Chemistry Reference
In-Depth Information
Fig. 4.11 a
Representation of the different non-equivalent bonds of La@
C
2v
-C
82
; numbers de-
note [6, 6] bonds and lower-case letters denote [5, 6] bonds. Different colors are used to label
the different bond types (Fig.
4.1
; type A:
blue
; type B:
black
; type C:
green
; type D:
red
).
b
Molecular-orbital levels of the frontier orbitals of La@
C
2v
-C
82
, cyclopentadiene (Cp), and
1,2,3,4,5-pentamethylcyclopentadiene (Cp*). c) Representation of the SOMO (unoccupied
beta
)
and LUMOs (
alpha
and
beta
)ofLa@
C
2v
-C
82
(isosurface value 0.02 a.u.); only those bonds with
favorable orbitals for interactions with the HOMO of the diene are marked with ellipses. Energy
values of the levels are given in eV. (Reprinted with permission from (Garcia-Borràs et al.
2013a
).
Copyright 2013 Wiley)
that electronic effects of the methyl groups decrease the retro-barrier favoring the
dissociation of La@
C
2v
-C
82
Cp*, which goes against experimental observations. In
fact, we found that the higher stability of the Cp* adduct arises from the long-range
stabilizing dispersion interactions. If we analyze the effect of the dispersion-energy
contribution on both reactions pathways (see Fig.
4.12
), we can see that a lack of
dispersion corrections completely changes the reaction energy profile.
The reaction pathways for Cp and Cp* additions are quite similar when the initial
reactant complex is considered. Thus, as discussed before, the electronic effects due
to the methyl groups on Cp* diene do not play a determinant role on the different half-
life decomposition times of Cp and Cp*. Hence, we can see that without considering
