STRUCTURAL, MAGNETIC, AND SPECTROSCOPIC CHARACTERIZATION OF THE PYRIDINE COMPLEXES OF COPPER(II) TRIPHENYLACETATE - A DIMERIC COPPER(II) TRIPHENYLACETATE-PYRIDINE COMPLEX WITH DISTORTED TRIGONAL BIPYRAMIDAL GEOMETRY AROUND COPPER

The synthesis and characterization of three copper(II) triphenylacetate-pyridine complexes are reported along with their magnetic and spectral properties: [Cu2(O2CCPh3)4(py)2].C6H6 (1), [Cu2(O2CCPh3)4(py)2] (2), and Cu(O2CCPh3)2.2py (3). Crystal structure analyses of 1 and 3 have revealed unusual geometries around copper: 1, triclinic, space group P1BAR with a = 19.558(7) b = 16.605(6), c = 14.997(5) angstrom, alpha = 114.55(2)-degrees, beta = 97.11(2)-degrees, gamma = 111.65(2)-degrees, and Z = 2; 3, monoclinic, space group P2(1)/c with a = 8.931(1), b = 12.602(1), c = 19.578(1) angstrom, beta = 118.17(0.4)-degrees, and Z = 2. The coordination sphere around each copper in the dimeric complex 1 is a highly distorted trigonal bipyramid with bridging triphenylacetato ligands spanning the apical and equatorial positions, resulting in a long Cu-Cu distance of 3.086(1) angstrom. Temperature-dependent magntic susceptibility measurements on 1 indicate that the two coppers are antiferromagnetically coupled with -2J = 187 cm-1. The structure of the monomeric complex 3 is unusual in that the out-of-plane carboxylate oxygen is twisted 12-degrees from the normal. Two solid modifications are observed for 2. The magnetic and spectral properties of 2a (-2J = 173 cm-1) resemble those of 1, and 2b (-2J = 321 cm-1) those of copper(II) acetate monohydrate. Magneto-structural correlations are presented. The novel structural features of these complexes are suggested to arise from steric effects resulting from the spatial relationships both between and within the molecules in the crystal environment.