Electrochemical, spectroscopic and structural characterization of the mer isomer of ammonium bis(pyruvic acid thiosemicarbazone)cobalt(III)·benzene

Abstract

The crystal structure is reported of ammonium bis(pyruvic acid thiosemicarbazone)cobalt(III)·benzene, CoS 2O 4N 6C 16H 16, which forms dark red triclinic crystals with unit cell parameters: a=9.307(2), b=9.555(2), c=14.729(3) Å, α=67.04(1), β=118.89(2), γ=79.09(1)°, V=932.9(2) Å 3, space group P 1 . The final R factor for 3948 observed reflections is 3.1%. The distorted octahedral complex is held together by a hydrogen bonding system involving the ammonium and amine protons and the carboxylate oxygen and imine nitrogen atoms. The coordination polyhedron around the cobalt atom in the complex anion [Co(PVATSCH) 2] − is highly distorted from regular octahedral geometry as evidenced by the fact that the bond angles about the cobalt atom range from 83.40(6) to 96.75(5)°. The isolated meridional isomer contains a cis placement of the sulfur donor atoms with puckered ligand moieties arising from the non-planar hydrazinic chain with a folding angle of ca. 4° across the sulfur-nitrogen and oxygen-nitrogen atoms. The ligand H 2PVATSC provides a strong ligand field and thus results in a low spin cobalt(III) complex. The complex undergoes a reversible one-electron reduction at the metal center.