Dinuclear paddle-wheel copper(II) carboxylates in the catalytic oxidation of carboxylic acids. Unusual polymeric chains found in the single-crystal x-ray structures of [tetrakis(mu-1-phenylcyclopropane-1-carboxylato-O,O')bis(ethanol-O)dicopper(II)] and catena-poly[[bis(mu-diphenylacetato-O:O')dicopper](mu(3)-diphenylacetato-1-O:2-O':1'-O')-(mu(3)-diphenylacetato-1-O:2-O':2'-O')]

The X-ray structures and spectroscopic and magnetic properties of [tetrakis(mu-1-phenylcyclopropane-1-carboxylato-O,O')bis(ethanol-O)dicopper(II)], 1, and catena-poly[[bis(mu-diphenylacetato-O:O')dicopper](mu(3)-diphenylacetato-1-O:2-O':1'-O')(mu(3)-diphenylacetato-1-O:2-O':2'-O')], 2, two extended-chain copper(II) carboxylates with dinuclear paddle-wheel subunits, are reported. 1 crystallizes in the triclinic space group P (1) over bar, with a = 6.8873(3) Angstrom, b = 11.7367(6) Angstrom, c = 13.7899(7) Angstrom, alpha = 107.076(4)degrees, beta = 93.545(4)degrees, gamma = 103.967(4)degrees, Z = 1. The Cu...Cu distance is 2.6009(4) Angstrom, and the Cu...carboxylate O distances are in the range 1.937(2)-1.962(2) Angstrom. The ethanol at the apex forms an unsymmetrical bifurcated H bond to two carboxylate oxygens of another dinuclear unit with O...O distances 2.980(3) and 3.108(3) Angstrom, thereby extending the structure along the a-axis. The magnetic structure consists of isolated antiferromagnetically coupled dinuclear copper units, with a -2J value of 242 cm(-1), in concurrence with the EPR parameters, viz., g(x) = 2.03(1), g(y) = 2.07(1), g(z) = 2.35(1), A(parallel to) = 0.064(2) cm(-1), D = 0.316(15) cm(-1), E = 0.005(1) cm(-1). The -2J value is the smallest value measured for dinuclear copper carboxylates with oxygen-donor ligands at the axial position and no electron-withdrawing carboxylate R groups. 2 crystallizes in the monoclinic space group P2(1)/c, with a = 15.953(2) Angstrom, b = 5.385(6) Angstrom, c = 28.322(10) Angstrom, beta = 120.22(3)degrees, Z = 2. The compound contains tetrakis(diphenylacetato)dicopper(II) units, forming a polymeric structure along the b-axis by axial coordination of a carboxylate oxygen to copper of a subsequent dinuclear unit, at 2.323(11) Angstrom. The intradimer Cu...Cu distance is 2.594(4) Angstrom; the interdimer Cu...Cu distance is 3.425(5) Angstrom. The -2J value of 321 cm(-1) was interpreted as originated from isolated antiferromagnetically coupled dinuclear copper units. The EPR parameters are g(x) = 2.07(1), g(y) = 2.02(1), g(z) = 2.33(1), D = 0.347(10) cm(-1), E = 0.0034(5) cm(-1). The dinuclear subunits are likely candidates for the catalytically active Cu species in copper-(II)-catalyzed oxidation of carboxylic acids.