# Intermolecular interactions in a series of organoammonium tetraphenylborates

Abstract (Summary)

High quality, low temperature, x-ray crystallographic data sets were
collected for four organoammonium tetraphenylborates. On close scrutiny,
two types of N-H ...
X interactions were identified, the more "traditional"
N-H. ..N hydrogen bonds, and N-H....ir(Ph)
hydrogen bonds [centroid, edge or
single atom type], in which the phenyl ring of the anion serves as the
hydrogen bond acceptor. In addition, the four salts were found to form a
large number of close C-H...X type contacts. Some of these adopted
hydrogen bond type geometries while others were classified as "H...Hl1 type
contacts, using criteria developed in this work.
Charge density calculations were carried out on the four salts. From
the results, static and dynamic electron density maps were plotted in a
variety of planes to aee if evidence of the intermolecular interactions
would be visible. The convcntional N-H ...
N hydrogen bonds were used as the
interna1 standard with which the other, weaker, interactions could be
compared. Certain features were identified in the maps that could
consistently be attributed to the formation of N-H....ir( Ph) hydrogen bonds.
The electron density distributions calculated using the aspherical
models generated in the XD refinements were used as input for topological
analyses of the four salts. This allowed a more quantitative investigation
of the weak intermolecular interactions. The location of a rational bond
path and a (3,-1) bond critical point was characteristic of almost every
contact studied. The values, at the bond critical points, of the electron
density. p,(+), and the Laplacian of the electron density. v , were
calculated. They were always positive, typical of closed she11 interactions,
and were shown ta be correlated with the distance over which the
interaction occurred, specified in this work as the H...acceptor distance.
In both cases [p,(r)/v2p,(r) versus d(H.. .A)1, a simple exponential curve
was found to mode1 the collected experimental data reasonably well. The
experimentally derived topological data from this work were consistent
with literature values reported for more traditional hydrogen bonds, which
shows the N-H-..lr(Ph) hydrogen bonds behave topologically like al1 others.
Finally, the majority of the C-H...phenyl interactions were identified 3s
"
H...Hl1 type contacts, while the remainder were found to be hydrogen
bonds, behaving topologically like ather X-H....lr(Ph) hydrogen bonds.
Abbreviations and Symbols
B
d,
0
h,kJ
Mo-
A
x/a,y/b,z/c
Be,
U,,'
F(OO0)
Fo* Fobe
Fcf Fcal,
NdbS' d
NVI P
r
R
Rw, wR2
Rmerge
GOF
Formula weight
Number of molecules in the unit ce11
Unit ce11 dimensions
Angles between crystal axes
Volume of unit ce11
Linear absorption coefficient
Calculated density
Bragg angle
Miller indices of the reflecting plane
Molybdenum Ka radiation
Wavelength of X-radiation
Fractional coordinates
Isotropie temperature factor
Anisotropic temperature factors
Number of electrons in the unit ce11
Observed structure amplitude
Calculated structure factor
Number of observed reflections
Number of parameters refined
Number of reatraints applied
R-f
actor
Weighted R-value
Merging R-value for equivalent reflections
Goodness of fit parameter
W
TLS
rms
Weight in minimized function
Translation/Libration/Screw
Root mean square
Estirnated standard deviation
Correlation coefficient
Coefficient of determination
Standard deviation
Electron density in molecule
Difierence electron density
Vector to a point in real space
Scale factor
Vector to a point in reciprocal space
Observed structure factor amplitude
Calculated structure factor amplitude
Core atomic density
Valence density
Multipolar spherical harmonic
functions in real form
Expansion-contraction parameters
Core population parameters
Valence population parameters
Multipole population parameters
Radial functions
Normalization factor
Deformation electron density
Electron density at the bond critical point
Laplacian of the electron density at the bond critical
point
Eigenvalues of the Hessian matrix, principal curvatures
of the electron density at the bond critical point
Ellipticity of the electron density at the bond critical
point
Znternuclear separation, its equilibrium value, bond
path length
Hydrogen bond
X-H.. .r(Ph)
X-H...p
henyl
Hydrogen bond accepted by a phenyl ring
Any type of interaction involving a phenyl ring,
generally not HBs but as a group can include HBs
Distance characterizing the X-H...A HB
Phenyl ring centroid
[lOO (maximum - minimum X/H. ..Cr,- distance)
]
a parameter characterizing the X-H...
x(Ph) HB
HO
N
High order
Neutron
X
CP
BP
Critical point
Bond path
Ph
TB
CSD
Tetraphenylborate anion
Cambridge Structural Database
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Source Type:Master's Thesis

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Date of Publication:01/01/2001