Online coupled TG–FTIR and TG/DTA–MS analyses of the evolved gases from dichloro(thiourea) tin(II)

Identification and monitoring of gaseous species released during thermal decomposition of title compound 1, dichloro(thiourea) tin(II), Sn(tu)Cl2, [thiourea (tu), (NH2)2CS] in flowing air atmosphere have been carried out by both online coupled TG–FTIR and simultaneous TG/DTA–MS evolved gas analysis (EGA) instruments. The first gaseous products of 1, evolved from 170 °C, are cyanamide (NH2CN), carbonyl sulphide (COS), carbon disulfide (CS2) and water (H2O). At 240 °C isothiocyanic acid (HNCS) becomes the main product, accompanied by CS2, hydrogen cyanide (HCN) and traces of hydrogen chloride (HCl) according to EGA–FTIR analysis. Ammonia (NH3) occurs first only above 250 °C, while sulfur dioxide (SO2) formation is not observed till 400 °C. Air oxidation products of tin sulphides and organic residues, such as SO2, carbon dioxide (CO2) and NH2CN, occur suddenly at 425 °C together with a very sharp exothermic heat effect. All species identified by FTIR gas cells are confirmed by mass spectrometry, except HNCS. Evolution of H2S has not been observed at any stage of the degradation of 1 by either of the EGA methods.