Structure and phase transition in bis(pyrrolidinium) hexachlorometallates, (C₄H₈NH₂)₂MCl₆ (M = Sn, Te and Pt), studied by X- ray diffraction, ³⁵Cl NQR and DSC

Single crystal X-ray diffraction, ³⁵Cl nuclear quadrupole resonance (NQR) and differential scanning calorimetry (DSC) measurements were taken for bis(pyrrolidinium) hexachlorometallates, (C₄H₈NH₂)₂MCl₆ (M = Sn, Te and Pt). A solid-solid phase transition was observed at 150(1), 159(1) and 134(1) K for stannate, tellurate and platinate, respectively. ³⁵Cl NQR signals were observed in stannate and platinate, both of which showed a two-line spectrum in the high-temperature phase and a three-line spectrum in the low- temperature phase. The high-temperature phases of the three complexes were found to be isostructural with each other belonging to the space group C2/m (12). The C₄H₈NH₂⁺ and MCl₆/^2- ions are connected by N-H···Cl hydrogen bonds forming parallel sheets in the crystals. Disorder of the cation ring appears in these high-temperature phases. Semi-empirical MO calculations were performed to estimate the stable structure of the pyrrolidinium ion. (C) 2000 Elsevier Science B.V.