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Structure and vibrational spectra of Na5H3(SeO4)4·2H2O crystal
Journal of Molecular Structure, 213 (1989) 51-61 Elsevier Science Publishers B.V., Amsterdam - Printed
STRUCTURE AND VIBRATIONAL Na5H3(Se04)4-2H20 CRYSTAL
51 in The Netherlands
SPECTRA OF
J. BARAN, T. LIS and P. STARYNOWICZ Institute of Chemistry, Wroclaw University, F. Joliot-Curie 14,50-383 (Received 20 January
Wroc!aw (Poland)
1989)
ABSTRACT Pentasodium trihydrogen tetraselenate dihydrate crystals, Na,H,(SeO,),.2H,O, are triclinic, space group Pi, with a=5.959(3), b=7.268(4), c=9.958(4) A, (Y = 102.50(3),/I = 98.71(4), y = 100.36(4)” and 2 = 1. The crystal structure is determined from three-dimensional X-ray diffraction data taken on an automatic diffractometer with MO Ka radiation, and refined by leastsquares techniques to R = 0.0295 for 2497 non-zero reflections. Two selenate ions form hydroGendiselenate anion by means of a short centrosymmetric 0 *- -0 hydrogen bond of length 2.476 (4) A. Two crystallographically equivalent hydrogenselenate ions are linked to the hydrogendiselenate through the hydrogen bonds with the 0 *- *O distance of 2.592 (4) A. Trihydrogen tetraselenate moieties thus formed are joined into chains al?ng the [ 1111 direction via water molecules which form hydrogen bonds (2.859 (4) and 2.767 (5) A) with the 0 (4) atoms of two adjacent unit cells. Powder IR and Raman spectra of the title crystal and its deuterated analogue have been measured. Two bands at 2850 and 2475 cm-’ are assigned to the stretching vibrations of the O(5)H* **O (3) hydrogen bonds. The broad band at ca. 1330 cm-’ and a background in the low frequency part of a spectrum are assigned to the stretching vibrations of the short 0 (1) **-0 (1’) hydrogen bonds. An assignment of the internal vibrations of the selenate groups is proposed.
INTRODUCTION
The structures of MHSO, and MHSeO, crystals appear not to be similar. The HSO,- or HSeO,- ions form infinite chains by means of hydrogen bonds in the crystals of rubidium, ammonium and caesium hydrogensulphates and hydrogenselenates [l-8]. The structures of KHSO, [9] and KHSeO, [lo] crystals in addition to the chains of hydrogensulphates or hydrogenselenates also contain centrosymmetric dimers of these ions. The NaHSO, crystallizes in three different forms: as a monohydrate NaHSO,.H,O [ 11,121 and in anhydrous cr-NaHSO, [13] and P-NaHSO, [14] modifications. The NaHSO,.H,O crystal has a chain type structure [ 121. The crystals of P-NaHSO, are composed of centrosymmetric dimers [ 141. The structure of a-NaHSO, proved to be different from that of any other MHSO, crystals. It contains two types of the hydrogensulphate ions. The first type forms infinite chains. Con-
0022.2860/89/$03.50
0 1989 Elsevier Science Publishers
B.V.
52
sidering the S (2 ) -0 bond length and the shortest 0. . -0 distances of two adjacent ions in the chain, a disordered nature of their H atoms was suggested. The second type of ions are linked to the chain sulphates by the set of hydrogen bonds. Apart from powder IR and Raman spectra [151 no other data have been published on the NaHSeO, crystal so far. One could expect a centrosymmetric cyclic dimer type structure for this crystal as no band was observed in the region between 8004350 cm-’ of the IR spectrum. Therefore attempts were made to prepare single crystals in order to prove this by means of X-ray diffraction and polarized vibrational studies. However, the crystals of the title compound were obtained instead. The crystal structure and powder IR spectra of Na,H, (SeO,),*2H,O are the subject of this paper. EXPERIMENTAL
The well-developed single crystals of Na,H, (SeO,),*2H,O were grown from the saturated aqueous solution containing Na+ and HSeO,- ions in the ratio 1: 1 at room temperature. The crystals have the shape of flat rhombic plates. The deuterated analogue was obtained by threefold recrystallization of Na,H, ( SeO,),. 2Hz0 from a heavy water (DzO ) solution. The IR spectra of the powdered crystal suspensions in Nujol and hexachlorobutadiene were recorded on a Perkin Elmer 180 spectrophotometer. A roughly cubic fragment, with edges of 0.2 mm, of Na5H, (SeO,),.2H,O covered with protective lacquer TABLE 1 Summary of crystal data, data collection, Compound Molecular weight Space group Unit cell parameters Distances (A) Angles (deg ) Unit cell volume, V (AO3) Density Measured (Mg rnm3) Calculated C,Mgm-‘) Wavelength (A) Absorption coefficient, p (cm-‘) Final shift/error ratio Weighting scheme Final difference synthesis (e k3) Final R and R, Atom scattering factors from ref. 19
and refinement
conditions
Na5H3(Se04)4*2H20 725.8 Pi a = 5.959(3), b = 7.268(4), c = 9.958(4) a! = 102.50(3),/l = g&71(4), y = 100.36(4) 406.0 (4) 2.932 (CHJJCHBr,) 2.969(3) 0.71069 (MO Ka) 99.56 GO.14 I/a’(F) -0.83tdpc0.91 0.0295 and 0.0278
53
was set on the four-circle Syntex P2, diffractometer with graphite monochromator. Preliminary Weissenberg photographs showed no symmetry, thus indicating the triclinic system. The cell parameters were determined from the angular setting of 15 reflections with 28 between 19 and 29’. The 4265 intensities with 28 below 70” were collected in 20/13 mode. Two control reflections were recorded after each 50 reflections measured. No significant variation was observed, Rint was 0.0288. The structure was solved by direct methods [ 161. An absorption correction following the DIFABS procedure [ 171 was applied on isotropically refined data, the corrections being between 0.812 and 1.200. Full-matrix least-squares refinement, based on F values, was performed with SHELX76 [ 181 on the positional and anisotropic (isotropic for H) thermal parameters. The H atoms were refined with the constraint that do-n = 0.97 A (except the H (1) atom which occupies the centre of symmetry). The refinement was based on 2497 reflections, for which 12 30(I). The isotropic extinction correction g was included in the form F,,, = F ( 1- 0.001 -gF ‘/sinB), where g refined to 0.0038 (2 ). The other X-ray experimental and crystal data are given in Table 1. RESULTS AND DISCUSSION
Structure
description
The final atomic positions and anisotropic temperature factors are given in Table 2 and the bond lengths and angles in Table 3. All the distances and angles TABLE 2 Final positional and thermal parameters” (10’ A*) with e.s.d. values in parentheses for Na,H,(Se0,),.2H,O H(91)
I
Y
2
Se(l)
0.74916(‘7)
Se(Z) O(l) O(2)
0.58810(7)
0.31156(5) 0.20558(5)
0X2733(3) 0.17854(3)
0.1661(4) 0.1824(4)
0.5556(3) 0.6036(3)
0.4858(4) 0.3901(4) 0.4387(4) 0.0873(5)
0.5487(3) 0.7913(3) 0.2789(3) 0.2269(4)
0.3338(6) 0.9060 (7 )
0.2314(5) 0.1247(5) 0.7023(5)
0.0228(3) 0.2073(3) 1.0373(4)
0
0
0.8686(3) 0.3430(4) 0.5 0.742(10) 0.996(14) 0.835(14)
0.8293(3) 0.2598(3)
0 0.6037(2) 0.8069(2)
0 0.433(7) 0.658(g) 0.598(7)
0.5 0.375(2) 1.108(6) 0.954(5)
O(3) O(4) O(5) O(6) O(7) O(8) O(9) Na(l) Na(2) Na(3) H(l) H(5) H(9) H(91)
0.4859(5) 0.9435 (5) 0.7754(6) 0.7431(6) 0.6882 (6) 0.7791(6) 0.5868 (7 )
U,, 1.08(2) 1.17(2) 1.25(13) l&(14) 2.95( 16) 2.40( 15) 3.00(17) 2.28(16) 3.23(19) 1.74( 14)
Uzi,,
Ux
Uz,
U13
UI,
0.97(2) 1.53(2)
1.16(2) 1.22(2)
0.21(2) 0.07(2)
1.32(12) 1.55(12)
3.10(14) 2.29(13) 1.92(12)
0.20(2) 0.29(2) 0.14(10)
0.27(2) 0.36(2) O.OB(10)
1.29(11) 2.30 (13) 1.37(12) 2.17(14) 3.99(18) 2.79(15)
l.OO(lO) 1.88(12) 3.53(16) 1.27(11) 2.24(13)
0.33 ( 10 ) 0.77(10) 0.13(9) 0.34 ( 10 ) 0.39(12) 0.91(12) 0.40(11) 0.20(13)
3.09(M) 6.16(24)
2.79(16) 4.01(17)
2.75(15) 3.61(15)
1.36(13)
1.68(8) 3.11(11)
1.83(7)
2.01(7) 3.40(9)
0.44(6) 1.28(7)
2.68(g)
-0.01(11) 0.64(11) 0.46(12) 0.25(11) -0.15(12) -0.83(14) 0.59(12) 0.90(12) -0.08(14) -0.02(16) 0.32(6) 1.20(9)
0.79(11) 0.23(12) 0.79(12) 0.15(12) 1.18(13) 0.17(15) 0.14(12) 1.46(15) - -2.17(17) 0.48(6) 0.32(8)
8.8(35) 4.1(16) 12.7(34) 11.9(32)
“The form of temperature the anisotropic U.,,12~*2+2U,2hka*b*+2Lj23k16*C*+2U,~k~~~c~)].
factors
is
exp[-2n2(U,,h2a*2+U,,kZb*2+
54 TABLE 3 Principal bond lengths and bond angles in the Na,H,(SeO,),.2H,O Parameter Bond lengths (A) Se(l)-O(1) Se(l)-O(2) Se(l)-O(3) Se(l)-O(4) Bond angles (degrees) O(l)-Se(l)-O(2) O(l)-Se(l)-O(3) O(l)-Se(l)-O(4) O(2)-Se(l)-O(3) O(2)-Se(l)-O(4) O(3)-Se(l)-O(4) Se(l)-0(1)-H(l)
Value
crystal
Parameter
1.681(3) 1.629(3) 1.624(3) 1.617(3)
Se(2)-O(5) Se(2)-O(6) Se(2)-O(7) Se(2)-O(8)
107.6(2) 106.8(2) 105.2(2) 112.5(2) 112.7(2) 111.5(2) 112(l)
O(5)-Se(2)-O(6) O(5)-Se(2)-O(7)
O(5)-Se(2)-O(8) O(6)-Se(2)-O(7) O(6)-Se(2)-O(8) O(7)-Se(a)-O(8) Se(2)-0(5)-H(5)
Value
1.717(3) 1.622 (3) 1.601(3) 1.615(3)
105.8(2) 102.3 (2) 108.2 (2) 112.6(2) 112.9(2) 114.1(2) 108(3)
TABLE 4 Geometries of the hydrogen bonds in the Na,H,( Se0,).,*2H20 crystal D-H.. .A”
Distances (A)
Angles ( ’ )
H.--A
D...A
D-H. - .A
O(l)**.H(l).**O(l’) O(5)-H(5)...0(3) O(9)-H(9)...0(4”) O(9)-H(91)...0(4)
1.24(l) 1.66(2) 1.84(8) 1.90(5)
2.476(4) 2.592(4) 2.767(5) 2.859 (4)
180 159(5) 159(6) 171(6)
“Symmetry code: (i) l--x, -y, 1-z;
(ii) 2-x,
l-y,
2-z.
are within normal range. The structure consists of hydrogenselenate anions, hydrogendiselenate anions, sodium cations, and water molecules. The hydrogendiselenate anion is composed of two selenate moieties joined by a common hydrogen placed in the centre of symmetry. The Se-O(H) distance in this anion is intermediate between the Se-O and Se-O(H) ones in the hydrogenselenate anions. There are four kinds of hydrogen bonds (Table 4): the above mentioned Ol-Hl-Ol’bond in the hydrogendiselenate, the interselenate bond O(5)-H(5)-.-O(3), and the water-selenate O(9)-H(9)*..0(4) and 0(9)H (91) *. -0 (4”) bonds. There are three crystallographically independent sodium cations in the structure (Table 5). Two of them are six-coordinate, and the third one is seven-coordinate (six selenate oxygens and the water). The
55 TABLE 5 The Na-0 distances (A) in the Na,H,(SeO,),.2H,O
crystal
Bond
Length
Bond”
Length
Na(l)-O(6’) Na(l)-O(8) Na(l)-O(9”) Na(2)-O(1”‘) Na(2)-O(2”) Na(2)-O(2’) Na(2)-O(3) Na(2)-O(6’)
2.796(3)
Na(2)-O(P) Na(3)-O(1) Na(3)-O(2’) Na(3)-O(4) Na(3)-O(5”‘) Na(3)-O(6”) Na(3)-O(7’“) Na(3)-O(9’“‘)
2.381(3) 2.751(4) 2.766(4) 2.443(4) 2.545(3) 2.430(4) 2.475(4) 2.311(4)
2.517(3) 2.260(3) 2.452(3) 2.525(3) 2.466(3) 2.379(3) 2.377(4)
“Symmetry code: (i) x-l,y, z; (ii) x-l,y-1, z-l; 2-q l-y, l-2; (vi) l-x, -y, 1-z; (vii) x,y, l+z;
Fig. 1. View of the NaSH,(Se04),*2Hz0
(iii) l-x, (viii) l-r,
l-y, 1-z; l-y,2-2.
(iv) x, l+y, z; (v)
crystal structure.
unit cell packing diagram with the system of hydrogen bonds is shown in Fig. 1. Powder IR spectra of Na5H,(Se04),~2H,0
and its deuterated analogue
The IR spectra of the powder samples recorded in the 4000-250 cm -’ region are shown in Fig. 2. The powder Raman spectrum in the region 1000-300 cm-’
56
1500
2000
3000
LOO0
Wavenumbericdl
Fig. 2. Powder IR spectra of Na,H,(SeO,),-2H,O Nujol and Fluorolube emulsion.
300
600
1000
Fig. 3. Powder Raman spectrum 4880 A line of the Ar+ laser.
(upper)
and Na5D,(Se0,),-2D,O
(lower) in
J
AShi')
of Na5H,(Se0,)4-2H,0
measured
on a Jeol spectrometer
with
is shown in Fig. 3. The wavenumbers, relative intensities and the proposed assignment are given in Table 6. The bands are assigned in terms of the hydrogen bond OH group vibrations, the internal and librational vibrations of the water molecules and the internal vibrations of the distorted selenate groups of the hydrogendiselenate and hydrogenselenate anions (Fig. 1). Since both selenium atoms occupy the general C, positions, all selenates modes are therefore allowed in IR and Raman spectra and the degenerate modes (v,, V~and v,) should be split. The correlation field (Davydov) coupling splits additionally each internal vibration of the selenates, water molecules and hydrogen bond (0 (5 )-H ***0 (3 ) ) vibrations into A, and A,, type modes of the primitive
57
TABLE 6 The wavenumbers (cm-‘), relative intensities” and tentative assignment of the bands in the powder IRb spectra of Na,H, (SeO,),* 2Hz0 and its partly deuterated analogue Na,H, ( Se04),*2H20
Na,D,(SeO,),*2D,O
Tentative assignment
3510 m
2610 m 2580 msh 2500 m 2390 VW 2110 w 1830 w
v,H,O, v,D,O
3400 mb 3258 w 2850 w 2475 w 2200 vwsh
1205 VW 1185 w 1450 wb 975 ssh
1617 w 1305 VW 1150 vwsh 1110 vwsh
961 s 917 vs 910 vssh 870 s 840 m
(968) (923)
730 vs 710 ssh
(732)
640mb 540 wsh 442 m 412 vs 390 vs 365 s 330 m 315 m
(875) (814)
1070 wsh 1030 vwsh 957 s 918 vs 900 vssh 871 s 840 msh(?) 750 ssh 720 s 680 ssh 480 m
(438) (407) (388)
(342) (322)
435 ssh 412 vs 390 vs 360 msh
vOH(A), uOD(A) vOH(B), uOD(B)
60H, 60D
v:SeO, ( u;SeOzu:SeO,
) ( ul SeOz- )
u,SeO, (u,SeO~-
)
vSeO(H) (vj”SeO:-
)
TH,O, rD,O
u,SeOz
v,SeO~316 w
“Abbreviations: vs, very strong; s, strong; m, medium; w, weak; VW,very weak; sh, shoulder; b, broad. bThe wavenumbers of Raman bands are given in parentheses.
unit ceil due to the Ci factor group. The vibrations of the short 0 (1) - - -0 ( li) hydrogen bonds are allowed only in the IR spectra. The selection rules are given in the Table 7. Vibrations of the water molecules As the water molecules are involved in two hydrogen bonds (2.859 (4) and 2.767(5) A) with the O(4) atoms of the adjacent selenate ions, the V, (3400
58 TABLE 7 Results of the vibrational analysis for the Na,H,( SeO,),*2H,O” Ci
4 Au
T,
0 3
T
R SeO:-
15 9 15 9
I-W
HB(I)
HB(I1)
v1
v2
us
vq
vi
vz
v3
VdY
VdY
2 2
4 4
6 6
6 6
1 1
1 1
1 1
111000f 1 1 1
1
IR
Raman
X,Y,Z
f
%YY,~~,~Y,YW~
1
1
“Notation: T., acoustic modes; T, translational modes; R, rotational modes; v,, v2, vQ,v,, internal vibrations of the Se(l)Oiand Se(2)0:ions; vl, vz, v3, internal vibrations of water; v, 6, y, stretching, in-plane and out-of-plane bending modes of the protons in the hydrogen bonds; HB (I), O(5)-H(5)*..0(3) hydrogenbonds; HB(II), O(l)**~H(l)*~~O(l’) hydrogen bonds.
cm-‘) and V, (3510 cm-’ ) stretching vibrations are therefore shifted towards lower frequencies with respect to those in the “free” Hz0 [ 201. On deuteration they shift to 2500 cm-’ and 2610 cm-’ with the isotopic ratios of 1.36 and 1.34, respectively. The v~--zJ~ splitting (110 cm-‘) is larger than the one predicted (50-80 cm-’ ) from the model calculations performed by Erikson and Lindgren [ 211; however such splitting can be expected on the ground of the 1: 2 complex spectra of water with bases [ 201. It is interesting that the v,D,O band is narrower than that of the v,H,O (see Fig. 2). The v,H,O band is quite broad. This may indicate that these two bands (v,, v,) are in fact the stretching vibrations of two hydrogen bonds formed by the water molecules. The bending mode v,HzO appears at 1617 cm-l. Its frequency is lower than that (ca. 1650 cm-‘) predicted from the model calculations [ 211. It is also lower by 12 cm-’ than the value of v,H,O obtained from the correlation between v,H,O and YOH ( = l/2 (Y, + v,) ) proposed by Falk [ 221. The deuteration splits the v2 mode into two components observed at 1185 cm-l and 1205 cm-‘. A very broad band at ca. 640 cm-’ is assigned to the torsional motion of the water molecules. Its isotopic ratio shift of 1.34 does not allow us to decide the type of torsional motion (rocking, wagging or twisting) from which it arises. Hydrogen bonds vibrations Two weak and broad bands at 2850 cm-’ (A) and 2475 cm-l (B ) arise from the stretching vibrations of the 0 (5) -H (5 ) **-0 (3 ) hydrogen bonds whose O*..O distance is equal to 2.592(4) A. On deuteration these bands shift to 2110 cm-’ and 1830 cm-’ with the isotopic ratio shift of 1.35. The in-plane bending 60H mode of this hydrogen bond is observed at 1305 cm-’ and shifts to 975 cm-l on deuteration (1.34). The splitting of the vOH vibration of this hydrogen bond into two components (A and B) results from the Fermi reso-
59
nance [ 231 of vOH with the overtone of the 60H bending mode. The doubled frequencies of 60H and 60D (ca. 2610 cm-’ and 1950 cm-‘) are close to the minima between the A and B bands (2640 cm- ’ and 1970 cm-l ). The frequencies of the A and B bands and also the frequency of the &OH band are unexpectedly high for such long hydrogen bonds. The A and B bands appear at 2750 cm-’ and 2380 cm-l in the powder IR spectrum of the CsHSeO, crystal [ 241 which contains the hydrogen bonds of length 2.603 (5) A [ 81. The 60H band appears there at 1255 cm-‘. This may be related to the different arrangements of the hydrogen bond in both these crystals. The vOH stretching vibration of the short centrosymmetric 0 (1 )-H (1)-O ( 1’) hydrogen bond (doe = 2.476(4) A) gives rise to a broad band observed in between 1000-1700 cm-’ with maximum at ca. 1330 cm-‘. The enhancement of the background below 1000 cm-l is noticeable. On deuteration the band at ca. 1330 cm-’ disappears and a substantial increase of the background below 1000 cm-’ is observed. Therefore it is very likely that the vOH of the 0 (1 )-H ( 1)-O (1’) hydrogen bond gives rise not only to the band at ca. 1330 cm-’ but also to the broad absorption below 1000 cm-‘. A similar broad absorption was observed in the spectra of some M3H (SO,), type crystals [ 25,261. Internal vibrations of the selenate ions The measured spectra contain many fewer bands in the stretching v1 and ZJ~ vibrations region (700-1000 cm-‘) and also in the region of the Y, and v4 deformation (450-300 cm-’ ) vibrations than those predicted in Table 7. The vibrational properties of the selenate groups in the hydrogendiselenate ions have not yet been described in the literature. Taking into account the data on the MBH ( S04)2 crystals [ 25,261 and MHS04 crystals [ 27-291 one can expect some differences in vibrational properties of the selenate groups in the hydrogendiselenate ions and in the HSeO,- ions. A very strong band at 730 cm-’ with a shoulder at 710 cm-’ arises, in our opinion, from the vSeOH vibration of the HSe(2)0,ions since its frequency corresponds to those observed in the spectra of CsHSeO, [24] and KHSeO, [ 301 crystals containing the Se-O (H ) bonds of the lengths of 1.711(11) and 1.712(6) A, respectively [8,10], which are similar to the Se(2)-O(5) bond (1.717(3)~).TheanalogousmodeoftheSe(1)-O(1)(H)bond(1.681(3)~) is quite difficult to find in the spectra of the undeuterated crystal (shoulder at 710 cm-l ?). However in the spectrum of the deuterated crystal this mode gives rise to the shoulder observed at 750 cm-‘. These vibrations are correlated with components of the v3Se042- mode. Bands at 870 cm- ’ and 840 cm-’ can be assigned to the v,SeO, ( = y,SeO,‘- ) of the HSe(2)0,and hydrogendiselenate ions, respectively. The frequency of the former bond (870 cm- ’ ) is close to that observed in the Raman spectra
60
of the HSeO,- ions in aqueous solution [ 151 and the IR spectra of CsHSeO, [24] and KHSe04 [30,31] crystals. The powder Raman spectrum of the Na,H3(Se0,),.2H,0 (Fig. 3) contains two bands in this region: a very strong one at 875 cm-’ and a weak one at 814 cm-‘. As the two HSe(2)0,ions are apart from each other in the crystal, the Davydov type splitting of their vSe0, mode is very small (875 cm-‘, 870 cm-’ ). However, the coupling between the v,SeO, modes inside the hydrogendiselenate ions gives one band at 840 cm-l (A,) and the second one at 814 cm-’ (A,), observed in the IR and Raman spectra, respectively. Note that the 840 cm-l band is sensitive to deuteration (Fig. 2); therefore it may arise from the out-of-plane yOH bending mode as well. However, in the expected region for the yOD mode (600 + 50 cm-‘) no band is observed. This problem can be solved by means of the polarized IR and Raman spectra of the title crystal and its deuterated analogue. This will be the subject of a forthcoming paper. ACKNOWLEDGEMENT
This paper was financially (CPBP-01.12).
supported
by the Polish Academy
of Sciences
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20
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STRUCTURE AND VIBRATIONAL Na5H3(Se04)4-2H20 CRYSTAL
51 in The Netherlands
SPECTRA OF
J. BARAN, T. LIS and P. STARYNOWICZ Institute of Chemistry, Wroclaw University, F. Joliot-Curie 14,50-383 (Received 20 January
Wroc!aw (Poland)
1989)
ABSTRACT Pentasodium trihydrogen tetraselenate dihydrate crystals, Na,H,(SeO,),.2H,O, are triclinic, space group Pi, with a=5.959(3), b=7.268(4), c=9.958(4) A, (Y = 102.50(3),/I = 98.71(4), y = 100.36(4)” and 2 = 1. The crystal structure is determined from three-dimensional X-ray diffraction data taken on an automatic diffractometer with MO Ka radiation, and refined by leastsquares techniques to R = 0.0295 for 2497 non-zero reflections. Two selenate ions form hydroGendiselenate anion by means of a short centrosymmetric 0 *- -0 hydrogen bond of length 2.476 (4) A. Two crystallographically equivalent hydrogenselenate ions are linked to the hydrogendiselenate through the hydrogen bonds with the 0 *- *O distance of 2.592 (4) A. Trihydrogen tetraselenate moieties thus formed are joined into chains al?ng the [ 1111 direction via water molecules which form hydrogen bonds (2.859 (4) and 2.767 (5) A) with the 0 (4) atoms of two adjacent unit cells. Powder IR and Raman spectra of the title crystal and its deuterated analogue have been measured. Two bands at 2850 and 2475 cm-’ are assigned to the stretching vibrations of the O(5)H* **O (3) hydrogen bonds. The broad band at ca. 1330 cm-’ and a background in the low frequency part of a spectrum are assigned to the stretching vibrations of the short 0 (1) **-0 (1’) hydrogen bonds. An assignment of the internal vibrations of the selenate groups is proposed.
INTRODUCTION
The structures of MHSO, and MHSeO, crystals appear not to be similar. The HSO,- or HSeO,- ions form infinite chains by means of hydrogen bonds in the crystals of rubidium, ammonium and caesium hydrogensulphates and hydrogenselenates [l-8]. The structures of KHSO, [9] and KHSeO, [lo] crystals in addition to the chains of hydrogensulphates or hydrogenselenates also contain centrosymmetric dimers of these ions. The NaHSO, crystallizes in three different forms: as a monohydrate NaHSO,.H,O [ 11,121 and in anhydrous cr-NaHSO, [13] and P-NaHSO, [14] modifications. The NaHSO,.H,O crystal has a chain type structure [ 121. The crystals of P-NaHSO, are composed of centrosymmetric dimers [ 141. The structure of a-NaHSO, proved to be different from that of any other MHSO, crystals. It contains two types of the hydrogensulphate ions. The first type forms infinite chains. Con-
0022.2860/89/$03.50
0 1989 Elsevier Science Publishers
B.V.
52
sidering the S (2 ) -0 bond length and the shortest 0. . -0 distances of two adjacent ions in the chain, a disordered nature of their H atoms was suggested. The second type of ions are linked to the chain sulphates by the set of hydrogen bonds. Apart from powder IR and Raman spectra [151 no other data have been published on the NaHSeO, crystal so far. One could expect a centrosymmetric cyclic dimer type structure for this crystal as no band was observed in the region between 8004350 cm-’ of the IR spectrum. Therefore attempts were made to prepare single crystals in order to prove this by means of X-ray diffraction and polarized vibrational studies. However, the crystals of the title compound were obtained instead. The crystal structure and powder IR spectra of Na,H, (SeO,),*2H,O are the subject of this paper. EXPERIMENTAL
The well-developed single crystals of Na,H, (SeO,),*2H,O were grown from the saturated aqueous solution containing Na+ and HSeO,- ions in the ratio 1: 1 at room temperature. The crystals have the shape of flat rhombic plates. The deuterated analogue was obtained by threefold recrystallization of Na,H, ( SeO,),. 2Hz0 from a heavy water (DzO ) solution. The IR spectra of the powdered crystal suspensions in Nujol and hexachlorobutadiene were recorded on a Perkin Elmer 180 spectrophotometer. A roughly cubic fragment, with edges of 0.2 mm, of Na5H, (SeO,),.2H,O covered with protective lacquer TABLE 1 Summary of crystal data, data collection, Compound Molecular weight Space group Unit cell parameters Distances (A) Angles (deg ) Unit cell volume, V (AO3) Density Measured (Mg rnm3) Calculated C,Mgm-‘) Wavelength (A) Absorption coefficient, p (cm-‘) Final shift/error ratio Weighting scheme Final difference synthesis (e k3) Final R and R, Atom scattering factors from ref. 19
and refinement
conditions
Na5H3(Se04)4*2H20 725.8 Pi a = 5.959(3), b = 7.268(4), c = 9.958(4) a! = 102.50(3),/l = g&71(4), y = 100.36(4) 406.0 (4) 2.932 (CHJJCHBr,) 2.969(3) 0.71069 (MO Ka) 99.56 GO.14 I/a’(F) -0.83tdpc0.91 0.0295 and 0.0278
53
was set on the four-circle Syntex P2, diffractometer with graphite monochromator. Preliminary Weissenberg photographs showed no symmetry, thus indicating the triclinic system. The cell parameters were determined from the angular setting of 15 reflections with 28 between 19 and 29’. The 4265 intensities with 28 below 70” were collected in 20/13 mode. Two control reflections were recorded after each 50 reflections measured. No significant variation was observed, Rint was 0.0288. The structure was solved by direct methods [ 161. An absorption correction following the DIFABS procedure [ 171 was applied on isotropically refined data, the corrections being between 0.812 and 1.200. Full-matrix least-squares refinement, based on F values, was performed with SHELX76 [ 181 on the positional and anisotropic (isotropic for H) thermal parameters. The H atoms were refined with the constraint that do-n = 0.97 A (except the H (1) atom which occupies the centre of symmetry). The refinement was based on 2497 reflections, for which 12 30(I). The isotropic extinction correction g was included in the form F,,, = F ( 1- 0.001 -gF ‘/sinB), where g refined to 0.0038 (2 ). The other X-ray experimental and crystal data are given in Table 1. RESULTS AND DISCUSSION
Structure
description
The final atomic positions and anisotropic temperature factors are given in Table 2 and the bond lengths and angles in Table 3. All the distances and angles TABLE 2 Final positional and thermal parameters” (10’ A*) with e.s.d. values in parentheses for Na,H,(Se0,),.2H,O H(91)
I
Y
2
Se(l)
0.74916(‘7)
Se(Z) O(l) O(2)
0.58810(7)
0.31156(5) 0.20558(5)
0X2733(3) 0.17854(3)
0.1661(4) 0.1824(4)
0.5556(3) 0.6036(3)
0.4858(4) 0.3901(4) 0.4387(4) 0.0873(5)
0.5487(3) 0.7913(3) 0.2789(3) 0.2269(4)
0.3338(6) 0.9060 (7 )
0.2314(5) 0.1247(5) 0.7023(5)
0.0228(3) 0.2073(3) 1.0373(4)
0
0
0.8686(3) 0.3430(4) 0.5 0.742(10) 0.996(14) 0.835(14)
0.8293(3) 0.2598(3)
0 0.6037(2) 0.8069(2)
0 0.433(7) 0.658(g) 0.598(7)
0.5 0.375(2) 1.108(6) 0.954(5)
O(3) O(4) O(5) O(6) O(7) O(8) O(9) Na(l) Na(2) Na(3) H(l) H(5) H(9) H(91)
0.4859(5) 0.9435 (5) 0.7754(6) 0.7431(6) 0.6882 (6) 0.7791(6) 0.5868 (7 )
U,, 1.08(2) 1.17(2) 1.25(13) l&(14) 2.95( 16) 2.40( 15) 3.00(17) 2.28(16) 3.23(19) 1.74( 14)
Uzi,,
Ux
Uz,
U13
UI,
0.97(2) 1.53(2)
1.16(2) 1.22(2)
0.21(2) 0.07(2)
1.32(12) 1.55(12)
3.10(14) 2.29(13) 1.92(12)
0.20(2) 0.29(2) 0.14(10)
0.27(2) 0.36(2) O.OB(10)
1.29(11) 2.30 (13) 1.37(12) 2.17(14) 3.99(18) 2.79(15)
l.OO(lO) 1.88(12) 3.53(16) 1.27(11) 2.24(13)
0.33 ( 10 ) 0.77(10) 0.13(9) 0.34 ( 10 ) 0.39(12) 0.91(12) 0.40(11) 0.20(13)
3.09(M) 6.16(24)
2.79(16) 4.01(17)
2.75(15) 3.61(15)
1.36(13)
1.68(8) 3.11(11)
1.83(7)
2.01(7) 3.40(9)
0.44(6) 1.28(7)
2.68(g)
-0.01(11) 0.64(11) 0.46(12) 0.25(11) -0.15(12) -0.83(14) 0.59(12) 0.90(12) -0.08(14) -0.02(16) 0.32(6) 1.20(9)
0.79(11) 0.23(12) 0.79(12) 0.15(12) 1.18(13) 0.17(15) 0.14(12) 1.46(15) - -2.17(17) 0.48(6) 0.32(8)
8.8(35) 4.1(16) 12.7(34) 11.9(32)
“The form of temperature the anisotropic U.,,12~*2+2U,2hka*b*+2Lj23k16*C*+2U,~k~~~c~)].
factors
is
exp[-2n2(U,,h2a*2+U,,kZb*2+
54 TABLE 3 Principal bond lengths and bond angles in the Na,H,(SeO,),.2H,O Parameter Bond lengths (A) Se(l)-O(1) Se(l)-O(2) Se(l)-O(3) Se(l)-O(4) Bond angles (degrees) O(l)-Se(l)-O(2) O(l)-Se(l)-O(3) O(l)-Se(l)-O(4) O(2)-Se(l)-O(3) O(2)-Se(l)-O(4) O(3)-Se(l)-O(4) Se(l)-0(1)-H(l)
Value
crystal
Parameter
1.681(3) 1.629(3) 1.624(3) 1.617(3)
Se(2)-O(5) Se(2)-O(6) Se(2)-O(7) Se(2)-O(8)
107.6(2) 106.8(2) 105.2(2) 112.5(2) 112.7(2) 111.5(2) 112(l)
O(5)-Se(2)-O(6) O(5)-Se(2)-O(7)
O(5)-Se(2)-O(8) O(6)-Se(2)-O(7) O(6)-Se(2)-O(8) O(7)-Se(a)-O(8) Se(2)-0(5)-H(5)
Value
1.717(3) 1.622 (3) 1.601(3) 1.615(3)
105.8(2) 102.3 (2) 108.2 (2) 112.6(2) 112.9(2) 114.1(2) 108(3)
TABLE 4 Geometries of the hydrogen bonds in the Na,H,( Se0,).,*2H20 crystal D-H.. .A”
Distances (A)
Angles ( ’ )
H.--A
D...A
D-H. - .A
O(l)**.H(l).**O(l’) O(5)-H(5)...0(3) O(9)-H(9)...0(4”) O(9)-H(91)...0(4)
1.24(l) 1.66(2) 1.84(8) 1.90(5)
2.476(4) 2.592(4) 2.767(5) 2.859 (4)
180 159(5) 159(6) 171(6)
“Symmetry code: (i) l--x, -y, 1-z;
(ii) 2-x,
l-y,
2-z.
are within normal range. The structure consists of hydrogenselenate anions, hydrogendiselenate anions, sodium cations, and water molecules. The hydrogendiselenate anion is composed of two selenate moieties joined by a common hydrogen placed in the centre of symmetry. The Se-O(H) distance in this anion is intermediate between the Se-O and Se-O(H) ones in the hydrogenselenate anions. There are four kinds of hydrogen bonds (Table 4): the above mentioned Ol-Hl-Ol’bond in the hydrogendiselenate, the interselenate bond O(5)-H(5)-.-O(3), and the water-selenate O(9)-H(9)*..0(4) and 0(9)H (91) *. -0 (4”) bonds. There are three crystallographically independent sodium cations in the structure (Table 5). Two of them are six-coordinate, and the third one is seven-coordinate (six selenate oxygens and the water). The
55 TABLE 5 The Na-0 distances (A) in the Na,H,(SeO,),.2H,O
crystal
Bond
Length
Bond”
Length
Na(l)-O(6’) Na(l)-O(8) Na(l)-O(9”) Na(2)-O(1”‘) Na(2)-O(2”) Na(2)-O(2’) Na(2)-O(3) Na(2)-O(6’)
2.796(3)
Na(2)-O(P) Na(3)-O(1) Na(3)-O(2’) Na(3)-O(4) Na(3)-O(5”‘) Na(3)-O(6”) Na(3)-O(7’“) Na(3)-O(9’“‘)
2.381(3) 2.751(4) 2.766(4) 2.443(4) 2.545(3) 2.430(4) 2.475(4) 2.311(4)
2.517(3) 2.260(3) 2.452(3) 2.525(3) 2.466(3) 2.379(3) 2.377(4)
“Symmetry code: (i) x-l,y, z; (ii) x-l,y-1, z-l; 2-q l-y, l-2; (vi) l-x, -y, 1-z; (vii) x,y, l+z;
Fig. 1. View of the NaSH,(Se04),*2Hz0
(iii) l-x, (viii) l-r,
l-y, 1-z; l-y,2-2.
(iv) x, l+y, z; (v)
crystal structure.
unit cell packing diagram with the system of hydrogen bonds is shown in Fig. 1. Powder IR spectra of Na5H,(Se04),~2H,0
and its deuterated analogue
The IR spectra of the powder samples recorded in the 4000-250 cm -’ region are shown in Fig. 2. The powder Raman spectrum in the region 1000-300 cm-’
56
1500
2000
3000
LOO0
Wavenumbericdl
Fig. 2. Powder IR spectra of Na,H,(SeO,),-2H,O Nujol and Fluorolube emulsion.
300
600
1000
Fig. 3. Powder Raman spectrum 4880 A line of the Ar+ laser.
(upper)
and Na5D,(Se0,),-2D,O
(lower) in
J
AShi')
of Na5H,(Se0,)4-2H,0
measured
on a Jeol spectrometer
with
is shown in Fig. 3. The wavenumbers, relative intensities and the proposed assignment are given in Table 6. The bands are assigned in terms of the hydrogen bond OH group vibrations, the internal and librational vibrations of the water molecules and the internal vibrations of the distorted selenate groups of the hydrogendiselenate and hydrogenselenate anions (Fig. 1). Since both selenium atoms occupy the general C, positions, all selenates modes are therefore allowed in IR and Raman spectra and the degenerate modes (v,, V~and v,) should be split. The correlation field (Davydov) coupling splits additionally each internal vibration of the selenates, water molecules and hydrogen bond (0 (5 )-H ***0 (3 ) ) vibrations into A, and A,, type modes of the primitive
57
TABLE 6 The wavenumbers (cm-‘), relative intensities” and tentative assignment of the bands in the powder IRb spectra of Na,H, (SeO,),* 2Hz0 and its partly deuterated analogue Na,H, ( Se04),*2H20
Na,D,(SeO,),*2D,O
Tentative assignment
3510 m
2610 m 2580 msh 2500 m 2390 VW 2110 w 1830 w
v,H,O, v,D,O
3400 mb 3258 w 2850 w 2475 w 2200 vwsh
1205 VW 1185 w 1450 wb 975 ssh
1617 w 1305 VW 1150 vwsh 1110 vwsh
961 s 917 vs 910 vssh 870 s 840 m
(968) (923)
730 vs 710 ssh
(732)
640mb 540 wsh 442 m 412 vs 390 vs 365 s 330 m 315 m
(875) (814)
1070 wsh 1030 vwsh 957 s 918 vs 900 vssh 871 s 840 msh(?) 750 ssh 720 s 680 ssh 480 m
(438) (407) (388)
(342) (322)
435 ssh 412 vs 390 vs 360 msh
vOH(A), uOD(A) vOH(B), uOD(B)
60H, 60D
v:SeO, ( u;SeOzu:SeO,
) ( ul SeOz- )
u,SeO, (u,SeO~-
)
vSeO(H) (vj”SeO:-
)
TH,O, rD,O
u,SeOz
v,SeO~316 w
“Abbreviations: vs, very strong; s, strong; m, medium; w, weak; VW,very weak; sh, shoulder; b, broad. bThe wavenumbers of Raman bands are given in parentheses.
unit ceil due to the Ci factor group. The vibrations of the short 0 (1) - - -0 ( li) hydrogen bonds are allowed only in the IR spectra. The selection rules are given in the Table 7. Vibrations of the water molecules As the water molecules are involved in two hydrogen bonds (2.859 (4) and 2.767(5) A) with the O(4) atoms of the adjacent selenate ions, the V, (3400
58 TABLE 7 Results of the vibrational analysis for the Na,H,( SeO,),*2H,O” Ci
4 Au
T,
0 3
T
R SeO:-
15 9 15 9
I-W
HB(I)
HB(I1)
v1
v2
us
vq
vi
vz
v3
VdY
VdY
2 2
4 4
6 6
6 6
1 1
1 1
1 1
111000f 1 1 1
1
IR
Raman
X,Y,Z
f
%YY,~~,~Y,YW~
1
1
“Notation: T., acoustic modes; T, translational modes; R, rotational modes; v,, v2, vQ,v,, internal vibrations of the Se(l)Oiand Se(2)0:ions; vl, vz, v3, internal vibrations of water; v, 6, y, stretching, in-plane and out-of-plane bending modes of the protons in the hydrogen bonds; HB (I), O(5)-H(5)*..0(3) hydrogenbonds; HB(II), O(l)**~H(l)*~~O(l’) hydrogen bonds.
cm-‘) and V, (3510 cm-’ ) stretching vibrations are therefore shifted towards lower frequencies with respect to those in the “free” Hz0 [ 201. On deuteration they shift to 2500 cm-’ and 2610 cm-’ with the isotopic ratios of 1.36 and 1.34, respectively. The v~--zJ~ splitting (110 cm-‘) is larger than the one predicted (50-80 cm-’ ) from the model calculations performed by Erikson and Lindgren [ 211; however such splitting can be expected on the ground of the 1: 2 complex spectra of water with bases [ 201. It is interesting that the v,D,O band is narrower than that of the v,H,O (see Fig. 2). The v,H,O band is quite broad. This may indicate that these two bands (v,, v,) are in fact the stretching vibrations of two hydrogen bonds formed by the water molecules. The bending mode v,HzO appears at 1617 cm-l. Its frequency is lower than that (ca. 1650 cm-‘) predicted from the model calculations [ 211. It is also lower by 12 cm-’ than the value of v,H,O obtained from the correlation between v,H,O and YOH ( = l/2 (Y, + v,) ) proposed by Falk [ 221. The deuteration splits the v2 mode into two components observed at 1185 cm-l and 1205 cm-‘. A very broad band at ca. 640 cm-’ is assigned to the torsional motion of the water molecules. Its isotopic ratio shift of 1.34 does not allow us to decide the type of torsional motion (rocking, wagging or twisting) from which it arises. Hydrogen bonds vibrations Two weak and broad bands at 2850 cm-’ (A) and 2475 cm-l (B ) arise from the stretching vibrations of the 0 (5) -H (5 ) **-0 (3 ) hydrogen bonds whose O*..O distance is equal to 2.592(4) A. On deuteration these bands shift to 2110 cm-’ and 1830 cm-’ with the isotopic ratio shift of 1.35. The in-plane bending 60H mode of this hydrogen bond is observed at 1305 cm-’ and shifts to 975 cm-l on deuteration (1.34). The splitting of the vOH vibration of this hydrogen bond into two components (A and B) results from the Fermi reso-
59
nance [ 231 of vOH with the overtone of the 60H bending mode. The doubled frequencies of 60H and 60D (ca. 2610 cm-’ and 1950 cm-‘) are close to the minima between the A and B bands (2640 cm- ’ and 1970 cm-l ). The frequencies of the A and B bands and also the frequency of the &OH band are unexpectedly high for such long hydrogen bonds. The A and B bands appear at 2750 cm-’ and 2380 cm-l in the powder IR spectrum of the CsHSeO, crystal [ 241 which contains the hydrogen bonds of length 2.603 (5) A [ 81. The 60H band appears there at 1255 cm-‘. This may be related to the different arrangements of the hydrogen bond in both these crystals. The vOH stretching vibration of the short centrosymmetric 0 (1 )-H (1)-O ( 1’) hydrogen bond (doe = 2.476(4) A) gives rise to a broad band observed in between 1000-1700 cm-’ with maximum at ca. 1330 cm-‘. The enhancement of the background below 1000 cm-l is noticeable. On deuteration the band at ca. 1330 cm-’ disappears and a substantial increase of the background below 1000 cm-’ is observed. Therefore it is very likely that the vOH of the 0 (1 )-H ( 1)-O (1’) hydrogen bond gives rise not only to the band at ca. 1330 cm-’ but also to the broad absorption below 1000 cm-‘. A similar broad absorption was observed in the spectra of some M3H (SO,), type crystals [ 25,261. Internal vibrations of the selenate ions The measured spectra contain many fewer bands in the stretching v1 and ZJ~ vibrations region (700-1000 cm-‘) and also in the region of the Y, and v4 deformation (450-300 cm-’ ) vibrations than those predicted in Table 7. The vibrational properties of the selenate groups in the hydrogendiselenate ions have not yet been described in the literature. Taking into account the data on the MBH ( S04)2 crystals [ 25,261 and MHS04 crystals [ 27-291 one can expect some differences in vibrational properties of the selenate groups in the hydrogendiselenate ions and in the HSeO,- ions. A very strong band at 730 cm-’ with a shoulder at 710 cm-’ arises, in our opinion, from the vSeOH vibration of the HSe(2)0,ions since its frequency corresponds to those observed in the spectra of CsHSeO, [24] and KHSeO, [ 301 crystals containing the Se-O (H ) bonds of the lengths of 1.711(11) and 1.712(6) A, respectively [8,10], which are similar to the Se(2)-O(5) bond (1.717(3)~).TheanalogousmodeoftheSe(1)-O(1)(H)bond(1.681(3)~) is quite difficult to find in the spectra of the undeuterated crystal (shoulder at 710 cm-l ?). However in the spectrum of the deuterated crystal this mode gives rise to the shoulder observed at 750 cm-‘. These vibrations are correlated with components of the v3Se042- mode. Bands at 870 cm- ’ and 840 cm-’ can be assigned to the v,SeO, ( = y,SeO,‘- ) of the HSe(2)0,and hydrogendiselenate ions, respectively. The frequency of the former bond (870 cm- ’ ) is close to that observed in the Raman spectra
60
of the HSeO,- ions in aqueous solution [ 151 and the IR spectra of CsHSeO, [24] and KHSe04 [30,31] crystals. The powder Raman spectrum of the Na,H3(Se0,),.2H,0 (Fig. 3) contains two bands in this region: a very strong one at 875 cm-’ and a weak one at 814 cm-‘. As the two HSe(2)0,ions are apart from each other in the crystal, the Davydov type splitting of their vSe0, mode is very small (875 cm-‘, 870 cm-’ ). However, the coupling between the v,SeO, modes inside the hydrogendiselenate ions gives one band at 840 cm-l (A,) and the second one at 814 cm-’ (A,), observed in the IR and Raman spectra, respectively. Note that the 840 cm-l band is sensitive to deuteration (Fig. 2); therefore it may arise from the out-of-plane yOH bending mode as well. However, in the expected region for the yOD mode (600 + 50 cm-‘) no band is observed. This problem can be solved by means of the polarized IR and Raman spectra of the title crystal and its deuterated analogue. This will be the subject of a forthcoming paper. ACKNOWLEDGEMENT
This paper was financially (CPBP-01.12).
supported
by the Polish Academy
of Sciences
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