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The use of 18O substitution in the characterization of MReO4 molecules. The IR spectrum of matrix-isolated CsReO4
Volume 99. number 3
THE USE OF t80 SU~STl~IO~
IN THE C~~CTER~ZAT~O~
THE IR SPECTRUM OF MAT~X-ISOLATED
L. BENCIVENNI
5 August 1983
CHEMICAL PHYSiCS LFXTERS
*_ H.M. NAGARATHNA
OF MRe04 MOLECULES.
CsReOq
and K.A. GINGERICH
Dcparrmmt of Cimnisrry, Texas A Lp.M Uttivcrsiry, CoIiege Station. T~XQS 77813. USA Rcceiwd
IS April 1983: in final form 3 June 1963
Tlxc molceul~r strurturc of g.xscous CsRe04 lxts been studied by mntrb isolrttion IR spectroscopy. The 180 substitution c~periments indhtc a bidentate structure of C zv s? mmetry in t\ I&It tltc perrhenate anion is sli$ttIy distorted from the tctrnhcdr~l gcomctry.
I. introduction
2. Experimental
Alkaii-tttetal perrhenates along with rhenium oxides and oxyhaiides are important molecules responsibie for tfte corrosive transport of rhenium in oxidizing atmosphere at moderately bigb temperature. Mass spectrometric studies have shown that alkali perrhenates are remarkably stable gaseous species [ 1 ,Z]. Spiridinov et al, ]3f have proposed a classical covalent structure for gaseous KReO, in which the alkali metal atont is linked to one oxygen atom, while Ugarov et al. have interpreted the electron diffraction data ofTlKe0, [4] and CsRe04 [Sl in terms of a bidentate model. Only recently the bidcntatc binding has been accepted as the most likely metal cation and oxyanion coordination_ Since the publicatior~ of the JR and Raman spectra of matrix isoIated PZa$Oa and K,SO, [6], we have been concerned witb the spectroscopic characterization of metal coordinated vxyanivns such as X0:(X = S. Cr. MO and W) 173, and AsO- and SbOz [S]. in order to clarify the confusing status on gaseous perrhenatss. hlRe04. and unambiguously determine their molecular structure we have performed a detailed IR spectroscopic study of CsRe04. Since structure deductions are most reliable when based on IR isotopic frequency and band intensity patterns, IsO substitution experiments have been performed to provide_such data.
Commercially available CsReO, (99.999%) has been vaporized at = 770 K from an alumina crucible and the effusing vapours have been isolated in a very dilute N2 matrix at a 13 K. ISO isotopicaliy pure and enriched CsReO, samples have been conveniently prepared from Re2 1807 and I41 lg0 (99% lsO)solutions and Csz IsO or CS~C’~O, as starting materials. Details of our matrix isolation apparatus have been described in 3 previous paper [6] _
* Present Address- istituto di Cltimiw I‘isica, Universit;i di Kom3. Of 16-1 Rome. Italy. 25s
3. Results and discussion The IR spectrun~ of CsReO, isolated in a I$ matrix is shown in fig. fa. It consists of a prominent triplet with &lost identical intensity components at 94&S, 913.6 and S92.7 cnl-i and of a weaker absorption at 969.9 cnl-l. These bands are in the region of the stretching modes p1 (Al) and v3(T2) of the free perrhenate anion typically at 971 and 920 cm-1 respectively [9] - The perrhenate anion is likely to coordinate cesium via two equivalent oxygen atoms as one would expect for ionic vapours. A prelinlinary assignment of the observed bands can be performed by assuming the bidentate structure of C2, symmetry shown in fig. 2. The vl(Al) and v3(T2) stretching modes of the Td ReOg anion are corraleted in the C,, symmetry as vr(Al)and +(A1 f B, + B2) respec-
0 OOS-2614/83/0000-OOOolS
03.00 0 1983 ~o~h-~o~and
5 August 1983
CHEMICAL PHYSICS LETTERS
Volume 99. cumber 3 850
1000
I
crna
originating from the same degenerate vibration are of equal intensity. The tentative assignnlent of the IR spectrum of CsReO4 based on the i&v symmetry has been confirmed by IsO substitution experiments in the present investigation. If **O random substitution occurs in the Cz,, symmetry of CsReO4, nine isotopomers belonging to C,,, CI and Cs symmetries are obtained and their stretching modes are correlated in various symmetries as shown in table 1. Ultimately the 1R spectrum of l*O enriched CsReO4 will consist of thirty-six stretching frequencies, whose bands must follow a typical intensity pattern, The expected IR pattern can be calculated adopting a simplified model to describe the stretching vibrations of the ReOz anion in the C,, symmetry. This model requires the use of FR and F, as principal stretching force constants for the temnnal and bridged ReO$ bonds and of FRR, F, and FR,. as interaction force constants between the terminal, bridged and temlin~-budged bonds, respectively_ The additional constraint is that FRR
Fig. 1. N2 matrix isohted IR spectra of: (a) CsRe04, (b) CsRe1S04 and (c) “0 enriched CsReOg. (d) Calculated line d&ram of t*O enriched CsReO, (50% ‘*O enrichment)_
tively. Thus, the highest frequency of matrix isolated CsRe04 occurring at 9699 cm-l might be the or@nally Raman active vl(A1) mode, which is IR active in the C,v symmetry. The three almost equally intense peaks at 940.8,913.6 and 892-7 cm-’ might be the components of the splitting of the T2 mode. It may be expected that if the coordination of a Td oxyanion does not produce a significant distortion from the tetrahedral geometry, the components of the splitting
,P ,’
\
cs:\ ‘\ ‘0
/
&A0 LO
Fig. 2. C2v symmetry bidentate structure of CsReOe.
’ FRr‘57
-
In order to compute the four stretching frequencies of CsRe1604, various cycles of calculations have been carried out assuming tetrahedral angles for the ReO,anion, The same force field which simulates quite well the vibrations of CsRei604, predicts the observed IR bands of CsRe’*O, (9163, S94,5,868_6 and 848.0 cm -I) less satisfactorily, The agreement between the experimental and calculated frequencies of CsRe1604 and CsRel*O, has been improved adopting a slightly Table 1 ReO, anion stretching vibrations in an IsO substituted CsReO4 molecule Isotopomers
Statistical weight
VibrationaI analysis
Cs’60~Ret60~ Cs180160Re160 Cs’60ZRe’80’6: CS’~O~ Re’“O 2 Cs’60t80Re160180 CS’~O~R~‘~O 2 Cs’*02Rex80160 Cs180x60Re180 2 Cs1802Re180 2
1 2 2 1 4 1 2 2
C,, (2_41 + B, + B1) C, (3.4’ + A”) Cs (3X’ + A”)
1
C2,(=1
+B2”Bl)
Cl (4A) Cl, (?A1 + B2 f B1) ts (3A’ f- A”) Cs (3A’ + A”) C2v (2A1 + Bz + B1)
259
Volume 99. number 3
CHEMICAL
PffYSiCS
distorted ReOg anion with terminal and bridged OReO bond angles as 109* 30’ and I OS”, respectively, and constraining the force constants, in order to minimize the difference between the measured and calculated 160/1s0 isotopic shifts on the ReOq stretching vibrations. This set of force constants has then been used to calculate the stretching frequencies of the mixed G,, CI and C,. The IR isotopic band intensities are evaluated from the well known relationships based on bond moment additivity approximation [lo].
(1)
LIZI-IERS
Table I? Assignment of the observed IR frequencies (cm-‘) substitution in CsReO+ Observed
Calculated a)
969.9
969.8
AI
Cst602Ret60
966.3
968.0
A’
Cs’80160Re160
963.9
966.4
Cs1802Re160
959.1
959.i
AI A’
CS’~O~R~‘~O~~O
956.3 9535
957.8 956.3
A A’
Cs1601sORe160180 Cs’802Re’60180
940.7
BZ A”
Cs’602Re160+
940.s 917.9 920.6
Relations (1) and (2) lead to useful relationships between relative IR band intensities. The calculated isotopic frequencies and intensity patterns are used to simulate the IR spectra of an lsO enriched CsReO, sample. The assignment of the bands of I80 enriched CsReO, is reported in table 3. These calculations anticipate that some vibrations of certain isotopomers occur at identical or almost coincident frequencies and tfiey may result in a single band with reinforced intensity. The most evident predicted overlaps are: the U,-A”+ modes calculated at 940.7 cm-t, the Bt-A”-B,-B,-B2--A” at -892.5 cm-l, the At-A-A’ at 25-4.5 cm-l and the 13, -8, -A” at 846.5 CI~-~. The other possible overlaps arising from closely lying sibrations are: the AI -At -A modes calculated at =91-I cm-l, the A’-A’-A at 2897 cm-f and the A, -A’-A, at 2867 cm-I_ The experimental results confirm these overlaps of the bands. The experimental IR spectra of CsReI*OJ and of the Is0 enriched CsReOq are shown in figs 1b and lc. The calculated line diagram in fig. Id simulates the IR isotopic pattern of ‘“0 enriched CsReO.+, The observed and calculated spectra are in satisfactory agreement. The small differences between the observed and calculated frequencies (see table 2) are due to the use of observed. rather than the hamlonic frequencies of CsRet604 in the calculation to predict the vibrations of the emiched species. They cannot be regarded as significant in view of the adopted simplified model. Our results unequivocally establish for CsRe04 the 260
5 August 1983
930.7
from l*O
Assignment of the vibrations 2
c2v 2
2
CS czv CS
C, Cs Czv
Cs’80’60Re1d0
2
Cs
940.7
B2
CS’~O~R~‘~O~
CIIY
931.0
Al
Cs160zRe1g0
c2v
923.4
A’
Cs160180Re’z02
Cs
i 917.7 9151
A’
Cs160~Re1S0160
CS
Al
Cs1802Re1807
czv
Al A
CS’~O~R~=O;
c2v
Cs160180Re160180
C1
A’
Cs180160Re160~
Cs
913.6
913.7
906.7
i 910.2 905.7
904.5
901.3
A’
Cs’80~Re160180
901.2
9OOJ
Cs’602Re180
896.5
Al A;
696.8
A’
CS~~O~R~~~O*~O
[ S96-3
A
Cs160180Re160180
Cs C1
S92.6
Bl A”
CS’~O~RC’~O~
czv
S92.6 592.6
896.3
s93.3
S67.4
S56.2
646.3
Cs 2
Cs160180Re1s0
czv 2
cs
CS’~O, Re180t60
CS
81
Csr60;Rers02
c 2V
s92.3
B2
CS~~O,R~~~O,
S9X3
B2
Cs’602Re180
I 592.3 S67.6
A”
Cs’60180Re’80
Al
CS’~O~R~‘~O
866.9
A’
Cs’802Re160tS0
i 866.3
Cs180,Re’80
654.6
AI A’
854J
A
Cs160180Re160180
[ 651.4
A’
Cs1601sORe180
BI
Csrs02
RI A”
Cs1802Re160
C7v 2 2 2
Cs*802Re1601S0
G czv
Cs 2
Cs180160Re160
Re”O
C2v
C2V
1
2
CS C1 G
2
c2v
2
CJV
Cs
a) Force constans (mdyne!A): FR = 7.908. F, = 7.156, Fm = 0.385, FRY = 0.361 and Frr=0.361_OReO bond angles: ~09°30’(tem~~~l) and 103” (bridged).
bidentate structure shown in fig_ 2. The electron diffraction studies on TIReO, [43 and CsReO, E.51by Ugarov et al. are consistent with our conclusions, which
Volume 99, rmmber 3
CHEMICAL PHYSICS LEXTERS
cast serious doubts an the earlier investigation on RReOq by Spiridanov et al. [3f and thus make a systematic invest&&%x2on ail the alkali perrhena@S d&ral&z Such a systematic ~ves~~~~~ is in progress.
The support of this w&c by the Robert A. W&h Found&km under Grant A-387 is gratefully acknowIedged.
Referettcos [I ] Kc,Skudlarski, J. &“owart, G. Essteen and A, Vander Auwen-Malilieu, Trans. Faraday Sot. 63 (1967) 1146.
5 Auast
1983
[2] I& Skudiarski, Roczniki Cbemii 47 (1973) I61 I. [3] VP. Spiridonov, AX Kbodcbenkov and F.A_ Akisbio. V&n. hliosk Unk 6 (1965) 34_ {4] XM. Roddatis, SM. Totmaebev, V-V, Ugtrov, Yu.S. Ezhov and N.G. Rambidi, Zb. Strukt- RhIm, 15 (1974) 693. fS] K.P* Petrov, V-V. Ugarov and N.G. Rambidi, Zb, Strukt. Kbim. 2f (1980) IS9_ t6] R&i. Atkinsnnd EEA. Ginger%&,Chem. Pbys. Letters 53 (1978) 341. [7 f H_hI. Na_pratlma, K.AA.Gingericb and L. Bencivermi, .I_ Cbem. Pbys. submitted for publication. IS] L. BencIverml and K_A. Gingericb, J. Mol. Struct., to be published. [9] I?. Gonzalez-Vilcbez and W.P. CrifXth, J. Chem. Sot. Dalton (1972) 1416. [IO] E,B. Wilson Jr., 3.C Decius and PC Cross, Molecular vibrations. The theory of infrared and Raman vibrational spectra (12over, New York, 1980).
THE USE OF t80 SU~STl~IO~
IN THE C~~CTER~ZAT~O~
THE IR SPECTRUM OF MAT~X-ISOLATED
L. BENCIVENNI
5 August 1983
CHEMICAL PHYSiCS LFXTERS
*_ H.M. NAGARATHNA
OF MRe04 MOLECULES.
CsReOq
and K.A. GINGERICH
Dcparrmmt of Cimnisrry, Texas A Lp.M Uttivcrsiry, CoIiege Station. T~XQS 77813. USA Rcceiwd
IS April 1983: in final form 3 June 1963
Tlxc molceul~r strurturc of g.xscous CsRe04 lxts been studied by mntrb isolrttion IR spectroscopy. The 180 substitution c~periments indhtc a bidentate structure of C zv s? mmetry in t\ I&It tltc perrhenate anion is sli$ttIy distorted from the tctrnhcdr~l gcomctry.
I. introduction
2. Experimental
Alkaii-tttetal perrhenates along with rhenium oxides and oxyhaiides are important molecules responsibie for tfte corrosive transport of rhenium in oxidizing atmosphere at moderately bigb temperature. Mass spectrometric studies have shown that alkali perrhenates are remarkably stable gaseous species [ 1 ,Z]. Spiridinov et al, ]3f have proposed a classical covalent structure for gaseous KReO, in which the alkali metal atont is linked to one oxygen atom, while Ugarov et al. have interpreted the electron diffraction data ofTlKe0, [4] and CsRe04 [Sl in terms of a bidentate model. Only recently the bidcntatc binding has been accepted as the most likely metal cation and oxyanion coordination_ Since the publicatior~ of the JR and Raman spectra of matrix isoIated PZa$Oa and K,SO, [6], we have been concerned witb the spectroscopic characterization of metal coordinated vxyanivns such as X0:(X = S. Cr. MO and W) 173, and AsO- and SbOz [S]. in order to clarify the confusing status on gaseous perrhenatss. hlRe04. and unambiguously determine their molecular structure we have performed a detailed IR spectroscopic study of CsRe04. Since structure deductions are most reliable when based on IR isotopic frequency and band intensity patterns, IsO substitution experiments have been performed to provide_such data.
Commercially available CsReO, (99.999%) has been vaporized at = 770 K from an alumina crucible and the effusing vapours have been isolated in a very dilute N2 matrix at a 13 K. ISO isotopicaliy pure and enriched CsReO, samples have been conveniently prepared from Re2 1807 and I41 lg0 (99% lsO)solutions and Csz IsO or CS~C’~O, as starting materials. Details of our matrix isolation apparatus have been described in 3 previous paper [6] _
* Present Address- istituto di Cltimiw I‘isica, Universit;i di Kom3. Of 16-1 Rome. Italy. 25s
3. Results and discussion The IR spectrun~ of CsReO, isolated in a I$ matrix is shown in fig. fa. It consists of a prominent triplet with &lost identical intensity components at 94&S, 913.6 and S92.7 cnl-i and of a weaker absorption at 969.9 cnl-l. These bands are in the region of the stretching modes p1 (Al) and v3(T2) of the free perrhenate anion typically at 971 and 920 cm-1 respectively [9] - The perrhenate anion is likely to coordinate cesium via two equivalent oxygen atoms as one would expect for ionic vapours. A prelinlinary assignment of the observed bands can be performed by assuming the bidentate structure of C2, symmetry shown in fig. 2. The vl(Al) and v3(T2) stretching modes of the Td ReOg anion are corraleted in the C,, symmetry as vr(Al)and +(A1 f B, + B2) respec-
0 OOS-2614/83/0000-OOOolS
03.00 0 1983 ~o~h-~o~and
5 August 1983
CHEMICAL PHYSICS LETTERS
Volume 99. cumber 3 850
1000
I
crna
originating from the same degenerate vibration are of equal intensity. The tentative assignnlent of the IR spectrum of CsReO4 based on the i&v symmetry has been confirmed by IsO substitution experiments in the present investigation. If **O random substitution occurs in the Cz,, symmetry of CsReO4, nine isotopomers belonging to C,,, CI and Cs symmetries are obtained and their stretching modes are correlated in various symmetries as shown in table 1. Ultimately the 1R spectrum of l*O enriched CsReO4 will consist of thirty-six stretching frequencies, whose bands must follow a typical intensity pattern, The expected IR pattern can be calculated adopting a simplified model to describe the stretching vibrations of the ReOz anion in the C,, symmetry. This model requires the use of FR and F, as principal stretching force constants for the temnnal and bridged ReO$ bonds and of FRR, F, and FR,. as interaction force constants between the terminal, bridged and temlin~-budged bonds, respectively_ The additional constraint is that FRR
Fig. 1. N2 matrix isohted IR spectra of: (a) CsRe04, (b) CsRe1S04 and (c) “0 enriched CsReOg. (d) Calculated line d&ram of t*O enriched CsReO, (50% ‘*O enrichment)_
tively. Thus, the highest frequency of matrix isolated CsRe04 occurring at 9699 cm-l might be the or@nally Raman active vl(A1) mode, which is IR active in the C,v symmetry. The three almost equally intense peaks at 940.8,913.6 and 892-7 cm-’ might be the components of the splitting of the T2 mode. It may be expected that if the coordination of a Td oxyanion does not produce a significant distortion from the tetrahedral geometry, the components of the splitting
,P ,’
\
cs:\ ‘\ ‘0
/
&A0 LO
Fig. 2. C2v symmetry bidentate structure of CsReOe.
’ FRr‘57
-
In order to compute the four stretching frequencies of CsRe1604, various cycles of calculations have been carried out assuming tetrahedral angles for the ReO,anion, The same force field which simulates quite well the vibrations of CsRei604, predicts the observed IR bands of CsRe’*O, (9163, S94,5,868_6 and 848.0 cm -I) less satisfactorily, The agreement between the experimental and calculated frequencies of CsRe1604 and CsRel*O, has been improved adopting a slightly Table 1 ReO, anion stretching vibrations in an IsO substituted CsReO4 molecule Isotopomers
Statistical weight
VibrationaI analysis
Cs’60~Ret60~ Cs180160Re160 Cs’60ZRe’80’6: CS’~O~ Re’“O 2 Cs’60t80Re160180 CS’~O~R~‘~O 2 Cs’*02Rex80160 Cs180x60Re180 2 Cs1802Re180 2
1 2 2 1 4 1 2 2
C,, (2_41 + B, + B1) C, (3.4’ + A”) Cs (3X’ + A”)
1
C2,(=1
+B2”Bl)
Cl (4A) Cl, (?A1 + B2 f B1) ts (3A’ f- A”) Cs (3A’ + A”) C2v (2A1 + Bz + B1)
259
Volume 99. number 3
CHEMICAL
PffYSiCS
distorted ReOg anion with terminal and bridged OReO bond angles as 109* 30’ and I OS”, respectively, and constraining the force constants, in order to minimize the difference between the measured and calculated 160/1s0 isotopic shifts on the ReOq stretching vibrations. This set of force constants has then been used to calculate the stretching frequencies of the mixed G,, CI and C,. The IR isotopic band intensities are evaluated from the well known relationships based on bond moment additivity approximation [lo].
(1)
LIZI-IERS
Table I? Assignment of the observed IR frequencies (cm-‘) substitution in CsReO+ Observed
Calculated a)
969.9
969.8
AI
Cst602Ret60
966.3
968.0
A’
Cs’80160Re160
963.9
966.4
Cs1802Re160
959.1
959.i
AI A’
CS’~O~R~‘~O~~O
956.3 9535
957.8 956.3
A A’
Cs1601sORe160180 Cs’802Re’60180
940.7
BZ A”
Cs’602Re160+
940.s 917.9 920.6
Relations (1) and (2) lead to useful relationships between relative IR band intensities. The calculated isotopic frequencies and intensity patterns are used to simulate the IR spectra of an lsO enriched CsReO, sample. The assignment of the bands of I80 enriched CsReO, is reported in table 3. These calculations anticipate that some vibrations of certain isotopomers occur at identical or almost coincident frequencies and tfiey may result in a single band with reinforced intensity. The most evident predicted overlaps are: the U,-A”+ modes calculated at 940.7 cm-t, the Bt-A”-B,-B,-B2--A” at -892.5 cm-l, the At-A-A’ at 25-4.5 cm-l and the 13, -8, -A” at 846.5 CI~-~. The other possible overlaps arising from closely lying sibrations are: the AI -At -A modes calculated at =91-I cm-l, the A’-A’-A at 2897 cm-f and the A, -A’-A, at 2867 cm-I_ The experimental results confirm these overlaps of the bands. The experimental IR spectra of CsReI*OJ and of the Is0 enriched CsReOq are shown in figs 1b and lc. The calculated line diagram in fig. Id simulates the IR isotopic pattern of ‘“0 enriched CsReO.+, The observed and calculated spectra are in satisfactory agreement. The small differences between the observed and calculated frequencies (see table 2) are due to the use of observed. rather than the hamlonic frequencies of CsRet604 in the calculation to predict the vibrations of the emiched species. They cannot be regarded as significant in view of the adopted simplified model. Our results unequivocally establish for CsRe04 the 260
5 August 1983
930.7
from l*O
Assignment of the vibrations 2
c2v 2
2
CS czv CS
C, Cs Czv
Cs’80’60Re1d0
2
Cs
940.7
B2
CS’~O~R~‘~O~
CIIY
931.0
Al
Cs160zRe1g0
c2v
923.4
A’
Cs160180Re’z02
Cs
i 917.7 9151
A’
Cs160~Re1S0160
CS
Al
Cs1802Re1807
czv
Al A
CS’~O~R~=O;
c2v
Cs160180Re160180
C1
A’
Cs180160Re160~
Cs
913.6
913.7
906.7
i 910.2 905.7
904.5
901.3
A’
Cs’80~Re160180
901.2
9OOJ
Cs’602Re180
896.5
Al A;
696.8
A’
CS~~O~R~~~O*~O
[ S96-3
A
Cs160180Re160180
Cs C1
S92.6
Bl A”
CS’~O~RC’~O~
czv
S92.6 592.6
896.3
s93.3
S67.4
S56.2
646.3
Cs 2
Cs160180Re1s0
czv 2
cs
CS’~O, Re180t60
CS
81
Csr60;Rers02
c 2V
s92.3
B2
CS~~O,R~~~O,
S9X3
B2
Cs’602Re180
I 592.3 S67.6
A”
Cs’60180Re’80
Al
CS’~O~R~‘~O
866.9
A’
Cs’802Re160tS0
i 866.3
Cs180,Re’80
654.6
AI A’
854J
A
Cs160180Re160180
[ 651.4
A’
Cs1601sORe180
BI
Csrs02
RI A”
Cs1802Re160
C7v 2 2 2
Cs*802Re1601S0
G czv
Cs 2
Cs180160Re160
Re”O
C2v
C2V
1
2
CS C1 G
2
c2v
2
CJV
Cs
a) Force constans (mdyne!A): FR = 7.908. F, = 7.156, Fm = 0.385, FRY = 0.361 and Frr=0.361_OReO bond angles: ~09°30’(tem~~~l) and 103” (bridged).
bidentate structure shown in fig_ 2. The electron diffraction studies on TIReO, [43 and CsReO, E.51by Ugarov et al. are consistent with our conclusions, which
Volume 99, rmmber 3
CHEMICAL PHYSICS LEXTERS
cast serious doubts an the earlier investigation on RReOq by Spiridanov et al. [3f and thus make a systematic invest&&%x2on ail the alkali perrhena@S d&ral&z Such a systematic ~ves~~~~~ is in progress.
The support of this w&c by the Robert A. W&h Found&km under Grant A-387 is gratefully acknowIedged.
Referettcos [I ] Kc,Skudlarski, J. &“owart, G. Essteen and A, Vander Auwen-Malilieu, Trans. Faraday Sot. 63 (1967) 1146.
5 Auast
1983
[2] I& Skudiarski, Roczniki Cbemii 47 (1973) I61 I. [3] VP. Spiridonov, AX Kbodcbenkov and F.A_ Akisbio. V&n. hliosk Unk 6 (1965) 34_ {4] XM. Roddatis, SM. Totmaebev, V-V, Ugtrov, Yu.S. Ezhov and N.G. Rambidi, Zb. Strukt- RhIm, 15 (1974) 693. fS] K.P* Petrov, V-V. Ugarov and N.G. Rambidi, Zb, Strukt. Kbim. 2f (1980) IS9_ t6] R&i. Atkinsnnd EEA. Ginger%&,Chem. Pbys. Letters 53 (1978) 341. [7 f H_hI. Na_pratlma, K.AA.Gingericb and L. Bencivermi, .I_ Cbem. Pbys. submitted for publication. IS] L. BencIverml and K_A. Gingericb, J. Mol. Struct., to be published. [9] I?. Gonzalez-Vilcbez and W.P. CrifXth, J. Chem. Sot. Dalton (1972) 1416. [IO] E,B. Wilson Jr., 3.C Decius and PC Cross, Molecular vibrations. The theory of infrared and Raman vibrational spectra (12over, New York, 1980).