Matrix isolation FTIR and DFT studies of methyl isocyanide-boron trifluoride complex

Article abstract of DOI:10.1016/j.molstruc.2004.11.068

The FTIR spectra of CH₃NC and BF₃ as well as their isotopomers co-deposited in low temperature Ar matrices were recorded. We observed several new infrared bands absent in the spectra of each component. These bands were assigned to the 1:1 EDA complex of CH₃NC and BF ₃ based on the DFT calculations at the B3LYP/6-311++G** level. The vibrational assignments and frequencies of the observed bands are the NC stretching at 2319.9 cm^-1, the BF₃ degenerate stretching at 1203.8 cm^-1, the BF₃ symmetric stretching at 840.4 cm^-1 and the BF₃ symmetric deformation at 638.0 cm^-1 for the CH₃NC-¹¹BF₃ isotopomer. Although the BF₃ symmetric stretching is infrared inactive for free BF₃ of D_3h symmetry, complexation with methyl isocyanide would have induced a structural change in the BF₃ moiety and the activation of this mode. Apart from some numerical discrepancies, the observed frequency shifts on complexation were in good agreement with the results of DFT calculation. Therefore, the structure of CH₃NC-BF₃ in solid Ar would be similar to the optimized C_3v geometry, which corresponds to the gas phase structure.

Full text of DOI:10.1016/j.molstruc.2004.11.068

Journal of Molecular Structure 738 (2005) 165–170
www.elsevier.com/locate/molstruc
Matrix isolation FTIR and DFT studies of methyl isocyanide-boron
trifluoride complex
*
Ryuichi Hattori, Eiichi Suzuki , Kenji Shimizu
Department of Chemical Engineering, Iwate University, 020-8551 Morioka, Japan
Received 9 September 2004; revised 29 November 2004; accepted 30 November 2004
Available online 18 January 2005
Abstract
The FTIR spectra of CH
observed several new infrared bands absent in the spectra of each component. These bands were assigned to the 1:1 EDA complex of CH NC
3 3
NC and BF as well as their isotopomers co-deposited in low temperature Ar matrices were recorded. We
3
3
and BF based on the DFT calculations at the B3LYP/6-311CCG** level. The vibrational assignments and frequencies of the observed
K1
bands are the NC stretching at 2319.9 cm , the BF
K1
K1
K1
3
3
degenerate stretching at 1203.8 cm , the BF symmetric stretching at 840.4 cm and
11
the BF symmetric deformation at 638.0 cm
3
for the CH NCK BF isotopomer. Although the BF symmetric stretching is infrared
3 3 3
3 3
inactive for free BF of D3h symmetry, complexation with methyl isocyanide would have induced a structural change in the BF moiety and
the activation of this mode. Apart from some numerical discrepancies, the observed frequency shifts on complexation were in good
agreement with the results of DFT calculation. Therefore, the structure of CH NC-BF in solid Ar would be similar to the optimized C
3v
3
3
geometry, which corresponds to the gas phase structure.
q 2004 Elsevier B.V. All rights reserved.
Keywords: Matrix isolation; Infrared spectroscopy; DFT calculation; Methyl isocyanide; Boron trifluoride
˚
2.011 A and 95.68, respectively, from microwave spectra [17].
1
. Introduction
Although the CH CN–BF complex is a molecular species, its
3
3
Boron trifluoride is one of the typical Lewis acids, and its
EDA bonding strength appears to be significantly different
between solid and gas phases. Beattie et al. observed the CN
stretching infrared bandof the CD CN–BF complex in a low-
electron donor–acceptor (EDA) complexes with various
inorganic or organic bases are well known. Numbers of
experimental and theoretical studies on these complexes have
been published up to these days [1–9]. Nxumalo et al. have
3
3
temperature Ar matrix, and suggested that the structure of the
complex is similar to that in the solid phase [18]. Recently,
Wells et al. reported more detailed infrared spectra of the
CH CN–BF complex and its isotopomers trapped in Ar
reported the EDA complexes of BF with various base
3
molecules, such as NH , N O, CO , CO, O(CH ) and
3 2
3
2
2
3
3
S(CH ) , in low-temperature matrices [10–14]. The complex
3
matrices [19]. They concluded that the structure and bonding
of the complex must differ significantly between the matrix
and crystalline environments, which is in great contrast to the
previous report. Similar situations are also found in other
systems. Burns et al. reported that the NB bond length and the
2
with acetonitrile (CH CN–BF ) was also studied and its
3
3
structure in different environments has been a matter of
interest. The X-ray diffraction of the CH CN–BF crystal was
3
3
first investigated by Hoard et al. [15], and afterwards Swanson
et al. precisely determined the molecular structure of the
complex [16]. The NB bond length and the FBN bond angle of
NBF bond angle of the HCN–BF complex differ between
3
solid and gas phases [20].
Methyl isocyanide (CH NC) is an isomer of acetonitrile,
˚
the complex in the crystalline solid were 1.630 A and 105.68,
3
respectively. On the other hand, Dvorak et al. reported that the
NB bond length and the FBN bond angle in the gas phase were
which is expected to form a similar but stronger EDA
complex with Lewis acid [21]. Thus, the structure
and the bonding strength of the CH NC–BF complex in
3
3
different environments is an interesting issue. Based on
these backgrounds, here we report the infrared spectra of
*
Corresponding author. Tel./fax.: C81 19 621 6344.
E-mail address: esuzuki@iwate-u.ac.jp (E. Suzuki).
0022-2860/$ - see front matter q 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2004.11.068

166
R. Hattori et al. / Journal of Molecular Structure 738 (2005) 165–170
the CH NC–BF complex trapped in an Ar matrix. We also
3
3
discuss the structure of the complex based on the density
functional theory (DFT) calculations.
2
. Experimental and computational methods
BF (99.99%) was purchased from Takachiho Chemical
3
1
Industrial Co., Ltd. BF was prepared from HF (Morita
0
3
1
3
0
Chemical Industries Co., Ltd), H BO (Aldrich, 99%) and
3
1
0
B O (Aldrich, 99%) [22]. CH NC was prepared from
2
3
3
AgCN (Kanto Chemical Co., Ltd, 99%) and CH3I
Katayama Chemical Industries Co., Ltd, 99.5%) [21].
CD NC was prepared in a similar manner with CD I
(
3
3
(
Aldrich Chem. Co., 99%) instead of CH I. All samples
3
Fig. 2. FTIR spectra of methyl isocyanide and boron trifluoride
co-deposited in an Ar matrix, in the BF degenerate stretching region.
a) CH NC/BF /ArZ1/1/400, 20 K; (b) BF /ArZ1/400, 12 K; (c) CH NC/
ArZ1/400, 20 K. The bands assigned to the CH NC–BF complex are
were purified by the trap-to-trap method in an all-glass
vacuum line. Ar gas (99.9995%) was purchased from
Nippon Sanso Corp. and used without further purification.
The gas mixtures of CH NC and BF with excess Ar were
3
(
3
3
3
3
3
3
indicated with arrows.
3
3
prepared using standard manometric techniques. CH NC/Ar
3
In the spectrum of the co-deposited sample (a), a new
K1
band appeared at 2319.9/2318.1 cm , which was split due
and BF /Ar were co-deposited on a CsI plate maintained at
3
2
0 or 12 K. Subsequent annealing procedures were carried
to a matrix site effect. The corresponding new band for
K1
out at 33 K. The cryostat used was CTI Cryogenics LT-21,
coupled with Tristan Technologies, Inc. LTC-20 tempera-
ture controller. Reagent/matrix ratios (R/M) were in the
range of 1/200–1/400. All spectra were recorded on a
Nicolet Magna 750 FTIR spectrometer, in the wavenumber
1
CH NC/ BF /Ar was observed at 2320.0/2318.0 cm
0
.
The band due to free CH NC was also observed at 2168.2/
3
3
3
K1
2
samples in the region of BF degenerate stretching. In this
160.8 cm
[24]. Fig. 2 shows the spectra of the same
3
K1
K1
range from 4000 to 400 cm at 1 cm resolution.
DFT calculations were carried out at the B3LYP/
region, new bands appeared at 1247.2/1244.1 and 1207.9/
K1
10
1203.8 cm . For the experiment with BF
, only the
was observed. The
absorptions of BF monomer were also observed at 1498.4
3
K1
6
-311CCG** level using the Gaussian 03 program [23].
absorption at 1247.3/1244.0 cm
3
K1
K1
10
and 1447.2/1442.6 cm
(1498.4 cm
for BF ) in this
3
region, which were accompanied by the bands of BF dimer
3
3
. Results and discussion
or higher aggregates at 1476.3, 1468.7, 1464.5, 1456.0,
K1
1436.1, 1425.8, 1420.8 and 1415.4 cm (1475.8, 1470.5,
Fig. 1 shows the spectra of CH NC/BF /Ar (a), BF /Ar
3
3
3
(
b) and CH NC/Ar (c) in the NC stretching region.
3
Fig. 1. FTIR spectra of methyl isocyanide and boron trifluoride
co-deposited in an Ar matrix, in the NC stretching region. (a) CH NC/
BF /ArZ1/1/400, 20 K; (b) BF /ArZ1/400, 12 K; (c) CH NC/ArZ1/400,
0 K. The band assigned to the CH NC–BF complex is indicated with an
arrow.
Fig. 3. FTIR spectra of methyl isocyanide and boron trifluoride
3
co-deposited in an Ar matrix, in the BF
BF symmetric deformation regions. (a) CH
(b) BF /ArZ1/400, 12 K; (c) CH NC/ArZ1/400, 20 K. The bands
assigned to the CH NC–BF complex are indicated with arrows.
3
symmetric stretching and the
3
3
3
3
3
NC/BF /ArZ1/1/400, 20 K;
3
2
3
3
3
3
3
3

R. Hattori et al. / Journal of Molecular Structure 738 (2005) 165–170
167
K1
10
for BF ) [25]. The regions of
1
464.2 and 1456.0 cm
Table 2
K1
Observed infrared frequencies (cm ) of co-deposited CD
3
3 3
NC and BF in
BF symmetric stretching and BF symmetric deformation
3
3
solid Ar
are shown in Fig. 3. In the BF symmetric stretching region,
3
K1
new bands appeared at 860.1, 852.2 and 840.4 cm . The
a,b
Co-deposited matrices
CD NCC CD NCC
BF BF
2322.0
Components
CD NC BF
Species
1
0
corresponding band for CH NC/ BF /Ar was observed at
3
3
3
3
3
3
K1
10
8
52.4 cm . In the BF symmetric deformation region, new
3
K1
3
3
11,10
bands appeared 651.7 and 638.0 cm . The corresponding
2322.3
2320.0
2259.8
2232.2
2168.6
2165.8
2160.9
2128.1
2085.1
1498.4
CD
CD
CD
CD
3
3
3
3
NC–
NC–
BF
BF
3
11,10
1
band for CH NC/ BF /Ar was observed at 651.7 cm
0
K1
2319.9
2259.8
2232.2
3
, site
.
The absorptions of BF monomer were also observed at
3
3
2259.9
2232.2
2168.6
2165.8
2160.9
2128.1
2085.1
NC M, D
NC M
3
K1
K1
10
for BF ) in this
3
7
03.3 and 675.9 cm
(703.2 cm
2168.6
2165.8
CD NC D
3
3
region [25].
CD NC P
2
2
160.9
128.1
CD
CD
CD
3
3
3
NC M
NC M
NC M
Table 1
K1
Observed infrared frequencies (cm ) of co-deposited CH
2085.1
3 3
NC and BF in
10
1
498.4
464.7
1498.4
1464.6
1447.0
1441.3
1426.0
1420.9
1395.0
BF
BF
BF
BF
3
3
3
3
M
solid Ar
1
1
1
D
a,b
Species
11
Co-deposited matrices
CH NCC CH NCC
BF BF
Components
CH NC BF
1447.2
440.8
1425.9
420.8
M
11
1
M, site
3
3
3
3
10
1424.2
1419.0
BF
BF
3
P?
D
3
1
3
3012.5
2959.3
2896.1
2319.9
2318.1
2168.2
2160.8
1498.4
1476.3
1468.7
1464.5
1456.0
1447.2
1442.6
1436.1
1425.8
1420.8
1415.4
1247.2
1244.1
1207.9
1203.8
3012.4
2959.4
2896.1
CH
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
3
NC M, D
NC M
1395.2
1257.6
1255.5
1241.8
1208.5
1204.6
1202.5
1111.4
1052.2
893.0
890.4
872.0
869.4
847.5
836.1
820.0
817.8
703.2
700.1
680.3
675.9
673.2
660.9
650.7
636.7
519.3
479.8
3
BF P?
10
1257.6
1255.5
1241.8
CD NC– BF , site
3
3
10
NC M
3
CD NC– BF
3
1
1,10
2320.0
2318.0
2168.1
2160.8
1498.4
1475.8
1470.5
1464.2
1456.0
NC–
NC–
BF
BF
3
Complex with BF P?
3
11,10
11
CD NC– BF , site
3
, site
3
3
11
2168.2
2160.7
NC D
NC M
3
CD NC– BF
3
11
CD NC– BF , site
3
3
3
3
3
3
3
10
1498.4
1476.4
1469.0
1464.6
1456.1
1447.0
1441.3
BF
3
M
1111.4
1052.2
893.0
890.4
872.0
869.4
847.6
1111.5
1052.2
892.9
890.4
872.1
869.4
CD NC M
BF
3
P?
CD NC M
11
BF
BF
3
D
D
CD NC D
11
1464.1
1456.1
3
CD NC M
CH NC M or BF
3
3
P
CD NC M
1
1
BF
BF
3
M
CD NC D
3
11
10
CD NC– BF
3
M, site
3
3
11
?
CD NC– BF
3
3
1426.0
1420.9
1415.3
BF
3
P?
D or CH
P?
820.0
817.6
703.2
700.1
681.1
819.9
817.7
703.3
700.1
680.2
676.0
673.2
660.7
BF D?
3
11
1421.7
937.8
BF
BF
3
3
NC M
BF D?
3
1
0
3
BF M
3
10
10
1247.3
1244.0
CH
CH
CH
CH
CH
3
3
3
3
3
NC– BF
3
3
3
3
, site
BF D
3
10
NC– BF
BF P?
3
11
3
11
NC– BF
, site
675.1
BF M
11
11
3
NC– BF
BF D?
9
9
8
8
8
8
8
7
7
6
6
6
6
6
6
6
6
5
4
37.8
16.2
60.1
52.2
40.4
20.0
17.8
03.3
00.1
80.3
75.9
73.2
70.0
60.7
55.0
51.7
38.0
19.3
79.5
937.8
916.2
NC M
661.2
650.7
BF P
3
10
CD NC– BF
3
1
1
10
D ( B, B)
916.3
BF
?
3
3
11
CD NC– BF
3
11
BF D?
3
1
0
852.4
CH
CH
3
NC– BF
3
519.3
481.6
519.0
479.7
3
11
11,10
3
3
NC– BF
D?
3
BF M
820.0
817.9
703.2
700.1
819.9
817.7
703.3
700.1
680.2
676.0
673.2
669.1
660.7
655.0
BF
BF
3
a
3 3
BF and CD NC species were specified by reference to [10], [24] and
3
D?
1
0
[25].
b
BF
BF
3
M
D
10
Abbreviations used: M, monomer; D, dimer; P, polymer.
3
BF
3
P?
1
1
The observed vibrational frequencies for CH NC/BF /Ar
3
3
BF
BF
3
M
11
D?
and CD NC/BF /Ar are summarized in Tables 1 and 2,
3 3
3
BF
3
BF
3
BF
3
P
respectively. The frequencies of the new bands at 2319.9/
P
P
2
6
318.1, 1247.2/1244.1, 1207.9/1203.8, 852.2, 840.4, 651.7,
K1
38.0 cm for CH NC/BF were not affected by the R/M
1
0
3
3
651.7
CH
CH
3
NC– BF
3
11
concentrations and the deposition temperature. Since the
magnitude of the frequency shifts of these bands from
the monomer absorptions was not so large, the formation of
new covalent species is not expected. Thus, the newly
appeared bands must be attributed to the EDA complex of
methyl isocyanide with boron trifluoride. All of these bands
3
NC– BF
D?
3
11
519.3
481.5
519.0
479.7
BF
BF
3
3
M
a
BF
3
and CH
3
NC species were specified by reference to [10], [24] and
[25].
b
Abbreviations used: M, monomer; D, dimer; P, polymer.

168
R. Hattori et al. / Journal of Molecular Structure 738 (2005) 165–170
were still observed at the most dilute conditions. The
relative intensities among these bands were unchanged even
after annealing, and no other new distinguishable bands
were observed throughout all the experiments we examined.
We therefore concluded that only one kind of methyl
isocyanide–boron trifluoride 1:1 complex was formed in
a low-temperature Ar matrix, even though several site-split
infrared bands were observed.
Table 3
B3LYP/6-311CCG** optimized geometrical parameters of the 1:1
CH
3 3
NC–BF complex
Parameter
CH
3
NC–BF
3
3 3
CH NC or BF
Bond length [ A˚ ]
R(CN)
1.425
1.090
1.152
1.761
1.374
1.423
1.091
1.170
–
R(CH)
R(NC)
R(BC)
Geometry optimizations of the CH NC–BF complex
3
3
R(BF)
1.318
and the related monomers were carried out by using the DFT
calculations. The symmetries of BF and CH NC monomers
Bond angle [8]
q (HCN)
q (FBC)
109.0
103.8
109.8
–
3
3
were maintained at D3h and C3v [26], respectively, during
the optimization processes. We assumed C3v symmetry for
the CH NC–BF complex, which is reasonable from the
3
3
very weak. No new absorptions were detected in these
regions of the co-deposited spectra probably because of
their weak intensity.
previous studies of CH CN–BF [6], CH CN–BH [27] and
3
3
3
3
CH NC–BH [21]. Our preliminary calculations showed
3
3
that the rotational energy barrier of the BF moiety about the
3
C axis of the complex is too small (less than 0.2 kJ/mol) to
3
3
.2. NC stretching region
determine the local minimum conformation by the DFT
calculations. We therefore assumed the eclipsed confor-
mation, which was preferred at the MP2/6-31G** level of
calculation. The optimized geometry of the complex at the
B3LYP/6-311CCG** level is shown in Fig. 4, and its
geometrical parameters are listed in Table 3. The calculated
K1
In this region, a new band appeared at 2319.9 cm in
the spectra of CH NC–BF . The corresponding band was
3
3
10
observed at almost the same position for the CH NC– BF
3
3
isotopomer. The infrared intensity of the band increased on
annealing. No absorptions were observed in this region for
free CH NC and BF . For deuterated species, CD NC, new
˚
BC bond length and the FBC bond angle were 1.761 A and
3
3
3
1
03.88, respectively. The D3h planar geometry of free BF3
K1
bands appeared at 2322.0 cm
K1
with BF3 and at
was distorted about 148 from the plane by the complexation.
The harmonic vibrational frequencies of the complex
calculated at this geometry and the approximate descriptions
of normal modes are summarized in Table 4. The assign-
ment of newly appeared infrared bands in the co-deposited
spectra was carried out based on these calculated frequen-
10
2
observed in this region. We therefore assigned the band at
322.3 cm
with BF . No other absorptions were
3
K1
2
complex. The observed frequency shift on complexation,
319.9 cm to the NC stretching mode of the CH NC–BF
3 3
K1
Dn, was a blue shift of 159.2 cm , which is in good
K1
agreement with the calculated value of 147.3 cm
.
1
1
cies, and the results for the CH NC– BF isotopomer are
3
3
also shown in Table 4. Although several bands reveal site-
splitting as previously mentioned, hereafter we simply show
the frequency of a major peak. Detailed considerations for
characteristic spectral regions are described below.
3
deformation regions
.3. CH degenerate deformation and CH symmetric
3 3
The predicted Dn of the CH degenerate deformation and
3
the CH symmetric deformation modes are red shifts of 6.6
3
3
stretching regions
.1. CH degenerate stretching and CH symmetric
3 3
K1
and 1.7 cm , respectively. The calculated infrared inten-
sities of these bands are rather weak. No absorptions
attributable to the complex were observed in this region of
the co-deposited spectra. Weak infrared intensity and the
Calculation predicted that both the CH3 degenerate
stretching and the CH symmetric stretching modes reveal
blue shifts on complexation, but their infrared intensities are
3
overlapping by the strong BF degenerate stretching modes
3
of free BF and its aggregates would be responsible for the
3
absence of the complex bands.
3
.4. BF degenerate stretching region
3
In this region, new bands appeared at 1244.1 and
K1
1
2
203.8 cm
54.3 and 243.2 cm
in the spectra of CH NC–BF , which are
3 3
K1
lower than the BF degenerate
3
1
0
11
stretchings of free BF and BF , respectively. These
3
3
bands were the strongest among the newly appeared bands
in the co-deposited spectra. The corresponding bands were
observed at similar positions for CD NC–BF . The infrared
Fig. 4. B3LYP/6-311CCG** optimized geometry of the 1:1 CH
complex. Determined values of geometrical parameters are listed in Table 3.
3 3
NC–BF
3
3

R. Hattori et al. / Journal of Molecular Structure 738 (2005) 165–170
169
Table 4
K1
Calculated and experimental fundamental frequencies (cm ) of the CH
11
NC– BF
3
3
complex
Experimental
a
Mode
Calculated
Approximate
b
description
n
complex
n
monomer
Dn
n
complex
n
monomer
Dn
a
1
n
n
n
n
n
n
n
n
n
n
n
n
n
1
3060.1
2379.7
1451.0
973.6
(2.8)
3046.2
2232.4
1452.7
953.7
869.0
682.0
–
(18.4)
(146.5)
(3.6)
C13.9
C147.3
K1.7
C19.9
K42.8
K57.3
–
–
2959.4
2160.7
1421.7
937.8
–
–
CH
NC str
CH sym def
3
sym str
2
(82.3)
(1.0)
2319.9
C159.2
–
3
–
3
4
(11.2)
(339.4)
(225.4)
(3.3)
(14.1)
(0.0)
–
–
CN str
1
1
5
826.2
840.4
–
BF
BF
3
sym str
sym def
11
6
624.7
(102.1)
638.0
676.0
–
K38.0
3
7
259.1
–
–
NB str
Torsion
a
e
2
8
17.2
(0.0)
–
–
–
–
–
9
3142.4
1484.7
1174.4
1147.4
520.8
(0.2)
3118.6
1491.3
1417.1
1145.1
465.8
(6.6)
C23.8
K6.6
K242.7
C2.3
C55.0
–
3012.4
1456.1
1447.0
1128.9
479.7
–
CH
CH
3
deg str
10
11
12
13
(15.9)
(362.0)
(2.0)
(12.0)
(487.5)
(0.1)
–
–
3
deg def
11
1203.8
K243.2
BF
3
deg str
rock
–
–
–
–
CH
3
1
1
(0.06)
(14.8)
BF
3
deg defCCNC
bend
1
1
n
14
401.0
(10.0)
278.7
(1.2)
C122.3
–
–
–
BF
bend
3
deg defCCNC
n
n
15
16
244.8
78.1
(2.0)
(0.4)
–
–
–
–
–
–
–
–
–
–
LibrationCCNC bend
Libration
a
Calculated infrared intensities (km/mol) are in parentheses.
b
Abbreviations used: sym, symmetric; deg, degenerate; str, stretch; def, deformation.
intensity ratio of these bands was about 1:4, and the lower
frequency band was not observed in the spectra of
considerable infrared intensity by the DFT calculation. We
K1
therefore assigned the bands at 852.2 and 840.4 cm to the
1
CH NC– BF . The calculated Dn of the BF degenerate
0
11
10
11
BF3 and BF3 symmetric stretching modes of the
complex, respectively.
3
3
3
K1
stretching mode was a red shift of 242.7 cm . Calculation
also predicted that this mode reveals the highest infrared
intensity among all the vibrations of the complex. We
3.7. BF symmetric deformation region
3
K1
therefore assigned the bands at 1244.1 and 1203.8 cm to
1
the BF and BF degenerate stretchings, respectively.
0
11
3
3
In this region, new bands appeared at 651.7 and
K1
1
The experimental Dn for CH NC– BF , a red shift of
1
3
3
6
5
38.0 cm
1.6 and 38.0 cm lower than the BF symmetric (out-of-
in the spectra of CH NC–BF , which were
3 3
K1
43.2 cm , is in excellent agreement with the calculated
2
value.
K1
3
11
10
plane) deformations of free BF and BF , respectively.
3
3
Their intensity ratio was also about 1:4, and only the higher
1
0
3
.5. CH rocking and CN stretching regions
3
frequency band was observed for CH NC– BF . The
3 3
corresponding bands were observed at almost the same
1
1
The predicted Dn of the CH3 rocking and the CN
K1
positions for CD NC–BF . The calculated Dn of the BF3
3 3
K1
stretching modes are blue shifts of 2.3 and 19.9 cm
,
symmetric deformation was a red shift of 57.3 cm , which
is consistent with experiment in terms of the shift direction,
though the numerical value is somewhat large. We therefore
respectively. The calculated infrared intensities of these
bands are rather weak. We could not detect the absorptions
of these modes probably because of their weak intensity.
K1
10
assigned the bands at 651.7 and 638.0 cm to the BF3
1
and BF symmetric deformation modes, respectively.
1
3
3
.6. BF symmetric stretching region
3
3
.8. BF degenerate deformation region
3
K1
New bands appeared at 852.2 and 840.4 cm in the
spectra of CH NC–BF , and their intensity ratio was about
The predicted Dn of the BF degenerate deformation was
3
3
3
K1
1
CH NC– BF . The corresponding bands were at 847.5 and
:4. Only the higher frequency band was observed for
1
a blue shift of 55.0 cm , which would be partially
influenced by the coupling with the CNC bending mode.
The calculated infrared intensity, however, was quite weak.
We could not observe any new absorption in this region
probably because of its weak intensity.
0
3
3
K1
8
Although the BF symmetric stretching mode is infrared
36.1 cm , respectively, in the CD NC–BF spectra.
3 3
3
inactive for free BF , complexation with methyl isocyanide
3
would be expected to induce a structural change in the BF3
moiety and the activation of this mode. Actually, this mode
From the comparison of the observed infrared frequen-
cies, or especially the frequency shifts, with the DFT
1
of the CH NC– BF was predicted at 826.2 cm
1
K1
with
3
3

170
R. Hattori et al. / Journal of Molecular Structure 738 (2005) 165–170
computational results described above, we concluded that
the 1:1 EDA complex of methyl isocyanide with boron
trifluoride was formed in low temperature solid Ar.
Although some discrepancies can be seen between the
numerical values of the observed and the calculated Dn,
the structure of the complex in solid Ar would be essentially
the same as the C3v geometry predicted by the DFT
calculation, which corresponds to the gas phase structure.
Numerical differences between the observed and the
calculated values might be due to a minor influence of a
[4] L.M. Nxumalo, M. Andrzejak, T.A. Ford, J. Mol. Struct. 509 (1999)
87.
2
[
[
5] S. Fau, G. Frenking, Mol. Phys. 96 (1999) 519.
6] V. Jonas, G. Frenking, M.T. Reetz, J. Am. Chem. Soc. 116 (1994)
8
741.
[
7] S.D. Williams, W. Harper, G. Mamantov, L.J. Tortorelli, G. Shankle,
J. Comp. Chem. 17 (1996) 1696.
¯
[8] R. Nakane, T. Oyama, J. Phys. Chem. 70 (1966) 1146.
[
9] A.A. Stolov, W.A. Herrebout, B.J. Van der Veken, J. Am. Chem. Soc.
20 (1998) 7310.
10] L.M. Nxumalo, M. Andrzejak, T.A. Ford, Vib. Spectrosc. 12 (1996)
21.
1
[
2
matrix environment. The observed red shift of the BF
3
[11] L.M. Nxumalo, T.A. Ford, Spectrochim. Acta Part A 53 (1997) 2511.
[12] L.M. Nxumalo, T.A. Ford, J. Mol. Struct. 436–437 (1997) 69.
[13] L.M. Nxumalo, T.A. Ford, S. Afr. J. Chem. 48 (1995) 30.
K1 11
degenerate stretching (243.3 cm for BF ) is larger than
3
that of the corresponding mode of the CH CN–BF complex
3
3
K1
11
[
14] L.M. Nxumalo, T.A. Ford, Mikrochim. Acta [Suppl.], 14 (1997)
83.
15] J.L. Hoard, T.B. Owen, A. Buzzell, O.N. Salmon, Acta Crystallogr. 3
1950) 130.
( for BF ) [19]. This seems to indicate that
3
CH NC forms a stronger EDA complex with BF than
199 cm
3
3
3
[
CH CN, which is consistent with the previous results for
3
(
their adducts with BH3 [21,27]. However, the BF3
symmetric deformation reveals the opposite feature. The
[
[
16] B. Swanson, D.F. Shriver, J.A. Ibers, Inorg. Chem. 8 (1969) 2182.
17] M.A. Dvorak, R.S. Ford, R.D. Suenram, F.J. Lovas, K.R. Leopold,
J. Am. Chem. Soc. 114 (1992) 108.
K1 11
red shift of the CH CN–BF complex (75 cm for BF3)
3
3
[
18] I.R. Beattie, P.J. Jones, Angew. Chem. Int. Ed. Engl. 35 (1996)
1527.
[
(
19] is considerably larger than that of the CH NC–BF
3 3
K1
38.0 cm for BF ). Further investigations based on the
11
3
[
[
[
[
[
19] N.P. Wells, J.A. Phillips, J. Phys. Chem. A 106 (2002) 1518.
20] W.A. Burns, K.R. Leopold, J. Am. Chem. Soc. 115 (1993) 11622.
21] F. Watari, Inorg. Chem. 21 (1982) 1442.
force constants in terms of the internal coordinates are
needed to explain this contradiction.
22] H.S. Booth, K.S. Wilson, Inorg. Syn. 1 (1939) 21.
23] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,
J.R. Cheeseman, J.A. Montgomery, Jr., T. Vreven, K.N. Kudin, J.C.
Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B.
Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M.
Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li,
J.E. Knox, H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R.
Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P.
Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D.
Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S.
Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P.
Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-
Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill,
B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A. Pople, Gaussian
4
. Conclusions
The infrared spectra of CH NC and BF as well as their
3
3
isotopomers co-deposited in low temperature Ar matrices
were recorded. Several new absorptions were observed,
which can be assigned to the 1:1 EDA complex of methyl
isocyanide with boron trifluoride. The observed frequency
shifts on complexation were in good agreement with
the calculated Dn based on the C3v geometry optimized at
the B3LYP/6-311CCG** level.
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3, Revision B.05, Gaussian, Inc., Pittsburgh PA, 2003.
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[
[
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2] W.A. Herrebout, J. Lundell, B.J. Van der Veken, J. Mol. Struct.
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(
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