Properties and Hydrogen Atom Transfer Reactivity of Copper(III)-Hydroxide Complexes

Abstract

The conversion of C-H bonds in hydrocarbons to C-O bonds is one of the grand challenges in chemistry as it involves the energy demanding preliminary step of removing a hydrogen atom from the strong C-H bond via an initial hydrogen atom transfer step. A number of high-valent reactive transition metal-oxygen species are proposed to be the key intermediates that perform such hydrogen atom transfer reactions in biological and synthetic systems. The mononuclear copper(III)-hydroxide unit has been demonstrated to be a potent reactive species in this regard. The work in this thesis is focused on the chemistry of such synthetic mononuclear copper(III)-hydroxide cores generated using strongly electron donating pyridine di-carboxamido based ligand scaffolds. In particular the spectroscopic properties and hydrogen atom transfer reactivity of a series of such copper(III)-hydroxide complexes is explored in the light of the well established proton-coupled-electron transfer theory. The effects of ligand electronic perturbations on the properties and reactivity patterns of these compounds is explored through detailed spectroscopic and mechanistic invetsigations, with the ultimate aim of elucidating the intrinsic factors that contribute to the high efficiency of such species as hydrogen atom transfer reagents. A key conclusion from all of these studies is that the thermodynamic driving force plays a crucial role in determining the rates and mechanism of such hydrogen atom transfer reactions, and that a systematic tuning of the supporting ligand electronics modulates these intrinsic thermodynamic driving forces.