Ligand effects on the stability of some Mo(VI) and W(VI) peroxo complexes: Part 2. Study of the thermal stability

Twenty four peroxo complexes of Mo(VI) and W(VI) of the types (a) K2[MO(O2)2(L)]·xH2O where L=C2O42−, C4H3O42−, C6H6O72−, C4H2O42−, (OH)2C2H2O42− NC5H7O42−, NC7H3O42− and x=0 for C2O42− and 1–2 for the rest and (b) K2[M2O2(O2)4(L′)]. xH2O where L′=C3H2O42−, (OH)2C4H2O42−, NC6H4O2−, C6H4NO3−, and H2NC2H2O2− and x=1–4 were used to study thermal stability by both conventional heating as well as by thermogravimetry (TG), derrivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). Decomposition temperatures of Mo(VI) complexes were found to be much higher than those of the corresponding W(VI) analogues. Peroxo complexes containing ligands having electron withdrawing functional group(s) decomposed explosively at temperatures lower than those without them. Decomposition reactions were established by mass loss, the peroxide content versus temperature, elemental analyses, and infrared (ir) spectroscopy.