Ligand exchange reactions between copper(II)- and nickel(II)-chelates of different sulfur- and selenium-containing ligands. VI [1]. Kinetics of ligands exchange reactions studied by stopped-flow ESR

Abstract

Abstract The kinetics of ligand exchange reactions studied by means of stopped-flow ESR measurements are reported. The concentrations-time curves recorded for all reactions investigated correspond ton simple second-order rate laws. The rate constants of the reactions between copper(II) dithiolenes and Cu(Et 2 dsc) 2 (Et 2 dsc = diethyldiselenocarbamate) or Ni(Et 2 -dsc) 2 were found to be: [Cu(mnt) 2 ] 2– (mnt = maleo-nitriledithiolate) + Cu(Et 2 dsc) 2 , k 2 = (2.3 ±0.3)· 10 2 1 mol −1 s −1 ; [Cu(mnt) 2 ] 2− + Ni(Et 2 dsc) 2 , k 2 = (2.1 ± 0.1)· 10 2 1 mol −1 s −1 and [Cu(dmit) 2 ] 2− (dmit = isotrithione-3.4-dithiolate) + Ni(Et 2 dsc) 2 , k 2 = (2.5 ± 0.3)· 10 2 1 mol −1 s −1 . A rate constant of k 2 = (2.0 ± 0.3)· 10. 2 1 mol −1 s −1 was determined for the reaction between (Cu(Et 2 dsc) 2 and Cu(Et 2 -dtc) 2 (Et 2 dtc = diethyldithiocarbamate). Additional experiments suggest a chain mechanism for the ligand exchange reactions in which the mono-chelates e.g. [Cu(mnt)] s react as active sites.