Halogen and hydrogen bonds in compressed pentachloroethane?

CrystEngComm Pub Date: 2016-05-30 DOI: 10.1039/C6CE01025C

Abstract

In pentachloroethane, C2HCl5, high pressure initially strongly compresses the C–H?Cl bonds in phase I; however, in phase II which is stable above 0.62 GPa the role of hydrogen bonds is diminished and molecular aggregation is dominated by halogen bonds Cl?Cl. Both phases have been determined by X-ray diffraction and the phase diagram of C2HCl5 has been outlined. The transition between phases I and II retains some relation between their structures and reduces the symmetry from class mmm (space group Pnma) to 2/m (space group P21/n11). The discontinuous transition, with the shear strain exceeding 21°, is so strong that its progress can be visually observed even for powdered samples. The single-crystal growth suggests a surface-roughening transition, as phase I grows in the form of dendrites combining into oval plates, while phase II forms prisms with sharp edges.

Graphical abstract: Halogen and hydrogen bonds in compressed pentachloroethane
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