Are Carbon-Halogen Double and Triple Bonds Possible?

作者：Kalescky Robert^*; Kraka Elfi; Cremer Dieter

来源：International Journal of Quantum Chemistry, 2014, 114(16): 1060-1072.

DOI：10.1002/qua.24626

• carbon halogen bonds
• carbon chalcogen bonds
• local mode analysis
• relative bond strength order-halonium ions

The carbon-halogen and carbon-chalcogen bonding of 84 molecules was investigated utilizing local vibrational modes calculated at the M06-2X/cc-pVTZ level of theory including anharmonicity corrections in all cases. The relative bond strength order of each CX or CE bond (X = F, Cl; E = O, S) was derived from the local CX or CE stretching force constant and compared with trends of calculated bond lengths r and bond dissociation energies (BDE) obtained at the G3 level of theory. It is shown that both bond length r and BDE are not reliable bond strength descriptors. The CX double bond is realized for some Cl-substituted carbenium ions, however, not for the corresponding F-derivatives. Diatomic CF+ and CCl- possess fully developed double bonds but not, as suggested in the literature, triple bonds. Halonium ions have fractional (electron-deficient) CX bonds, which can be stabilized by r-donor substituents or by an increased polarizability of the halogen atom as with Cl. Bridged halonium ions are more stable than their acyclic counterparts, which results from more effective two-electron-three-center bonding.

• 出版日期2014-8-15