CEQUINOR   05415
CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Unidad Ejecutora - UE
artículos
Título:
Three-Center-Two-Electron and Four-Center-Four-Electron Bonds Charge Density over the Structure of Methonium Cations
Autor/es:
N.B.OKULIK; A.H.JUBERT; N.PERUCHENA
Revista:
Journal Physcial Chemistry
Editorial:
Americal Chemical Society
Referencias:
Año: 2006 vol. 110 p. 9974 - 9982
Resumen:
We study the electronic density charge topology of
CH5+ species 1 (Cs), 2 (Cs), and 3 (C2v) at ab initio level using the theory of
atoms in molecules developed by Bader. Despite the reports of previous studies
concerning carbocationic species, the methane molecule is protonated at the
carbon atom, which clearly shows its pentacoordination. In addition to the fact
that hydrogen atoms in the methonium molecule behave in a very fluxional
fashion and that the energy difference among the species 1, 2, and 3 are very
low, is important to point out that two different topological situations can be
defined on the basis of our study of the topology of the electronic charge
density. Then, the species 1 and 2 present a three-center-two-electron (3c-2e)
bond of singular characteristics as compared with other carbocationic species,
but in the species 3, the absence of a 3c-2e bond is noteworthy. This structure
can be characterized through the three bond critical points found, corresponding
to saddle points on the path bonds between the C-H(2,3,5) that lie in the same
plane. These nuclei define a four-center interaction where the electronic
delocalization produced among the (C-H)
bonds provide a stabilization of the three C-H bonds involved in this
interaction (the remaining two C-H bonds are similar to those belonging to the
nonprotonated species). Our results show that bonding situations with a higher
number of atom arrays are possible in protonated hydrocarbons.