Low-temperature single crystal X-ray diffraction and high-pressure Raman studies on [(CH3)2NH2]2[SbCl5]

The structure of bis(dimethylammonium) pentachloroantimonate(III), [(CH3)2NH2]2[SbCl5], BDP, was studied at 15 K and ambient pressure by single-crystal X-ray diffraction as well as at ambient temperature and high pressures up to 4.87(5) GPa by Raman spectroscopy. BDP crystallizes in the orthorhombic Pnma space group with a=8.4069(4), b=11.7973(7), c=14.8496(7) A, and Z=4; R1=0.0381, wR2=0.0764. The structure consists of distorted [SbCl6]3- octahedra forming zig-zag [{SbCl5}n]2n- chains that are cross-linked by dimethylammonium [(CH3)2NH2]+ cations. The organic and inorganic substructures are bound together by the N-H...Cl hydrogen bonds. The distortions of [SbCl6]3- units increase, partly due to the influence of the hydrogen bonds which became stronger, with decreasing temperature. The preliminary room temperature, high-pressure X-ray diffraction experiments suggest that BDP undergoes a first-order phase transition below ca. 0.44(5) GPa that destroys single-crystal samples. The transition is accompanied by changes in the intensities and positions of the Raman lines below 400 cm-1. - Graphical abstract: On cooling to 15 K [(CH3)2NH2]2[SbCl5] shows significant changes in the geometries of the longest Sb-Cl bonds that are correlated with the changes in the geometry of the N-H...Cl hydrogen bonds. Applying of quite modest pressures far exceed observed temperature-induced changes-[(CH3)2NH2]2[SbCl5] undergoes a first-order phase transition below ca. 0.44(5) GPa that destroys single-crystal samples