Four-Center Six-Electron Interaction versus Lone Pair−Lone Pair Interaction between Selenium Atoms in Naphthalene Peri Positions

The X-ray crystallographic analysis of bis[8-(phenylselanyl)naphthyl]-1,1‘-diselenide (1) and 1-(methylselanyl)-8-(phenylselanyl)naphthalene (2) showed that the four selenium atoms in 1 aligned linearly, while the Se−C(Me) and Se−C(Ph) bond in 2 declined by about 50° and 40° from the naphthyl plane, respectively. Ab initio molecular orbital calculations were performed on the models of 1 and 2, model a (HbHc2Se···Ha1Se3SeHa···4SeHbHc) and model b (HaHb1Se···2SeHa‘Hb‘), respectively, with the 6-311++G(3df,2pd) basis sets at the HF and MP2 levels, and the calculations reproduced well the observed structures and revealed the nature of the bonds constructed by the selenium atoms containing nonbonded interactions. The bond with four linearly aligned selenium atoms in model a can be analyzed with the 4c-6e model constructed with the nonbonded interaction between the two p-type lone pairs on the outside selenium atoms and the σ*(Se−Se) orbital of the inside Se−Se bond, which results in charge transfer from the ou...