CO 2 was obtained. Photofragmentation favors N-NC over NN-C bond cleavage as a route to cyanide and a transient metallonitrene complex.