Cu^I Thiolate Reactivity with Dioxygen: The Formation of Cu^II Sulfinate and Cu^II Sulfonate Species via a Cu^II Thiolate Intermediate

CuI(Py2NS) (1) is formed by addition of CuI 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 CuII sulfinate and CuII sulfonate complexes, providing a model for the oxidative degeneration of copper–sulfur enzymes. Crystal structures were obtained for two CuII sulfinate complexes, [CuII2(Py2NSO2)2]­(BF4)2·2­(CH3)2CO (4a) and [CuII2(Py2NSO2)2(OTf)2] (4b), which were further characterized by UV–vis and EPR spectroscopy and cyclic voltammetry. Furthermore, two CuII sulfonate complexes with the proposed formulas CuII2(Py2NSO3)2(BF4)2 (5a) and CuII2(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 CuII μ-thiolate complex (3); as an intermediate an octanuclear mixed-valent CuI4CuII4 cluster with formula [CuI4CuII4(Py2NS)4(μ-OH)2­(CH3CN)6]­(ClO4)6·2CH3CN (2) was isolated and characterized by X-ray single crystal structure determination.