Structural characteristics of areneselenenyl bromide and areneselenenyl chloride stabilized by hypervalent coordination with a halide anion in the solid state

Solid-state molecular structures of 2-[(N-cyclohexyl-N-methylamino)methyl]benzeneselenenyl bromide (ArSeBr) and chloride (ArSeCl), stabilized by hypervalent coordination with a halide anion (Br− or Cl−, respectively), were determined by X-ray diffraction method. By comparing bond parameters of the observed hypervalent BrSe⋯Br fragment with those reported previously for other organoselenium compounds, which have a similar T-shaped selenium fragment, it was revealed that there is decent hyperbolic relationship between the two linear SeBr atomic distances in the solid state, reflecting the possibility of a pathway for the addition reaction of benzeneselenenyl bromide (PhSeBr) in solution. In addition, the existence of significant bond-shortening (∼0.1 Å) due to intermolecular weak packing interactions was strongly suggested by comparison of the extrapolated SeBr covalent bond length (2.220 Å) in the solid state with that reported for PhSeBr (2.325 Å) in the gas phase. Ab initio molecular orbital calculations at the RHF/6-31G(d,p) level using Ahlrichs pVDZ basis sets for Se and Br estimated the perturbation energy in the solid state to be roughly 1.5 kcal mol−1 independent of the packing structure.