No abstract

Tetrakis β‐diketonates were synthesized with quadrivalent thorium and 1,1,1‐heptafluoro‐7,7‐dimethyloctane‐4,6‐dione (fod) and with 1,1,1‐trifluoropentane‐2,4‐dione (tfa). They were characterized by elemental analysis. Temperature‐dependent X‐ray diffraction data were recorded. It was found that Th(tfa)4 can be obtained as a hydrate Th(tfa)4 · H2O and also water‐free. Visual determination gives a melting point of 423 K for Th(tfa)4 · H2O and DSC gives a melting point of 407 K for water‐free Th(tfa)4. DSC also showed a phase transition in Th(fod)4 at 366 K, the second phase transition at 424 K being identical with the melting point. Vapour pressures of Th(tfa)4 and of Th(fod)4 were determined by the flow method using nitrogen as a carrier gas. The experimental data have been fitted to an equation of the form The results are ΔRH298 = 151.2 kJ · mol−1, ΔRS298 = 310.0 J · K−1 · mol−1, ΔRcp = −259.2 J · K−1; · mol −1; for the low temperature α‐modification of Th(fod)4, ΔRH298 = 130.6 kJ · mol−1, ΔRS298 = 253.5 J · K−1 · mol−1 and ΔRcp = −259.2 J · K−1 · mol−1 for the β‐modification at temperatures above 366 K, and ΔRH298 = 154.6 kJ · mol−1, ΔRS298 = 326.1 J · K−1 · mol−1, ΔRcp = −170.8 J · K−1 · mol−1 for water‐free Th(tfa)4.