THERMOANALYTICAL AND X-RAY DIFFRACTOMETRIC OBSERVATIONS OF A PLASTICALLY CRYSTALLINE PHASE IN MOLECULAR MIXED-LIGAND COMPLEX

Thermal properties and structures of molecular complexes [M(hfac)(2)(t men)] (M = Ni, Cu) were examined by a differential thermal analysis an d an X-ray diffractometry above room temperature. The Ni- and Cu-compl ex crystals were found to melt through two, II-to-I and I-to-L, phase transitions at 373 K and 403 K respectively, and through a I-to-L phas e transition at 410 K, respectively. The phase I of the Ni-complex was concluded to be in the plastically crystalline state and in the face- centered cubic system. It was noted that the difference between the ph ase relations of the two complexes should originate from the different coordination bonds as correlated with the electronic configurations o f the central metal ions.