University of Groningen
Small three membered carbon ring compounds. Crystal structures and electron
density distributions of cyclopropane, bicyclopropyl and cinylcyclopropane
Nijveldt, Dirk
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Publication date:
1985
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Citation for published version (APA):
Nijveldt, D. (1985). Small three membered carbon ring compounds. Crystal structures and electron density
distributions of cyclopropane, bicyclopropyl and cinylcyclopropane Stichting Drukkerij C. Regenboog
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SU}"1MARY
The present
study
a brlef
outline
concerned with
is
(CP),
compounds cyclopropane
the research
of
is already preceded bv delailed
project
consldered
posslble
given
in
abslracts.
conjugative
the
character
of
groups in
this
of
summary since
accurate
the
three
electron
discussion indicatcs
electron
density
rotational
with
respect
to
about
the
density
the compounds
membered carbon ring:
the
1 treats
between the
group ln
and vinyl
The BCP ring
two
VCP on Lhe
bonds are
the CP C-C bonds. For VCP the qualitative
an asymmetryof the ring
distribution
rhe chapters
part of
electron
delocalization)
BCP or between the cyclopropyl
co be lengthened
each of
is
double C-C bond. Chapter
molecular geometry and elecLron density distribulion.
expected
(VCP). Only
An inLerest ing feaLure of
an unsaturated
(or
conjugation
membered carbon ring
The chosen subject
bonding by means of
shows some analogy with
influences
cyclopropyl
is
sma11 three
(BCP) and vinylcyclopropane
obtained from X-rav analysis".
is
carbon rlng
chemlcal
of
"Study
disLributions
the
blcyclopropyl
geometry. For both BCPand VCP the
the central
bond is
expected
to
deviate
from
symmetry.
The crysLaJlizaLion
procedure applied
lor
t h e t h r e e v o l a t i ) e c o m p o u n d si s
described in Chapter 2. Because the X-rav diffraction
highest accuracy, special
capillaries
m e a s u r e m e n L sr e q u i r e
atLenLion is given to Lhe modelling of
in whith the crystals
Lhe
the glass
a r e g r o v r n . T h e c o m p o u n d sa r e c r y s L a l l i z e d
in
siLu
on the diffractometer.
The precautlons
intensities
(for
taken
to
obtain
an accurate
are Lrcated in Chapter 3. The intensity
CP two crystals
of
independent reflect
of
In Chapter
scope of
ions for
approximately
each oI
intensrt.y series
structures
alom) modej.0nly
Multipole
functlons
yields
for
consisLency
the
are deLermined within
wiLh BCPLhe geomeLry
to the presence of conjugation,
refinementsare
thettbestttor
Lo one series of
BCP Lurns ouL to belong to
a centrosymmeLric (orLhorhombic) space group. Tn contrast
obtain
reflecLion
I Z.
4 Lhe space groups and crystal
points
of
m e a s u r e m e n t so n f o u r c r y s L a ) s
the compoundsrenders internal
lhe convenlional (spherical
of VCP clearly
set
Lhe same sample have been used) are perlormed at a
Lemperatureof ca 100 K. Reductron of several
factors
and extensive
ultimate
the
introCucedin
multipole
lorv order
Chapter
5. Much attention
models. The use of diffuse
regions
excellenl
109
fiLs
of
is
paid
to
deformation
calculated
to
observed
factor
structure
range from 0.32
amplltudes:
Z for
VCP via
models give
multipole
discussion
in
0,39
% for
the most accurate
Chapter
4).
_ t= 0.65 A
up to (sin0)/f
the weighted residuals
BCP. The ultimate
CP to 0.57 % for
positional
parameters.(used for
The average o(C-C) amounts to 4 l0-*
A for
the geometrlr'
BCP and VCP,
t.
and to
A for
8 l0-*
CP. The filrered
the bent bond character
of
the deformation
for
model deformation
each of
(Eig.
the rings
around the VCP double
densitv
maps clearly
density
S.:1a,b,c))
show
and the elongalion
the n-direction
bond in
(rig. :.:1i1).
I n Chaoter 6 t he fheoreL ical
chemical
without
calculations
comparison with
the
limited
the central
(with
polarization
the n-direction.
asymmetry parameter ap defined
bond the theoretical
the opposiLe is
is
ap is
If
purpose the
account
Lhe overalI
functions)
due to
in Table
inadequacies
L ' r e
in
experimental
! , v " b q r
6.1.
It
turns
is
taken of
the
agreement beLween
maps is
good, apart
frorn
the densitv
in lhese
is represenLed by the
out
that
for
the VCP central
smaller Lhan the experimenlal ap, whereas
t h e V C Pd o u b l e b o n d . J t
Tn VCP rhe elonsal ion of
gives a significanL
T h i s a s v m m erty
significantlv
Lhe case for
BCP and VCP the
.^ninoAt inn
are made static.
are used for
For this
rhe VCPcentra] and doubIe bond show that
planes is elongated in
Both for
functlons
densities.
Lhe experimental densities,
and theoretlcal
obLained Ir,,m oilantum
and double bond region in VCP. SecLions perpendicular to and Lhrough
the midnoinls oI
discrepancy
deformation
model densities
resoluLion of
experimental
polarization
and with
experlmental
dynamic experimental
d e f o r m a Li o n d e n s i t i e s
the experimental
and t.heoretical
Lhe rpntril
is
not clear
or in
central
the
yet whether Lhis
theoretical
bond ap's
point
model.
Lo
hond dcnsilV in the n-dirertiOn
supporL Lo the geometrical evidencc Ior conjugation.
In casc
of BCP Lhe probabil iLv LhaL the experimental cenLral bond ap equals the value Ior
roLaLional symmetry is only
occurs
in
I %, which makos iL mosL likely
BCP.
/!4
,/ /,'
110
thaL conjugation also