Variable-valent rhenium chemistry of conjugated nitrogenous ligands: structure and reactivity

Abstract

The valence states of particular concern in this review are VI–I and the ligand types are diimine, azoimine, imineamide and azooximeall bidentate and N,N-coordinating. Metal reduction potentials and stability of oxidation states are subject to control via variation of the nature and extent of N,N-chelation and coligation. Back-bonding plays a major role in determining stability and isomer specificity, particularly in the valence domain III–I. Three types of mediated oxygen atom transfer processes have been scrutinized and modeled: from Re^VO to tertiary phosphanes and variable-spacer diphosphanes, from water to diimine and from oxime to metal/coligand. Other reactivity topics include isomerizations associated with ligand substitution, stable azo anion radical generation and azo cleavage.