The thermal decomposition behavior of tris(2,4-pentanedionato-O,O') iridium(III) (1) has been studied with TG-DTA and GC-MS. The results show that compound 1 combusts, decomposes, sublimates and loses weight simultaneously at 258℃ in oxygen, and the heat emitting from the combustion is far greater than that absorbed by sublimation. Compound 1 decomposes, producing Ir, 2,4-pentanedione, carbon dioxide and 3-acetyl-2,5-dimethyl furan etc. in oxygen. Compound 1 absorbs a great deal of heat to sublimate and loses weight sharply from 239℃ in inert argon. Compound 1 can not combust with the increase of temperature in argon but sublimation is accelerated. When heated above 300℃, compound 1 decomposes, forming Ir, 2,4-pentanedione, 3-butene-2-one and 2,5-dimethyl furan etc. in argon. When compound 1 decomposed in oxygen, fewer kind of thermolytic products can be obtained. However, CVD experiments indicate that better Ir coatings on Re base can be prepared by adopting an inert gas with the addition of oxygen in appropriate amount (e.g. Ar flow of 50 mL·min^-1, O₂ flow of 1 mL·min^-1) as carrier gas flow, for oxygen can prevent carbon from co-depositing with Ir on base. The forming mechanisms of thermolytic products were also proposed on the basis of the recombination of free radicals and oxidation of the organic ligands.

Key words: tris(2,4-pentanedionato-O,O)iridium(Ⅲ), thermal decomposition behavior, chemical vapor deposition, free-radical reaction