An in situ structural study of the thermal decomposition reactions of the ammonium thiomolybdates, (NH4)2Mo2S12•2H2O and (NH4)2Mo3S13•2H2O

A combined in situ Mo K-edge extended X-ray absorption fine structure (EXAFS) and X-ray powder diffraction study has been carried out to follow the evolution of structure in the thermal decomposition of the ammonium thiomolybdates, (NH4)(2)Mo3S13. 2H(2)O and (NH4)(2)Mo2S12. 2H(2)O, under nitrogen. Additional information on the course of the decomposition reactions has been obtained from thermogravimetric and differential thermal analysis, and from IR spectroscopy. Molybdenum-molybdenum bonded triangular units are found to persist in all the amorphous intermediate decomposition products of (NH4)(2)Mo3S13. 2H(2)O, and are also formed during the decomposition of (NH4)(2)Mo2S12. 2H(2)O. Structural models for the intermediates are presented. The final decomposition product in both cases is poorly crystalline MoS2.