Volatile trends are established for a series of MU(β-diketonate)n complexes, where MU = Cu (n = 2); Al, Sc, Cr, Fe, Co, Ga (n = 3); Zr (n = 4) and β-diketonate = acetylacetonate (acac), trifluoroacetylacetonate (tfac), hexafluoroacetylacetonate (hfac) and 2,2,6,6-tetramethyl-3,5-heptanedionate (tmhd). Sublimation enthalpies (ΔHsub) were calculated from thermogravimetric analysis (TGA) data, which show that the dependence of ΔHsub on the number and type of intermolecular interactions appears to be more substantial than molecular mass effects. Irrespective of the metal, the ΔHsub values for the MU(tmhd)3 derivative have a ΔHsub value of between 93 and 99% of that of the MU(acac)3 derivative. In contrast, the MU(tfac)3 and MU(hfac)3 derivatives have ΔHsub values of ca. 82% and 54% of the values for the corresponding MU(acac)3. Similar trends are observed for MU(β-diketonate)2 and MU(β-diketonate)4 derivatives. The relationship between the ΔHsub and (Tsub) of the substituted β-diketonate derivatives as compared with the values for parent MU(acac)n may be used to predict either quantity for a range of MU(β-diketonate)n complexes where the values for MU(acac)n are known. Using the TGA sublimation data, vapour pressures have been calculated for each of the MU(β-diketonate)n complexes. Copyright © 2000 John Wiley & Sons, Ltd.

Substituent effects on the volatility of metal ?-diketonates

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