Azavinylidene complexes of metalloporphyrins and metallophthalocyanines

Abstract

Metal azavinylidene (M−N=CR1R2) complexes have received much attention due to their involvement in catalysis and their intriguing structures and reactivities. We have been endeavoring to develop the chemistry of metal azavinylidene complexes supported by macrocyclic chelating ligands including porphyrins and phthaocyanines.1,2 These macrocyclic tetradentate ligands have been found to well support the formation of trans-bis(azavinylidene) complexes of a high-valent transition metal, as well as trans-bis(imine) and trans-bis(secondary amine) complexes of low-valent transition metals. A synthetic route to metal azavinylidene complexes by oxidative deprotonation of metal imine complexes with a hypervalent iodine compound has been developed; such reaction provides useful insight into the mechanism of related nitrene transfer reactions mediated/catalyzed by metal complexes. The trans-bis(azavinylidene) complexes of metalloporphyrins or metallophthalocyanines exhibit a number of unprecedented spectral/structural features and/or reactivities. Attempts to extend similar chemistry to other types of cyclic chelating ligands, such as cuboidal Fe3S4 clusters as inorganic cyclic tridentate ligands, are also discussed.