Kinetics of reduction of tris(dithiocarbamato)iron(III) complexes by oxalic acid - influence of added dithiocarbamate ligand on the rate of reaction

Abstract

The reduction of tris(diethyldithiocarbamato)iron(III), (Fe( dedtc)₃); tris(dimethyldithiocarbamato)iron(III), (Fe(dmdtc)₃); tris(N-methyl,N-phenyldithiocarbamato)iron(III), (Fe(N-me,N-phdtc)₃) and tris(morpholine- Ncarbodithioato) iron(III), (Fe(morphdtch) by oxalic acid in benzene-methanol mixtures has been found to proceed with a first order dependence on the [complexes]. The order with respect to oxalic acid increases with an increase in

[oxalic acid). An induction period has been observed in the presence of added dithiocarbamate ligand and variation in the concentration of the ligand increases the rate of reduction of [Fe(dmdtc)₃] and [Fe(dedtc)₃] and decreases the rate of reduction of [Fe(N-me,N-phdtc)₃], while it has no effect on the rate of reduction of [Fe(morphdtc)₃]. Increase in the dielectric constant of the medium increases the rate of the reaction. The rates of reduction of the various complexes employed were in the order, [Fe(dedtc)₃] < [Fe(dmdtc)₃] ~ [Fe(morphdtc)₃] < [Fe(N-me,N-phdtc)₃]. These results are explained by assuming a dissociation equilibrium between tris(dithiocarbamato)iron(III) and a bis(dithiocarbamato)iron(III) species through the dithiocarbamate ligand. A suitable mechanism has been proposed.