THE CRYSTAL AND MOLECULAR-STRUCTURE OF TETRAKIS[MU-PROPIONATO]BIS(NICOTINAMIDE)DICOPPER(II)

The crystal and molecular structure of the tetrakis[mu-propionato]bis(nicotinamide)-dicopper(II), [Cu(CH3CH2COO)2(nia)2]2 (nia = nicotinamide), was determined by direct methods and Fourier techniques. The compound crystallizes in the triclinic space group P1BAR with two dimeric formula units in a cell with dimensions a = 9.895(7), b = 11.204(7), c = 13.509(7) angstrom, alpha = 87.36(5), beta = 89.17(5) and gamma = 74.25(5)-degrees. The structure was refined by full-matrix least-squares methods to a weighted R factor of 0.059, based on 2830 independent reflections. the compound is dimeric, with square-pyramidal geometry at each copper centre. The two copper atoms are bridged by four carboxylate groups, while the apical ligands are nicotinamides. The Cu-Cu distance is 2.635(2) angstrom. The Cu atoms are displaced by 0.20 angstrom from the plane containing four oxygen atoms towards the apical nicotinamides. The structural data are compared with those found in similar copper(II) propionates and with the nicotinamide adduct of copper(II) acetate.