Stabilisation of copper(I) by an azoimine ligand: Redox properties and reactions of bis(phenylazoacetaldoximato)bis(phenylacetaldoxime)dicopper(I)

Abstract

The high preference of phenylazoacetaldoxime, MeC(=NOH)N=NPh (HL), for copper(I) is rationalised in terms of electronic and steric factors. The complex [Cu2(HL)2(L)2] (1) undergoes a one-electron oxidation at ∼0.8 V vs. saturated calomel electrode to an unstable CuIICuI species. Tertiary phosphines displace HL from (1) affording [CuL(PR3)2] [R = Ph (2a) or C6H4Me-p (2b)]. (2a) reacts with HCl to form [{Cu(PPh3)Cl}4] and with HClO4 to give the complex [Cu(HL)(PPh3)2 (ClO4)]. All complexes having the chelated CuL or Cu(HL) fragment are shown to have a characteristic low-energy metal-to-ligand charge-transfer transition (700-900 nm).