Crystal polymorphism of (μ4–O)-body centered adamantanoid Cu(II) complexes

Abstract

Two novel polymorphs of [Cu4(μ4–O)(μ–Cl)6(DASO)4], (DASO = diallyl sulfoxide; C6H10OS), rhombic (C) and triclinic (D), were obtained and examined by single crystal X-ray diffraction analysis at two temperatures, 295(2) and 100(1) K. This study, in addition to our recent work on the tetragonal (A) and trigonal (B) forms of the title compound, allowed determining the nature of polymorphism and temperature-induced phase transitions. It is stated that both the packing arrangement and the displacive transformation integrate these structures, forming the symmetrically and thermodynamically related series: A,B → C → D. The C3h → C4 distortion of Cu(II) trigonal bipyramidal coordination geometry underlies the static disorder of adamantanoid cage, resulting in the thermal order–disorder phase transition. The square–pyramidal distortion degree as well as the disorder rate may be crucial for anomalous magnetic behaviour of (μ4–O)-body centered adamantanoid Cu(II) complexes.