S···π Chalcogen Bonds between SF2 or SF4 and C-C Multiple Bonds.

摘要: SF2 and SF4 were each paired with a series of unsaturated hydrocarbons including ethene, ethyne, 1,3-butadiene, benzene, in case forming chalcogen bond between the S atom carbon π-system. MP2 ab initio calculations reveal that is situated directly above one specific C═C bond, even when more than are present. The binding energies range 3.3 6.6 kcal/mol. engages stronger, shorter, noncovalent does for all systems exception to which tightly bound. cis-Butadiene complexes contain shortest if not necessarily strongest. internal S–F covalent bonds elongate upon formation bond. molecules held together largely by charge transfer forces, particularly from π-bonds σ*(SF) antibonding orbitals. In SF2, sulfur lone pair can into π* MOs alkene, back-transfer difficult SF4.