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Structural investigation of indium halide compounds: Single crystal Raman study of monohydrated potassium hexachloroindate
058b8539/81/121021-07$02.00/0 @ 1981 Pergamon Press Ltd.
Specrrochimica Ado, Vol. 37A. No. 12, pp. 1021-1027, 1981 Printed in Great Britain.
Structural investigation of indium halide compounds: single crystal Raman study of monohydrated potassium hexachloroindate A, LORRIAUX-RUBBENS and F. WALLART Laboratoire de Spectrochimie Infrarouge et Raman, C.N.R.S., UniversitC des Sciences et Techniques de Lille, Bit. C.5, 59655 Villeneuve d’Ascq Cedex, France and
J. P. WIGNACOURT*, P. BARBIER and G. MAIRESSE Laboratoire de Cristallochimie et de Physicochimie du Solide, Universitt des Sciences et Techniques de Lille, BLt. C.8, 59655 Villeneuve d’Ascq Cedex, France (Received 24 March 1981) Abstract-The Raman spectrum of KJnC&, Hz0 single crystal is assigned on the basis of the crystal structure knowledge. The main feature is the splitting of the V, vibrational band into two components, that are assigned in relation to the indium site occupation ratio. In Raman spectroscopy, the superposition of the internal mode frequency range (characteristic of different anionic species), does not contribute to any improvement of the ionic isomerisation found by X-ray investigation. INTRODUCTION crystal structure determination of K31nC16, H,O [l] showing the existence of an ionic isomerism, makes it interesting to investigate this compound by spectroscopic methods, and first by spectroscopy. In the literature, molecular
The
numerous works related to InC&,- vibrations [2lo] and done as well in Raman scattering as in i.r. absorption, mainly concern solution studies and they only report the spectrum bands assigned to the fundamentals of the In&anion. The knowledge of the K31nCl,, H,O structure enable us to propose a complete assignment of the Raman spectrum of oriented single crystal at both room and liquid nitrogen temperature.
anions are located InC&respectively: 8[In(l)Cl$ in 8d (C,) sites, and 4[In(2)Cl$ in 4c (&) sites, but the two remaining In(3) atoms, in 2a(C4,) sites are surrounded each by five Cl and one 0 atoms, the global geometry[l] being intermediate between the octaedral (InCl,, H,O)‘- and the square pyramidal (InCI,)‘~ anions. The K31nCl, stoichiometry is matched with the location of two disordered Cl atoms in a 8d position. (b) Raman scattering study of K,InC&, H,O Internal modes. The (InCl,, H,O)‘- cluster proportion being l/6, the crystal Raman spectrum is mainly characteristic of the (InCl,)3m anions. In the isolated state (InC1,)3m has Oh symmetry, with a vibration distribution given by
EXPERIMENTAL (a) Preparation Single crystals of K,InC&, Hz0 are obtained by slow evaporation of aqueous solutions of lab-made InCI, and reagent grade KCI, in appropriate molecular ratio, as shown in the ternary solubility diagram InCI,-KClH,O[ll-121. (b) Molecular spectroscopy Raman spectra are recorded using a triple monochromator spectrometer built in our laboratory[l3]. The spectra are obtained using the 514.5 nm exciting line of a Spectra Physics ionized Argon Laser. The studies of air stable K,InCl,, Hz0 single crystals are done at room and nitrogen temperatures. 1.r. spectra are recorded on Perkin-Elmer 225 spectrometer, and in the low frequency region, on a FS 2000 Coderg Fourier Transform Spectrometer.
(a) Crystallographic
RESULTS results
K,InCl,, H,O crystallizes in the tetragonal system with 2 = 14 in space group I 4 mm (Cz.); *To whom correspondence
should be addressed.
rvib = A,,(R) + E,(R) + 2F,,(i.r.)
on group theoretical considerations. The Raman spectrum of a K31nC16, H,O aqueous solution shows the three active modes: a strong polarized band at 291 cm-’ (A,, mode) and two weak and depolarized ones at 150 and 129cm-‘, respectively assigned to the E, and F,, species. As for the two F,. i.r. active modes, they are given in the literature at about 250 and 160 cm-‘. In solid state, the anions are singularized by different orientations and site symmetries; we have tried to identify their respective vibration modes, taking into account their crystal environment. (1) Raman study of the [In(l)C1,13- anion located in 8c(C,). From the crystallographic data, we can establish the correlation table using the Halford method[l4]; this analysis shows (Table 1) that the v,(A,,) frequency band splits into three A,, B, and
1021 SAA Vol. 37A. No. 12-A
+ F,,(R) + F,,
A. LORRIAUX-RUBBENSetal.
1022
Table 1. Correlation table for the [In(l)Cl.$ MOLECULAR GROUP Oh
SITE GROUP CS $1
Ak
anion in the 8c site FACTOR GROUP %"
*
2
22 +Y,Z
A2g E g
F2g A
2 x
2 -Y
lu
E lines; that vz(Eg) one splits into six species: 2A1 +2&+2E and that vs(Fzs) one gives nine components: A, + Bz + E -t 2A, + 2 B, + 2E. The site effect and the intermolecular coupling make the v3, v4 (F,.) and v6 (&) bands active, each of them splitting into nine species: 2A, -t 2B, + 2E + A,+B,+E. On the [In{ 1)Cls]3- crystal environment representation (Fig. l), the axial chlorine atoms (Cl 1.1) are surrounded by four K’ cations ranging from 3.147 to 3.451 A, but the equatorial ones anly have three neighbouring K’, between 3.140 and 3.372 A. Moreover, the following interionic bond
Fig. 1. Environment of the [In( l)Cl,J3- anion in the crystal 5tructure.
Cl( 1.4)-O(3) = 3.248 A; Cl( 1.2)-O(4) = lengths: 3.189 A; C1(1.5)-0(4) = 3.201 A, are shorter than the sum of the oxygen and chlorine atoms Van der Walls radii (3.28 A), and presumably characterize O-H.. .Cl hydrogen bonds as in the KJnCG, HZ0 example [ 151. From these structural informations a detailed assignment of the we propose [In( I)Cl,]‘- vibrational modes. The v, frequency of A,, species in the isolated ion is identified at 291 cm-’ in aqueous solution. The main characteristic of the single crystal Raman spectra (Fig. 2) is the existence of two strong bands located at 288 and 274cm-’ at room temperature, which shift to higher frequency respectively 292 and 277 cm-’ at values, 80 K. As the symmetrical stretching frequency value is considered to be representative of equatorial In-Cl bonds, the differences[l] observed between these bond lengths are not marked enough to explain the existence of the two bands. The [In( l)Cl,]“- anion lies approximately between two K’ planes, which barely affect the stretching motions of the In(1 )-Cl bonds in the equatorial plane quite logically then, we get a frequency value quite close to the one obtained for the sample in aqueous solution. Thus, we assign the 288 cm-’ band (292 cm-’ at 80 K) to v,In(l)-Cl frequency. The E, mode relative to the v2 frequency is found at ISOcm- on the aqueous solution spectrum, and represents the antisymmetric stretching motion of In-Cl bonds. As for vI, the K’ interactions are weak and barely affect the vibration and we localize this mode at 162cm-’ at room
1023
Structural investigation of indium halide compounds -
100
Fig. 2. Raman spectra
of K,InC16, Hz0 single crystal temperature.
(162 and 168 cm-’ at 80 K with the intermolecular coupling effect). The F,, mode of the vj frequency implies a motion of the In (I) central atom; its value is about 250cm-’ in the literature. We note that two weak bands located at 227cm-r and 188 cm-’ (room temperature) shift to higher frequency values when the temperature decreases respectively 232 and 194 cm-’ at 80 K. As the same phenomenon is noted for the A,, species, and the [In(l)Cl$ clusters being the most numerous in the unit cell: 8 we assign this mode to the strongest band, with the highest frequency value. The second F,, species relative to vq is given at about 160cm-’ in the literature, and corresponds to out of the plane deformations. It is not so sensitive to K’ environmental effects as the stretching motions, which explains why it is localized at 168-169 cm-’ (80 K). The v5 frequency (Fzg mode) is found at 129cm-’ on the aqueous solution Raman spectrum. On the crystal one, it is located at 149cm-’ at liquid nitrogen temperature. The last fundamental v6 (F2J is given at different calculated values[S, 8, lo] from 94 to 130 cm-‘. At 80 K, it is identified as weak bands at 116-125 cm-‘. (2) Raman study of the [In(2)Cls13- anion in 4b sites (C,,). The correlation table (Table 2) established by the Halford method, led to the theoretical numbering. The A,, mode gives two components A, + B,; the E, mode splits into four: A, + B, + A, + Bz; the Fzg species splits into four: A, + B, +2E;
temperature
300
200 A i, cm-'
in the low frequency
range at ambient
each of the Flu modes leads to four lines: A, + B, + 2E, as well as Fzu, which gives: A2 + B1 + 2E. The crystal environment of the [In(2)Cl$ anion appears on the Fig. 3. The chlorine-potassium coordination number is 4 for the axial chlorine atoms [C1(2-1) and C1(2-2)] and 5 for the equatorial ones. As for [In(l)ClJpreviously described, the differences between the bond lengths within the [In(2)C16]3- anion are not important enough to explain the double band of the A,, mode at 288 and 274 cm-’ (room temperature). The K, atom, lying in the equatorial plane of the [In(2)Cl6]‘- cluster, is approximately in the In(2)Cl (2.3) direction, at 3.131 A of it. This localization of K, atom strongly affects the equatorial bond stretching motions and explains why the A,, mode frequency value is weaker. Thus, in this cluster, the 274cm-’ line is assigned to v,(In-Cl), two components of which A, and B, are identified at
K5 B/O00
I’
\ -------
Fig. 3. Environment of the [In(2)C&]‘- anion in the crystal structure.
A. LORRIAUX-RUBBENS et al.
1024
Table 2. Correlation table for the [In(2)C&13- anion in the 4b site rlOLECULARGROUP Oh
SITE GROUP c2”
FACTOR GROUP C4”
((J”)
Alg A2g E g Fig F2g A
lu
A2” E” Flu F2u
277 cm-’ at 80K. The antisymmetric stretching vibration of E, mode, is here more affected by the cationic surrounding than in [In(l)C&]3-. When this vibrational mode is concerned, we have previously shown[l5] that the perturbation effect and the frequency value vary in the same way; using the depolarization ratio measurements on the bands of an oriented crystal Raman spectra, at 80 K, we can localize the species at 177 cm-‘. The v3 frequency (F,, species) corresponds to an ‘umbrella’ motion including the In(2) central atom. It is sensitive to the K’ environment, and is more affected here than the corresponding one in [In(l)Cl$. This mode is assigned to the weak band noted at 188 cm-’ at room temperature. The chlorine-potassium interactions being identical for the different anionic clusters affected by out of the plane deformation, we identify the second F,, mode at the same value (168-169 cm-’ at 80 K) as the corresponding one in the [In( I)Cl,]‘ion. For the F,, mode (v5 vibration), the deformation in the equatorial plane is only disturbed by the K( 1) atoms, whereas those in the two other perpendicular planes are strongly affected by the K(2), K(3), K(4), and K(5) ions. Taking into account these interactions and the depolarization ratio measurements, we assign the A, and B, components at the 141 cm-’ frequency value, and the E ones at 134 cm-’ at 80 K. The cationic surrounding equally concerns the twisting motion of the Fzu mode in the [In(l)ClJ3and [In(2)Cl,]‘- clusters; we consequently localize
the corresponding band at 122 cm-’ at liquid nitrogen temperature. (3) Raman study of the [In(3)C15, H20]*- cluster in a 2a site (Cd”). The O(l)H, water molecule included in the In(3) coordination octaedron, is not concerned by interactions like hydrogen bonding; the shortest interanionic distance is 0(1 jCl( 1.2) = 3.509 A. Thus the water molecule can be said to be ponctual and the [In(3)CI,, H,O]‘- symmetry is C,,,. The fundamental vibrations are given by I’, = 4A,(R, i.r.) + 2&(R) + B,(R) + 4E(R, i.r.). As the molecular group, site group and factor group symmetries are identical; C.,,, there is no site and intermolecular coupling effects. Figure 4 shows the cationic surrounding of the
K3 4,000
Fig. 4. Environment
K3 5/000
of the [In(3)C15H20]‘- anion in the crystal structure.
Structural investigation
[In(3)Cl,, OH,]‘- anion; the Cl-K coordination number is 4 for the equatorial chlorine atoms and 0 for the axial one [C1(3.1)-K(3) = 4.648 81. The [In(3)Cl,, H,O]‘- anion proportion in the unit cell is weak
DnWL
H201zm =1
[InC1,13-
6’
Thus we should not expect observing the characteristic bands of the In(3)-O(1) bond, the strongest one being v, (In-O), given at 360 cm-’ in literature[lS, 161. The existence of the very strong band on the spectrum at 288 cm-’ hinders the obtainment of this v,(In-0) band owing to 360 cm-’ spectral region. Thus we mainly try to identify the InC&- vibration modes. In the C.,” symmetry group, three modes A, + E are due to the existence of the In(3)-O(1) bond in the [In(3)ClS, OH,]*- cluster and come from the F,, and Fzg species in the 0, symmetry group. When these modes are neglected, we take into account the anion orientation in the unit cell, and the correlation between the O,, and C,, groups is given by O,,:A,p
&:A,
E,
A,
F,.
E
B,
I 3350
A,
F,.
Kg
E
&
I 3400
Ku
B,
E
1025
of indium halide compounds
The stretching vibrations of the equatorial ln(3)Cl bonds are slightly less disturbed than those of [In(2)C1,13-, the K’ ions lying in bisector planes of Cl-In(3)-Cl angles. Furthermore, the existence of a water molecule at 2.278 A of In(3) can create important interactions. It is quite logical then to assign the v, In(3)-Cl vibration at the same value 274 cm-’ (room temperature) as v, In(2)-Cl frequency. Two bands are assigned to symmetrical stretching vibrations in the different clusters: 288 and their intensity ratio is: and 274 cm-‘, (I(288 cm-‘)/I(274 cm-‘)) = 8/6 in the spectrum keeping the A, modes unchanged. This 8/6 value is also found in the crystallographic occupation site ratio of the different clusters: (8In(1)/4In(2) + 2In(3)). This corroborates the proposed assignments and this ratio value is kept at liquid nitrogen temperature. The v,,(In-Cl) are equally disturbed in the In(3)ClS2- and In(2)C&- clusters, the two A, and B, components of the E, mode are located at 177 cm-‘. The ‘umbrella’ bending motion of the F,, mode (vJ is quite perturbed both by the C1(3.2)-K interactions and the water molecule; the resulting perturbation being found similar to those received by [In(2)C1,]3-, we identify the E mode at 194 cm-’ (80 K). The vibration frequency of the [In(3)Cl,]‘pyramid, equivalent to vq (second F,, mode in the O,, symmetry group) is concerned by the same
I 3450
3500
A V,
Fig. 5. Raman spectra of K&C&, Hz0 in the Hz0 fundamental The Y, and v3 frequency
3550
Cm-’
region at ambient temperature. range. (b) The v2 frequency.
(a)
A. LORRIAUX-RUBBENSet al.
1026
Table 3. Proposed assignment for the internal modes of K31nC&, Hz0 single crystal CryardloBraphic
of the
sir*
central
Imlaccd
ion
Sit*
affect
Intermlecul~r
couplinB
Valuer
A,
+ I2
l
E
292 cm-’
A, * az + L A,
In(l)
in
8c
+ E
I62
l
B2 + E
232
em
l
B2 + E
232
cm
+ 11, + E
232
em-’
* B2
l
168
and
169
cm-’
.
12
+ E
168.and
I69
l
B,
169
cm-’ -I cm
L
I68
and
I69
+ B,
+ E
I09
cm
+ B,
+ E
-1 149 cm II6
B2 + E
l
277 z
ICI(~)
in
2a
interactions
cm-’ -I
cm-I
-I I94 cm 194 cm-I
BI
-1
E
I94
+ BI E
168 and 168 and
169 cm-’ 169 cm-1
E
I68
169
+ Bl E
-I I4 I CID -I 134 CIQ
E
136
CD
and
-I cm
a-’
122 cm-’
2
E
122
E
122 cm-’
Al
277 cm-’
cm-’
CBv
5
5
I
-1 177 cm
Al
x
Bl
-u 177 cm-’
E
E
PA
5 E
E
Pzg-B2
B2
B2
B,
Bl
P2”
E
IS
Flu-B
122 cm-’
2
l B
EB
md
177 cm 177
E
%g-
-I
I25 end 122 cm-’ -I 122 cm
+ E
II
+B
*
-I
+ E
l
s
-I
+ B2 + E
+ 81
Correlation
-I
12
+ 8,
4b
em
l
l
in
I68
-I cm
+ B2 + E
III(Z)
frequmcy
Propomd
modem
aCOI
as the [In(l)Cl$ and [In(2)CM3anions; so the A, and E components are located at 168-169 cm-‘. As for the K atoms lying in the bissector planes of the C1(3.2)-In(3)-Cl(3.2) angles, they strongly affect the cissor motion of the InClsz- pyramid,
196 cm-I -I I68 cm 169 cm-1 -I33
El
-I
122 cm-’ 122 cm-I
corresponding to the vs(FZy) vibration in the O,, group. A Bz species is identified at 134 cm-’ @OK). The B, and E components of the twisting mode is assigned at 122 cm-‘. The proposed assignment is summarized in Table 3.
1027
Structural investigation of indium halide compounds
External modes. The expected lattice modes are: lSA, + lOA, + 9B, + 14B, + 27E. On the Raman spectra some species are noted at 80 K: A, + &(17 cm-‘), E (59 cm-‘) assignable to translation modes and B2 (195 cm-‘), A, + B, + E (300 cm-‘) for the libration ones. The existence of the internal mode spectrum in the low frequency range makes it impossible to observe more lattice modes.
(c) Spectroscopic studies of water in K,InC&, H,O The existence of different water molecules is suggested by a critical look on the interionic distances from the crystallographic data [ 11 O(1) belongs to a coordinated water molecule but is in too small quantity in the unit cell (l/6) to identify its vibrations on the Raman spectrum O(2), O(3) and O(4) are part of hydration water. But, if O(2) and O(4) are presumably concerned by hydrogen bonding, O(3) is free of any linkage in the crystal. According to Nakamoto [ 171 the hydration water, in i.r. absorption, is characterized by the stretching frequencies of O-H bond about 355032OOcm-‘, the bending one appearing at 16001630cm-‘. On the i.r. spectrum of KJnCl,, H,O polycrystalline sample, we observe a double band corresponding to the bending vibration of water, at 1607 and 1635 cm-‘, and an asymmetric large band about 3450cm-‘. On a single crystal Raman spectrum (Fig. 5), we find once more a double line at and also two bands at 1602 and 1636cm-‘, 3442 cm-’ and 3484 cm-’ in the v,(O-H) frequency region, with intensities ratio value I(3484 cm-‘) _ I( 1602 cm-‘) _ 2 I(3442 cm-‘) - I( 1636 cm-‘) also obtained
by the site occupation
ratio
8 40(2) + 40(4) 40(3) = 5 = 2. Thus, the 3484 and 1602 cm-’ frequency values are assigned to the H,0(2) and H,0(4) molecules involved in H-bonding, and the 3442 and 1636 cm-’ to the Hz0(3) molecules. From the weakasymmetric shape of the highest band at 3510 cm-‘, we identify v,,(O-H) vibration. In the low frequency range, two libration modes are observed at room temperature a wagging one at 626 cm-’ and the rocking one at 429 cm-‘. This vibrational spectroscopy study of the water molecules is summarized in Table 4. CONCLUSION
The KJnCl,, H,O crystal structure knowledge enables us to propose a complete assignment of its
Table 4. Raman and i.r. frequency values obtained for the water molecules in K?InCl&, Hz0
Infrared
Raman
assignment
3510
"_
3484
v (O-H) in O(Z)-H2 a;d 0(4)-H*
3400
3442
us (O-H) in 0(3)-H*
1635
1602
6 (H 0) in H200) and A20(4)
1607
1636
630
626
0
wagging
429
P
rocking
3500
(O-H)
(H20) in H20(3)
low frequency Raman spectrum, the main characteristic being the v, doublet assigned according to the indium site occupation ratio. Moreover vibrational molecular spectroscopy clearly shows the existence of different types of water molecules in the compound. Unfortunately, in this method, the superposition of the characteristic frequency range of the InCls3- and (InCl,, H,O)‘- anions, as well as their relative concentration, does not enable any improvement of the ionic isomerization proposed in the radiocrystallographic study. REFERENCES
[l] J. P. WIGNACOURT,G. NOWOGROCKI,G. MAIRESSEet P. BARBIER,Reo. Znorg. Chem. 2, 207 (1980). [2] L. A. WOODWARDand M. J. TAYLOR, J. Chem. Sot. 4473 (1960). [3] T. BARROWCLIFE,I. R. BEATIE, P. DAY and K. LIVINGSTONE.J. Chem. SOL. A 1810 (1967). [4] D. M. ADAM; and D. M. MORRIS, J. ‘Chetk. Sot., A 694 (1968). [5] M. N. AVATSHI and M. L. MEHTA, Spect. Letters 2 383 (1969). [6] A. W. ATKINSONand B. 0. FIELD, .I. Znorg. Nucl. Chem. 32,2615 (1970). [7] J. GISLASON, M. H. LLOYD, D. G. TUCK, Znorg. Chem. 10, 1907 (1971). [8] D. M. ADAMS and P. J. LOCK, J. Chem. Sot. A 2801 (1971). [9] J. G. CONTRERASand D. G. TUCK, Znorg. Chem. 11
2967 (1972).
[lo] G. P. BH~VSAR and K. SATKIANANDAN,Znd. J. Pure
Appl. Phys. 11, 429 (1973).
[II] J. P. WIGNACOURT, Thtse de 3Cme Cycle, University of Lille (1974). [12] E. M. KARTZMARK,Can. J. Chem. 55, 2792 (1977). [13] R. DEMOL, D.E.S., Lille (1974). [14] R. S. HALFORD,J. Chem. Phys. 14, 8 (1946). [15] J. P. WIGNACOURT,A. LORR~AUX-RUBBENS, P. BARBIER, G. MAIRESSE and F. WALLART. Suectrochim.
Acta 36A, 403 (1980). [16] D. M. ADAMS and D. C. NEWTON, J. Chem. Sot., Dalton 681 (1973). [17] K. NAKAMOTO, Infrared Spectra of Inorganic and Coordination Compounds. Wiley-Interscience (1970).
Specrrochimica Ado, Vol. 37A. No. 12, pp. 1021-1027, 1981 Printed in Great Britain.
Structural investigation of indium halide compounds: single crystal Raman study of monohydrated potassium hexachloroindate A, LORRIAUX-RUBBENS and F. WALLART Laboratoire de Spectrochimie Infrarouge et Raman, C.N.R.S., UniversitC des Sciences et Techniques de Lille, Bit. C.5, 59655 Villeneuve d’Ascq Cedex, France and
J. P. WIGNACOURT*, P. BARBIER and G. MAIRESSE Laboratoire de Cristallochimie et de Physicochimie du Solide, Universitt des Sciences et Techniques de Lille, BLt. C.8, 59655 Villeneuve d’Ascq Cedex, France (Received 24 March 1981) Abstract-The Raman spectrum of KJnC&, Hz0 single crystal is assigned on the basis of the crystal structure knowledge. The main feature is the splitting of the V, vibrational band into two components, that are assigned in relation to the indium site occupation ratio. In Raman spectroscopy, the superposition of the internal mode frequency range (characteristic of different anionic species), does not contribute to any improvement of the ionic isomerisation found by X-ray investigation. INTRODUCTION crystal structure determination of K31nC16, H,O [l] showing the existence of an ionic isomerism, makes it interesting to investigate this compound by spectroscopic methods, and first by spectroscopy. In the literature, molecular
The
numerous works related to InC&,- vibrations [2lo] and done as well in Raman scattering as in i.r. absorption, mainly concern solution studies and they only report the spectrum bands assigned to the fundamentals of the In&anion. The knowledge of the K31nCl,, H,O structure enable us to propose a complete assignment of the Raman spectrum of oriented single crystal at both room and liquid nitrogen temperature.
anions are located InC&respectively: 8[In(l)Cl$ in 8d (C,) sites, and 4[In(2)Cl$ in 4c (&) sites, but the two remaining In(3) atoms, in 2a(C4,) sites are surrounded each by five Cl and one 0 atoms, the global geometry[l] being intermediate between the octaedral (InCl,, H,O)‘- and the square pyramidal (InCI,)‘~ anions. The K31nCl, stoichiometry is matched with the location of two disordered Cl atoms in a 8d position. (b) Raman scattering study of K,InC&, H,O Internal modes. The (InCl,, H,O)‘- cluster proportion being l/6, the crystal Raman spectrum is mainly characteristic of the (InCl,)3m anions. In the isolated state (InC1,)3m has Oh symmetry, with a vibration distribution given by
EXPERIMENTAL (a) Preparation Single crystals of K,InC&, Hz0 are obtained by slow evaporation of aqueous solutions of lab-made InCI, and reagent grade KCI, in appropriate molecular ratio, as shown in the ternary solubility diagram InCI,-KClH,O[ll-121. (b) Molecular spectroscopy Raman spectra are recorded using a triple monochromator spectrometer built in our laboratory[l3]. The spectra are obtained using the 514.5 nm exciting line of a Spectra Physics ionized Argon Laser. The studies of air stable K,InCl,, Hz0 single crystals are done at room and nitrogen temperatures. 1.r. spectra are recorded on Perkin-Elmer 225 spectrometer, and in the low frequency region, on a FS 2000 Coderg Fourier Transform Spectrometer.
(a) Crystallographic
RESULTS results
K,InCl,, H,O crystallizes in the tetragonal system with 2 = 14 in space group I 4 mm (Cz.); *To whom correspondence
should be addressed.
rvib = A,,(R) + E,(R) + 2F,,(i.r.)
on group theoretical considerations. The Raman spectrum of a K31nC16, H,O aqueous solution shows the three active modes: a strong polarized band at 291 cm-’ (A,, mode) and two weak and depolarized ones at 150 and 129cm-‘, respectively assigned to the E, and F,, species. As for the two F,. i.r. active modes, they are given in the literature at about 250 and 160 cm-‘. In solid state, the anions are singularized by different orientations and site symmetries; we have tried to identify their respective vibration modes, taking into account their crystal environment. (1) Raman study of the [In(l)C1,13- anion located in 8c(C,). From the crystallographic data, we can establish the correlation table using the Halford method[l4]; this analysis shows (Table 1) that the v,(A,,) frequency band splits into three A,, B, and
1021 SAA Vol. 37A. No. 12-A
+ F,,(R) + F,,
A. LORRIAUX-RUBBENSetal.
1022
Table 1. Correlation table for the [In(l)Cl.$ MOLECULAR GROUP Oh
SITE GROUP CS $1
Ak
anion in the 8c site FACTOR GROUP %"
*
2
22 +Y,Z
A2g E g
F2g A
2 x
2 -Y
lu
E lines; that vz(Eg) one splits into six species: 2A1 +2&+2E and that vs(Fzs) one gives nine components: A, + Bz + E -t 2A, + 2 B, + 2E. The site effect and the intermolecular coupling make the v3, v4 (F,.) and v6 (&) bands active, each of them splitting into nine species: 2A, -t 2B, + 2E + A,+B,+E. On the [In{ 1)Cls]3- crystal environment representation (Fig. l), the axial chlorine atoms (Cl 1.1) are surrounded by four K’ cations ranging from 3.147 to 3.451 A, but the equatorial ones anly have three neighbouring K’, between 3.140 and 3.372 A. Moreover, the following interionic bond
Fig. 1. Environment of the [In( l)Cl,J3- anion in the crystal 5tructure.
Cl( 1.4)-O(3) = 3.248 A; Cl( 1.2)-O(4) = lengths: 3.189 A; C1(1.5)-0(4) = 3.201 A, are shorter than the sum of the oxygen and chlorine atoms Van der Walls radii (3.28 A), and presumably characterize O-H.. .Cl hydrogen bonds as in the KJnCG, HZ0 example [ 151. From these structural informations a detailed assignment of the we propose [In( I)Cl,]‘- vibrational modes. The v, frequency of A,, species in the isolated ion is identified at 291 cm-’ in aqueous solution. The main characteristic of the single crystal Raman spectra (Fig. 2) is the existence of two strong bands located at 288 and 274cm-’ at room temperature, which shift to higher frequency respectively 292 and 277 cm-’ at values, 80 K. As the symmetrical stretching frequency value is considered to be representative of equatorial In-Cl bonds, the differences[l] observed between these bond lengths are not marked enough to explain the existence of the two bands. The [In( l)Cl,]“- anion lies approximately between two K’ planes, which barely affect the stretching motions of the In(1 )-Cl bonds in the equatorial plane quite logically then, we get a frequency value quite close to the one obtained for the sample in aqueous solution. Thus, we assign the 288 cm-’ band (292 cm-’ at 80 K) to v,In(l)-Cl frequency. The E, mode relative to the v2 frequency is found at ISOcm- on the aqueous solution spectrum, and represents the antisymmetric stretching motion of In-Cl bonds. As for vI, the K’ interactions are weak and barely affect the vibration and we localize this mode at 162cm-’ at room
1023
Structural investigation of indium halide compounds -
100
Fig. 2. Raman spectra
of K,InC16, Hz0 single crystal temperature.
(162 and 168 cm-’ at 80 K with the intermolecular coupling effect). The F,, mode of the vj frequency implies a motion of the In (I) central atom; its value is about 250cm-’ in the literature. We note that two weak bands located at 227cm-r and 188 cm-’ (room temperature) shift to higher frequency values when the temperature decreases respectively 232 and 194 cm-’ at 80 K. As the same phenomenon is noted for the A,, species, and the [In(l)Cl$ clusters being the most numerous in the unit cell: 8 we assign this mode to the strongest band, with the highest frequency value. The second F,, species relative to vq is given at about 160cm-’ in the literature, and corresponds to out of the plane deformations. It is not so sensitive to K’ environmental effects as the stretching motions, which explains why it is localized at 168-169 cm-’ (80 K). The v5 frequency (Fzg mode) is found at 129cm-’ on the aqueous solution Raman spectrum. On the crystal one, it is located at 149cm-’ at liquid nitrogen temperature. The last fundamental v6 (F2J is given at different calculated values[S, 8, lo] from 94 to 130 cm-‘. At 80 K, it is identified as weak bands at 116-125 cm-‘. (2) Raman study of the [In(2)Cls13- anion in 4b sites (C,,). The correlation table (Table 2) established by the Halford method, led to the theoretical numbering. The A,, mode gives two components A, + B,; the E, mode splits into four: A, + B, + A, + Bz; the Fzg species splits into four: A, + B, +2E;
temperature
300
200 A i, cm-'
in the low frequency
range at ambient
each of the Flu modes leads to four lines: A, + B, + 2E, as well as Fzu, which gives: A2 + B1 + 2E. The crystal environment of the [In(2)Cl$ anion appears on the Fig. 3. The chlorine-potassium coordination number is 4 for the axial chlorine atoms [C1(2-1) and C1(2-2)] and 5 for the equatorial ones. As for [In(l)ClJpreviously described, the differences between the bond lengths within the [In(2)C16]3- anion are not important enough to explain the double band of the A,, mode at 288 and 274 cm-’ (room temperature). The K, atom, lying in the equatorial plane of the [In(2)Cl6]‘- cluster, is approximately in the In(2)Cl (2.3) direction, at 3.131 A of it. This localization of K, atom strongly affects the equatorial bond stretching motions and explains why the A,, mode frequency value is weaker. Thus, in this cluster, the 274cm-’ line is assigned to v,(In-Cl), two components of which A, and B, are identified at
K5 B/O00
I’
\ -------
Fig. 3. Environment of the [In(2)C&]‘- anion in the crystal structure.
A. LORRIAUX-RUBBENS et al.
1024
Table 2. Correlation table for the [In(2)C&13- anion in the 4b site rlOLECULARGROUP Oh
SITE GROUP c2”
FACTOR GROUP C4”
((J”)
Alg A2g E g Fig F2g A
lu
A2” E” Flu F2u
277 cm-’ at 80K. The antisymmetric stretching vibration of E, mode, is here more affected by the cationic surrounding than in [In(l)C&]3-. When this vibrational mode is concerned, we have previously shown[l5] that the perturbation effect and the frequency value vary in the same way; using the depolarization ratio measurements on the bands of an oriented crystal Raman spectra, at 80 K, we can localize the species at 177 cm-‘. The v3 frequency (F,, species) corresponds to an ‘umbrella’ motion including the In(2) central atom. It is sensitive to the K’ environment, and is more affected here than the corresponding one in [In(l)Cl$. This mode is assigned to the weak band noted at 188 cm-’ at room temperature. The chlorine-potassium interactions being identical for the different anionic clusters affected by out of the plane deformation, we identify the second F,, mode at the same value (168-169 cm-’ at 80 K) as the corresponding one in the [In( I)Cl,]‘ion. For the F,, mode (v5 vibration), the deformation in the equatorial plane is only disturbed by the K( 1) atoms, whereas those in the two other perpendicular planes are strongly affected by the K(2), K(3), K(4), and K(5) ions. Taking into account these interactions and the depolarization ratio measurements, we assign the A, and B, components at the 141 cm-’ frequency value, and the E ones at 134 cm-’ at 80 K. The cationic surrounding equally concerns the twisting motion of the Fzu mode in the [In(l)ClJ3and [In(2)Cl,]‘- clusters; we consequently localize
the corresponding band at 122 cm-’ at liquid nitrogen temperature. (3) Raman study of the [In(3)C15, H20]*- cluster in a 2a site (Cd”). The O(l)H, water molecule included in the In(3) coordination octaedron, is not concerned by interactions like hydrogen bonding; the shortest interanionic distance is 0(1 jCl( 1.2) = 3.509 A. Thus the water molecule can be said to be ponctual and the [In(3)CI,, H,O]‘- symmetry is C,,,. The fundamental vibrations are given by I’, = 4A,(R, i.r.) + 2&(R) + B,(R) + 4E(R, i.r.). As the molecular group, site group and factor group symmetries are identical; C.,,, there is no site and intermolecular coupling effects. Figure 4 shows the cationic surrounding of the
K3 4,000
Fig. 4. Environment
K3 5/000
of the [In(3)C15H20]‘- anion in the crystal structure.
Structural investigation
[In(3)Cl,, OH,]‘- anion; the Cl-K coordination number is 4 for the equatorial chlorine atoms and 0 for the axial one [C1(3.1)-K(3) = 4.648 81. The [In(3)Cl,, H,O]‘- anion proportion in the unit cell is weak
DnWL
H201zm =1
[InC1,13-
6’
Thus we should not expect observing the characteristic bands of the In(3)-O(1) bond, the strongest one being v, (In-O), given at 360 cm-’ in literature[lS, 161. The existence of the very strong band on the spectrum at 288 cm-’ hinders the obtainment of this v,(In-0) band owing to 360 cm-’ spectral region. Thus we mainly try to identify the InC&- vibration modes. In the C.,” symmetry group, three modes A, + E are due to the existence of the In(3)-O(1) bond in the [In(3)ClS, OH,]*- cluster and come from the F,, and Fzg species in the 0, symmetry group. When these modes are neglected, we take into account the anion orientation in the unit cell, and the correlation between the O,, and C,, groups is given by O,,:A,p
&:A,
E,
A,
F,.
E
B,
I 3350
A,
F,.
Kg
E
&
I 3400
Ku
B,
E
1025
of indium halide compounds
The stretching vibrations of the equatorial ln(3)Cl bonds are slightly less disturbed than those of [In(2)C1,13-, the K’ ions lying in bisector planes of Cl-In(3)-Cl angles. Furthermore, the existence of a water molecule at 2.278 A of In(3) can create important interactions. It is quite logical then to assign the v, In(3)-Cl vibration at the same value 274 cm-’ (room temperature) as v, In(2)-Cl frequency. Two bands are assigned to symmetrical stretching vibrations in the different clusters: 288 and their intensity ratio is: and 274 cm-‘, (I(288 cm-‘)/I(274 cm-‘)) = 8/6 in the spectrum keeping the A, modes unchanged. This 8/6 value is also found in the crystallographic occupation site ratio of the different clusters: (8In(1)/4In(2) + 2In(3)). This corroborates the proposed assignments and this ratio value is kept at liquid nitrogen temperature. The v,,(In-Cl) are equally disturbed in the In(3)ClS2- and In(2)C&- clusters, the two A, and B, components of the E, mode are located at 177 cm-‘. The ‘umbrella’ bending motion of the F,, mode (vJ is quite perturbed both by the C1(3.2)-K interactions and the water molecule; the resulting perturbation being found similar to those received by [In(2)C1,]3-, we identify the E mode at 194 cm-’ (80 K). The vibration frequency of the [In(3)Cl,]‘pyramid, equivalent to vq (second F,, mode in the O,, symmetry group) is concerned by the same
I 3450
3500
A V,
Fig. 5. Raman spectra of K&C&, Hz0 in the Hz0 fundamental The Y, and v3 frequency
3550
Cm-’
region at ambient temperature. range. (b) The v2 frequency.
(a)
A. LORRIAUX-RUBBENSet al.
1026
Table 3. Proposed assignment for the internal modes of K31nC&, Hz0 single crystal CryardloBraphic
of the
sir*
central
Imlaccd
ion
Sit*
affect
Intermlecul~r
couplinB
Valuer
A,
+ I2
l
E
292 cm-’
A, * az + L A,
In(l)
in
8c
+ E
I62
l
B2 + E
232
em
l
B2 + E
232
cm
+ 11, + E
232
em-’
* B2
l
168
and
169
cm-’
.
12
+ E
168.and
I69
l
B,
169
cm-’ -I cm
L
I68
and
I69
+ B,
+ E
I09
cm
+ B,
+ E
-1 149 cm II6
B2 + E
l
277 z
ICI(~)
in
2a
interactions
cm-’ -I
cm-I
-I I94 cm 194 cm-I
BI
-1
E
I94
+ BI E
168 and 168 and
169 cm-’ 169 cm-1
E
I68
169
+ Bl E
-I I4 I CID -I 134 CIQ
E
136
CD
and
-I cm
a-’
122 cm-’
2
E
122
E
122 cm-’
Al
277 cm-’
cm-’
CBv
5
5
I
-1 177 cm
Al
x
Bl
-u 177 cm-’
E
E
PA
5 E
E
Pzg-B2
B2
B2
B,
Bl
P2”
E
IS
Flu-B
122 cm-’
2
l B
EB
md
177 cm 177
E
%g-
-I
I25 end 122 cm-’ -I 122 cm
+ E
II
+B
*
-I
+ E
l
s
-I
+ B2 + E
+ 81
Correlation
-I
12
+ 8,
4b
em
l
l
in
I68
-I cm
+ B2 + E
III(Z)
frequmcy
Propomd
modem
aCOI
as the [In(l)Cl$ and [In(2)CM3anions; so the A, and E components are located at 168-169 cm-‘. As for the K atoms lying in the bissector planes of the C1(3.2)-In(3)-Cl(3.2) angles, they strongly affect the cissor motion of the InClsz- pyramid,
196 cm-I -I I68 cm 169 cm-1 -I33
El
-I
122 cm-’ 122 cm-I
corresponding to the vs(FZy) vibration in the O,, group. A Bz species is identified at 134 cm-’ @OK). The B, and E components of the twisting mode is assigned at 122 cm-‘. The proposed assignment is summarized in Table 3.
1027
Structural investigation of indium halide compounds
External modes. The expected lattice modes are: lSA, + lOA, + 9B, + 14B, + 27E. On the Raman spectra some species are noted at 80 K: A, + &(17 cm-‘), E (59 cm-‘) assignable to translation modes and B2 (195 cm-‘), A, + B, + E (300 cm-‘) for the libration ones. The existence of the internal mode spectrum in the low frequency range makes it impossible to observe more lattice modes.
(c) Spectroscopic studies of water in K,InC&, H,O The existence of different water molecules is suggested by a critical look on the interionic distances from the crystallographic data [ 11 O(1) belongs to a coordinated water molecule but is in too small quantity in the unit cell (l/6) to identify its vibrations on the Raman spectrum O(2), O(3) and O(4) are part of hydration water. But, if O(2) and O(4) are presumably concerned by hydrogen bonding, O(3) is free of any linkage in the crystal. According to Nakamoto [ 171 the hydration water, in i.r. absorption, is characterized by the stretching frequencies of O-H bond about 355032OOcm-‘, the bending one appearing at 16001630cm-‘. On the i.r. spectrum of KJnCl,, H,O polycrystalline sample, we observe a double band corresponding to the bending vibration of water, at 1607 and 1635 cm-‘, and an asymmetric large band about 3450cm-‘. On a single crystal Raman spectrum (Fig. 5), we find once more a double line at and also two bands at 1602 and 1636cm-‘, 3442 cm-’ and 3484 cm-’ in the v,(O-H) frequency region, with intensities ratio value I(3484 cm-‘) _ I( 1602 cm-‘) _ 2 I(3442 cm-‘) - I( 1636 cm-‘) also obtained
by the site occupation
ratio
8 40(2) + 40(4) 40(3) = 5 = 2. Thus, the 3484 and 1602 cm-’ frequency values are assigned to the H,0(2) and H,0(4) molecules involved in H-bonding, and the 3442 and 1636 cm-’ to the Hz0(3) molecules. From the weakasymmetric shape of the highest band at 3510 cm-‘, we identify v,,(O-H) vibration. In the low frequency range, two libration modes are observed at room temperature a wagging one at 626 cm-’ and the rocking one at 429 cm-‘. This vibrational spectroscopy study of the water molecules is summarized in Table 4. CONCLUSION
The KJnCl,, H,O crystal structure knowledge enables us to propose a complete assignment of its
Table 4. Raman and i.r. frequency values obtained for the water molecules in K?InCl&, Hz0
Infrared
Raman
assignment
3510
"_
3484
v (O-H) in O(Z)-H2 a;d 0(4)-H*
3400
3442
us (O-H) in 0(3)-H*
1635
1602
6 (H 0) in H200) and A20(4)
1607
1636
630
626
0
wagging
429
P
rocking
3500
(O-H)
(H20) in H20(3)
low frequency Raman spectrum, the main characteristic being the v, doublet assigned according to the indium site occupation ratio. Moreover vibrational molecular spectroscopy clearly shows the existence of different types of water molecules in the compound. Unfortunately, in this method, the superposition of the characteristic frequency range of the InCls3- and (InCl,, H,O)‘- anions, as well as their relative concentration, does not enable any improvement of the ionic isomerization proposed in the radiocrystallographic study. REFERENCES
[l] J. P. WIGNACOURT,G. NOWOGROCKI,G. MAIRESSEet P. BARBIER,Reo. Znorg. Chem. 2, 207 (1980). [2] L. A. WOODWARDand M. J. TAYLOR, J. Chem. Sot. 4473 (1960). [3] T. BARROWCLIFE,I. R. BEATIE, P. DAY and K. LIVINGSTONE.J. Chem. SOL. A 1810 (1967). [4] D. M. ADAM; and D. M. MORRIS, J. ‘Chetk. Sot., A 694 (1968). [5] M. N. AVATSHI and M. L. MEHTA, Spect. Letters 2 383 (1969). [6] A. W. ATKINSONand B. 0. FIELD, .I. Znorg. Nucl. Chem. 32,2615 (1970). [7] J. GISLASON, M. H. LLOYD, D. G. TUCK, Znorg. Chem. 10, 1907 (1971). [8] D. M. ADAMS and P. J. LOCK, J. Chem. Sot. A 2801 (1971). [9] J. G. CONTRERASand D. G. TUCK, Znorg. Chem. 11
2967 (1972).
[lo] G. P. BH~VSAR and K. SATKIANANDAN,Znd. J. Pure
Appl. Phys. 11, 429 (1973).
[II] J. P. WIGNACOURT, Thtse de 3Cme Cycle, University of Lille (1974). [12] E. M. KARTZMARK,Can. J. Chem. 55, 2792 (1977). [13] R. DEMOL, D.E.S., Lille (1974). [14] R. S. HALFORD,J. Chem. Phys. 14, 8 (1946). [15] J. P. WIGNACOURT,A. LORR~AUX-RUBBENS, P. BARBIER, G. MAIRESSE and F. WALLART. Suectrochim.
Acta 36A, 403 (1980). [16] D. M. ADAMS and D. C. NEWTON, J. Chem. Sot., Dalton 681 (1973). [17] K. NAKAMOTO, Infrared Spectra of Inorganic and Coordination Compounds. Wiley-Interscience (1970).