Synthesis and spectroscopic studies of cobalt(III) complexes with 5-methyl-3-formylpyrazole-N(4)-diethylthiosemicarbazone (HMP zNEt 2): X-ray crystallography of [Co(MP zNEt 2) 2]ClO 4·2H 2O ( I) and [Co(MP zNEt 2) 2]BF 4·2H 2O ( II)

Abstract

The co-ordination mode of the title ligand, HMP zNEt 2 (synthesised for the first time and characterised by elemental analyses, mass, IR and 1H NMR spectral parameters), is reported by solid state isolation and physico-chemical identification of cobalt(III) complexes, [Co(MP zNEt 2) 2]X·2H 2O (X=Cl, Br, ClO 4, BF 4 and NO 3). Electronic spectral features of these diamagnetic Co(III) species classify them as six co-ordinate distorted octahedral ones. IR spectra (4000–200 cm −1) indicate that the Co(III) complexes have monoanionic tridentate NNS co-ordination of the title ligand through the pyrazolyl (tertiary) ring nitrogen, azomethine nitrogen and thiolato sulfur atoms. 1H NMR data (in CDCl 3 at 300 MHz) for the uncomplexed ligand and those of its Co(III) complexes are commensurate with the NNS function of the monodeprotonated HMP zNEt 2, as ascertained from downfield shift of the relevant protons adjacent to the bonding sites. X-ray crystallographic data of I and II (both P1̄, triclinic) have authenticated a CoN 4S 2 octahedral co-ordination in both the complex ions.