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; ΔHt° 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)+ 3C5H8O2(g)= Fe(C5H7O2)3(g)+H2(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.