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) Å, 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.

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.Figure optionsDownload as PowerPoint slide