MASS-SPECTROMETRIC STUDY OF THERMOLYSIS MECHANISM OF METAL ACETYLACETONATES VAPOR

The processes of thermal decomposition of aluminium(III) and scandium( III) acetylacetonates (Al(aa)(3) and Sc(aa)(3)) were investigated in t he 160-650 degrees C temperature range using a high-temperature molecu lar beam source with mass spectrometric sampling of the gas phase comp osition directly at the outlet from the reaction zone. A scheme of the rmal decomposition of aluminium(III) and scandium(III) acetylacetonate s vapour is suggested. It is established that the common mechanism of thermolysis of these complexes is due to the commonness of electronic structure of ions Mg2+, Al3+, Sc3+ and Hf4+. According to the scheme, the process proceeds along three parallel routes, one of them being po ssible only for complexes possessing more than two ligands; in this ca se the gaseous products resulting from cyclic dimerization of ligand f ragments are formed. The influence of oxygen and hydrogen on the compo sition of the gaseous products and the mechanism of thermolysis of the complexes vapour are also established. From temperature curves, the e ffective values of kinetic parameters in Arrhenius equation are calcul ated for the first order reaction.