Reactivity of Copper Complexes with Tripodal Tetradentate Ligands based on Camphoric Acid towards Dioxygen

Abstract

AbstractThe reaction of dioxygen with copper(I) complexes containing camphor‐derived ligands was investigated. Stopped‐flow measurements revealed the formation of bis(μ‐oxido) copper complexes at low temperatures. However, these intermediates were not stable enough to be isolated and decomposed quickly. Sterically more demanding alkyl groups slowed the formation of the bis(μ‐oxido) copper complexes. A kinetic analysis was performed and showed ‐ in line with previous reports ‐ that the rate‐determining step could be assigned to forming a mononuclear superoxido copper complex. For one of the reactions investigated, a product could be structurally characterized and turned out to be a copper(II) complex with an additional hydroxide as a ligand (most likely caused by a C−H abstraction from the solvent acetone). One of the complexes oxidized thioanisole to the corresponding sulfoxide (conversion of 34 % according to GC‐MS) with no byproducts. Chiral GC gave an enantiomeric excess of 14 %.