Volatile metal beta-diketonates--new precursors for the sonochemical synthesis of nanosized materials--sonolysis of thorium(IV) beta-diketonates.

Ultrasonic irradiation (22 kHz, Ar atmosphere) of Th(IV) beta-diketonates Th(HFAA)4 and Th(DBM)4, where HFAA and DBM are hexafluoroacetylacetone and dibenzoylmethane respectively, causes them to decompose in hexadecane solutions, forming solid thorium compounds. The first-order rate constants for Th(IV) beta-diketonate degradation were found to be (9.3 +/- 0.8) x 10(-3) for Th(HFAA)4 and (3.8 +/- 0.4) x 10(-3) min-1 for Th(DBM)4, (T = 92 degrees C, I = 3 W cm-2). The rate of the sonochemical reaction increased with the rising beta-diketonate volatility and decreased with the rising hydrocarbon solvent vapor pressure. Solid sonication products consisted of a mixture of thorium carbide ThC2 and Th(IV) beta-diketonate partial degradation products. The average ThC2 particle size was estimated to be about 2 nm. ThC2 formation was attributed to the high-temperature reaction occurring within the cavitating bubble. The thorium beta-diketonate partial degradation products formed in the liquid reaction zones surrounding the cavitating bubbles.