Acta Cryst. (2013). C69, 247-250 [ doi:10.1107/S010827011300231X ]
Abstract: (1RS,3RS,4RS,10SR)-2,2,3,10-Tetrabromo-1,2,3,4-tetrahydro-1,4-ethanonaphthalene, C12H10Br4, (I), is the first structure to be reported with four Br atoms bound to a 1,4-ethanonaphthalene framework and also the first which possesses three Br atoms in exo positions. Interactions between the Br atoms [three short intramolecular BrBr distances of 3.1094 (4), 3.2669 (4) and 3.4415 (5) Å] have little effect on the C-C bond lengths but lead to significant twisting of the cage structure compared with the parent hydrocarbon, which is expected to be fully eclipsed at the two saturated C2H4 bridge positions. Chemically related (1SR,4RS)-2,3-dibromo-1,4-ethenonaphthalene, C12H8Br2, (II), obtained by double dehydrobromination of (I), represents the first structure of any halogen-substituted benzobarrelene. This cis-dibromide shows little evidence of steric congestion at the double bond [BrBr = 3.5276 (8) Å] as a consequence of the large C-C-Br angles [average C=C-Br angle = 126.15 (10)°].
Formula: C12H10Br4 and C12H8Br2
Structure factor file (CIF format) (150.8 kbytes)
Structure factor file (CIF format) (116.9 kbytes)
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