Mechanistic Study of the Oxidative N-Dealkylation Reactions of Bis(μ-oxo)dicopper Complexes

The results of experiments designed to probe the mechanism by which the bis(μ-oxo)dicopper complexes [(LCu)2(μ-O)2](ClO4)2 (L = 1,4,7-tribenzyl-, 1,4,7-triisopropyl-, and 1,4-diisopropyl-7-benzyl-1,4,7-triazacyclononane ligands; LBn3, LiPr3, and LiPr2Bn, respectively) decompose to products arising from macrocyclic ligand N-dealkylation are described. After removal of copper from the decomposed solutions, analysis of the organic products revealed N-dealkylated ligands and aldehyde or ketone, the oxygen atoms in the latter being derived from the bis(μ-oxo)dicopper core as shown by 18O-isotope labeling experiments. Thus, the overall N-dealkylation is akin to monooxygenase reactions carried out by various metalloenzymes such as cytochrome P450, dopamine β-monooxygenase, and peptidyl glycine α-amidating monooxygenase. Direct, intramolecular attack of the bis(μ-oxo)dicopper core at a ligand substituent C−H bond during the rate-determining step was indicated by the observed first-order kinetics, the results of H...