title: Protonation of a biologically relevant Cu(II) μ-thiolate complex: ligand dissociation or formation of a protonated Cu(I) disulfide species?
abstract: The proton-induced electron-transfer reaction of a Cu(II) μ-thiolate complex to a Cu(I) -containing species has been investigated, both experimentally and computationally. The Cu(II) μ-thiolate complex [Cu(II) 2 (L(Me) S)2 ](2+) is isolated with the new pyridyl-containing ligand L(Me) SSL(Me) , which can form both Cu(II) thiolate and Cu(I) disulfide complexes, depending on the solvent. Both the Cu(II) and the Cu(I) complexes show reactivity upon addition of protons. The multivalent tetranuclear complex [Cu(I) 2 Cu(II) 2 (LS)2 (CH3 CN)6 ](4+) crystallizes after addition of two equivalents of strong acid to a solution containing the μ-thiolate complex [Cu(II) 2 (LS)2 ](2+) and is further analyzed in solution. This study shows that, upon addition of protons to the Cu(II) thiolate compound, the ligand dissociates from the copper centers, in contrast to an earlier report describing redox isomerization to a Cu(I) disulfide species that is protonated at the pyridyl moieties. Computational studies of the protonated Cu(II) μ-thiolate and Cu(I) disulfide species with LSSL show that already upon addition of two equivalents of protons, ligand dissociation forming [Cu(I) (CH3 CN)4 ](+) and protonated ligand is energetically favored over conversion to a protonated Cu(I) disulfide complex.
authors.affiliation: Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P. O. Box 9502, 2300 RA Leiden (The Netherlands).
authors.forename: Erica C M
authors.initials: EC
authors.lastname: Ording-Wenker
authors.forename: Martijn
authors.initials: M
authors.lastname: van der Plas
authors.forename: Maxime A
authors.initials: MA
authors.lastname: Siegler
authors.forename: Célia
authors.initials: C
authors.lastname: Fonseca Guerra
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Bouwman
mesh_terms: D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004220:Disulfides / Q000737:chemistry*; D004579:Electron Transport; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011522:Protons; D012997:Solvents / Q000737:chemistry
chemical_list: D004220:Disulfides; D008024:Ligands; D009942:Organometallic Compounds; D011522:Protons; D012997:Solvents; D003300:Copper
keywords: biomimetic synthesis; coordination chemistry; copper; protonation; redox chemistry