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Dalton Transactions

The international journal for inorganic, organometallic and bioinorganic chemistry



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Dalton Trans., 2009, 10231 - 10243, DOI: 10.1039/b909252h

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

Yukie Takemura, Takayuki Nakajima and Tomoaki Tanase

Linearly ordered tetraphosphine, meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm), readily reacted with 4 equiv. of CuX in dichloromethane to afford octanuclear copper(I) complexes, [Cu8(-X)8(-dpmppm)2] (X = Cl ( 1a), Br ( 1b), I ( 1c)), which involve a ladder-type {Cu8(-X)2(3-X)6} core supported by two dpmppm ligands in anti arrangement. Complex 1a was further transformed by treatment with Cu(OTf)2 into [Cu8(-X)6(OTf)2(-dpmppm)2] ( 2) in which two TfO anions attached to both end of the Cu8 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, [Cu4X(-X)3(-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, [Cu4(-Cl)3(-dpmppm)2(dmf)2][CuCl2] ( 4) and [Cu4(-I)3(-dpmppm)2(py)2]I ( 5). A series of tetracopper(I) complexes with terminal isocyanide ligands, [Cu4(-X)3(-dpmppm)2(RNC)2]PF6 (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 NH4PF6. Complexes 3–8 possess a bending Cu4(-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 AgPF6 in a CH3CN–CH2Cl2 mixed solvent, the soft Lewis acidic Ag(I) ions took the copper(I)-binding dpmppm off and the resultant two {Cu4(-I)3(-dpmppm)(tBuNC)2}+ fragments were zipped up to form the ladder-type octacopper(I) complex, [Cu8(-I)6(-dpmppm)2(tBuNC)2](PF6)2 ( 9). The apparent interconversion between the Cu8 ladder and the Cu4 chain might proceed through a labile intermediate with a {Cu4(-X)3(-dpmppm)}+ unit, which could be useful synthon of further extended copper(I) halide clusters.

Graphical abstract image for this article (ID: b909252h)