Tungsten(V) binuclear thiocomplexes with diethyldithiocarbamate. Synthesis, spectral, thermal and kinetic studies

Abstract

We report the synthesis, using reactions in different solvents, and the study of di-μ-sulfido-bis(sulfido N,N-diethyldithiocarbamate) dy-tungsten(V) adducts with pyridine or substituted pyridines, with formula assigned as W 2S 4(diethyldtc) 2B 2, where dtc=dithiocarbamate; B=pyridine (Py), 3-methylpyridine (3-MP), 4-methylpyridine (4-MP), 3,5-dimethylpyridine (3,4-DMP), 3-aminopyridine (3-AP) and 4-aminopyridine (4-AP). The complexes obtained have been identified by IR and electronic spectra, magnetic susceptibility measurements and analytical data. We have also studied the thermal behaviour and kinetic parameters, by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), of the thermal decomposition of these adducts in the solid state. From the DSC curves, the activation energies and pre-exponential Arrhenius factors for the endothermic process corresponding to the loss of two moles of coordinated base were calculated. We have also deduced the mechanism of the reaction using a new non-isothermal kinetic method. The effects of steric hindrance and the inductive effects exercised by the functional groups, amino and methyl of the pyridine, in the formation of the adducts are discussed. The relationship between the basicity of the pyridines, IR and electronic spectral data and activation energies has also been explored.