Formation of a Bridged Butterfly-Type μ-η2:η2-Peroxo Dicopper Core Structure with a Carboxylate Group

A new μ-η2:η2-peroxo dicopper(II) complex, [CuII2(αSp)2(μ-η2:η2-O2)(Bz-)]SbF6 (αSp = α-isosparteine, Bz- = benzoate) was synthesized by oxygenation of [CuI(αSp)(CH3CN)]SbF6 with Bz- at −80 °C in acetone. X-ray crystallographic analysis of the dark blue crystal revealed that the “bridged butterfly core” is formed by bridging Bz- bound in the axial position. The weaker σ-electron donation of αSp causes the axial coordination of Bz- to stabilize the butterfly-type μ-η2:η2-peroxo dicopper(II) species as an intermediate of stepwise O2-activation to bis(μ-oxo) dicopper(III) species.