Spectroscopic and structural studies on cobalt complexes of the methyl esters of dithiocarbazic and 2-methyldithiocarbazic acids. Crystal structure of [Co{NH2NHC(S)SMe}{NH2NC(S)SMe}2]Cl·H2O

Abstract

The ligand behaviour of methyl esters of dithiocarbazic acid NH₂NHC(S)SMe (HL) and of 2-methyldithiocarbazic acid NH₂NMeC(S)SMe (MeL) in cobalt complexes has been investigated. Complexes of Co^II and Co^III have been prepared under different conditions and characterized by their electronic and i.r. spectra. HL can act as a ligand when neutral or when deprotonated (L^–); MeL can be deprotonated at the terminal N only after co-ordination. The crystal structure of [Co(HL)L₂] Cl·H₂O has been determined by X-ray diffraction methods: crystals are monoclinic, space group P2₁/c, Z= 4, in a unit cell of dimensions a= 12.085(9), b= 8.903(8), c= 17.287(16)Å, and β= 104.2(1)°. The structure has been solved by Patterson and Fourier methods and refined by block-diagonal least squares to R= 0.042 for 1 993 reflections. It consists of cis-octahedral [Co(HL)L₂]⁺ cations, in which one neutral and two deprotonated molecules of methyl dithiocarbazate act as chelating ligands, chloride anions, and water molecules, held together by a network of hydrogen bonds. The bond distances in the co-ordination polyhedron are: Co–S 2.203(4), Co–N 1.993(6)Å for the neutral ligand; Co–S 2.212(5) and 2.218(3), Co–N 1.977(6) and 1.980(6)Å for the deprotonated ligands. The conformation of the three ligands is cis,cis, i.e. with both NHNH₂ and SMe groups bent towards the CS bond.