Thermal decomposition of [Cu4O(Cl+Br)6(OPPh3)4], starts at temperatures about 200°C. The decomposition proceeds in several steps. The intermediate formed in the first decomposition
step (weight loss 2–4%) is a new crystalline phase with slightly different structure but with preserved central unit Cu4O. The only crystalline phases found in the further decomposition products was CuBr in all cases when the bromine atoms were
present, the presence of CuCl was only observed at the decomposition of the hexachlorocomplex.