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Issue 10, 2008
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Isostructural relations in dihalomethanes and disproportionation of bromoiodomethane

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Abstract

The directional character of halogen⋯halogen forces has been evidenced by specific structural features of bromoiodomethane crystals, CH2BrI. The crystals were in-situ grown in isobaric conditions in a glass capillary and in isothermal and isochoric conditions in a diamond-anvil cell, and the structures have been determined by single-crystal X-ray diffraction at 0.10 MPa/220 K, 0.10 MPa/100 K, 0.54 GPa/295 K. The freezing point for isothermal compression at 295 K is 0.47 GPa. At 0.80 GPa/490 K CH2BrI disproportionates to CH2I2 and CH2Br2. The ambient-pressure/low-temperature and 0.54 GPa/ambient-temperature CH2BrI crystals are monoclinic, space-groupC2/c, isostructural with CH2Br2, CH2I2 and CH2BrCl phases. High-pressure structure of CH2I2, determined at 0.80 GPa/295 K, is orthorhombic, space-group Fmm2. Crystals of CH2Br2, CH2BrI and CH2I2 are 2-dimensionally isostructural. The polar arrangement of molecular sheets in CH2I2 is favoured by CH⋯I hydrogen bonds, which are absent in the centrosymmetric CH2BrI structure. The temperature at which CH2BrI disproportionates into CH2Br2 and CH2I2 is raised by pressure, as this process requires that CH2BrI be liquid.

Graphical abstract: Isostructural relations in dihalomethanes and disproportionation of bromoiodomethane

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Publication details

The article was received on 26 Mar 2008, accepted on 07 Jul 2008 and first published on 05 Aug 2008


Article type: Paper
DOI: 10.1039/B805065A
Citation: CrystEngComm, 2008,10, 1436-1442
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    Isostructural relations in dihalomethanes and disproportionation of bromoiodomethane

    M. Podsiadło and A. Katrusiak, CrystEngComm, 2008, 10, 1436
    DOI: 10.1039/B805065A

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