THERMAL DELIGATION OF MO(6)S(8)L(6) CLUSTER COMPLEXES - EXAFS AND OTHER SPECTROSCOPIC TECHNIQUES SUPPORT RETENTION OF THE MO6S8 CLUSTER UNIT UP TO 500-DEGREES-C

Thermal deligation reactions of N-ligated Mo(6)S(8)L(6) cluster complexes (L = propylamine, pyrrolidine, and piperidine) have been explored at a variety of temperatures in an attempt to form the Mo6S8 binary Chevrel phase. Direct heating of the cluster complexes (100-500 degrees C) under dynamic vacuum has led to varying degrees of ligand removal while retaining the Mo6S8 cluster unit in amorphous products. Support for the presence of the cluster unit has been gained by the characteristic Raman band at 445-450 cm(-1), XPS data, and results of a Mo EXAFS study. Mo-Mo and Mo-S bond distances derived from the fitting of the EXAFS data for the amorphous products are in good agreement with those for crystalline Mo6S8 and Mo(6)S(8)L(6) complexes with well-determined structures. Both XPS and EXAFS show that disproportionation to MoS2 and Mo does not occur during deligation below 500 degrees C.