The heat of formation of tris(acetylacetonato)iron(III) and the metal–oxygen bond energy

Abstract

The standard heat of formation of tris(acetonato)iron(III) has been evaluated at 25° by reaction calorimetry; ΔH_t° Fe(C₅H₇O₂)₃=–313·2 ± 0·7 kcal./mole. Enthalpy changes at 25° for the following hypothetical gaseous reactions have been subsequently derived: Fe_(g)+ 3C₅H₈O_2(g)= Fe(C₅H₇O₂)_3(g)+H_2(g); ΔH=–112·2 ± 0·6 kcal./mole, Fe_(g)+ 3C₅H₇O˙_2(g)= Fe(C₅H₇O₂)_3(g); ΔH=–270·9 ± 8·7 kcal./mole, Fe³⁺_(g)+ 3C₅H₇O₂^–_(g)= Fe(C₅H₇O₂)_3(g); ΔH= 1435 kcal./mole

The corresponding heterolytic (E′) and homolytic (E′) metal–oxygen bond-energy parameters are calculated: E′_Fc-O= 239; E′_Fe-O= 45 kcal./mole respectively.