Thermochemistry of dichlorobis(triphenylphosphine oxide)-zinc(II), -cadmium(II), and -mercury(II)

Abstract

The standard enthalpy change (ΔH_R^⊖) 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 (ΔH_f^⊖) of the crystalline anhydrous metal chlorides and the ligand, the ΔH_f^⊖ 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.