Zeitschrift für Kristallographie 199, 177-184 (1992)© by R. Oldenbourg Verlag, Miinchen 1992

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0044-2968/92 $ 3.00 + 0.00

Structure of Be(I03)2" 2HI03 6H20Josef MacicekInstitute of Applied Mineralogy, Bulgarian Academy of Sciences,Rakovski str. 92, 1000 Sofia, Bulgaria

Maria Maneva-Petrova and Mitko GeorgievHigh Institute of Chemical Technology, Department of Inorganic Chemistry,Bul. Kl. Ohridski 8, 1156 Sofia, Bulgaria

Received: January 15, 1991

Crystal structure / Beryllium hydrogen iodate hexahydrate

Abstract. Crystal data: Be(I03)2•

2HI03•

6H20, Mr = 818.73, ortho-rhombic, Pnam, a = 7.842(1), b = 8.613(1), c = 24.407(2) A, V= 1648.5(5)A3, Z = 4, Dx = 3.299 g- cm"3, MoKa, X = 0.70930 A, (i= 75.7 cm"1,77(000) = 1496, T=292 K, R = 0.030 for 3018 observed reflections withI> 3ct(7). The iodic acid and iodate groups are arranged in along the b-axis corrugated slabs with the HI03 molecules at the crests and troughs.The channels between them are extended along the a-axis and filled withBe(H20)4+ cations and water molecules. All the structural fragments takepart in a H-bonding scheme.

Introduction

Be(I03)2•

2HI03

6H20 was firstly synthesized and characterized bychemical, IR spectral and X-ray powder diffraction analyses by Manevaand Georgiev (1989a). Further thermal and calorimetric study of this com-

pound (Maneva and Georgiev, 1989b) supported the previously proposedcrystal chemical formula [Be(H20)4](I03)2

•

2HI03 • 2H20. New and more

precise X-ray powder data have been evaluated and stored in the PowderData File as phase no. 40-756 (Macicek, 1989).

Recently we improved the original synthetic procedure which allowedgrowing crystals suitable for X-ray structural analysis and other physicalmeasurements. Thus it was possible to carry out the present single crystalstructure determination.

178 Josef Macícek, Maria Maneva-Petrova and Mitko Georgiev

ExperimentalThe title compound was obtained by mixing of 50 cm3 1 M HI03 (Merckp.a.) and 14.13 g Be(I03)2 -4H20, prepared according to Biber, Neumanand Bragina (1941), at room temperature under rigorous stirring. Thecolourless solution was filtered and left to evaporate in air. Transparentwell formed crystals appeared after 20 days. Dm was not determined.

A crystal with approximate dimensions 0.13 x 0.20 x 0.27 mm was in-vestigated on an Enraf-Nonius CAD-4 diffractometer (graphite mono-

chromator, MoKa radiation); m-29 scan: speed 2 to 7°min~1, width =

[1.0 +0.50 tan0]°.Cell constants were evaluated from least-squares fitting of 25 reflections

with 24.0 < 9 < 25.0°. 4120 reflections were measured within (sind)/X < 0.806 A"1 (It. 0 to 12, k: 0 to 13, /: 0 to 39). Three standard reflectionswere monitored every 4.0 h. Since the intensity variation was less than0.6% no decay correction was considered. Lorentz and polarization correc-tion along with empirical absorption corrections based on xp-scans (trans-mission from 63.90 to 99.89%), and spherical absorption correction forriR = 1.45 (transmission from 13.63 to 17.10%) were applied. 1102 reflec-tions were considered unobserved: 58 systematically absent and those with

Table 1. Positional and equivalent isotropic thermal parameters and their e.s.d.'s.

Atom y Ueq (A2)1(1)1(2)0(11)0(12)0(13)0(21)0(22)0(23)Be0(W1)0(W2)0(W3)0(W4)HH(W1)H(W2)H(W31)H(W32)H(W41)H(W42)

0.02715(3)0.26141(3)

-0.1809(3)0.1373(4)

-0.0282(4)0.2783(5)0.4304(4)0.0803(4)0.298(1)0.1444(7)0.4899(6)0.2820(4)0.5255(4)

-0.124(9)0.095(8)0.559(8)0.15(1)0.37(1)0.472(9)0.56(1)

0.20800(3)-0.01775(2)0.1240(4)0.0895(3)0.3655(4)

-0.2248(3)0.0271(3)0.0002(3)0.610(1)0.4910(6)0.5397(6)0.7110(4)0.7716(4)0.401(8)0.478(7)0.511(8)0.725(8)0.726(8)0.83(1)0.696(9)

0.11594(1)0.00693(1)0.1176(1)0.1651(1)0.1691(1)0.0070(2)0.0552(1)0.0544(1)0.2500.2500.2500.3066(1)0.3777(1)0.162(3)0.278(3)0.219(3)0.329(3)0.340(3)0.399(3)0.399(3)

0.01572(4)0.01481(4)0.0240(6)0.0250(6)0.0277(7)0.0344(8)0.0252(6)0.0236(6)0.025(2)0.043(1)0.030(1)0.0293(7)0.0270(7)0.05a0.05a0.05a0.05a0.05a0.05a0.05a

Hydrogen atoms were refined with fixed [/iso.= (1/3)11

Structure of Be(I03)2•

2HI03•

6H20 179

I < 3ct(7). The analysis of extinction conditions and results of statisticaltests (programs NORMAL and NZTEST) indicated the possibility of theacentric space group Pna2t. The positions of iodine atoms in this spacegroup were found by MULTAN 11/82 and the structure was completedby subsequent difference Fourier syntheses and full-matrix least-squaresrefinement on F's. Although the R-factor of 0.045 was promising, thevalues of bond lengths and angles deviated significantly from the usualones. The analysis of the mutal disposition of the structural fragmentsrevealed a mirror plane perpendicular to the z-axis and the centric spacegroup Pnam was thus chosen instead. The consequent refinement convergedrapidly; the H atoms were localized and refined with fixed C/'s. Final R =

0.030, wR = 0.040 and S= 1,476; weights w = 4F2/[a2(T) + (0.04Fo)2].Max. (A/a) = 0.87 was for H(W31).

The residual density ripples failed within 1.42 and —1.26 e A~3. Second-ary extinction correction Fc¡ oort

= Fc (1+4.18 • 10"7)"1 was applied.Atomic scattering factors and anomalous-dispersion coefficients were takenas quoted in SDP/PDP V3.0 software package (Enraf-Nonius, 1985). Allcalculations were performed on a PDP11/44 computer at the Institute ofApplied Mineralogy.

Results and discussionFinal fractional coordinates are listed in Table I1. The interatomic dis-tances, angles and I O bond valences are given in Table 2. The dispositionof the structural fragments HI03,103, Be(H20)4 + and water moleculeswithin the unit cell is shown in Figure 1.

The 1(1) atom of the iodic acid has distorted octahedral environmentof six oxygen atoms2 (Fig. 2a). Although the three closest oxygen neigh-bours are at different distances [1.785(3)-1.927(3) A], the trigonal I03pyramid base is isosceles triangular with sides of 2.710(4) (2x) and2.767(4) A [0(11)....0(12)]. The next three oxygen atoms at 2.373(3)-2.825(3) A constitute the octahedron's opposite triangular face with sides3.508(5), 4.045(5), and 4.238(5) A long. The dihedral angle between bothfaces is 7.9°. 1(1) is disposed closer to the base face (0.936) than to itsopposite (1.252 A). The acidic H atom is located only 0.1 A below the base

1 Additional material to this paper can be ordered from the Fachinformations-zentrum Energie-Physik-Mathematik, D-7514 Eggenstein-Leopoldshafen 2, FRG. Pleasequote reference no. CSD 53549, the names of the authors and the title of the paper.

2 Derivation of the coordination spheres as well as calculation of the I—

O bondvalences (see Table 2) has been done with the program BROWN (Macicek, 1989). Themain feature of this Fortran 77 program is construction of the Voronoi domain of atomsin series of 'radially expanded structures'. The last ones are obtained from the set ofexperimental atomic coordinates by elongation of all interatomic vectors radiating froma particular central atom to the others.

180 Josef Macicek, Maria Maneva-Petrova and Mitko Georgiev

Table 2. Interatomic distances (Á), angles (°), I —O bond valences and hydrogen bondsgeometry. The e.s.d.'s are given in parentheses.

HI03 group1(1) —0(11) 1.785(3) 1.801a I(l)-0(23) 2.373(3) 0.368aI(l)-0(12) 1.797(3) 1.747a I(l)-0(11¡) 2.709(3) 0.148a1(1)-0(13) 1.927(3) 1.228a I(l)-0(22") 2.825(3) 0.108a

0(11)-I(1)-0(12) 101.2(1) 0(12)-I(l)-0(22¡i) 159.8(1)0(11)-I(1)-0(13) 93.7(1) 0(13)-I(l)-0(23) 175.3(1)0(ll)-I(1)-0(23) 82.5(1) 0(13)-I(1)-0(11¡) 78.7(1)0(11) —1(1) —O(ll') 171.4(1) 0(13)-1(1)-0(22") 74.0(1)0(ll)-I(l)-0(22") 95.4(1) 0(23)-I(l)-0(lli) 105.3(1)0(12)-I(1)-0(13) 93.3(1) 0(23)-I(l)-0(22") 108.9(1)0(12)-I(l)-0(23) 84.8(1) O(lf)-1(1)-0(22") 78.7(1)0(12) -1(1)-0(1 V) 85.5(1) I(l)-0(13)-H 109(5)

IOJ groupI(2)-0(21) 1.788(3) 1.789a I(2)-0(21m) 2.565(3) 0.219aI(2)-0(22) 1.814(4) 1.664a I(2)-0(22iv) 2.854(3) 0.100aI(2)-0(23) 1.841(3) 1.553a I(2)-0(23v) 3.074(3) 0.055a

I(2)-0(llv) 3.236(4) 0.036a

0(21)-1(2)-0(22) 99.1(2) Q(23)-I(2)-0(21m) 84.7(1)0(21)-I(2)-0(23) 98.1(1) 0(23)-1(2)-0(22iv) 172.2(1)0(21)-I(2)-0(21"¡) 171.9(1) 0(23)-I(2)-0(23v) 68.3(2)0(21)-I(2)-0(22iv) 84.8(1) 0(23)-1(2)-0(11V) 117.7(2)0(21)-I(2)-0(23V) 96.6(1) 0,(21"i)-I(2)-0(22iv) 93.4(2)0(21)-I(2)-0(11V) 74.5(1) 0(21¡ii)-I(2)-0(23v) 77.4(1)0(22)-I(2)-0(23) 97.9(1) 0(21¡il)-I(2)-0(llv) 97.5(2)0(22)-I(2)-0(21üi) 88.0(1) 0(22iv)-I(2)-0(23v) 118.74(8)0(22)-1(2)-0(22iv) 74.5(1) 0(22iv)-I(2)-0(llv) 70.02(8)0(22)-1(2)-0(23v) 160.5(2) 0(23T)-I(2)-O(llv) 52.13(7)0(22)-I(2)-0(llv) 144.3(2)

Be(H20)4 group

Be-O(Wl) 1.58(1) Be-0(W3) 1.640(6)Be-0(W2) 1.619(9)0(W1)-Be-0(W2) 117.9(6) 0(W2)-Be-0(W3) 105.7(4)0(W1)-Be-0(W3) 106.6(4) 0(W3)-Be-0(W3vi) 114.9(5)

Hydrogen bondsbD-H...A D-H H...A D...A D-H...A0(13)-H...O(12") 0.83(7) 1.87(7) 2.653(4) 156(7)0(Wl)-H(Wl)...0(13vi) 0.80(7) 1.88(7) 2.626(5) 156(7)0(W2)-H(W2)...0(12vii) 0.96(7) 1.69(7) 2.620(4) 161(6)0(W3)-H(W31)...0(W4viii) 1.16(8) 1.55(7) 2.661(5) 159(6)0(W3)-H(W32)...0(W4) 1.07(7) 1.58(7) 2.633(5) 165(7)0(W4)-H(W41)...0(22ix) 0.83(8) 2.07(8) 2.842(4) 156(7)0(W4)-H(W42)...0(23vii) 0.86(8) 2.05(8) 2.899(4) 168(7)

Structure of Be(I03)2 2HI03 6H20 181

Fig. 2. Six-coordination of 1(1) of the iodic acid (a) and seven-coordination of 1(2) of theiodate group (6) viewed in projection on the I03-trigonal pyramide base.

a Bond valences (s) were calculated from the bond lengths (r) using the formula s =

exp[(2.003-

r)/0.37] according to Brown and Altermatt (1985). For 1(1) and 1(2) the threeshortest I —O bond-valence sums are 4.776 and 5.006 while the total sums are 5.402 and5.417 respectively, which is obviously much more than the oxidation state of iodine (V).

b D and A denote H-bond donor and acceptor respectively. Symmetry codes: (i) 1/2+x,l/2-y,z; (ii) -Í/2 +x,\/2-y,z; (iii) 1/2-x,l/2+^,-z; (iv) 1 -x,-y,-z; (v) -x,-y,-z; (vi) x,y,l/2-z; (vii) l/2 + x,1/2-.y,l/2-z; (viii) -1/2 + x,3/2-y,z; (ix)x,l +y,l/2—z.

182 Josef Macícek, Maria Maneva-Petrova and Mitko Georgiev

plane and is oriented to the 0(12) atom of a symmetrically equivalent HI03group [H...O 1.87(7), 0...0 2.653 (4) A]. The H...O linkage is almostparallel to the a-axis.

The 1(2) atom of the iodate anion has seven close oxygen neighbours(Fig. 2b). The I —O bond lengths in the principal I03 pyramid are within1.788(3) —1.841(3) Á. The base triangle is again isosceles with sides of2.740(4) (2x) and 2.755(4) A [0(22).. .0(23)]. The three next-neighbouroxygen atoms at distances of 2.565(3) —3.074(3) Á form the opposite tri-angular face with sides of 3.546(5), 3.950(5), and 5.102(6) Á. The seventhmost distant oxygen atom at 3.236(4) Á lies 0.974 Á above this plane. 1(2)deviates from the base face by 0.882 and from its opposite

—

by 1.376 Á.These two faces are again nearly parallel, the dihedral angle being only5.2°.

The observed "strong" I —O bond lengths, which cover the whole rangeofvalues from 1.785(3) to 1.927(3) Á, fall within the empirical I

—

O distancelimits proposed by Kunze and Hamid (1977): from 1.78 +0.02 Á for acovalent I-O bond to 1.93 +0.02 Á for an I-OH bond. One of the"weak" I.. .O bonds [1(1).. .0(23), 2.373(3) Á] found in this structure is, tothe authors' knowledge, the shortest one encountered so far in iodates. Inthe orthorhombic modification of KH(I03)2 (Kunze und Hamid, 1977) theminimum I...O distance is 2.396 A and in NH4I03 • 2HI03-2.499(2) Á(Baranov et al., 1981). The segregation of the oxygens around the iodine(V) atom in two distance ranges, i.e. the formation of "strong" and "weak"I —O bonds, is caused by the presence of a voluminous electron lone pair(E) at the vertex of the I03E tetrahedron. According to Galy et al. (1981)the I —E distance is 1.23 Á, but Coquet et al. (1983) reported much smallervalue of 1.007 Á. As is to be expected, the observed "opposite" triangularfaces are more distant from the iodine atoms than the lone pair is.

The iodine atoms alone form a loose framework composed of 1(1 )2I(2)2tetrahedra. 1(1) has six closest neighbours [2 x 1(1), 4 x 1(2); I.. .1 3.773(1)-4.306(1) Á]. The seven-atom assemblage of two corner-shared tetrahedrahas geometry similar to that of the oxygen tetrahedra in the Cr207 anion(Kharitonov et al., 1969). The 1(1).. .1(1).. .1(1) line is directed along thea-axis. 1(2) has eight closest iodine neighbours [4x1(1), 4x1(2); I...I3.770(1) —4.323(1) Á]. The five 1(2) atoms form a distorted square planarsystem and the 1(1) atoms at the tetrahedra corners are disposed above andbelow this plane. In general, the iodic acid and iodate groups are arrangedin slabs corrugated along the ¿-axis, with the HI03 molecules at the crestsand troughs. The spread along the a-axis channels are filled withBe(H20)| + cations and water molecules.

In the Be(H20)4+ unit (Fig. 3a) the beryllium atom and two of thetetrahedrally coordinated water oxygen atoms [O(Wl), 0(W2)] are dis-posed on the mirror plane at z = 0.25 (0.75). The remaining two symmetri-cally related oxygen atoms [2 x 0(W3)] lie on a line perpendicular to this

Structure of Be(I03)2

2HI03•

6H20 183

<22) 0<23)Q

^ HCU41) /"lH<U42)

\

CKU4)

\\HCU31)

0<U3)

CKUI3)

Fig. 3. Participation of the Bc(H20)l + cationic group (a) and the uncoordinated watermolecule (b) in the hydrogen bonding.

plane. The Be —O distances in the symmetry plane [1.580(10) and1.619(9) Á] are shorter than the out-of-plane ones [2 x 1.640(2) A]. Theaverage Be —O bond length is 1.620(28) Á. These values may be comparedwith those found in the only experimentally determined structure of a

beryllium tetraaquacomplex-

BeS04-4H20: 1.610(4) Á (X-ray data,Dance and Freeman, 1969) and 1.618(4) Á (neutron data, Sikka andChidambaram, 1969), as well as the 1.648 Á value obtained during thetheoretical study of isolated hydrated Be2+ ions (Hashimoto et al., 1987).The Be04 tetrahedron's 0...0 edge lengths vary from 2.582(6)

184 Josef Macícek, Maria Maneva-Petrova and Mitko Georgiev

[0(W1)...0(W3)] to 2.763(5) Á [0(W3)...0(W3)], the intermediate ones

being 2.597(5) [0(W2).. .0(W3)] and 2.741(7) A [O(Wl).. .0(W2)]. Thedistortion of this tetrahedron results from a different participation of thewater molecules in intermolecular hydrogen bonding. The waters' Wl andW2 hydrogen atoms are directed to the highly polarized oxygen atoms ofthe HI03 group, whereas the water's W3 hydrogen atoms approach the0(W4) atom belonging to the uncoordinated water molecule (Fig. 3b).

ReferencesBaranov, A. I., Dobrzhanskiy, G. F., Ilyukhin, V. V., Ryabkin, V. S., Sokolov, Yu. N.,

Sorokina, N. I., Shuvalov, L.A.: Protonic conductivity in the NH4IO3•

2HI03 andKI03

2HI03 crystals (in Russian). Kristallografiya 26 (1981) 1259-1268.Biber, V., Neuman, I., Bragina, A.: About hydrates of beryllium iodates and periodates.

Zh. Obsch. Khim. (Russ.) 11 (1941) 861-869.Brown, I. D., Altermatt, D.: Bond-Valence parameters obtained from a systematic

analysis of the inorganic crystal structure database. Acta Crystallogr. B41 (1985)244-247.

Coquet, E., Crettez, J. M., Pannetier, J., Bouillot, J., Damien, J. C.: Effect of temperatureon interatomic distances in pyroelectric <x-LiI03. Acta Crystallogr. B39 (1983) 408

—413.Dance, I. G., Freeman, H. C: Refinement of the crystal structure of beryllium sulphate

tetrahydrate. Acta Crystallogr. B25 (1969) 304-310.Galy, J., Meunier, G., Andersson, S., Ástrom, A.: Stereochimie des elements comportant

des paires non liees: Ge(II), As(III), Se(IV), Br(V), Sn(II), Sb(III), Te(IV), I(V),Xe(VI), T1(I), Pb(II), et Bi(IIl) (oxydes, fluorures et oxyfluorures). J. Solid StateChem. 36 (1981) 142-159.

Hashimoto, K., Yoda, N., Iwata, S.: Theoretical study of hydrated Be2+ ions. Chem.Physics 116 (1987) 193 -202.

Kharitonov, Yu. A., Kuzmin, E. A., Ilyukhin, V. V., Belov, N. V.: Dense and densestpacking of quasispherical particles (in Russian). Kristallografiya 14 (1969) 788

—

794.Kunze, G., Hamid, S. A.: The crystal structure of a new KH(I03)2 modification. Acta

Crystallogr. B33 (1977) 2795-2803.Macícek, J.: Beryllium Hydrogen Iodate Hydrate; PDF card no. 40-756. JCPDS Grant-

in-Aid report (1989).Macícek, J.: BROWN

—

a program for automatic interpretation of inorganic crystalstructures. (1989) Unpublished.

Maneva, M., Georgiev, M.: Synthesis and properties ofberyllium iodates—

III. Synthesis,IR spectra and X-ray difraction analysis of Be(I03)2 2HI03

•

6H20. Polyhedron8 (1989a) 357-360.

Maneva, M., Georgiev, M.: Synthesis and properties of beryllium iodates—

IV. Thermaland calorimetric investigation of Be(I03)2

2HI03•

6H20. J. Thermal Anal. 35(1989b) 867-871.

Sikka, S. K., Chidambaram, R.: A neutron diffraction determination of the structure ofberyllium sulphate tetrahydrate, BeSo4

4H20. Acta Crystallogr. B25 (1969) 310-315.