Weakly coordinating anions HA(2)(-) generated from oxoanions A(-) and their conjugate acids. Coordination equilibria, ionic conductivities, and the structures of {Cu-2(H(CH3SO3)(2))(4)}(n) and [Cu(CO)(H(CF3CO2)(2))](2)

The coordination or ion pairing of the hydrogen-bonded anions H(CF3CO2)(2)( -) and H(CH3SO3)(2)(-) to NEt4+, Li+ Cu+, and/or CU2+ was investigated. The structure of {Cu-2(H(CH3SO3)(2))(4)}(n) consists of centrosymmetric dimeri c moieties that contain two homoconjugated. (CH3SO2O-H ... OSO2CH3)(-) anio ns per CU2+ ion, forming typical Jahn-Teller tetragonally elongated CuO6 co ordination spheres. The oxygen atoms involved in the nearly linear O-H ... O hydrogen bonds (O ... O similar to 2.62 Angstrom) are not coordinated to the Cu2+ ions. The structure of Cu-2(CO)(2)(H(CF3-CO2)(2))(2) consists of p seudo-C-2-symmetric dimers that contain one homoconjugated (CF3COO-H ... OC OCF3)(-) anion per Cut ion, forming highly distorted tetrahedral Cu(CO)O-3 coordination spheres. Three of the four oxygen atoms in each hydrogen-bonde d H(CF3CO2)(2)(-) anion are coordinated to the Cu+ ions, including one of t he oxygen atoms in each O-H ... O hydrogen bond (O ... O similar to 2.62 An gstrom). Infrared spectra (v(CO) values) of Cu(CO)(CF3CO)(2) or Cu(CO)(CH3S O3) dissolved in acetonitrile or benzene, with and without added CF3COOH or CH3SO3H, respectively, demonstrate that HA(2)(-) anions involving carboxyl ates or sulfonates are more weakly coordinating than the parent anions RCO2 - and RSO3-. Direct current conductivities of THF solutions of Li(CF3CO2) c ontaining varying concentrations of added CF3COOH further demonstrate that Li+ and NEt4+ ion pair much more weakly with H(CF3CO2)(2)(-) than with CF3C O2-.