Structural Characterization of Areneselenenyl Chloride Stabilized by the Stereoelectronic Effect of an Intramolecular Nitrogen Atom
作者:Michio Iwaoka、Shuji Tomoda
DOI:10.1021/jo00121a058
日期:1995.8
The first X-ray structural characterization of areneselenenyl chloride (ArSeCl) was achieved with a single crystal obtained from a 1:2 mixture of 2,2'-diselenobis[N,N-di[2-(2-pyridyl) ethyl]benzylamine] (3) and copper(II) chloride. The structure of the complex, 4 = 3 . 2Cl . 2CuCl(2) . CHCl3, contained a Se-Cl bond strongly stabilized by an intramolecular tertiary nitrogen atom. Selected bond parameters were Se-Cl = 2.432(3) Angstrom, Se-C = 1.919(12) Angstrom, Se ... N = 2.191(8) Angstrom, angle C-Se-Cl = 96.5(3)degrees, and angle Cl-Se ... N = 178.4(2)degrees. In order to characterize the observed Se ... N interaction, the electronic structure around the selenium was investigated by MO and NBO methods at various basis set levels using model compound 6. The optimized geometries, obtained at 3-21G* and LANL1DZ basis set levels, were reasonably consistent with the results of the X-ray analysis of 4. The shape of the LUMO and the large NBO deletion energy (47 kcal) between the Se-Cl bond and N suggested that the observed Se ... N interaction arises from the orbital interaction between a low-lying unoccupied sigma* orbital of the selenium and the nitrogen lone pair electrons, showing that the electronic structure around the selenium is similar to the transition-state of a bimolecular nucleophilic substitution at selenium.