Generation of a high symmetry 2D-polybromide network in the structure of {[(o-SCH3C6H4)3PBr][Br]·0. 5(μ-Br2)3}n. the templating effect of the C3 symmetric [(o-SCH3C6H4) 3PBr]+ cation

Abstract

The reaction of (o-SCH3C6H4)3P with three equivalents of dibromine produces the unusual salt {[(o-SCH 3C6H4)3PBr][Br]·0.5(μ- Br2)3}n, which contains a bromo-phosphonium cation and a polybromide network built up of [Br]- anions and dibromine molecules. This structure is the first reported compound with an R3PBr5 stoichiometry, and exhibits a network structure, which propagates via bromide anions interacting with three different dibromine molecules, {(Br)-(μ-Br2)3}n. Each bromide anion also interacts with one [(o-SCH3C6H 4)3PBr]+ cation. The two-dimensional polybromide network that is formed is templated around the [(o-SCH 3C6H4)3PBr]+ cation, with both the cation and the polybromide network exhibiting crystallographically imposed C3 symmetry. The crystal packing allows [(o-SCH 3C6H4)3PBr]+ cations to pack in a back-to-back fashion, with formation of an (EF)6 aryl embrace. This type of commonly observed aryl embracing motif is possible as the (o-SCH3C6H4) rings adopt an exo3 conformation. The polybromide network is arranged around the cations, and forms 18-membered hexagonal rings (consisting of six bromide anions and six dibromine molecules), and the rings adopt a chair conformation. The structure and connectivity of the network is discussed and compared with other known polybromide species. © 2013 Elsevier Ltd. All rights reserved