Stabilizing Doubly Deprotonated Diazomethane: Isolable Complexes with CN22- and CN2- Radical Ligands

Transition metal complexes with a doubly deprotonated diazomethane (CNN2-) ligand have been proposed as fleeting intermediates in nitrogen transfer reactions. However, in contrast to isoelectronic azide (N3-), well-defined examples are unknown. We here report the synthesis , characterization of isolable complexes with terminal and bridging CNN2- 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 CO2 was obtained. Photofragmentation favors N-NC over NN-C bond cleavage as a route to cyanide and a transient metallonitrene complex.

Automated summary

The synthesis and characterization of isolable complexes with a doubly deprotonated diazomethane (CNN2-) ligand are reported, providing new fleeting intermediates for nitrogen transfer reactions. The bonding within the allenic dimetallanitrilimine core was investigated through the oxidation of the bridging ligand. Enhanced reactivity towards [3 + 2]-cycloaddition with CO2 was observed. Photofragmentation experiments favor the cleavage of the N-NC bond to generate cyanide and a transient metallonitrene complex.