An X-Ray Diffraction Study of the Substructure-Superstructure Transformation in α-Bis(1,2-Benzoquinonedioximato)palladium(II), α-Pd(bqd)₂

Abstract

X-Ray diffraction studies of the structure of the α-form of bis(1,2-benzoquinonedioximato)palladium(II), α-Pd(bqd)₂, at four different temperatures are reported. At 108K a mainly second-order phase transformation from a centrosymmetric subcell structure (space group Ibam, with cell vectors a, b, and c) to a polar, commensurate supercell structure (Pcc2, with á = a, [bacute] = 4b, ć = c) takes place. The superstructure results from both translation and rotation of the molecules. It can be described in terms of a transverse modulation wave extending perpendicular to the stacking direction resulting in an undulation of the stacks with a maximum displacement of 0.84Å at 19.5K. There is no evidence of dimerization within the stacks.