title: Bond stretching and redox behavior in coinage metal complexes of the dichalcogenide dianions [(SPh2P)2CEEC(PPh2S)2]2- (E=S, Se): diradical character of the dinuclear copper(I) complex (E=S).
abstract: The metathetical reactions of a) [Li(tmeda)](2)[(S)C(PPh(2)S)(2)] (Li(2)·3c) with CuCl(2) and b) [Li(tmeda)](2)[(SPh(2)P)(2)CSSC(PPh(2)S)(2)] (Li(2)·4c) with two equivalents of CuCl both afford the binuclear Cu(I) complex {Cu(2)[(SPh(2)P)(2)CSSC(PPh(2)S)(2)]} (5c). The elongated (C)S-S(C) bond (ca. 2.54 and 2.72 Å) of the dianionic ligand observed in the solid-state structure of 5c indicate the presence of diradical character as supported by theoretical analyses. The treatment of [Li(tmeda)](2)[(SPh(2)P)(2)CSeSeC(PPh(2)S)(2)] (Li(2)·4b) and Li(2)·4c with AgOSO(2)CF(3) produce the analogous Ag(I) derivatives, {Ag(2)[(SPh(2)P)(2)CEEC(PPh(2)S)(2)]} (6b, E=Se; 6c, E=S), respectively. The diselenide complex 6b exhibits notably weaker Ag-Se(C) bonds than the corresponding contacts in the Cu(I) congeners, and the (31)P NMR data suggest a possible isomerization in solution. In contrast to the metathesis observed for Cu(I) and Ag(I) reagents, the reactions of Li(2)·4b and Li(2)·4c with Au(CO)Cl involve a redox process in which the dimeric dichalcogenide ligands are reduced to the corresponding monomeric dianions, [(E)C(PPh(2)S)(2)](2-) (3b, E=Se; 3c, E=S), and one of the gold centers is oxidized to generate the mixed-valent Au(I)/Au(III) complexes, {Au[(E)C(PPh(2)S)(2)]}(2) (7b, E=Se; 7c, E=S), with relatively strong aurophilic Au(I)···Au(III) interactions. The new compounds 5c, 6b,c and 7b,c are characterized in solution by NMR spectroscopy and in the solid state by X-ray crystallography (5c, 6b, 7b and 7c) and by Raman spectroscopy (5c and 6c). The UV-visible spectra of coinage metal complexes of the type 5, 6 and 7 are discussed in the light of results from theoretical analyses using time-dependent density functional theory.
authors: Department of Chemistry, University of Calgary, Calgary, AB T2N 1N4, Canada.
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