Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by Simon R. T. Neil and Corey J. Evans
Supplementary Data:
~1
Table 1: Vibrational frequencies (in cm-1)a [Intensities (in km/mole)] and equilibrium rotational constants (in GHz) of the seven lowest [H Si, N, C, S] isomers in the X A
state at MP2/aug-cc-pVTZ the level of theory. Dipole moments in Debye, are given the square brackets [μ x/μy].
Species
Vibrational Frequencies (Intensities)
Rotational Constants (A, B, C)
HSi(S)CN
[-0.44/2.50]
129.8(11), 233.7(4), 343.7(1), 518.2(9), 578.1(51), 765.1(19), 865.9(145),
2099.1(75), 2330.6(48)
19.67213, 2.22863, 2.00184
HSi(S)NC
[-0.41/2.40]
122.1(8), 164.4(1), 299.0(6), 524.0(12), 620.1(70), 793.4(48), 881.1(209),
2073.1(382), 2348.9(43)
21.49728, 2.41538, 2.17141
trans-HSSiCN
[-3.38/2.05]
121.4(3), 214.4(1), 343.5(2), 489.0(5), 543.5(75), 561.1(79), 796.7(13),
2077.9(64), 2737.6(7)
10.37841, 2.80702, 2.20944
cis-HSSiCN
[-2.21/0.92]
124.2(8), 214.2(14), 366.8(1), 424.9(18), 527.3(73), 555.7(89), 714.9(5),
2076.4(58), 2744.1(8)
10.28256, 2.76371, 2.17825
trans-HSSiNC
[-3.30/1.79]
121.3(3), 157.2(1), 294.4(2), 441.6(5), 536.1(83), 609.9(153), 776.3(18),
2041.0(306), 2742.4(8)
11.57719, 2.93459, 2.34116
cis-HSSiNC
[-2.14/0.73]
126.8(7), 153.6(7), 313.9(3), 388.2(19), 525.0(95), 588.8(137), 697.1(16),
2036.7(290), 2742.9(7)
11.59105, 2.87779, 2.30541
HSiNCS
[0.30/-1.39]
90.2(1), 124.7(2), 454.4(40), 508.1(0), 513.0(78), 872.8(130), 1044.4(21),
2042.1(1940), 2099.4(216)
147.12891, 1.60527, 1.58795
a
Unscaled frequencies.
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by Simon R. T. Neil and Corey J. Evans
Table 2: Distances (pm) and Angles (in degrees) for Molecules Containing the Isothiocyanate Group.
 (N=C=S)
 (X-N=C)
r(X-N)
156.65(6)
173.8(23)
131.7(19)
99.28(64)
MW substitution1
119.2(6)
159.7(5)
180.0a
141.57(40)
147.9(8)
ED (ra basis)2
CH3NCS
121.6
156.1
180.0a
145.16
MW substitution3
CH3CH2NCS
119.2(6)
158.7(5)
189.6(48)
142.6(35)
144.2(7)
ED (ra basis, cis conf.)4
(CH3)2HCNCS
120.1(6)
159.8(5)
166(3)
132.6(10)
146.0(8)
ED (ra basis)5
H3SiNCS
119.7(7)
156.3(6)
180.0a
163.8(2.6)
170.4(6)
ED (ra basis)6
H3SiNCS
119.7(7)
156.3(6)
180.0a
170.4(6)
MW substitution7,8
SiH2(CH3)NCS
119.5(4)
157.8(3)
180.0a
156.4(16)
172.4(6)
ED (ra basis)9
(CH3)2HSiNCS
121.2(5)
157.9(5)
180.0a
154.7(22)
172.3(8)
ED (ra basis)10
(CH3)3SiNCS
119.1(6)
158.7(4)
176(4)b
158.2(10)
174.3(6)
ED (ra basis)11
F2PNCS
122.1(6)
-
180.0a
140.5(7)
168.6
ED (ra basis)12
Compound
r(N=C)
r(C=S)
HNCS
120.68(24)
CH3NCS
a
-
-
Angle is assumed to be 180.0°.
NCS angle was poorly determined, refining to 176(4), it was therefore fixed at this optimum value.
c
Assumed.
b
Reference
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
Table 3: Enthalpy of formation at 0 and 298 K of the seven lowest [H, Si, N, C, S] isomers
(in kJ/mol). For comparison the seven lowest [H, Si, N, C, O] isomers are also included.a
Isomer
 f H 0 [G3MP2]
 f H 0 [G3B3]
0K
298 K
HSi(S)CN
192.5
206.3
195.8
209.6
HSi(O)CN
13.7
27.0
10.6
24.0
HSi(S)NC
199.1
213.0
206.3
220.1
HSi(O)NC
15.0
28.6
15.9
29.6
trans-HSSiCN
217.6
231.8
221.8
236.0
trans-HOSiCN
-19.3
-5.65
-21.8
-8.12
trans-HSSiNC
223.4
238.1
231.0
245.6
trans-HOSiNC
-27.2
-13.1
-26.3
-12.3
cis-HSSiCN
226.3
241.0
230.1
244.8
cis-HOSiCN
-23.3
-9.50
-26.2
-12.3
cis-HSSiNC
231.8
246.4
238.5
253.6
cis-HOSiCN
-32.0
-17.8
-31.5
-17.3
HSiNCS
263.2
277.4
264.8
279.1
HSiNCO
34.1
47.7
30.3
43.9
a
0K
Updated values to those in CJ Evans and MR Dover, J. Phys. Chem. A, 111(50), 13148-13156
298 K
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
Out-of-Plane Bending Analysis of HSi(O)CN/HSi(O)NC/HSi(S)CN/HSi(S)NC
The potential function of the hydrogen atom bending out of the molecular plane for both
isomers is shown in Figure 1. This was calculated at the CIS/aug-cc-pVDZ level of theory
with the OOP angle ranging from -110° to +110° with 0° being the planar structure; the step
increment was 5°. In order to fit the potential to a convenient double-minimum potential the
remaining structural parameters of the molecule were fixed to the optimized excited state
planar structure (at the CIS level of theory). The potential was fitted to the double-minimum
function used by Coon et al.13:
V (Q) 
1
Q 2  e  exp( Q 2 / 2 )
2
[1]
where ,  and  are fitting parameters and Q is the mass-weighted coordinate of the OOP
bend. The mass-weighted coordinates were calculated using the planar excited state and the
expressions derived by Clouthier and Goddard (based on a rigid bender model).14 The data
points for each molecule were fitted using the function given in equation [1], from which the
parameters B and 0 were determined. The results from these fits are given in Table 4. The
barrier height (B 0) for the HSi(S)NC is substantially higher than HSi(S)CN, 3351.5 to
1907.9 cm-1; also the position of the potential minimum (m) is larger for HSi(S)NC (53.0°)
than HSi(S)CN (49.1°). This difference is probably a result of changes in conjugation
between the -CN/NC groups with the Si=S bond. The same type of calculation was carried
out on the analogous oxygen species. In previous work on HSi(O)CN and HSi(O)NC only the
~
planar excited ( A1A ) states were investigated and like the sulphur analogues they gave one
imaginary vibrational frequency which is indicative of a transition state. A comparison
between the sulphur and the oxygen species shows the barrier to the planar structure is
substantially higher in the oxygen species (4861.4 cm-1 for HSi(O)NC and 2788.5 cm-1 for
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
HSi(O)CN) than the sulphur species. This shows the conjugation between the Si=O and the –
CN/-NC group is less than that between Si=S and the –CN/-NC group. In comparison it has
been predicted that HC(O)CN has a relatively low barrier of inversion of only ~75 cm-1 in its
first excited state (S1). At present there is no information available on the excited electronic
states of HC(S)CN, but it could be assumed the barrier to inversion in the analogous S1 state
for HC(S)CN to be less the HC(O)CN.
Table 4: Fitted parameters to the HSi(S)NC, HSi(S)CN, HSi(O)NC and HSi(O)CN inversion
potential.
HSi(S)NC
HSi(S)CN
HSi(O)NC
HSi(O)CN
0 (cm-1)
472.6
468.7
476.3
474.8
B
7.092
4.071
10.206
5.873
3351.5
1907.9
4861.4
2788.4
1.01
0.725
1.181
0.869
1.521
1.439
1.623
1.529
52.2
49.1
56.8
53.2
B0 (cm-1)

1
Qm×10-20 ( g 2 cm )
m (Deg)
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by Simon R. T. Neil and Corey J. Evans
HSiSCN
HSiSNC
HSiOCN
HSiONC
12000
-1
Relative Energy (cm )
10000
8000
6000
4000
2000
0
-20
-3.0x10
-20
-2.0x10
-20
-20
0.0
-1.0x10
1/2
Q (g
1.0x10
-20
2.0x10
-20
3.0x10
cm)
Figure 1: Out-of-plane bending potentials for HSi(S)CN, HSi(S)NC, HSi(O)CN and
HSi(O)NC. The points are calculated at five degree intervals for out-plane angles from 0° to
110° using the CIS/aug-cc-pVTZ level of theory.
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
Triplet State Analysis:
Calculations were carried out on the 3 A triplet state of the seven lowest [H, Si, C, N, S]
isomers at the B3LYP level of theory. The 3 A triplet state was found to be the lowest lying
triplet state for each species with the
3
A state being substantially higher in energy.
Frequency analysis of the optimized structures indicated that only the a~ 3A state of HSiNCS
was a true minimum, while the optimised structures of the other isomers gave one negative
frequency indicating a transition state. Subsequent calculations were carried out using the
B3LYP method to look at the a~ 3A state for isomers 1 to 6. Frequency calculations on the
optimized structures of the isomers in the a~ 3A state indicated the structures were true
minima. Figure 6 show the structures of the a~ 3A state of HSiNCS and the a~ 3A state of
~
remaining isomers and their energies relative to their X 1A isomers as given in Figure 1 at the
B3LYP level of theory. For HSiNCS the electronic configuration of the triplet species was
14a  2 15a 1 3a  2 4a 1 .
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
T7( a~ 3A ) [132.2]
DCSiSH=-94.4°
DSSiCN=1.6°
T3/T5 ( a~ 3A ) [155.2/162.8]
DSSiCH=117.1°
DCSiSN=2.1°
T1 ( a~ 3A ) [167.8]
DNSiSH=-92.4°
DSSiNC=1.1°
T4/T6 ( a~ 3A ) [182.0/189.1]
DSSiNH=116.3°
DNSiSC=3.1°
T2 ( a~ 3A ) [181.2]
~3
Figure 2: B3LYP/aug-cc-pVTZ optimized geometries of the a A excited state of the six
lowest [H, Si, N, C, S] isomers (bond lengths in pm; bond angles in degrees). All energies, in
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
kJ/mol, are relative to their corresponding 1A′ isomers as in Figure 1 in the paper. For
~3
HSiNCS the B3LYP/aug-cc-pVTZ optimized geometry for the a A excited state is given.
Transition State Structures:
SiNC=72.8°; SiCN=75.2°
DHSSiN=-15.5°; DHSSiC=15.7°
ts 5/6 ( 1 A ) [113.0]
DSiNCS=-3.0°;
DCNSiH=-85.6°
ts 7/8 ( 1 A ) [136.0]
DNSiSH=89.7°; DSSiNC=-179.1°
DCSiSH=90.0°; DSSiCN=-175.9°
ts 4/6 ( 1 A ) [74.1]
ts 3/5 ( 1 A ) [82.0]
DSSiCN=97.9°; DHSiCN=-92.8°
DSSiCN=-169.3°
ts 1/2 ( 1 A ) [364.0]
SiNC=72.6°; SiCN=75.3°
DHSSiN=-15.4°; DHSSiC=15.9°
ts 3/4 ( 1 A ) [107.1]
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
Figure 3: Optimized geometries of some of the interconversion transition states between the
seven lowest [H, Si, N, C, S] isomers in their ground electronic state at the B3LYP/aug-ccpVTZ level of theory. Bond lengths in pm and angles in degrees. All energies (in kJ/mol) are
relative to the lowest lying isomer, HSi(S)CN as given in Figure 1 in the paper.
Transition State Structures continue:
DNSiSH=118.0°;
DSSiNC=-18.5°
ts 2/7 ( 1 A ) [233.0]
SSiH=109.1°
DCSiSH=107.1°;
DSSiCN=-19.9°
ts 1/16 ( 1 A ) [320.5]
∠HSiS=61.9° ; ∠HSiC=124.8°
DSSiCH=-69.4°; DSSiCN=161.5°
ts 1/3 ( 1 A ) [207.4]
NSiH=126.0°; SSiH=62.7°
DNSiSH=120.0°; DSSiNC=158.5°
ts 2/4 ( 1 A ) [209.6]
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
Figure 3 cont.: Optimized geometries of some of the interconversion transition states
between the seven lowest [H, Si, N, C, S] isomers in their ground electronic state at the
B3LYP/aug-cc-pVTZ level of theory. Bond lengths in picometres and angles in degrees. All
energies (in kJ/mol) are relative to the lowest lying isomer, HSi(S)CN as given in Figure 1 in
the paper.
S9 [ 106.8]
S10 [111.5]
S7 [44.1]
S8 [102.3]
S5 [25.7]
S6 [28.2]
S3 [18.1]
S4 [21.2]
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
S1 [ 0.00]
S2 [5.22]
Figure 4: Optimized geometries of some of the different isomers of [H, Si, N, C, S] at the
B3LYP/aug-cc-pVTZ level of theory. Bond lengths in pm and angles in degrees. All energies
(in kJ/mol) are relative to the lowest lying isomer, HSi(S)CN as given in Figure 1 in the
paper. All structures are planar.
S17 [ 224.8]
S18 [259.6]
S15 [ 211.13]
S16 [ 216.9]
S14 [ 200.62]
S13 [ 135.2]
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
SiCN=67.8°; SiNC=68.2°
CSiN=43.9°
S11 [ 112.9]
S12 [ 126.0]
Figure 4 cont..: Optimized geometries of some of the different isomers of [H, Si, N, C, S] at
the B3LYP/aug-cc-pVTZ level of theory. Bond lengths in pm and angles in degrees. All
energies (in kJ/mol) are relative to the lowest lying isomer, HSi(S)CN as given in Figure 1 in
the paper. All structures are planar.
S21[ 492.4]
S22[ 583.6]
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
S19[ 302.8]
S20[ 386.7]
Figure 4 cont..: Optimized geometries of some of the different isomers of [H, Si, N, C, S] at
the B3LYP/aug-cc-pVTZ level of theory. Bond lengths in pm and angles in degrees. All
energies (in kJ/mol) are relative to the lowest lying isomer, HSi(S)CN as given in Figure 1 in
the paper. All structures are planar.
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by Simon R. T. Neil and Corey J. Evans
Table 5: Table of [H, Si, N, C, S] isomers in their ground electronic state and their associated energies calculated at the
B3LYP/VTZ level of theory.
GS/B3LYP/VTZ
Isomers
HSi_S_CN
HSi_S_NC
transHSSiCN
transHSSiNC
cisHSSiCN
cisHSSiNC
HSiNCS
transHSiSCN
cyclic-HNCSSi(c)
cyclic-HNCSSi(t)
cisHSiSCN
cyclic-SSiNCH
cyclic-SiCN(S)H
cis-HSCNSi
transHSiSNC
HSiCNS
cisHSiSNC
HNSiCS
cis-HSNCSi
HC(S)SiN
HCSiNS
HSiCSN
B3LYP (Energy)
-781.2360123
-781.2336228
-781.2290872
-781.2272846
-781.2258415
-781.2242846
-781.2185453
-781.1962034
-781.1984649
-781.1968468
-781.1920519
-781.1908939
-781.1877878
-781.159032
-781.1539397
-781.1522062
-781.1485262
-781.1377191
-781.1202592
-781.0894602
-781.0473778
-781.0096854
ZPE
0.018143
0.017743
0.018095
0.017505
0.017751
0.017162
0.017459
0.017315
0.021274
0.021429
0.0171677
0.0210012
0.0214225
0.0175738
0.0164864
0.0169331
0.0162878
0.0187104
0.0177113
0.0188673
0.0170519
0.0140986
Final Energy
-781.2178693
-781.2158798
-781.2109922
-781.2097796
-781.2080905
-781.2071226
-781.2010863
-781.1788884
-781.1771909
-781.1754178
-781.1748842
-781.1698927
-781.1663653
-781.1414582
-781.1374533
-781.1352731
-781.1322384
-781.1190087
-781.1025479
-781.0705929
-781.0303259
-780.9955868
Relative
Energy (au)
0
0.0019895
0.0068771
0.0080897
0.0097788
0.0107467
0.016783
0.0389809
0.0406784
0.0424515
0.0429851
0.0479766
0.051504
0.0764111
0.080416
0.0825962
0.0856309
0.0988606
0.1153214
0.1472764
0.1875434
0.2222825
Relative
Energy
(kcal/mol)
0.00
1.25
4.32
5.08
6.14
6.74
10.53
24.46
25.53
26.64
26.97
30.11
32.32
47.95
50.46
51.83
53.73
62.04
72.37
92.42
117.69
139.48
Relative
Energy
(kJ/mol)
0.00
5.22
18.06
21.24
25.67
28.22
44.06
102.34
106.80
111.46
112.86
125.96
135.22
200.62
211.13
216.86
224.82
259.56
302.78
386.67
492.40
583.60
isomer
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Computational study on the Energies and Structures of the [H, Si, N, C, S] Isomers by
Simon R. T. Neil and Corey J. Evans
References:
(1)
Yamada, K.; Winnewisser, M.; Winnewisser, G.; Szalanski, L. B.; Gerry, M.
C. L. J. Mol. Spectrosc. 1980, 79, 295.
(2)
Anderson, D. W.; Rankin, D. W. H.; Robertson, A. J. Mol. Struct. 1972, 14,
385.
(3)
Koput, J. J. Mol. Spectrosc. 1986, 118, 189.
(4)
Cradock, S.; Durig, J. R.; Sullivan, J. F. J. Mol. Struct. 1985, 131, 121.
(5)
Cradock, S.; Sullivan, J. F.; Durig, J. R. J. Mol. Struct. 1986, 140, 199.
(6)
Glidewel.C; M., S. G.; Robiette, A. G. Chem. Phys. Lett. 1972, 16, 526.
(7)
Dossel, K. F.; Robiette, A. G. Z. Naturforsch., A: Phys. Sci. 1977, 32, 462.
(8)
Dossel, K. F.; Sutter, D. H. Z. Naturforsch., A: Phys. Sci. 1977, 32, 473.
(9)
Anderson, D. G.; Cradock, S.; Huntley, C. M.; Rankin, D. W. H. J. Chem.
Soc., Dalton Trans. 1988, 1193.
(10) Cradock, S.; Huntley, C. M.; Rankin, D. W. H.; Robertson, H. E. J. Chem.
Soc., Dalton Trans. 1986, 859.
(11) Huntley, C. M.; Rankin, D. W. H.; Robertson, H. E. J. Mol. Struct. 1987, 156,
103.
(12) Rankin, D. W. H.; Cyvin, S. J. J. Chem. Soc., Dalton Trans. 1972, 1277.
(13) Coon, J. B.; Naugle, N. W.; McKenzie, R. D. J. Mol. Spectrosc. 1966, 20, 107.
(14) Clouthier, D. J.; Goddard, J. D. J. Chem. Phys. 1982, 76, 5034.