Thiol-copper(I) and disulfide-dicopper(I) complex O₂-reactivity leading to sulfonate-copper(II) complex or the formation of a cross-linked thioether-phenol product with phenol addition

In order to better understand copper mediated oxidative chemistry via ligand-Cu^I/O₂ reactivity employing S-donor ligands for copper, O₂-reactivity studies of the copper(I) complexes (1 and 2, Chart 2) have been carried out with a tridentate N₂S thiol ligand (1-(N-methyl-N-(2-(pyridin-2-yl)ethyl)amino)propane-2-thiol; L^SH) or its oxidized disulfide form (L^SS). Reactions of [L^SHCu^I]⁺ (1) and [L^SS(Cu^I)₂(X)₂]²⁺ (2) with O₂ give ∼90% and ∼70% yields of [L^SO3Cu^II(MeOH)₂]⁺ (3), respectively, where L^SO3 is S-oxygenated sulfonate; 3 was characterized by electrospray ionization (ESI) mass spectrometry and X-ray crystallography. Mimicking TyrCys galactose oxidase cofactor biogenesis, a new C-S bond is formed (within new thioether moiety L^SPhOH) from cuprous complex (both 1 and 2) dioxygen reactivity in the presence of 2,4-tBu₂-phenolate. In addition, the disulfide ligand (L^SS) reacts with 2 equiv. cupric ion salts and the phenolate to efficiently give the cross-linked product L^SPhOH in high yield (>90%) under anaerobic conditions. Separately, complex [L^SPhOCu^II(ClO₄)] (4), possessing the cross-linked L^SPhOH, was characterized by ESI mass spectrometry and X-ray crystallography.