Successive Change in Conformation Caused by p-Y Groups in 1-(MeSe)-8-(p-YC6H4Se)C10H6: Role of Linear Se···Se−C Three-Center−Four-Electron versus n(Se)···n(Se) Two-Center−Four-Electron Nonbonded Interactions

The structure of 1-(methylselanyl)-8-(p-anisylselanyl)naphthalene (2) and 1-(methylselanyl)-8-(p-chlorophenylselanyl)naphthalene (3) was studied by X-ray crystallographic analysis. The structures around the Se−Me and Se−C6H4OMe-p (Se−CAn) groups in 2 are close to type A and type B, respectively: type A if the Se−C bond is almost perpendicular to the naphthyl plane and type B when the Se−C bond is placed on the plane. Those around the Se−Me and Se−C6H4Cl-p (Se−CAr) groups in 3 are type B and type A, respectively. The nonbonded Se···Se distances of 2 and 3 are 3.0951(8) and 3.1239(7) A, respectively. The structure of 3 is very different from that observed in 1-(methylselanyl)-8-(phenylselanyl)naphthalene (1), the structure of which is type C, where the two Se−C bonds decline by about 45° from the naphthyl plane. The structure of 3 strongly suggests the contribution of the nonbonded n(SeAr)···σ*(Se−CMe) three-center−four-electron (3c−4e) type interaction. The nonbonded n(SeMe)···σ*(Se−CAn) 3c−4e type intera...