Reactions of copper complexes with dioxygen and oxo transfer reagents: toward elusive copper-oxyl species.

Abstract

The binding and activation of dioxygen by Cu ions is central to the function of numerous biological systems. Among the enzymes activate dioxygen for the functionalization of organic substrates, those catalyzed by the mononuclear copper enzymes dopamine β-monooxygenase (DβM) and peptidylglycine α-hydroxylating monooxygenase (PHM) are less understood. Despite extensive research on these enzymes, the exact nature of the active species responsible for substrate functionalization is not resolved, with two provocative proposals involving either a CuII-superoxo or a mononuclear CuII-oxyl species having been put forth. The goal of this research is to understand the reaction catalyzed by the PHM and DβM enzymes on a fundamental chemical level via a small molecule synthetic model approach, with particular emphasis on generating and/or characterizing a Cu-oxygen species that is capable of performing similar reactions to those seen in the DβM and PHM enzymes. Chapter 1 contains a general overview of dioxygen activation in biological systems and gives a review of the structure and proposed catalytic mechanisms of DβM and PHM, followed by a summary of recent synthetic efforts toward mononuclear Cu/O2 adducts and Cu-oxyl species. Chapter 2 describes the synthesis and characterization of the copper(I) complexes of the electron-deficient β-diketiminate and analogous 4- nitroformazan supporting ligands, and their O2-reactivity studies, portions of which have been previously reported.1 Chapter 3 describes a bio-inspired synthetic route toward a mononuclear Cu-oxyl species that involves decarboxylation of copper(I)-α- ketocarboxylate complexes by dioxygen; portions of the work have been communicated previously.2 Chapter 4 then describes results obtained from reactions of copper(I) complexes of bidentate N-donor ligands with pyridine- and trimethylamine N-oxides or PhIO. Portions of this work were previously reported.3