Chemistry Reference
In-Depth Information
three types of C-C bonds (single, double, and bent), but with intermediate bond-
orders due to extended
-electron delocalization. The refinement of ADPs, using
the U-SPAs projected from the MP2 density, yields basically the same reliability
factor as that obtained using the HC-PAs (
R
w
¼
p
2.32%) with 63 extra-adjusted
parameters, but a slightly better residual and a considerably different deformation
ED map (Fig.
3
), especially in the plane of the cyclopropane ring. It is to be
emphasized that no density parameters were adjusted and the H-atom's positions
and ADPs were fixed to their values derived by neutron diffraction. The subsequent
refinement, including the ADPs of H-atoms (still with the fixed SPA density), led
to thermal parameters in fair agreement with those derived from neutron data
Fig. 3 (a, c) Experimental Fourier residual and (b, d) static deformation density maps in the plane
of the cyclopropane ring of
Bullvalene
.
Upper row
: HC-PA refinement;
lower row
: ADP-only
refinement at the same geometry using MP2/cc-pVTZ stockholder pseudoatoms.
Contour lines
are
drawn at 0.05 and 0.1 e
˚
3
for the residual and the deformation maps, respectively.
Solid
,
dashed
,
and
dotted lines
are positive, zero, and negative, respectively
