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

The reaction of (o-SCH3C6H4)3P with three equivalents of dibromine produces the unusual salt {[(o-SCH3C6H4)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-SCH3C6H4)3PBr]+ cation. The two-dimensional polybromide network that is formed is templated around the [(o-SCH3C6H4)3PBr]+ cation, with both the cation and the polybromide network exhibiting crystallographically imposed C3 symmetry. The crystal packing allows [(o-SCH3C6H4)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.

Graphical abstractThe structure of the first compound of R3PBr5 stoichiometry has been elucidated and shown to be the unusual salt, {[(o-SCH3C6H4)3PBr][Br]·0.5(μ-Br2)3}n. The structure consists of a high symmetry (C3) cation which acts as a template around a C3 symmetric 2D polybromide network. This polymeric network is built up of 18-membered hexagonal rings consisting of six bromide anions and six dibromine molecules.Figure optionsDownload full-size imageDownload as PowerPoint slide