ELECTROCHEMICAL SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF BIS(TRIPHENYLPHOSPHINE)COPPER(I) FLUOROACETATES

Bis(triphenylphosphine)copper(I) fluoroacetate complexes have been prepared by the electrochemical oxidation of copper metal in acetonitrile solutions of triphenylphosphine and mono-, di- and tri-fluoroacetic acid respectively. Recrystallization from toluene yields unsolvated mononuclear complexes [Cu(PPh3)2(O2CCH3-nFn)], n = 1-3, which have been characterized by single-crystal X-ray crystallographic determinations. Crystals of the three complexes are isomorphous with the acetate complex (n = 0), crystallizing in the monoclinic space group P2(1)/a with cell dimensions a almost-equal-to 18.0, b almost-equal-to 11.0 and c almost-equal-to 19.3 angstrom and beta almost-equal-to 120-degrees. Residuals for the complexes with n = 1, 2 and 3 were R = 0.077, 0.045 and 0.048 for 3677, 2789 and 3527 'observed' [I > 3sigma(I)] reflections respectively. The bond distances Cu-P are 2.232(3), 2.222(3); 2.234(2), 2.219(2); and 2.235(2) 2.228(2) angstrom with the corresponding P-Cu-P angles increasing from 135.0(1) to 135.8(1) to 1 36.7(1)-degrees, this latter value being the largest recorded for [Cu(PPh3)2]+. The asymmetry of the co-ordination of the carboxylate group increases along the series with Cu-0 distances of 2.144(6) and 2.363(7); 2.118(4), 2.465(6); and 2.113(4), 2.545(5) angstrom for n = 1, 2 and 3 respectively. Crystallization of the difluoro- and trifluoro-acetate complexes from ethanol results in isomorphous orthorhombic Pb2(1)a crystals (a almost-equal-to 22.2, b almost-equal-to 18.5, c almost-equal-to 9.0 angstrom) with monodentate carboxylate and co-ordinated ethanol; the monofluoroacetate is unsolvated. For [Cu(PPh3)2(O2CCHF2)(EtOH)] R was 0.052 for 2090 'observed' reflections with Cu-P 2.248(3), 2.236(3) angstrom and P-Cu-P 120.5(1)-degrees; Cu-O(carboxylate) is 2.074(8) angstrom and Cu-O(ethanol) is 2.169(8) angstrom. For [Cu(PPh3)2(O2CCF3)(EtOH)] R was 0.043 for 2350 'observed' reflections, Cu-P being 2.248(2), 2.240(2) angstrom and P-Cu-P 120.8(1)-degrees; Cu-O(carboxylate) is 2.104(6) angstrom and Cu-O(ethanol) is 2.160(6) angstrom.