CuI Thiolate Reactivity with Dioxygen: The Formation of CuII Sulfinate and CuII Sulfonate Species via a CuII Thiolate Intermediate

Abstract

Cu(I)(Py2NS) (1) is formed by addition of Cu(I) to a solution of the pyridyl-thiol ligand N-(2-mercaptopropyl)-N,N-bis(2-pyridylmethyl)amine (Py2NSH). Oxidation of complex 1 by air leads to the formation of Cu(II) sulfinate and Cu(II) sulfonate complexes, providing a model for the oxidative degeneration of copper-sulfur enzymes. Crystal structures were obtained for two Cu(II) sulfinate complexes, [Cu(II)2(Py2NSO2)2](BF4)2·2(CH3)2CO (4a) and [Cu(II)2(Py2NSO2)2(OTf)2] (4b), which were further characterized by UV-vis and EPR spectroscopy and cyclic voltammetry. Furthermore, two Cu(II) sulfonate complexes with the proposed formulas Cu(II)2(Py2NSO3)2(BF4)2 (5a) and Cu(II)2(Py2NSO3)2(OTf)2 (5b) have been isolated and characterized. Monitoring the oxidation of 1 by UV-vis indicates that the oxidation proceeds via a dinuclear Cu(II) μ-thiolate complex (3); as an intermediate an octanuclear mixed-valent Cu(I)4Cu(II)4 cluster with formula [Cu(I)4Cu(II)4(Py2NS)4(μ-OH)2(CH3CN)6](ClO4)6·2CH3CN (2) was isolated and characterized by X-ray single crystal structure determination.