Synthesis, structure and dioxygen reactivity of a bis(μ-iodo)dicopper(I) complex supported by the [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine ligand

The air-sensitive bis(mu-iodo) dicopper( I) complex 1 supported by [N-(3,5- di-tert-butyl-2-hydroxybenzyl)-N, N- di-(2-pyridylmethyl)] amine (L) has been prepared by treating copper( I) iodide with L in anhydrous THF. Compound 1 crystallizes as a dimer in space group C2/c. Each copper(I) center has distorted tetrahedral N2I2 coordination geometry with Cu - N( pyridyl) distances 2.061( 3) and 2.063( 3) angstrom, Cu - I distances 2.6162( 5) and 2.7817( 5) and a Cu center dot center dot center dot Cu distance of 2.9086( 8) angstrom. Complex 1 is rapidly oxidized by dioxygen in CH2Cl2 with a 1 : 1 stoichiometry giving the bis(mu-iodo) peroxodicopper(II) complex [Cu(L)(mu-I)](2)O-2 ( 2). The reaction of 1 with dioxygen has been characterized by UV-vis, mass spectrometry, EPR and Cu K-edge X-ray absorption spectroscopy at low temperature ( 193 K) and above. The mass spectrometry and low temperature EPR measurements suggested an equilibrium between the bis(mu-iodo) peroxodicopper(II) complex 2 and its dimer, namely, the tetranuclear ( peroxodicopper(II)) 2 complex [Cu(L)(mu-I)](4)O-4 (2'). Complex 2 undergoes an effective oxo-transfer reaction converting PPh3 into O = PPh3 under anaerobic conditions. At sufficiently high concentration of PPh3, the oxygen atom transfer from 2 to PPh3 was followed by the formation of [Cu(PPh3)(3)I]. The dioxygen reactivity of 1 was compared with that known for other halo( amine) copper( I) dimers.