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

摘要

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(μ-X)_8(μ-dpmppm)_2] (X = Cl (1a), Br (1b), I (1c)), which involve a ladder-type {Cu_8(μ-X)_ 2(μ_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(μ-X)_6(OTf)_ 2(μ-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_4X(μ-X)_3(μ-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(μ-Cl)_3(μ-dpmppm)_2(dmf)_ 2][CuCl_2] (4) and [Cu_4(μ-I)_ 3(μ-dpmppm)_2(py)_2]I (5). A series of tetracopper(i) complexes with terminal isocyanide ligands, [Cu_ 4(μ-X)_3(μ-dpmppm)_2(RNC)_ 2]PF_6 (X = Cl, R = Xyl (6a); X = Br, R = Mes (7b); X = I, R = Xyl (8a), Mes (8b), ~tBu (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_4PF_6. Complexes 3-8 possess a bending Cu_4(μ-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_ 3CN-CH_2Cl_2 mixed solvent, the soft Lewis acidic Ag(i) ions took the copper(i)-binding dpmppm off and the resultant two {Cu_ 4(μ-I)_3(μ-dpmppm)(~tBuNC)_ 2}~+ fragments were zipped up to form the ladder-type octacopper(i) complex, [Cu_8(μ-I)_6(μ-dpmppm)_ 2(~tBuNC)_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(μ-X)_3(μ-dpmppm)}~+ unit, which could be useful synthon of further extended copper(i) halide clusters.