Journal of Molecular Structure 485–486 (1999) 163–173
Structure and conformations of
1,1,1-trifluoromethanesulfenylamine, CF3SNH2. Gas electron
diffraction, microwave spectroscopy and theoretical calculations
M. Asimus a, S. Schühle a, D. Christen a, H. Møllendal b, C.O. Della Vedova c, M. Lieb d,
H. Oberhammer a,*
a
Institut für Physikalische und Theoretische Chemie, Universität Tübingen, 72076Tübingen, Germany
b
Department of Chemistry, University of Oslo, Blindern, 0315Oslo, Norway
c
CEQUINOR (CONICET) and Laboratorio de Servicios a la Industria y al Systema Cientı́fico (UNLP-CIC-CONICET).
Departamento de Quı́mica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, 47 esq. 115, (1900)La Plata, Argentina
d
Lehrstuhl für Anorganische Chemie II, Ruhr-Universität Bochum, 44780Bochum, Germany
Received 30 November 1998; accepted 11 February 1999
Abstract
The geometric structure and the conformational composition of 1,1,1-trifluoromethanesulfenylamine, CF3SNH2, were investigated by gas electron diffraction (GED) and microwave spectroscopy (MW). In the MW spectra transitions of two conformers
were observed. Rotational constants of deuterated species demonstrated that the more intense transitions belong to the anti form
(nitrogen lone pair antiperiplanar to S–C bond). From relative intensities and dipole moments an energy difference DE ˆ
E…syn† 2 E…anti† ˆ 1:1…1† kcal mol21 was derived. A joint analysis of GED and MW data resulted in the following skeletal
parameters (rz values with 2s uncertainties): S–N ˆ 1.673(5) Å, S–C ˆ 1.836(5) Å and C–S–N ˆ 101.8(8)8. These parameters
and the energy difference are well reproduced by B3PW91/6-31G* calculations. q 1999 Elsevier Science B.V. All rights
reserved.
Keywords: 1,1,1-Trifluoromethanesulfenylamine; Gas electron diffraction; Microwave spectroscopy; Quantum chemical calculations;
Anomeric effect
1. Introduction
Anomeric effects are known to control the conformational properties of many compounds which
contain atoms with electron lone pairs [1]. Originally,
this effect has been formulated to rationalize conformational and structural properties and chemical reac* Corresponding author. Tel.: 1 49-7071-2976907; fax: 1 497071-295490.
E-mail address: heinz.oberhammer@uni-tuebingen.de (H.
Oberhammer)
tivities of oxygen containing hydrocarbons, especially
of sugars. The extension of analogous stereoelectronic
interactions to compounds containing other atoms
with lone pairs, such as N, P or S, has been termed
the generalized anomeric effect [2]. The influence of
this effect on the conformational and structural properties of sulfenylamines of the type XSNH2 (X ˆ H, F
and Cl) has been studied theoretically by Reed and
Schleyer [3]. The dominant stereoelectronic interaction in these compounds occurs between the nitrogen
lone pair and the antibonding S–X orbital, n(N) !
s*(S–X). This interaction favors the anti form
0022-2860/99/$ - see front matter q 1999 Elsevier Science B.V. All rights reserved.
PII: S0022-286 0(99)00089-7
164
M. Asimus et al. / Journal of Molecular Structure 485–486 (1999) 163–173
Scheme 1. Side view and Newman projection along N–S bond for
XNSH2 compounds.
relative to the syn form. Anti and syn describe the
orientation of the nitrogen lone pair with respect to
the S–X bond (Scheme 1). According to theoretical
calculations [3], the parent species HSNH2 prefers the
syn conformation and the anti form is higher in energy
by 0.53 kcal mol 21 (HF/6-31G*). Apparently, the
anomeric stabilization n(N) ! s*(S–H) is too weak
and other effects such as steric repulsion between the
hydrogen atoms dominate. These calculations reproduce earlier microwave spectroscopic investigations
of this compound where both conformers were
observed and their structures and relative energies
(0.25 kcal mol 21) were determined [4]. The situation
is quite different for FSNH2 and ClSNH2. For these
two compounds the ab initio calculations predict that
only the anti conformer is a stable structure and the
syn form does not correspond to a minimum on the
energy surface. This result has been interpreted in
terms of a strong n(N) ! s*(S–X) interaction, if
X ˆ F or Cl, which stabilizes the anti conformation.
To our knowledge, aminosulfenyl fluoride and
chloride have never been synthesized and presumably
do not exist as stable compounds.
Since the strength of the n(N) ! s*(S–X) interaction depends primarily on the relative energies of the
lone pair and antibonding S–X orbitals, we considered CF3SNH2 to be a suitable candidate for studying
the influence of the anomeric effect on the conformational properties. In this compound which is easily
accessible to an experimental study, an intermediate
n(N) ! s*(S–X) interaction is expected. The first
synthesis of trifluoromethane–sulfenylamine has
been reported by Emeleus and Nabi [5]. In 1994 this
Fig. 1. Experimental (dots) and calculated (full line) electron diffraction molecular intensities and residuals.
Fig. 2. MW spectrum around 30.7 GHz with Stark field of approximately 0 V cm 21.
M. Asimus et al. / Journal of Molecular Structure 485–486 (1999) 163–173
165
166
M. Asimus et al. / Journal of Molecular Structure 485–486 (1999) 163–173
compound has been examined in a theoretical and IR
spectroscopic investigation, primarily focusing on the
properties of the halogenmethanesulfenyl group [6].
The quantum chemical calculations (HF/3-21G* and
HF/6-31G*) indicate the presence of two conformations with the syn form less stable by DE ˆ 0.7 and
1.5 kcal mol 21, respectively, but the IR and Raman
spectra revealed the presence of only one conformer,
showing Cs symmetry. It was assumed that this was
the anti conformer. Our aim was the structural and
dynamical characterization of CF3SNH2, combining
the techniques of gas electron diffraction (GED) and
microwave spectroscopy (MW). The GED intensities
provide reliable values for the skeletal structural parameters. Because of the weak scattering power of the
hydrogen atoms, however, they do not allow for the
determination of the conformational properties.
Therefore, in addition to the GED experiment, MW
spectra were recorded for the normal, as well as for
the singly and doubly deuterated species. The experimental analyses are supported by new theoretical
calculations.
3. Theoretical calculations
The geometric structures of the anti and syn conformers were optimized with the hybrid method
B3PW91/6-31G* [9]. This is a computatioanlly very
efficient method which includes electron correlation.
The vibrational frequencies were calculated for the
more stable anti form. The experimental frequencies
[6] are reproduced with a mean deviation of Dn ˆ
26 cm21 ; except for the two N–H stretches which
are predicted too high by about 170 cm 21. The cartesian force constants were transformed to symmetry
constants and parallel and perpendicular vibrational
amplitudes were derived with the program ASYM40
[10]. The contributions of the low frequency CF3
torsion (61 cm 21) were neglected for the perpendicular amplitudes of interatomic distances which do
not depend on this torsional motion (C–F, F…F and
S…F).
4. Microwave spectroscopy
2. Experimental
CF3SNH2 and the deuterated species were prepared
by the reaction of CF3SCl with NH3 or ND3, respectively [5]. The purity of the samples were checked by
IR (gas) spectroscopy.
The electron diffraction intensities were recorded
with a Gasdiffraktograph KD-G2 [7] at 25 and
50 cm nozzle-to-plate distances and with an accelerating voltage of ca. 60 kV. The sample reservoir was
kept at 2 308C and the inlet system and gas nozzle
were at room temperature. The photographic plates
(Kodak Electron Image Plates 13 × 18 cm) were
analyzed with the usual methods [8]. Averaged molecular intensities in the s-ranges 2–18 and 8–35 Å 21,
in steps of Ds ˆ 0.2 Å 21, are shown in Fig. 1.
The MW spectra were recorded at a temperature of
2 308C with conventional Stark spectrometers in the
frequency ranges 8–18 and 30–36 GHz. Further
measurements were performed with the very sensitive
radio frequency–MW double resonance spectrometer
in Oslo. Finally, MW–MW double resonance
measurements were made in Tübingen.
The microwave spectra in the lower frequency
region (8–18 GHz) showed obvious m b type Qbranch-series with high J as well as clusters of—
albeit rather weak— m a-type lines separated by
approximately B 1 C according to the model calculations. But even so, no obvious assignment was found
at the beginning.
Instead, realizing that in the near prolate rotor
CF3SNH2 (k ˆ 2 0.83) the otherwise asymmetry
split K2-states for high Ks approach degeneracy, the
higher frequency range was searched for the m a Rbranch transitions J: 7 ← 6 and 8 ← 7 at a Starkfield of practically 0 V cm 21, utilizing the extremely
fast Stark effect of the degenerate states. These
spectra, although still surprisingly rich in lines,
revealed the typical pattern of the R-branch K2 < J
transitions, not only, as it turned out, for the vibrational ground state, but also for several excited vibrational states (Fig. 2).
In order to confirm this assignment, a radiofrequency–microwave (RF–MW) double resonance
experiment was performed with the very sensitive
instrument in Oslo, pumping the transitions between
the asymmetrically split J ˆ 2, K2 ˆ 2 states (RF)
Fig. 3. RF–MW-double-resonance spectrum of the J: 3 ← 2 MW transition. RF-Pump frequency: 7.2 MHz. Torsional states are connected, the d (CSN) and r (CF3) states are
marked individually.
M. Asimus et al. / Journal of Molecular Structure 485–486 (1999) 163–173
167
168
M. Asimus et al. / Journal of Molecular Structure 485–486 (1999) 163–173
Table 1
Rotational constants (MHz), inertial defects and inertial defect differences DD with the ground state (uÅ 2), asymmetry parameter and number of
lines included in the fit for different compounds under study
vˆ0
vT ˆ 1
vT ˆ 2
vT ˆ 3
vCSN ˆ 1
CF3SNH2 anti
A
B
C
DJ × 10 3
DJK × 10 3
DK × 10 3
d J × 10 3
DK × 10 3
Inertial defect
DD
k
N
4530.3400(30)
2294.6984(15)
2094.0307(15)
0.4088(29)
1.9960(28)
2 1.4497(66)
0.0523(14)
2 2.2587(56)
2 90.4486
–
2 0.8353
249
4530.4458(69)
2287.4743(35)
2094.6357(35)
0.6438(159)
1.6467(106)
4.3581(884)
0.0398(44)
2 1.9536(155)
2 91.2112
2 0.7626
4530.828(11)
2280.8685(89)
2095.4354(89)
0.7606(865)
2.0478(304)
1.774(128)
0.0430(7)
2 2.3537(524)
2 91.9337
2 1.4851
4531.254(18)
2274.424(18)
2096.351(18)
0.2823(1765)
2.2642(218)
2 1.115(263)
0.0461(3)
2 2.4834(201)
2 92.6564
2 2.2078
4540.0727(15)
2294.4405(10)
2090.6594(10)
1.3226(84)
2 1.0026(55)
1.9048(73)
0.1405(3)
8.9981(9)
2 89.8450
0.6036
CF3SNH2 syn
A
B
C
DJ × 10 3
DJK × 10 3
DK × 10 3
d J × 10 3
DK × 10 3
Inertial defect
DD
k
N
4528.694(957)
2308.488 (28)
2105.413(29)
0.9396(910)
0.3401(2370)
2 1.9770 a
2 2.0018 (163)
2 2.2439
2 90.4928
–
2 0.8324
37
4543.393(4480)
2301.259(59)
2105.710(66)
0.8159(2394)
1.0877(5638)
2 1.9770 a
2 2.2092(7348)
2 2.2439
2 90.8388
2 0.3460
Deuterated CF3SNH2 anti
CF3SNHD anti
A
B
C
DJ × 10 3
DJK × 10 3
DK × 10 3
d J × 10 3
d K × 10 3
Inertial defect, D
k
N
vˆ0
4456.157(76)
2250.480(52)
2052.120(53)
0.4067 a
1.8280(164)
2 0.6121(230)
0.0513(7)
2 2.0613(213)
2 91.7040
2 0.8350
83
a
146
26
116
4528.826 a
2295.406(288)
2105.234(331)
0.8363(2560)
0.4632(2467)
2 1.9770 a
2 2.075 (1656)
2 2.2439
2 91.1702
2 1.2095
19
CF3SND2 anti
(A 2 C)/2
vˆ0
1201.778
DJ × 10 3
DJK × 10 3
DK × 10 3
d J × 10 3
d K × 10 3
Inertial defect, D
k
N
0.407 a
1.991(18)
2 0.486(300)
0.054(1)
2 2.366(26)
2 91.7040
2 0.8411
75
102
53
4538.071 a
2308.089(153)
2101.476(175)
2 1.5928(3255)
2 0.6967(4963)
2 1.9770 a
2 12.1543(9130)
2 2.2439
2 89.8359
0.6569
18
Not refined in the least squares fit.
while searching for the K2 ˆ 2 components of the J:
3 ← 2 m a (MW)-transitions.
This spectrum (Fig. 3) not only showed the ground
state transitions of the anti conformer surrounded by
satellites from excited vibrational states, but also saw
the pattern repeated at higher frequencies and reduced
intensity. Thus, for the first time, the presence of a
second conformation of CF3SNH2 (syn) became
obvious. The assignment of the high frequency pattern
to the syn conformer was later confirmed by the
M. Asimus et al. / Journal of Molecular Structure 485–486 (1999) 163–173
Table 2
Estimated vibrational frequencies of the lowest lying vibrational
states
t (CF3)
d (CSN)
r (CF3, a 00 )
d (CF3, a 00 )
a
b
v ˆ 1,2,3,4
vˆ1
vˆ1
vˆ1
80 ^ 10 cm 21
186 ^ 50 cm 21
233 ^ 50 cm 21
226 ^ 50 cm 21
Ra a: 89 cm 21
Ra a: 205 cm 21
IR/Ra a: 315 cm 21
Not observed b
Ref. [6].
303 cm 21 from B3PW91/6-31G*.
analysis of the 7 ← 6 and 8 ← 7 transitions, which at a
low Stark field also appeared in the 30–36 GHz
region to somewhat higher frequencies than the corresponding transitions of the anti conformation.
The fit of the assigned m a-transitions for both
conformers led to improved models and quickly
allowed for the assignment of the m b-Q-branch transitions. The recorded transitions—measured with an
experimental accuracy of 100 kHz—are available
from the authors (DC) and have been stored at Strukturdokumentation, Universität Ulm, Germany. The
rotational constants (A-Reduction and IR Representation) are collected in Table 1.
A look at Fig. 3 reveals many populated excited
vibrational states. A thorough analysis was possible
for the spectra of the following states: CF3-torsion
(vT ˆ 1,2,3,(4)), CSN-deformation (v ˆ 1), (a 00 -CF3rocking (v ˆ 1) and a 00 -CF3-deformation (v ˆ 1)). The
assignment of these lines could be checked by MW–
MW double resonance spectroscopy concentrating on
the confirmation of a common origin of R- and
169
Q-branch transitions. An evaluation of the relative
intensities of transitions belonging to these excited
states yielded the wavenumbers shown in Table 2.
The ab initio calculations predict large differences
in the magnitude of the dipole moments for the two
conformers of CF3SNH2. It is therefore of great
interest to determine the dipole moments experimentally. The very crowded spectrum made it extremely
difficult to follow the Stark-shifted lines at different
Stark fields, but the analysis of the m a components
from the J: 303 ← 202 and 313 ← 212 transitions of
the syn and anti conformations, respectively, as well
as the m b-component from the J: 313 ← 202 transition
of the anti conformer, yielded the following values
(with the B3PW91/6-31G* values in parantheses):
ma …anti† ˆ 1:3 …0:73† D
ma …syn† ˆ 3:1 …2:80† D
mb …anti† ˆ 1:2 …1:63† D
mb …syn† ˆ – …0:15† D
The knowledge of the dipole moments allowed an
estimate of the energy difference between the two
conformers based on the relative intensities of the
DR-spectrum of the 32 ← 22 transitions. The energy
difference is 370 ^ 30 cm 21 (1.1(1) kcal mol 21).
Thus, the result of the B3PW91 calculations
(0.8 kcal mol 21) is in good agreement with the experiment.
After the transitions of the normal species had been
assigned, the assignment of the strong m b-Q-branch
transitions of the mono- and dideuterated isotopomers
was quite straightforward. It was hoped that this
Fig. 4. MW–MW-double-resonance spectrum of the J: 918 ← 827 transition of the monodeuterated species.
170
M. Asimus et al. / Journal of Molecular Structure 485–486 (1999) 163–173
Fig. 5. Experimental radial distribution function and residual curve. Important inter atomic distances are indicated by vertical bars.
assignment would provide a unique opportunity to
experimentally decide whether the anti form (as
predicted by all quantum chemical calculations) or
the syn conformer would experimentally be more
stable.
The size of the m a dipole component, however,
prohibited (using conventional Stark spectroscopy)
an identification of the R-branch transitions that are
needed in order to determine all rotational constants.
This is very unfortunate as the values for (A 2 C)/2
and k were predicted to be quite similar for the deuterated species of the syn and anti conformers. A
search for R-branch transitions was therefore started,
involving MW–MW double resonance spectroscopy,
pumping already identified m b-Q-branch transitions
and searching for m a- or m b-R-branch transitions for
both deuterated isotopomers. Only one line was
found, however, the 918 ← 827 transition of the monodeuterated species, as shown in Fig. 4. This signal was
predicted to be the strongest in the available
frequency range, thus the elusiveness of the other
transitions is consistent with the model. Nevertheless,
even when a double resonance provides more
certainty than a single line, we had hoped to locate
more transitions in order to ascertain this assignment.
The fitted rotational constants have been collected in
Table 1. The values of the rotational constants of the
monodeuterated species prove the more stable
conformer to be the anti conformation in agreement
with the ab initio calculations.
5. Structure analysis
In the first step the geometric structure was determined from the GED data only. The radial distribution
function (Fig. 5) was derived by Fourier transformation of the molecular intensities. In the least squares
analyses the intensities were multiplied with a diagonal weight matrix. Overall Cs symmetry and local
C3v symmetry for the CF3 group was assumed. A tilt
angle between the C3 axis of the CF3 group and the S–
C bond was introduced. The H–N–H angle was set to
the theoretical value. Because of the small scattering
M. Asimus et al. / Journal of Molecular Structure 485–486 (1999) 163–173
171
Table 3
Interatomic distances, vibrational amplitudes and vibrational corrections (without nonbonded distances involving hydrogen) Values in Å. Error
limits are 3s values. For atom numbering see Fig. 6
Distance
N–H
C–F
S–N
S–C
F…F
S…F1
S…F2
C…N
N…F2
N…F1
a
b
Amplitude (GED)
b
1.01
1.33
1.67
1.84
2.15–2.16
2.58
2.62
2.72
3.04
3.88
0.071
0.046 (2)
0.055 (5)
0.061 (3)
0.076 (7)
0.089 b
0.161 (23)
0.093 (22)
Amplitude (theor.) a
Dr ˆ ra 2 ra
0.071
0.045
0.048
0.052
0.057
0.075
0.069
0.089
0.219
0.076
0.0331
0.0016
0.0023
0.0011
0.0014
2 0.0001
2 0.0008
2 0.0010
0.0012
0.0015
From B3PW91/6-31G* force field.
Not refined.
amplitudes of the hydrogen atoms, the GED data do
not allow a clear distinction between anti and syn
conformations. Least squares refinements for both
conformers gave a slightly better fit of the intensities
for the anti form (R50 ˆ 0.049) than for the syn structure (R50 ˆ 0.053). R50 is the agreement factor for the
intensities of the long (50 cm) nozzle-to-plate
distance. This suggests that the anti conformer is
present or is at least the predominant form, in agreement with the result derived from the MW spectra (see
the preceding discussion). Since the GED intensities
are rather insensitive to the conformational composition, its determination was not attempted from GED
data.
In the subsequent step, the GED intensities were
combined with the rotational constants. The vibrational corrections for the interatomic distances Dr ˆ
ra 2 rz (Table 3) and for the rotational constants DB i ˆ
B0i 2 Bzi (B i ˆ A,B,C) (see Table 4) were calculated
from the theoretical force field. The uncertainties of
the Bzi constants were estimated to be 15% of the
corrections DB i. These uncertainties are considerably
larger than those of the B0i constants. The weight of
Table 4
Experimental and calculated rotational constants in MHz
B0i (exp)
Bzi(exp)
Bzi(calc)
4530.3400(30)
2294.6984(15)
2094.0307(15)
4531.97(24)
2.29360(17)
2.09380(4)
4.53209
2.29354
2.09378
the rotational constants relative to the electron diffraction intensities was increased until the calculated rotational constants reproduced the experimental Bzi
values within their estimated uncertainties (Table 4).
The combination of GED intensities and rotational
constants clearly demonstrates that only the constants
for the anti form are compatible with the GED intensities. Combination of GED intensities and rotational
constants for the syn form leads to higher agreement
factors. With the constraint of C3v symmetry for the
CF3 group it was not possible to fit simultaneously
GED intensities and rotational constants satisfactorily. Therefore, the symmetry of this group was
reduced to Cs and differences between the C–F bond
lengths, DCF ˆ (C–F2) 2 (C–F1), and between the
FCF bond angles, DFCF ˆ (F1CF2) 2 (F2CF2 0 ),
were introduced (atom numbering is given in Fig.
6). The rotational constants B and C are rather sentitive to the difference, DFCF, and this difference is
well determined in the joint analysis. The difference
between the bond lengths DCF was constrained to the
B3PW91 value and an uncertainty of ^ 0.003 Å was
estimated. The results of the joint GED/MW analysis
are collected in Table 3 (vibrational amplitudes) and
Table 5 (geometric parameters).
6. Discussion
A
B
C
The combination of GED and MW techniques
allowed the determination of the conformational
172
M. Asimus et al. / Journal of Molecular Structure 485–486 (1999) 163–173
Fig. 6. Molecular models with atom numbering of syn (left) and anti (right) conformer.
properties of CF3SNH2 in the gas phase. The
assumption made in the Introduction that this
compound poses an intermediate case with respect
to the strength of the anomeric effect can now be
tested. Whereas the lp(N) ! s*(S–H) interaction
in HSNH2 is too weak to stabilize the sterically
less favored anti conformer, the analogous interaction involving the s*(S–C) orbital in CF3SNH2
Table 5
Experimental and calculated structural parameters of the anti
conformer
S–N
S–C
(C–F)mean
DCFy(C–F2) 2 (C–F1)
C–F1
C–F2
N–H
C–S–N
(F–C–F)mean
DFCF ˆ (F1CF2) 2 (F2CF2 0 )
F1–C–F2
F2–C–F2 0
Tilt (CF3) c
S–N–H
H–N–H
GED/MW a
B3PW91/6-31G*
1.673(5)
1.836(5)
1.331(2)
0.007(3) b
1.326(4)
1.334(3)
1.012(8)
101.8(8)
108.4(3)
1.7(2)
108.9(4)
107.2(4)
2.0(13)
115.3(20)
111.3 d
1.692
1.824
1.342
0.007
1.337
1.344
1.015
102.9
107.9
2.0
108.6
106.6
2.8
113.4
111.3
Here rz parameters in Å and degree. Error limits are 2s values
and include possible systematic errors. For atom numbering see Fig.
6.
b
Not refined, but varied within the estimated uncertainty in
brackets for estimating possible systemetic errors in refined parameters.
c
Tilt angle of CF3 group in CSN plane and away from nitrogen.
d
Not refined.
a
leads to the preference of the anti form. The syn
form is present as well and higher in energy by
1.1(1) kcal mol 21. Going to the other extreme,
FSNH2 and ClSNH2, theoretical calculations predict
only the existence of the anti form. The experimental energy difference DE ˆ 1.1(1) kcal mol 21
between the two conformers of CF3SNH2 is reproduced reasonably well by ab initio [6] and density
functional calculations: 1.5 kcal mol 21 (HF/321G*),
0.7 kcal mol 21
(HF/6-31G*)
and
0.8 kcal mol 21 (B3PW91/6-31G*). The calculated
geometric parameters (Table 5) are in satisfactory
agreement with the experimental values.
In addition to the conformational properties, the
lp(N) ! s*(S–C) interaction also affects the
geometric parameters. From the corresponding nobond–double-bond mesomeric structure F3C 2S ˆ
N 1H2 we expect lengthening of the S–C bond, shortening of the S–N bond and an increase of the C–S–N
angle. The S–C bond in CF3SNH2 (1.836(5) Å) is
indeed longer than in other CF3SX compounds with
X ˆ H (1.800(5) Å [11]), X ˆ Cl (1.824(6) Å [8]),
X ˆ CF3 (1.819(3) Å [8]) and X ˆ F (1.805(3) Å [8]).
Only very few gas phase values for S(II)–N(sp 3) bond
lengths are known in the literature. The S–N bond in
CF3SNH2 (1.673(5) Å) is appreciably shorter than this
bond in HSNH2 (1.719(4) and 1.705(3) Å in the syn
and anti conformers, respectively), where the conformational properties indicate a weak lp(N) ! s*(S–H)
interaction [4]. The angle at sulfur in CF3SNH2
(101.8(8)8) is larger than that in other CF3SX
compounds [8]: 97.3(8)8 for X ˆ CF3, 98.9(4)8 for
X ˆ Cl and 97.1(7)8 for X ˆ F. Thus, the skeletal
parameters of CF3SNH2 are affected by an intermediate anomeric effect.
M. Asimus et al. / Journal of Molecular Structure 485–486 (1999) 163–173
173
Acknowledgements
References
D.C. thanks the Department of Chemistry at the
University of Oslo for their hospitality and the
Deutsche Forschungsgemeinschaft for financial
support of this cooperation between Tübingen and
Oslo. H.O. is grateful for financial support by the
Fonds der Chemischen Industrie. We thank the
Fundación Antorchas (República Argentina), Alexander von Humboldt Stiftung and DAAD (Deutscher
Akademischer Austauschdienst, Germany) for financial support and for the DAAD–Fundación Antorchas
and Alexander von Humboldt Stiftung–Fundación
Antorchas Awards to the German–Argentine cooperation. CODV also thanks the Consejo Nacional de
Investigaciones Cientı́ficas y Técnicas (CONICET),
and the Comisión de Investigaciones Cientı́ficas de
la Provincia de Buenos Aires (CIC), República
Argentina, for financial support. He is indebted to
the Facultad de Ciencias Exactas, Universidad
Nacional de La Plata, República Argentina for financial support and to the Fundación Antorchas for the
National Award to the Argentinean cooperation.
[1] A. Kirby, The Anomeric Effect and Related Stereoelectronic
Effects at Oxygen, Springer, Berlin, 1983.
[2] R.U. Lemieux, Pure Appl. Chem. 25 (1971) 527.
[3] A.E. Reed, P.v.R. Schleyer, Inorg. Chem. 27 (1988) 3969.
[4] F.J. Lovas, R.D. Suenram, W.J. Stevens, J. Mol. Spectrosc.
100 (1983) 316.
[5] H.J. Emeleus, S.N. Nabi, J. Chem. Soc. (1960) 1103.
[6] C.O. Della Vedova, H.-G. Mack, E.H. Cutin, A. Ben Altabef,
Spectrochim. Acta, 50A (1994) 1219.
[7] H. Oberhammer, Molecular Structure by Diffraction Methods,
4, The Chemical Society, London, 1976 p. 24.
[8] H. Oberhammer, W. Gombler, H. Willner, J. Mol. Struct. 70
(1981) 273.
[9] gaussian 94 (Revision B.1), M.J. Frisch, G.W. Trucks, H.B.
Schlegel, P.M.W. Gill, B.G. Johnson, M.A. Robb, J.R. Cheeseman, T.A. Keith, G.A. Peterson, J.A. Montgomery, K.
Raghavachari, M.A. Al-Laham, V.G. Zakrzewski, J.V.
Ortiz, J.B. Foresman, J. Cioslowski, B.B. Stefanov, A.
Nanayakkara, M. Challacombe, C.Y. Peng, P.Y. Ayala, W.
Chen, M.W. Wong, J.L. Andres, E.S. Replogle, R. Gomperts,
R.L. Martin, D.J. Fox, J.S. Binkley, D.J. Defrees, J. Baker, J.P.
Stewart, M. Head-Gordon, C. Gonzalez, J.A. Pople, Gaussian
Inc. Pittsburgh PA, 1955.
[10] L. Hedberg, I.M. Mills, J. Mol. Spectrosc. 160 (1993) 117.
[11] C.J. Marsden, J. Mol. Struct. 21 (1974) 168.