Publication
Diazo compounds of the type R1R2CN2 are widely used in organometallic catalysis and synthetic chemistry. Stable diazoolefins, R1R2C=CN2, have only been isolated recently. Diazoolefins undergo cycloaddition reactions and tend to be carbon donors when used as ligands. In N-heterocyclic diazoolefin coordination chemistry, the diazo group mostly stays intact. However, when combined with VCl3(THF)3, an N-heterocyclic alkenylidene complex was obtained after spontaneous dinitrogen extrusion. The diazo moiety can also be removed photochemically. Irradiation of diazoolefins gives triplet vinylidene carbene intermediates, which undergo intramolecular C-H activation. Irradiation of diazoolefin copper complexes gave a collection of complexes, including a bridged alkenylidene copper cluster and a C4-cumulene ligand. In crystallo irradiation resulted in a monomeric copper alkenylidene, which likely acts as a reactive intermediate in solution-based reactions. A new type of diazoolefin was obtained after deprotonation and subsequent borylation. The resulting anionic diazoolefin was used in salt metathesis reactions and showed distinct reactivity compared to neutral diazoolefins. Stable carbene, germylene and multiple neutral diazonium compounds were reported. Combining diazoolefins with Fischer carbenes formed mixed Arduengo - Fischer carbodicarbene ligands via formal vinylidene insertion into the metalbond. The resulting complexes were able to undergo transmetallation reactions, resulting in multiple metal complexes with this novel carbodicarbene ligand.