Crystal structures of (1) aquacyano(dimethylglyoxime)(dimethylglyoximato)cobalt(III) and (2) aquawo-cyano(dimethylglyoxime) (dimethylglyoximato)cobalt(III)

The crystal structures of two isostructural compounds of the type AH20(dmg) (dmgH2)Co(III), where A = cyano or z'so-cyano ligand have been determined by X-ray diffraction methods. The crystals are monoclinic, space group P2Jm, with the crystal data: (1) a = 10.867(3), b = 9.581(3), c = 7.156(2)A, ß = 101.86(2)°, V= 729.1(6)A3, c = 1.49Mg m3, Z = 2, and (2) a = 10.987(3), b = 9.728(3), c = 7242(2) Å, ß = 102.08(2)°, V = a757.0(6) A3, Dc = 1.44 Mg uT3, Z = 2. The first structure was determined by direct methods using the MULTAN system, and the second by isomorphous replacement. The refinements by full-matrix least-squares method convergedto R factors equal to 0.049 for 1325 and 0.053 for 1812 observed reflections, respectively. The X-ray analyses of the title compounds show that a crystallographic mirror plane is a molecular symmetry. Dimethylglyoxime and dimethylglyoximato ligands behaves as a bidentate N.N ligand. Coordination around Co3+ is close to that of an octahedra formed by four nitrogen atoms of chelated ligand (average Co –N bond distance is 1.90 A) in the equatorial plane and an aqua and cyano or isocyano molecule in the axial sites (Co-OH2, 2.00Å, Co-C 1.937 and Co-N 1.91). Half normal probability plot comparison between the bond distances of the two crystal structures shows that the main difference is in the intermolecular distances, in general, the values obtained in (2) are greater than those of (1). © 1983, Walter de Gruyter. All rights reserved.