Thermochemistry Of Dichlorobis(triphenylphosphine Oxide)-zinc(ii), -cadmium(ii), And -mercury(ii)

The standard enthalpy change (ΔHR ⊖) for the reaction MCl2(s) + 2PPh3O(s) → [MCl2(PPh3O)2](s) (M = Zn, Cd, or Hg) has been determined by solution calorimetry as -51.1 ± 2.2 (Zn), -16.3 ± 0.5 (Cd), and -12.3 ± 0.6 kJ mol-1 (Hg) respectively. From the standard enthalpies of formation (ΔHf ⊖) of the crystalline anhydrous metal chlorides and the ligand, the ΔHf ⊖ values of the zinc, cadmium, and mercury adducts are -586.6 ± 50, -528.3 ± 50, and -357.7 ± 50 kJ mol-1. The standard enthalpy change due to the sublimation of ligand (-66.0 kJ mol-1) has also been determined. Since the adducts do not sublime, the possibility of evaluating the enthalpy of the metal-oxygen bonds is discussed.91102110