The low-temperature phase of diisopropylammonium bromide

The title compound, C6H16N+.Br-, was refined against room-temperature data in space group P2(1) as a racemic twin by Kociok-Kohn, Lungwitz & Filippou [Acta Cryst. (1996). C52, 2309-2311]. At low temperature, we found a different phase, which is characterized by a different cell (twice as big as the cell at room temperature) and a different space group (P2(1)/n). Surprisingly, the cell parameters obtained at low temperature can be transformed into those measured at ambient temperature. Even the coordinates can be transformed and the structure can be refined in the small cell. However, some warning signs (e.g. a low \E-2 - 1\ value, apparent twinning and peaks in the electron-density map) point to the correct cell and space group.