Disulfide Versus Diselenide Complexes of Copper: Air-Free and Air-Exposed Syntheses Result in Variable Ligands and Coordination

Abstract

Reactions of bis(1-methylimidazole-2)disulfide (MMIDS) or bis(1-methylimidazole-2)diselenide (MMIDSe) with Cu(I) result in a variety of products depending on conditions. Under air-free conditions, dinuclear complexes [Cu2(µ,κ S -MMI)2(κ N,N’ -MMIDS)2][BF4]2 and [Cu2(µ,κ Se-MMISe)2(κ N,N’ -MMIDSe)2][BF4]2 were obtained and structurally characterized. Both complexes show reduction of the MMIDS or MMIDSe and subsequent bridging of the thione or selone between the dinuclear Cu(I) centers. Combining MMIDSe with Cu(I) in air resulted in crystallization of three different complexes from the same reaction mixture, as confirmed by X-ray crystallography. The various products, [Cu(κ N,N’ -MMIMSe)(κ N,N’ -MMITSe)(CH3CN)][BF4]2, [Cu(κ N,N’ -MMISe-CH2-MMISe)2[BF4]2, and the co-crystallized [[Cu(κ N,N’ -MMIDSe)2][Cu(κ N,N’ -MMISe-CH2-MMISe)][BF4]4, indicate that significant reactivity occurs with the availability of air and CH2Cl2 solvent. In addition to oxidation of Cu(I) to Cu(II), the MMIDSe ligands also react to form monoselenide, triselenide, and Se-CH2-Se bridged selenide ligands. Graphical Abstract: Although Cu(I) reactions with bis(1-methylimidazole-2)disulfide (MMIDS) or bis(1-methylimidazole-2)diselenide (MMIDSe) under air-free conditions result in formation of [Cu2(µ,κ S -MMI)2(κ N,N’ -MMIDS)2][BF4]2 and [Cu2(µ,κ Se -MMISe)2(κ N,N’ -MMIDSe)2][BF4]2, respectively, treating MMIDSe with Cu(I) in air results in crystallization of three different complexes from the same reaction mixture: [Cu(κ N,N’ -MMIMSe)(κ N,N’ -MMITSe)(CH3CN)][BF4]2, [Cu(κ N,N’ -MMISe-CH2-MMISe)2[BF4]2, and the co-crystallized [[Cu(κ N,N’ -MMIDSe)2][Cu(κ N,N’ -MMISe-CH2-MMISe)][BF4]4, indicating that significant reactivity occurs with the availability of air and CH2Cl2 solvent. [Figure not available: see fulltext.].