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]b e bromide (ArSeBr) and chloride (ArSeCl), stabilized by hypervalent coordin ation with a halide anion (Br- or Cl-, respectively), were determined by X- ray diffraction method. By comparing bond parameters of the observed hyperv alent Br-Se Br fragment with those reported previously for other organosele nium compounds, which have a similar T-shaped selenium fragment, it was rev ealed that there is decent hyperbolic relationship between the two linear S e-Br atomic distances in the solid state, reflecting the possibility of a p athway for the addition reaction of benzeneselenenyl bromide (PhSeBr) in so lution. In addition, the existence of significant bond-shortening (similar to 0.1 Angstrom) due to intermolecular weak packing interactions was strong ly suggested by comparison of the extrapolated Se-Br covalent bond length ( 2.220 Angstrom) in the solid state with that reported for PhSeBr (2.325 Ang strom) in the gas phase. Ab initio molecular orbital calculations at the RH F/6-31G(d,p) level using Ahlrichs pVDZ basis sets for Se and Br estimated t he perturbation energy in the solid state to be roughly 1.5 kcal mol(-1) in dependent of the packing structure. (C) 2000 Elsevier Science S.A. All righ ts reserved.