Enthalpies of formation of alkali-metal hexachloro-zirconates and -hafnates
Abstract
Enthalpies of reaction have been determined by solution calorimetry for the process (i) where M′= Na, K, or Cs 2 M′Cl(c)+ MCl4(c)→ M′2[MCl6](c)(i) and M = Zr or Hf. Heats of formation for the complexes, ΔHf⊖(298 K), have been calculated using mean values of ΔHf⊖ for MCl4 taken from the literature. The reaction is marginally more favourable when M = Hf but both ZrCl4 and HfCl4 are somewhat better acceptors of chloride ion than is NbCl4 and both are markedly better acceptors than SnCl4.