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On the formation of nitryl bromide and nitryl iodide and the infrared spectra of the matrix isolated molecules
JOURNAL
OF MOLECULAR
SPECTROSCOPY
77,429-439
(1979)
On the Formation of Nitryl Bromide and Nitryl Iodide and the Infrared Spectra of the Matrix Isolated Molecules M. FEUERHAHN,
R. MINKWITZ,
AND U. ENGELHARDT
lnstitut ftir Anorganische Chemie, Freie Universitiit Berlin. Berlin, Germany Mixtures of bromine or iodine and argon are passed through a microwave discharge. The resulting gas mixtures are condensed on a cold window at 9 K together with nitrogen dioxide and a large excess of argon as an inert matrix material. Six new absorptions are found in the infrared spectra in both cases. They can be assigned to nitryl bromide or nitryl iodide, respectively, according to a C,, point symmetry of the planar molecules. Frequencies, 15N-isotopic shifts, and calculated force constants are in good agreement with expected values extrapolated from the known nitryl fluoride and nitryl chloride. INTRODUCTION
Of the nitryl halogen compounds NO,X only nitryl fluoride and nitryl chloride have been investigated so far. According to Schmeisser and Schuster (1) the instability of nitryl bromide and nitryl iodide is due to a more covalent character of the nitrogen halogen bond in these compounds. Moreover the greater polarizability of the larger halogens should destabilize the nitrogen halogen bond. Many unsuccessful attempts to prepare nitryl bromide and nitryl iodide are reported in the literature. Though Zuskine (2) claimed the synthesis of nitryl bromide in high purity in 1925, his experiments could not be reproduced. Kuhn and Olah (3) tried to prepare nitryl bromide using several different methods, but their experiments yielded only decomposition products that proved the existence of nitryl bromide as a short living intermediate. Attempts to isolate nitryl iodide as such have been unsuccessful as well. However, solutions resulting from a reaction of silver nitrite with iodine in ether react with olefinic double bonds [Eq. (l)]. The reaction products formed lead to the conclusion that nitryl iodide as an intermediate adds to the double bonds via a free radical mechanism (4-8). \ =C
= <+
AgNOl
+ I2 -_)
-
F -
{ -
I
NO2
+ Agl
(1)
Similar reactions with cumulated double bonds have been found, using solutions of dinitrogen tetroxide and iodine in ether (9-11). Van den Bergh and Troe (12) investigated the kinetics of the recombination of iodine atoms in gas mixtures of nitrogen dioxide and argon. The results prove the formation of a chemical bond activation complex as a transition state of the reaction. This complex was postulated to be nitryl iodide. Thermochemical data of nitryl iodide derived from these experiments are in good agreement with extrapolated values. 429
0022-2852/79/100429-11$02.00/O Copyright 0 1979 by Academic Press, Inc. All rights of reproduction in any form reserved.
430
FEUERHAHN,
MINKWITZ,
AND ENGELHARDT
FIG. 1. Vacuum line and gas inlet system for the preparation of nitty1 iodide and bromide and their condensation in a liquid helium cryostate. Ar: J: K: M: N:
argon steel cylinder sample of iodine cryostate gas mixture needle valves
P:
Q: R: s: VP:
cold window mercury manometer microwave discharge unit tIow meter vacuum pump
We concluded that the matrix isolation technique should be an excellent tool for the synthesis of both nitryl bromide and nitryl iodide in sufficient yield for the investigation of their molecular spectra and thus proving the existence of these molecules at least at low temperatures. EXPERIMENTAL
DETAILS
The vacuum line and gas handling system used for the preparation and condensation of nitryl bromide and iodide is shown in Fig. 1. It consists of two gas inlet systems connected with a vacuum pump VP and an argon steel container Ar. Two glass needle valves N and flow meters S are provided to let a constant stream of a mixture of nitrogen dioxide and argon (molar ratio 1:75) pass from the glass container M1 into the evacuated helium cryostate K. A second stream of argon from the flask Mz passes at the same flow rate over a sample of iodine at 10°C in a small vessel L. The iodine is then transformed to iodine atoms in high yields in a microwave discharge unit R. The frequency of the microwave generator is 2.45 x lo9 Hz. The measured energy is 80 W, the pressure in the discharge unit is 0.8 mbar. The two gas streams are mixed at a distance of about 20 mm from the cold window in the cryostate. The condensation temperature at the window is 9 K. In a typical experiment 10 mmole of the mixture is condensed over 100-200 min. A Beckman IR-12 spectrometer was used for the registration of the spectra in the range 2004000 cm-‘, the cryostate being equipped with three CsI windows (thickness 5 mm). In the far infrared range 95-600 cm-’ a Beckman IR-11 was used with a silicon single crystal window as cold probe and polyethylene windows (thickness 2 mm). RESULTS
To check the effects of pure argon that passed through the microwave discharge on nitrogen dioxide, we conducted several experiments without adding bromine or
2400
2000
_
1800
"NO .,:
NO
v~'N~~oo
NO2 N
2’3
1400
.
cm-1
1,
N203
INO& “NO2
N2°3
1200
1000
.
800
.
600
.
400
.
FIG. 2. Infrared spectrum after cocondensing NOJAr = 1:75 with additional argon (same flow rate) passing through a microwave discharge. tion time 90 min, temperature 9 K, deposition rate 120 PmoVmin.
1
% T
Deposi-
200
*
,,,,
m
6
g
7
2000
lad0
FIG. 3. Infrared spectrum after cocondensation
2400
Iii00
x.
1400
cm-l
-iNO;
1200
1000
I
600
400
200 Effective molar ratio NO,:I,:Ar = 1:4: 150. x = absorptions of nitrogen oxides (vid.
800
of NOJAr with I,/Ar flowing through a microwave discharge. Deposition time 220 min, deposition rate 120 *moUrnin, temperature 9 K. Marking of the observed frequencies: Fig. 2); n = absorptions of nitrosyl iodide; + = new absorptions (nitryl iodide).
T
‘10T
FORMATION
OF NITRYL
BROMIDE
AND NITRYL
IODIDE
0 -0
s
-s *8
x
‘co -
x x
x c
-8
x x
0
;
w
434
FEUERHAHN,
MINKWITZ,
AND ENGELHARDT
0
_8 0
-: 8
-(D c-
0
8
‘0 hl
m
2000
L
1800
1600
I
1400
I
1200
1000
800
600
I
400
200
FIG. 5. Infrared spectra of matrix isolated nitryl chloride. (a) From chlorosulfonic acid and nitric acid independently prepared nitryl chloride condensed with krypton. CINO,:Kr = 1550. Deposition time 120 min, deposition rate 120 &mol/min, temperature 12 K. (b) Infrared spectrum after cocondensation of NOJAr with Cl,/Ar flowing through a microwave discharge. Effective molar ratio NO,:Cl,:Ar = 1:l: 160. Deposition time 150 min, deposition rate 120 FmoUmin, temperature 9 K. Marking of the observed frequencies. x = absorptions of nitrogen oxides (vid. Fig. 2); n = absorptions of nitrosyl chloride; -+ = absorption of nitryl chloride.
b
T
% T
g
5 EI
436
FEUERHAHN,
MINKWITZ,
AND ENGELHARDT
“NO I
I
IA,)
‘as,
2
1
cm-l -, 1500 FIG. 6. Spectrochemical
sequence
(B,) ,
2
1900
of nitryl halides.
iodine. A typical spectrum is shown in Fig. 2. Apparently nitrogen dioxide is slightly decomposed yielding mainly nitrogen monoxide, which partly reacts with the excess of nitrogen dioxide to form dinitrogen trioxide. The assignment of the found frequencies to the different molecules is made according to Fateley et al. (13). The assumed formation of nitrosyl cations (2350 cm-‘) is paralleled by many experiments of other authors, in which considerable amounts of charged species are found in low temperature matrices (14, 15). The stretching vibration of the azide radical was assigned according to Milligan et al. (16). If the argon stream is loaded with small amounts of iodine vapor as described before, several new absorptions are observed in the spectra (Fig. 3). Some of them can be assigned to nitrosyl iodide and to the cis dimer of nitrogen oxide (1770 cm-‘) that is formed during the decomposition of nitrosyl iodide (12) (Eq. 2). 21N0 + Iz + (NO),.
(2)
Some small bands in the region 1330-1400 cm-’ attributed to the nitrate anion have increased. They do not disappear, when the cryostate is warmed to room temperature, because some cesium nitrate is formed from nitrogen dioxide and cesium iodide from the cold window. Six new bands of medium or strong intensity are found that can.be attributed to nitty1 iodide (frequencies given in Table I). Passing a mixture of argon and bromine through the microwave discharge, spectra are obtained as shown in Fig. 4. Only small amounts of the cis dimer of
TABLE New Frequencies 1700s 1670s (1Abbreviations very weak.
(cm-l)
1279s 1266s of observed
Appearing
650~ 640~ intensities:
I
after Cocondensation 468~ 457w
569~s 563~s vs, very
of NO*/Ar with IJAr”
strong;
s, strong;
305m 300m m, medium;
(‘*N) (“N) w, weak;
VW,
FORMATIONOF NITRYL BROMIDEAND NITRYL IODIDE
437
TABLE II New Frequencies(cm-l) Appearingafter Cocondensationof NOJAr with Br.JAr” 1723s 1695s 0 Abbreviations very weak.
1239s 1278s of observed
641w 638~ intensities:
588vs 583~s
496m
360m
(‘W
492m
356m
PN)
vs. very strong; s. strong;
m, medium; W. weak; VW,
nitrogen monoxide are observed, whereas nitrosyl bromide is present in comparable larger quantities as in the case of the iodine compound. This is to be expected due to the greater stability of nitrosyl bromide. The decomposition leading to bromine and cis dinitrogen dioxide is much slower. The spectrum again reveals six new bands, different from those of the iodine compounds that can be readily assigned to nitryl bromide. The frequencies are listed in Table II together with those obtained using 15N0, as starting material. For comparison similar experiments were carried out with mixtures of argon and chlorine passing through the discharge tube. The spectrum (Fig. 5b) clearly shows the formation of nitryl chloride and nitrosyl chloride in high yields, other features being nearly identical to the experiment with bromine. Substitution of the argon matrix by a krypton matrix (spectrum Fig. 5a) does not result in frequency shifts in the case of nitryl chloride. DISCUSSION The two formerly known nitryl halides NO,F and NO&l are planar fouratomic molecules with point group symmetry CzO.Six fundamental vibrations, all ir active, TABLE III MolecularVibrationFrequenciesof Nitryl Halogenidesin cm-l”
B Abbreviations very weak.
of observed
:NOp
CINOI('7) CIN02 BrNOl INO
I 309”s
1293~
822”s
794”s
781”s
588”s
569”s
568s
367”s
365m
49&l!
46aw
1791”s
1685~s
1690~s
1723s
1291s
1289s
1279%
1700s
559s
4llw
41&v
360m
305m
742m
651m
65Om
64lW
650~
intensities:
vs. very strong; s, strong; m, medium; w, weak; VW,
438
FEUERHAHN,
MINKWITZ,
AND ENGELHARDT
TABLE IV Main Force Constants of Nitryl Halogenides (mdyn/A) (General Valence Force Field)
fz@Q f,(NW fa(ONW
fdONO) f,
CINOz
BrNOZ
INOz
9,93 2,Ol 0,73 2,05 0,38
951 1,91 0,67 1,91 0,39
9,49 1,87 056 1,87 0,39
are predicted by theory and found in their spectra. Our assignments of bands in the now obtained infrared spectra of nitryl iodide and nitty1 bromide are mainly based on those for nitryl chloride done by Bernitt et al. (27), later confirmed by microwave spectroscopic data (18, 19). Frequency shifts and relative intensities were used as a guide. A summary is given in Table III and Fig. 6. The results are supported by a GVFF calculation (simplified “Kopplungsstufenverfahren” (20)). Frequencies calculated for the 15N containing molecules using the obtained force constants are in very good agreement with our experimental values. Main force constants based on matrix data are given in Table IV for nitryl chloride, bromide, and iodide. ACKNOWLEDGMENTS We wish to thank W. Hilbig for the calculation of force constants and the Fonds der Chemischen Industrie for financialsupport of this work. RECEIVED:
November
27, 1978 REFERENCES
1. M. SCHMEISSERAND E. SCHUSTER,in “Bromine and Its Compounds” (Z. E. Jolles, Ed.), p. 212, Academic Press, New York, 1%6. 2. N. ZUSKINE,Bull. Sec. Chim. 37, 187 (1925). 3. S. U. KUHN AND G. A. OLAH, J. Amer. Chem. Sot. 83,4564-4571 (l%l). 4. A. HASSNER,C. H. HEATHCOCK,G. J. KENT, AND J. E. KROPP,“Abstracts. 148th Natl. Mtg. Am. Chem. Sot., Chicago, 1964,” p. 298. 5. A. HASSNER, in “Reagents for Organic Synthesis” (L. Fieser and M. Fieser, Eds.), p. 757, John Wiley, New York, 1967. 6. A. HASSNER,J. E. KROPP,AND G. J. KENT, J. Org. Chem. 34, 2628-2632 (1%9). 7. J. E. KROPP,Dissertation, Univ. of Colorado 1966, Dissert. Abs. B 27 (4), 1093 (1966). 8. W. A. SZAREK,D. G. LANCE, AND R. L. BEACH, Chem. Commun. 356 (1%8). 9. T. E. STEVENSAND W. D. EMMONS,J. Amer. Chem. Sot. 80, 338-341 (1956). IO. V. JAEGER AND H. G. VIEHE, Angew. Chem. Int. Ed. Engl. 8, 273 (1%9). Il. V. JAEGER AND H. J. GUNTHER,Angew. Chem. In?. Ed. Engl. 16, 246 (1977). 12. H. VAN DEN BERGHAND J. TROE,J. Chem. Phys. 64,736-742 (1976). 13. W. G. FATELEY, H. A. BENT, AND B. CRAWFORD, JR.,J. Chem. Phys. 31,204-217 (1959). 14. C. A. WIGHT, B. S. AULT, AND L. ANDREWS,J. Chem. Phys. 65, 1244-1249 (1976). 15. M. E. JACOX,InternationalConference on Matrix Isolation Spectroscopy, in Diskussionstagung der Deutschen Bunsen-Gesellschaftf. Phys. Chem., p. 16 (1977).
FORMATION 16. 17. 18. 19. 20.
OF NITRYL
BROMIDE
AND NITRYL
IODIDE
439
D. E. MILLJGAN,H. W. BROWN, AND G. C. PIMENTEL,J. Chem. Phys. 25, 1080 (1956). D. L. BERNITT,R. H. MILLER,AND I. C. HISATSUNE,Specrrochim. Acrn A 23, 237-248 (1%7). T. TANAKA AND Y. MORINO,J. Mol. Spectrosc. 32, 430-435 (l%Y). Y. MORINOAND T. TANAKA, J. Mol. Spectrosc. 16, 179-190 (1%5). H.-J. BECHERAND R. MATTES, Spectrochim. Acta A 23, 2449-2451 (1967).
OF MOLECULAR
SPECTROSCOPY
77,429-439
(1979)
On the Formation of Nitryl Bromide and Nitryl Iodide and the Infrared Spectra of the Matrix Isolated Molecules M. FEUERHAHN,
R. MINKWITZ,
AND U. ENGELHARDT
lnstitut ftir Anorganische Chemie, Freie Universitiit Berlin. Berlin, Germany Mixtures of bromine or iodine and argon are passed through a microwave discharge. The resulting gas mixtures are condensed on a cold window at 9 K together with nitrogen dioxide and a large excess of argon as an inert matrix material. Six new absorptions are found in the infrared spectra in both cases. They can be assigned to nitryl bromide or nitryl iodide, respectively, according to a C,, point symmetry of the planar molecules. Frequencies, 15N-isotopic shifts, and calculated force constants are in good agreement with expected values extrapolated from the known nitryl fluoride and nitryl chloride. INTRODUCTION
Of the nitryl halogen compounds NO,X only nitryl fluoride and nitryl chloride have been investigated so far. According to Schmeisser and Schuster (1) the instability of nitryl bromide and nitryl iodide is due to a more covalent character of the nitrogen halogen bond in these compounds. Moreover the greater polarizability of the larger halogens should destabilize the nitrogen halogen bond. Many unsuccessful attempts to prepare nitryl bromide and nitryl iodide are reported in the literature. Though Zuskine (2) claimed the synthesis of nitryl bromide in high purity in 1925, his experiments could not be reproduced. Kuhn and Olah (3) tried to prepare nitryl bromide using several different methods, but their experiments yielded only decomposition products that proved the existence of nitryl bromide as a short living intermediate. Attempts to isolate nitryl iodide as such have been unsuccessful as well. However, solutions resulting from a reaction of silver nitrite with iodine in ether react with olefinic double bonds [Eq. (l)]. The reaction products formed lead to the conclusion that nitryl iodide as an intermediate adds to the double bonds via a free radical mechanism (4-8). \ =C
= <+
AgNOl
+ I2 -_)
-
F -
{ -
I
NO2
+ Agl
(1)
Similar reactions with cumulated double bonds have been found, using solutions of dinitrogen tetroxide and iodine in ether (9-11). Van den Bergh and Troe (12) investigated the kinetics of the recombination of iodine atoms in gas mixtures of nitrogen dioxide and argon. The results prove the formation of a chemical bond activation complex as a transition state of the reaction. This complex was postulated to be nitryl iodide. Thermochemical data of nitryl iodide derived from these experiments are in good agreement with extrapolated values. 429
0022-2852/79/100429-11$02.00/O Copyright 0 1979 by Academic Press, Inc. All rights of reproduction in any form reserved.
430
FEUERHAHN,
MINKWITZ,
AND ENGELHARDT
FIG. 1. Vacuum line and gas inlet system for the preparation of nitty1 iodide and bromide and their condensation in a liquid helium cryostate. Ar: J: K: M: N:
argon steel cylinder sample of iodine cryostate gas mixture needle valves
P:
Q: R: s: VP:
cold window mercury manometer microwave discharge unit tIow meter vacuum pump
We concluded that the matrix isolation technique should be an excellent tool for the synthesis of both nitryl bromide and nitryl iodide in sufficient yield for the investigation of their molecular spectra and thus proving the existence of these molecules at least at low temperatures. EXPERIMENTAL
DETAILS
The vacuum line and gas handling system used for the preparation and condensation of nitryl bromide and iodide is shown in Fig. 1. It consists of two gas inlet systems connected with a vacuum pump VP and an argon steel container Ar. Two glass needle valves N and flow meters S are provided to let a constant stream of a mixture of nitrogen dioxide and argon (molar ratio 1:75) pass from the glass container M1 into the evacuated helium cryostate K. A second stream of argon from the flask Mz passes at the same flow rate over a sample of iodine at 10°C in a small vessel L. The iodine is then transformed to iodine atoms in high yields in a microwave discharge unit R. The frequency of the microwave generator is 2.45 x lo9 Hz. The measured energy is 80 W, the pressure in the discharge unit is 0.8 mbar. The two gas streams are mixed at a distance of about 20 mm from the cold window in the cryostate. The condensation temperature at the window is 9 K. In a typical experiment 10 mmole of the mixture is condensed over 100-200 min. A Beckman IR-12 spectrometer was used for the registration of the spectra in the range 2004000 cm-‘, the cryostate being equipped with three CsI windows (thickness 5 mm). In the far infrared range 95-600 cm-’ a Beckman IR-11 was used with a silicon single crystal window as cold probe and polyethylene windows (thickness 2 mm). RESULTS
To check the effects of pure argon that passed through the microwave discharge on nitrogen dioxide, we conducted several experiments without adding bromine or
2400
2000
_
1800
"NO .,:
NO
v~'N~~oo
NO2 N
2’3
1400
.
cm-1
1,
N203
INO& “NO2
N2°3
1200
1000
.
800
.
600
.
400
.
FIG. 2. Infrared spectrum after cocondensing NOJAr = 1:75 with additional argon (same flow rate) passing through a microwave discharge. tion time 90 min, temperature 9 K, deposition rate 120 PmoVmin.
1
% T
Deposi-
200
*
,,,,
m
6
g
7
2000
lad0
FIG. 3. Infrared spectrum after cocondensation
2400
Iii00
x.
1400
cm-l
-iNO;
1200
1000
I
600
400
200 Effective molar ratio NO,:I,:Ar = 1:4: 150. x = absorptions of nitrogen oxides (vid.
800
of NOJAr with I,/Ar flowing through a microwave discharge. Deposition time 220 min, deposition rate 120 *moUrnin, temperature 9 K. Marking of the observed frequencies: Fig. 2); n = absorptions of nitrosyl iodide; + = new absorptions (nitryl iodide).
T
‘10T
FORMATION
OF NITRYL
BROMIDE
AND NITRYL
IODIDE
0 -0
s
-s *8
x
‘co -
x x
x c
-8
x x
0
;
w
434
FEUERHAHN,
MINKWITZ,
AND ENGELHARDT
0
_8 0
-: 8
-(D c-
0
8
‘0 hl
m
2000
L
1800
1600
I
1400
I
1200
1000
800
600
I
400
200
FIG. 5. Infrared spectra of matrix isolated nitryl chloride. (a) From chlorosulfonic acid and nitric acid independently prepared nitryl chloride condensed with krypton. CINO,:Kr = 1550. Deposition time 120 min, deposition rate 120 &mol/min, temperature 12 K. (b) Infrared spectrum after cocondensation of NOJAr with Cl,/Ar flowing through a microwave discharge. Effective molar ratio NO,:Cl,:Ar = 1:l: 160. Deposition time 150 min, deposition rate 120 FmoUmin, temperature 9 K. Marking of the observed frequencies. x = absorptions of nitrogen oxides (vid. Fig. 2); n = absorptions of nitrosyl chloride; -+ = absorption of nitryl chloride.
b
T
% T
g
5 EI
436
FEUERHAHN,
MINKWITZ,
AND ENGELHARDT
“NO I
I
IA,)
‘as,
2
1
cm-l -, 1500 FIG. 6. Spectrochemical
sequence
(B,) ,
2
1900
of nitryl halides.
iodine. A typical spectrum is shown in Fig. 2. Apparently nitrogen dioxide is slightly decomposed yielding mainly nitrogen monoxide, which partly reacts with the excess of nitrogen dioxide to form dinitrogen trioxide. The assignment of the found frequencies to the different molecules is made according to Fateley et al. (13). The assumed formation of nitrosyl cations (2350 cm-‘) is paralleled by many experiments of other authors, in which considerable amounts of charged species are found in low temperature matrices (14, 15). The stretching vibration of the azide radical was assigned according to Milligan et al. (16). If the argon stream is loaded with small amounts of iodine vapor as described before, several new absorptions are observed in the spectra (Fig. 3). Some of them can be assigned to nitrosyl iodide and to the cis dimer of nitrogen oxide (1770 cm-‘) that is formed during the decomposition of nitrosyl iodide (12) (Eq. 2). 21N0 + Iz + (NO),.
(2)
Some small bands in the region 1330-1400 cm-’ attributed to the nitrate anion have increased. They do not disappear, when the cryostate is warmed to room temperature, because some cesium nitrate is formed from nitrogen dioxide and cesium iodide from the cold window. Six new bands of medium or strong intensity are found that can.be attributed to nitty1 iodide (frequencies given in Table I). Passing a mixture of argon and bromine through the microwave discharge, spectra are obtained as shown in Fig. 4. Only small amounts of the cis dimer of
TABLE New Frequencies 1700s 1670s (1Abbreviations very weak.
(cm-l)
1279s 1266s of observed
Appearing
650~ 640~ intensities:
I
after Cocondensation 468~ 457w
569~s 563~s vs, very
of NO*/Ar with IJAr”
strong;
s, strong;
305m 300m m, medium;
(‘*N) (“N) w, weak;
VW,
FORMATIONOF NITRYL BROMIDEAND NITRYL IODIDE
437
TABLE II New Frequencies(cm-l) Appearingafter Cocondensationof NOJAr with Br.JAr” 1723s 1695s 0 Abbreviations very weak.
1239s 1278s of observed
641w 638~ intensities:
588vs 583~s
496m
360m
(‘W
492m
356m
PN)
vs. very strong; s. strong;
m, medium; W. weak; VW,
nitrogen monoxide are observed, whereas nitrosyl bromide is present in comparable larger quantities as in the case of the iodine compound. This is to be expected due to the greater stability of nitrosyl bromide. The decomposition leading to bromine and cis dinitrogen dioxide is much slower. The spectrum again reveals six new bands, different from those of the iodine compounds that can be readily assigned to nitryl bromide. The frequencies are listed in Table II together with those obtained using 15N0, as starting material. For comparison similar experiments were carried out with mixtures of argon and chlorine passing through the discharge tube. The spectrum (Fig. 5b) clearly shows the formation of nitryl chloride and nitrosyl chloride in high yields, other features being nearly identical to the experiment with bromine. Substitution of the argon matrix by a krypton matrix (spectrum Fig. 5a) does not result in frequency shifts in the case of nitryl chloride. DISCUSSION The two formerly known nitryl halides NO,F and NO&l are planar fouratomic molecules with point group symmetry CzO.Six fundamental vibrations, all ir active, TABLE III MolecularVibrationFrequenciesof Nitryl Halogenidesin cm-l”
B Abbreviations very weak.
of observed
:NOp
CINOI('7) CIN02 BrNOl INO
I 309”s
1293~
822”s
794”s
781”s
588”s
569”s
568s
367”s
365m
49&l!
46aw
1791”s
1685~s
1690~s
1723s
1291s
1289s
1279%
1700s
559s
4llw
41&v
360m
305m
742m
651m
65Om
64lW
650~
intensities:
vs. very strong; s, strong; m, medium; w, weak; VW,
438
FEUERHAHN,
MINKWITZ,
AND ENGELHARDT
TABLE IV Main Force Constants of Nitryl Halogenides (mdyn/A) (General Valence Force Field)
fz@Q f,(NW fa(ONW
fdONO) f,
CINOz
BrNOZ
INOz
9,93 2,Ol 0,73 2,05 0,38
951 1,91 0,67 1,91 0,39
9,49 1,87 056 1,87 0,39
are predicted by theory and found in their spectra. Our assignments of bands in the now obtained infrared spectra of nitryl iodide and nitty1 bromide are mainly based on those for nitryl chloride done by Bernitt et al. (27), later confirmed by microwave spectroscopic data (18, 19). Frequency shifts and relative intensities were used as a guide. A summary is given in Table III and Fig. 6. The results are supported by a GVFF calculation (simplified “Kopplungsstufenverfahren” (20)). Frequencies calculated for the 15N containing molecules using the obtained force constants are in very good agreement with our experimental values. Main force constants based on matrix data are given in Table IV for nitryl chloride, bromide, and iodide. ACKNOWLEDGMENTS We wish to thank W. Hilbig for the calculation of force constants and the Fonds der Chemischen Industrie for financialsupport of this work. RECEIVED:
November
27, 1978 REFERENCES
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OF NITRYL
BROMIDE
AND NITRYL
IODIDE
439
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