Synthetic, structural and kinetic studies on the binding of cyclohexane-1,2-bis(4-methyl-3-thiosemicarbazone) to divalent metal ions (Co, Ni, Cu, Zn or Cd).
The reactions of cyclohexane-1,2-bis(4-methyl-3-thiosemicarbazone) (CHMTSC) with MCl2 (M = Co, Ni, Cu or Zn) and Cd(NO3)2 have been shown to produce complexes in which the thiosemicarbazone has been doubly deprotonated [[M(CHMTSC - 2H+)] (M = Co, Ni or Ni)], analogous to those reported earlier with other Schiff base thiosemicarbazones. However, with ZnCl2 and Cd(NO3)2, the complexes isolated are [ZnCl(CHMTSC)]Cl and [Cd(NO3)(CHMTSC)]NO3, containing the protonated forms of the ligand, which have been characterised by X-ray crystallography, as has free CHMTSC. The kinetics of the reactions between CHMTSC and all the various metal salts have been determined by stopped-flow spectrophotometry. In all cases, the reactions are complete on the seconds timescale. The reactions exhibit a first-order dependence on the concentration of metal salt and a first-order dependence on the concentration of CHMTSC. The thermodynamic and kinetic factors influencing the protonation state of the coordinated thiosemicarbazone are discussed.
Al-Karawi
Ahmed Jasim M
AJ
Al-Mustansiriya University, College of Sciences, Department of Chemistry, Baghdad, Iraq. a_jasim2006@yahoo.com
Clegg
William
W
Harrington
Ross W
RW
Henderson
Richard A
RA
D002104:Cadmium / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D018360:Crystallography, X-Ray; D003510:Cyclohexanes / Q000737:chemistry*; D007477:Ions; D007700:Kinetics; D008670:Metals / Q000737:chemistry*; D008956:Models, Chemical; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry; D013696:Temperature; D013882:Thiosemicarbazones / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry; D017967:Zinc Compounds / Q000737:chemistry
D002712:Chlorides; D003510:Cyclohexanes; D007477:Ions; D008670:Metals; D013882:Thiosemicarbazones; D017967:Zinc Compounds; C539303:cyclohexane-1,2-bis(4-methyl-3-thiosemicarbazone); D002104:Cadmium; D003035:Cobalt; C506365:Cyclohexane; D003300:Copper; D009532:Nickel; C016837:zinc chloride; D015032:Zinc