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.