PUB - Publikationen an der Universität Bielefeld

The thermal behaviour of the giant molybdenum ring cluster compound Na-14 [{Mo-2(VI) O-5 (H2O)(2)}(14)(2+) ({(Mo8O26)-O-VI/V(mu(3) - O)(2)HL3MoVI/V}(3-))(14)] . ca. 400H(2)O . ca. 10CH(3)OH drop Na-14[(MoO3)(154)(H2O)(62)(CH3OH)(8)H-14] . ca. 400 H2O . ca. 10 CH3OH (L-3 = H2O, CH3 OH) 1 - containing H2O ligands partly substituted by methanol molecules - was studied using TG, DTG and DTA analyses simultaneously, and mass spectrometric analysis of the decomposition products. Methanol is released from the sample quite rapidly even at room temperature (and even before the experiments start) but small traces of methanol are still present which we tried to use for characterising the different stages of giant ring transformation. The initial rapid loss of mass of the sample was accompanied by the DTA and DTG peak at 75degreesC. A small DTA endothermic peak at 165degreesC was assigned to an MS maximum indicating the increased emission of methanol and formaldehyde. Double exothermic peaks at 352 and 366degreesC corresponded to the loss of water formed from the abundant OH groups. Simultaneously, peaks indicating trace emission of formaldehyde, methanol, carbon dioxide as well as traces of hydrocarbons containing 2-4 carbon atoms per molecule were registered mass spectrometrically. The exothermic effect was attributed to a kind of "recrystallisation" process of the completely dehydrated product.