COBALT(III) COMPLEXES WITH THIOSEMICARBAZONES AS COORDINATING AGENTS - SPONTANEOUS RESOLUTION BY CRYSTALLIZATION AND ABSOLUTE-CONFIGURATION

gTwo new cobalt(lll) complexes with pyridoxal 5-(hydroxymethyl)-2-meth ylpyridine-4-carbaldehyde] and pyruvic acid thiosemicarbazones (H(2)L and H(2)pt) [Co(HL)(2)]Cl . EtOH 1 and [Co(Hpt)(pt)] 2 respectively. h ave been synthesized and characterized using single-crystal X-ray diff raction and IR and CD spectroscopic methods. The structure of 2-thio-6 -azathymine [6-methyl-3-thioxo-1 ,2,4-triazin-5-(2H,4H)-one] obtained upon cyclization of methyl pyruvate thiosemicarbazone in the course of its complexation reaction with cobalt(ii) salts is also described. Th e structure of 1 consists of discrete [Co(HL)(2)](+) cations, Cl- anio ns and ethanol solvate molecules, that of 2 consists of neutral monome rs and the two ligands are not equivalent. In both complexes the co-or dination geometry about cobalt is distorted octahedral and the two lig ands are in the mar configuration (S and O atoms cis to each other and the N atoms trans). Complex 1, an example of optical resolution by pr eferential crystallization. is chiral.