Metal-templated ligand architectures for trinuclear chemistry: tricopper complexes and their O2 reactivity

Abstract

A trinucleating framework was assembled by templation of a heptadentate ligand around yttrium and lanthanides. The generated complexes orient three sets of two or three N-donors each for binding additional metal centers. Addition of three equivalents of copper(I) leads to the formation of tricopper(I) species. Reactions with dioxygen at low temperatures generate species whose spectroscopic features are consistent with a μ₃,μ₃-dioxo-tricopper complex. Reactivity studies were performed with a variety of substrates. The dioxo-tricopper species deprotonates weak acids, undergoes oxygen atom transfer with triphenylphosphine to yield triphenylphosphine oxide, and performs hydrogen atom abstraction from tetramethylpiperidine-N-hydroxide (TEMPO-H). Thiophenols reduce the oxygenated species to a Cu₃^I complex and liberate two equivalents of disulfide, consistent with a four-electron four-proton process.