The Thermal Decomposition of Bis-2,4-pcntanedionato Metal (II) Complexes Under Low Pressure Conditions

摘要

Evolved gas analysis Fourier transform infrared spectroscopy has been used to investigate the thermal decomposition of the bis-2,4-pentanedionato complexes of Ca~(2+), Ba~(2+), Co~(2+), Cu~(2+), Mn~(2+), Ni~(2+), Sr~(2+), and Zn~(2+) in vacuo and in low pressure water vapor atmospheres. At least two competing decomposition mechanisms were identified. The first involved the loss of 2-propanone to form the metal carbonate or the metal oxide (and CO_2). The solid products of this reaction are often contaminated with carbon. Investigation of the reaction intermediates produced during the decomposition of the Sr~(2+) or the Ba~(2+) complexes indicated that the 2,4,6-heptanetrionato ligand and the 3,5-dimethyiphenol anions were formed as intermediates in this pathway. Thermal decomposition of the 3,5-dimethyiphenol anion produced the carbon. The second mechanism involved the reaction between water vapor and the metal complex to form 2,4-pentanedione. The experimental observations coupled with thermodynamic calculations indicated that this reaction contributed significantly to the decomposition mechanism when #DELTA#_(RXN) was < 160 kJ/ mol. It was the only pathway observed in water vapor atmospheres when #DELTA#_(RXN) was < 100 kJ/ mol. The metal was observed in the solid residue for Co~(2+), Cu~(2+), and Ni~(2+). Separate investigations have shown that the metal oxide reacted with the organic products to form the metal. This type of reaction maybe a key step in the production of metal films during metal organic CVD processes.