Metal-ligand multiple-bonds have long been of interest to organometallic chemists since they are the active intermediates for catalysis in oxidation reactions, such as epoxidation and aziridination. Particular attention has been paid to oxo, imido and nitrido complexes of earth-abundant first row transition metals, in particular iron, although little attention is given to earlier metals such as chromium. Most chromium complexes with these multiple bonds feature porphyrins or salens as auxiliary ligands, but these complexes have limited reactivity since they are high valent. A stronger s-donor ligand prepared by our group incorporating dianionic tetracarbenes combines the anionic charge of salen and porphyrin ligand systems with the improved s-donor strength of N-heterocyclic carbenes. This macrocyclic tetracarbene ligand platform stabilizes a rare electronically unsaturated, low valent, Cr(II) square planar complex that is highly reactive towards oxidants such as Me<sub>3</sub>NO and organic azides. Different levels of steric bulk gives rise to chromium oxo, imido, and tetrazene complexes and the first example of a chromium m-nitrido species. The synthesis, structure and reactivity trends of these novel chromium tetracarbene complexes will be shown and this research is the most detailed study done on chromium-ligand multiple-bonding supported by a single auxiliary ligand platform.

Unprecedented chromium-ligand multiple bonding and oxidative group transfer reactions supported by a macrocyclic N-heterocyclic tetracarbene

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.