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

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, (La-O), and the mean coordinate bond dissociation energy, CB>(La-O), respectively.