Interconversion between ladder-type octanuclear and linear tetranuclear copper(I) complexes supported by tetraphosphine ligands.

Linearly ordered tetraphosphine, meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm), readily reacted with 4 equiv. of CuX in dichloromethane to afford octanuclear copper(I) complexes, [Cu(8)(mu-X)(8)(mu-dpmppm)(2)] (X = Cl (1a), Br (1b), I (1c)), which involve a ladder-type {Cu(8)(mu-X)(2)(mu(3)-X)(6)} core supported by two dpmppm ligands in anti arrangement. Complex 1a was further transformed by treatment with Cu(OTf)(2) into [Cu(8)(mu-X)(6)(OTf)(2)(mu-dpmppm)(2)] (2) in which two TfO anions attached to both end of the Cu(8) ladder. When complexes 1 were dissolved in dimethyl sulfoxide (dmso) in the presence of 2 equiv. of dpmppm, the octacopper(I) ladder was unzipped to result in the linear tetranuclear copper(I) complex, [Cu(4)X(mu-X)(3)(mu-dpmppm)(2)(dmso)] (X = Cl (3a), Br (3b), I (3c)). Similar treatment of dpmppm with 2 equiv. of CuX in the presence of coordinative solvents, N,N'-dimethylformamide (dmf) and pyridine (py), yielded the symmetrical tetracopper(I) complexes, [Cu(4)(mu-Cl)(3)(mu-dpmppm)(2)(dmf)(2)][CuCl(2)] (4) and [Cu(4)(mu-I)(3)(mu-dpmppm)(2)(py)(2)]I (5). A series of tetracopper(I) complexes with terminal isocyanide ligands, [Cu(4)(mu-X)(3)(mu-dpmppm)(2)(RNC)(2)]PF(6) (X = Cl, R = Xyl (6a); X = Br, R = Mes (7b); X = I, R = Xyl (8a), Mes (8b), (t)Bu (8c)), were obtained from reactions of dpmppm with 2 equiv. of CuX in dmf or acetonitrile followed by addition of an excess of RNC and NH(4)PF(6). Complexes 3-8 possess a bending Cu(4)(mu-X)(3) chain supported by two dpmppm ligands in syn arrangement, where the terminal sites are reactive and accommodate a variety of terminal ligands. When complex 8c was treated with AgPF(6) in a CH(3)CN-CH(2)Cl(2) mixed solvent, the soft Lewis acidic Ag(I) ions took the copper(I)-binding dpmppm off and the resultant two {Cu(4)(mu-I)(3)(mu-dpmppm)((t)BuNC)(2)}(+) fragments were zipped up to form the ladder-type octacopper(I) complex, [Cu(8)(mu-I)(6)(mu-dpmppm)(2)((t)BuNC)(2)](PF(6))(2) (9). The apparent interconversion between the Cu(8) ladder and the Cu(4) chain might proceed through a labile intermediate with a {Cu(4)(mu-X)(3)(mu-dpmppm)}(+) unit, which could be useful synthon of further extended copper(I) halide clusters.