Identification of a Novel η2-Se2 Bonding Mode in Cu(I) Complexes of the Dimeric Selenocarbonyl Dianions, [(EPh2P)2CSeSeC(PPh2E)2]2− (E = S, Se)

A metathetical reaction between [Li(TMEDA)][(H)C(PPh2Se)2] and CuCl2 in a 2:1 molar ratio afforded the dimeric Cu(I) complex, {Cu2-η2:η2-[(EPh2P)2CSeSeC(PPh2E)2]} (E = Se), via a selenium−proton exchange and an internal redox process. The analogous sulfur-containing complex (E = S) was obtained by the reactions of the dianions [(Se)C(PPh2S)2]2− and [(SPh2P)2CSeSeC(PPh2S)2]2− with Cu(II) and Cu(I) halides, respectively. Structural characterization of the Cu(I) complexes reveals a unique η2-Se2 bonding mode for the generic diselenide ligand system RSe−SeR.