An in situ structural study of the thermal decomposition reactions of the ammonium thiomolybdates, (NH4)(2)Mo2S12 center dot 2H(2)O and (NH4)(2)Mo3S13 center dot 2H(2)O

A combined in situ Mo K-edge extended X-ray absorption fine structure (EXAF S) and X-ray powder diffraction study has been carried out to follow the ev olution of structure in the thermal decomposition of the ammonium thiomolyb dates, (NH4)(2)Mo3S13. 2H(2)O and (NH4)(2)Mo2S12. 2H(2)O, under nitrogen. A dditional information on the course of the decomposition reactions has been obtained from thermogravimetric and differential thermal analysis, and fro m 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.