Thermochemical properties of some f-electron element β-diketonates, and metal-oxygen bond energies. lanthanum(III)β-diketonates

Abstract

The standard molar enthalpies of formation of the crystalline lanthanum(III) chelate complexes with pentane-2,4-dione (acetylacetone, Hacac) and 1-phenylbutane-1,3-dione (benzoylacetone, Hbzac) were determined by the solution calorimetry method. The following values ofΔH f(s) 0 (kJ mol−1) were obtained: La(acac)3', −1916.2±7.0; La(bzac)3 · 2H2O, −2099.1 ±9.7. The enthalpies of the hypothetical complex dissociation reactions in the gaseous phase: $$LaL_{3(g)} = La_{(g)} + 3L_{(g)} and LaL_{3(g)} = La_{(g)}^{ + 3} + 3L_{(g)}^ - $$ were calculated as a measure of the mean bond dissociation energy, <D>(La-O), and the mean coordinate bond dissociation energy, <DCB>(La-O), respectively.