Synthesis, spectral, thermal and kinetic studies on the adducts with pyridines of tungsten(V) binuclear thiocomplexes with di-isopropyl-dithiocarbamate

We report the synthesis and the thermal and kinetic behaviour of di-μ-sulfido-bis-(sulfido N,N,di-i-propyldithiocarbamate)di-tungsten(V) adducts with pyridine or substituted pyridines, the formula of which is [W2S4(di-i-propyldtc)2B2], where dtc = dithiocarbamate and B = pyridine (Py), 3-methylpyridine (3-MP), 4-methylpyridine (4-MP), 3,5-dimethylpyridine (3,5-DMP), 3-aminopyridine (3-AP) and 4-aminopyridine (4-AP). The synthesized complexes have been identified by IR and electronic spectra, magnetic susceptibility measurements and analytical data. We have also inferred 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 reaction mechanism using a new non-isothermal kinetic method. Steric hindrance and inductive effects prompted by amino and methyl pyridine functional groups in the adducts formation are discussed. A relationship between the pyridines basicity, infrared and electronic spectral data and activation energies has also been explored.

When the thermal decomposition of di-μ-sulfido-bis-(sulfido N,N,di-i-propyldithiocarbamate)di-tungsten(V) adducts with pyridines was investigated, the DSC curves of all the compounds showed a first endothermic peak over 115–162 °C. The mass loss accompanying this transition corresponds on the TG curves to the loss of two moles of coordinated base.Figure optionsDownload as PowerPoint slide