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

Redox-Innocent Metal-Assisted Cleavage of S–S Bond in a Disulfide-Containing Ligand

“…35,38,39,67 Finally, the Cu1−Cu2 distance in 2 of 6.380 Å is longer than those in the recent report on sulfinato-bridged dicopper(II) compounds (3.63 and 3.47 Å) by Bouwman and colleagues. 35 The difference in the nature and the coordination mode of the sulfinato group (aromatic nature and covalently maintained between the two copper coordination spheres, whereas in the other cases it is aliphatic and terminal) is a reasonable explanation. It has to be noted that, to the best of our knowledge, this coordination mode has never been reported in the literature in the case of sulfinato dicopper complexes based on dinucleating ligands.…”

“…Indeed, Cu II −OSO 2 −CF 3 distances usually lie in the range 1.967−2.23 Å, 62−64 but larger values (2.600 and 2.415 Å) have been reported for a sulfinatocontaining dicopper complex having triflates in the metal coordination spheres. 35 Given that observation, the coordination geometry around Cu1 can be regarded as elongated and distorted octahedral, O3S2 and O2 being located on the pseudo-Jahn− Teller axis. Cu2 has a N 3 O 2 coordination sphere constituted by three nitrogen and one oxygen atoms from the sulfinato group of the modified ligand, and an extra water molecule.…”

Protonation of a Biologically Relevant CuII μ‐Thiolate Complex: Ligand Dissociation or Formation of a Protonated CuI Disulfide Species?

“…The ligands LSSL and L Me SSL Me were synthesized by using a combination of reported procedures (see the Supporting Information, Scheme S1). [18][19][20] 2 were obtained by vapor diffusion of pentane into this acetone solution; its structure was confirmed by single crystal X-ray crystallography. Projections of the cationic parts of the two structures are depicted in Figure 1.…”

“…The Cu II ÀS distance is 2.3130 (6) , which is similar to the Cu II ÀS distances in the related Cu II m-thiolate structure [Cu II 2 (LS) 2 ] 2 + (2.2909 (8) and 2.3159(9) ) [18] and in a similar multivalent complex [Cu II 4 Cu I 4 (LS) 4 (m-OH) 2 (CH 3 CN) 6 ] 6 + (2.34-2.36 ) that we recently reported. [19] The Cu II ions are in an N 4 S coordination environment, which can be best described as a highly distorted trigonal bipyramid (t = 0.65). [22] [Cu II 2 (L Me S) 2 ](BF 4 ) 2 crystallizes in the monoclinic space group P2 1 /n.…”

Oxidative dehydrogenation of 5-(pyridine-2-yl-methyl)-2-thioxo-4-imidazolidinones in complexation reaction with copper(II) chloride

“…after step (3) or step (6). Also it is possible that thiolate sulfur atom of organic ligand takes part in electron transfer processes as it is in cysteine-containing metalloenzymes and its low-molecular analogs (see [29] and the references therein). We also do not have detailed in Scheme 3 the process of oxidation by air oxygen (step 4).…”