Abstract
At 298.15 K, the following standard molar enthalpies of formation of the crystalline solids were determined by solution-reaction calorimetry, and the enthalpies of sublimation were measured by microcalorimetry. {A table is presented} (PD, pentan-2,4-dionato; piprm, 2,2-dimethylheptan-3,5-dionato; dibm, 2,6-dimethylheptan-3,5-dionato; ibpm, 2,2,6-trimethylheptan-3,5-dionato; dpm, 2,2,6,6-tetramethylheptan-3,5-dionato.) The mean molar bon-dissociation enthalpy <D>(CuO) was related to D(OH) in the enol form of the diketone, and {<D>(CuO)-0.5D(OH), Hl, enol} was found to equal -(41.8 ± 2.0) kJ · mol-1, constant to within experimental error for all these complexes. Accepting {D(OH), Hl, enol} = (400 ± 20) kJ · mol-1, then <D>(CuO) = (158 ± 10) kJ · mol-1 showing a negligible effect of methyl substitution in the ligand l upon <D>(CuO). © 1984.