Thermogravimetric studies of metal β-diketonates

Abstract

Thermogravimetric analysis (TGA) is applied to the rapid determination of the relative volatilities of various metal β-diketonate chelates. Differences are seen in the volatility of a series of thermally stable tris(2,2,6,6-tetramethyl-3,5-heptanedionato) rare earth chelates. The trend in volatility of the rare earth chelates is related to the size of the trivalent rare earth ion and is independent of chelate mass. The order of increasing volatility as seen from the thermograms of the volatile rare earth chelates parallels the order of increasing ease of elution of these chelates from non-polar gas chromatographic liquid partioning phases. Some of the chelates are considerably more volatile than alkane hydrocarbons of considerably lower carbon number. Volatilities of metal β-diketonates of Cr(III), Fe(III), Rh(III), Al(III), Na(I), Zr(IV), Sc(III), Y(III), and the trivalent lanthanides are compared. Differences in the volatilities of metal chelates, arising from substitution in the chelate ligand, are illustrated for metal chelate derivatives of various β-diketone ligands.