[(1S,2S,3R,4R)-3-Hydr-oxy-4,7,7-tri-methyl-bicyclo-[2.2.1]heptan-2-yl]methyl[(E)-3-(trimethyl-silyl)prop-2-enyl]selen-onium bromide.

The title compound, a seleno-nium bromide, C(17)H(33)OSeSi(+)·Br(-), was obtained from the reaction of enanti-omerically pure 4,7,7-trimethyl-2-methyl-selanylbicyclo-[2.2.1]heptan-3-ol and (3-bromopropen-yl)trimethyl-silane in acetone. Due to the chiral bicyclic substituent, the crystal structure is not centrosymmetric and has no symmetry plane, with four chiral C atoms in the cation. The asymmetric unit contains one seleno-nium cation and one bromide anion. C-H⋯Br and O-H⋯Br hydrogen bonds link the ions, forming a one-dimensional R-helical chain-like supra-molecular structure.