Structural characterisation of the diorganoselenium interhalogen compounds R2SeIBr (R = Ph or Me) and the ionic compound [Me3Se][IBr2]

The reaction of R2Se (R = Ph or Me) with iodine monobromide in diethyl ether solution produced the charge-transfer complexes R2SeI-Br. In the case of Ph2Se, Ph2SeIBr was produced quantitatively. However, for Me2Se, both Me2SeIBr and the ionic product [Me3Se][IBr2] were produced indicating ease of methyl migration for Me2SeIBr and that it lies close to the ionic/covalent structural borderline. The other product from this autoionisation is believed to be Me2Se2I2, although this was not extensively characterised. The compounds Ph2SeIBr and Me2SeIBr show markedly different d(I-Br) 2.640(2) and 2.797(5) Angstrom, respectively illustrating how the R groups on the selenium affect its donor power towards iodine monobromide. The three compounds Ph2SeIBr, Me2SeIBr and [Me3Se][IBr2] have been characterised by single-crystal X-ray diffraction.