SPECTROSCOPIC AND X-RAY-INVESTIGATION OF COBALT(III) COMPLEXES WITH 2-OXIMINOCARBOXYLIC ACIDS

Mixed complexes of Co(III) with 2-oximinopropionic (H2A) or 2-oximino- 3-phenylpropionic (H2B) acid and different amine (imidazole, benzimida zole, pyridine, beta-picoline, gamma-picoline) are reported. Character ization of the complexes was based upon elemental analysis, conductivi ty and JR, H-1 NMR, and electronic absorption spectra, and X-ray diffr action analysis. The organic ligands behave as O,N donors via the carb oxyl oxygen and the oxime nitrogen atoms. A trans-octahedral structure has been assigned to the bis(2-oximino-carboxylato)bis(amine)cobalt(I II) on the basis of H-1 NMR data. The crystal and molecular structures of the complexes rans-[bis(2-oximinopropionato)bis-(imidazole)]-(I) a nd [bis(2-oximinopropionato)bis(pyridine)]cobalt(III) (II) were determ ined. I crystallizes in space group P2/n with a = 14.167(2), b = 8.774 (1), c = 14.785(2) angstrom, beta = 113.37(1)degrees, Z = 4, D(calc) = 1.568 g.cm-3. II crystallizes in space group P1BAR with a = 9.122(2), b = 10.038(2), c = 11.759(2) angstrom, alpha = 69.95(1)degrees, beta = 67.47(2)degrees, gamma = 69.49(2)degrees, Z = 2, D(calc) = 1.547 g.c m-3. The structures were refined to unweighted R factors of 0.036 and 0.028, respectively. The coordination sphere around Co is pseudo-octah edral with the 2-oximinopropionato ligands occupying four equatorial p ositions, and the amines in axial positions.