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

Abstract

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) Å, 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.