Three-Component Copper-Phosphonate-Auxiliary Ligand Systems: Proton Conductors And Efficient Catalysts In Mild Oxidative Functionalization Of Cycloalkanes

The synthesis, structural characterization, topological analysis, proton conductivity, and catalytic properties are reported of two Cu(II)-based compounds, namely a dinuclear Cu(II) complex [Cu-2 (mu-VPA)(2) (phen)(2) (H2O)(2)]center dot 8H(2)O (1) (H(2)VPA = vinylphosphonic acid, phen = 1,10-phenanthroline) and a 1D coordination polymer [Cu(mu-SO4)(phen)(H2O)(2)](infinity) (2). Their structural features and H-bonding interactions were investigated in detail, showing that the metal-organic structures of 1 and 2 are extended by multiple hydrogen bonds to more complex 2D or 1D H-bonded architectures with the kgd [Shubnikov plane net (3.6.3.6)/dual] and SP 1-periodic net (4,4)(0,2) topology, respectively. These nets are primarily driven by the H-bonding interactions involving water ligands and H2O molecules of crystallization; besides, the (H2O)(4)/(H2O)(6) clusters were identified in 1. Both 1 and 2 are moderate proton conductors, with proton conductivity values, sigma = 3.65 X 10(-6) and 3.94 x 10(-6) S.cm(-1), respectively (measured at 80 degrees C and 95% relative humidity). Compounds 1 and 2 are also efficient homogeneous catalysts for the mild oxidative functionalization of C-5-C-8 cycloalkanes (cyclopentane, cyclohexane, cycloheptane, and cyclooctane), namely for the oxidation by H2O2 to give cyclic alcohols and ketones and the hydrocarboxylation by CO/H2O and S2O82- to the corresponding cycloalkanecarboxylic acids as major products. The catalytic reactions proceed under mild conditions (50-60 degrees C) in aqueous acetonitrile medium, resulting in up to 34% product yields based on cycloalkane substrate.