347
Z. Kristallogr. NCS 219 (2004) 347-348
© by Oldenbourg Wissenschaftsverlag, München
Crystal structure of scandium arsenate(V) monohydrate, ScAsC>4 • H2O,
thefirstM11M0O4 • HzO-type arsenate
U. Kolitsch* and K. Schwendtner
Universität Wien, Institut für Mineralogie und Kristallographie, Geozentrum, Althanstr. 14, 1090 Wien, Austria
Received July 15, 2004, accepted and available on-line October 11, 2004; CSD no. 409794
Abstract
ASH2O5SC, triclinic, PI (no. 2), a = 5.604(1) A ,
b = 5.679(1) A , c = 6.770(1) A , a = 98.63(3)°,/? = 94.35(3)°,
Y = 107.72(3)°, V= 201.2 A 3 , Z = 2, RgtfF) = 0.040,
wRrdF2) = 0.105, T= 293 K.
Source of material
The title compound was prepared by a hydrothermal method
(Teflon-lined stainless steel bomb, 493 K, 7 d, slow furnace cooling) from a mixture of SC2O3, arsenic acid, Li2CC>3 and distilled
water. The pH value of both starting and reacted solutions was
about 3. ScAsC>4 - H2O formed tiny indistinct colorless plates.
Discussion
ScAs04 • H2O, scandium arsenate(V) monohydrate, was obtained
during an ongoing study of the crystal-chemical behavior of Sc m
in oxysalts. It is a new, hydrothermally synthesized compound
which has not been reported in any of the previous studies of scandium arsenates [1-5].
SCASC>4 • H2O is isotypic with the phosphate I11PO4 • H2O [6], the
vanadate schubnelite [FeraVC>4 • H2O] [7] and the molybdates
and tungstates Ai"X0 4 • H 2 0 (M = Mg, Mn; X = Mo, W) [8,9].
Thus, the title compound represents the first arsenate within this
small family of isotypic oxysalts which contain Af20g(H20)2 (M=
di- or bivalent metal) dimers built of edge-sharing MOf, octahedra (see below for more details). Although ScPC>4 - H2O has not
been reported yet, it should be investigated if this compound exists and if it also adopts the structure type which was originally
described for M11M0O4 • H2O [8], The close crystal-chemical relation between Sc m and Fe m [10] suggests that isotypic triclinic
Fe M P04 • H2O and FemAsC>4 • H2O may also be prepared by hydrothermal methods.
The crystal structure of ScAsC>4 • H2O contains one crystallographically non-equivalent Sc, one As and Ave O atoms, all are
located in general positions. The OW5 atom represents a water
molecule. The Sc atom is octahedrally coordinated to six O ligands (including OW5), with Sc—O distances ranging between
1.996(4) A and 2.208(3) A [dav(Sc—O) = 2.106 A ] . The resulting, somewhat distorted Sc0s(H20) octahedron shares one
O l - O l edge with another equivalent octahedron, thus forming a
Sc2C>8(H20)2 dimer. The shared edge represents the shortest O-O
distance within this building unit, as would be expected from
Sc-Sc repulsion across the shared edge.
The Sc208(H20)2 dimers are comer-linked to slightly distorted
ASC>4 tetrahedra [Dav(As—O) = 1.679 A , range: 1.649(3) A to
1.708(3) A ] , The linkage results in a three-dimensional framework with small voids into which is pointing the apical water
ligand (OW5) of the ScOsilfeO) octahedron. Although the hydrogen atoms could neither be clearly identified nor refined, the residual electron densities close to the OW5 atom at least suggest
that the H positions are probably close to those in MnMo04 • H2O
[8]. Hydrogen-bonding is estimated to be weak. Distances between OW5 and possible acceptor atoms are all larger than
2.75 A.
Bond-valence sums for all atoms were calculated using the bondvalence parameters from Brese & O'Keeffe [11], They amount to
3.05 (Sc), 5.08 (As), 1.99 (Ol), 1.84 (02), 2.05 (03), 1.83 (04)
and 0.43 (OW5) valence units, and thus are all reasonably close to
ideal valencies. ScAsC>4 - H2O is the first compound to contain a
Sc2C>8(H20)2 dimer. However, a topologically very similar
SC2O10 dimer built of two edge-sharing ScC>6 octahedra exists in
the orthorhombic silicate Na4Sc2SuOi3 [12].
* Correspondence author (e-mail: [email protected])
Unauthenticated
Download Date | 6/19/17 3:21 AM
348
SCAS04 • H2O
Table 1. Data collection and handling.
Crystal:
Wavelength:
M-
Diffractometer, scan mode:
20mn'
N(hkl)measured,
Criterion for /obs,
N(param
Nfhkl)^ique:
N(hkl)p:
)rcfmai
Programs:
colorless, tabular,
size 0.03 x 0.03 x 0.04 mm
Mo Ka radiation (0.71073 Â)
98.84 cm"'
Nonius KappaCCD, <p/<u
59.98°
2238, 116
/obs > 2 ado)*), 976
65
SHELXS-97 [13], SHELXL-97 [14],
DIAMOND [15], ORTEP-3 [16]
Table 2. Atomic coordinates and displacement parameters (in  2 ).
Atom
Site
Sc
As
0(1)
0(2)
0(3)
0(4)
OW(5)
2i
2/
2/
2i
2/
21
2i
X
0.3614(2)
0.26193(9)
0.3738(6)
0.3484(7)
0.3833(8)
-0.0554(7)
0.0905(8)
y
0.2740(2)
0.12134(9)
0.3525(6)
-0.1274(7)
0.2345(7)
0.0417(7)
0.4741(8)
z
l/l !
0.0107(5)
-0.2116(1)
0.25549(7)
0.0105(3)
0.1192(5)
0.012(2)
0.1653(5)
0.013(2)
0.4931(5)
0.023(2)
0.2258(5) ' 0.011(2)
-0.2320(6)
0.013(2)
i/22
I/33
i/12
i/13
i/23
0.0145(5)
0.0140(3)
0.014(2)
0.019(2)
0.024(2)
0.017(2)
0.021(2)
0.0136(5)
0.0123(3)
0.013(2)
0.020(2)
0.012(2)
0.025(2)
0.040(2)
0.0048(4)
0.0038(2)
0.002(1)
0.007(2)
0.006(2)
0.005(1)
0.009(2)
0.0010(3)
0.0006(2)
0.000(1)
0.001(1)
0.000(1)
0.001(1)
0.001(2)
0.0031(3)
0.0028(2)
0.004(1)
0.003(1)
0.002(1)
0.004(1)
0.007(2)
Financial support by the Austrian Science Foundation
(FWF) (grant P15220-N06) and the International Centre for Diffraction Data
(grant 90-03 ET) is gratefully acknowledged.
Acknowledgments.
References
1. Komissarova, L. N.; Pushkina, G. Ya.; Khrameeva, N. P.: Preparation and
some properties of scandium arsenate dihydrate. Zh. Neorg. Khim. 16
(1971) 1538-1541 (in Russian).
2. Khrameeva, N. P.; Komissarova, L. N.; Pushkina, G. Ya.: Scandium arsenates. Zh. Neorg. Khim. 16 (1971) 2660-2664 (in Russian).
3. Ivanov-Emin, B. N.; Korotaeva, L. G.; Moskalenko, V. I.; Ezhov, A. I.:
Scandium arsenates. Zh. Neorg. Khim. 16 (1971) 2925-2928 (in Russian).
4. Khrameeva, N. P.; Pushkina, G. Ya.; Komissarova, L. N.; Teterin, E. G.:
Synthesis and properties of disubstituted scandium arsenate. Zh. Neorg.
Khim. 18 (1973) 867-872 (in Russian).
5. Komissarova, L. N.; Pushkina, G. Ya.; Khrameeva, N. P.; Teterin, E. G.:
Scandium arsenates. Zh. Neorg. Khim. 18 (1973) 2316-2323 (in Russian).
6. Tang, X.; Lachgar, A.: The missing link: synthesis, crystal structure, and
thermogravimetric studies of I11PO4H2O. Inorg. Chem. 37 (1998) 61816185.
7. Schindler, M.; Hawthorne, F. C.: Schubnelite, [Fe 3+ (V04)(H20)], a novel
heteropolyhedral framework mineral. Am. Mineral. 84 (1999) 666-668.
8. Clearfield, A.; Moini, A.; Rudolf, P. R.: Preparation and structure of manganese molybdates. Inorg. Chem. 24 (1985) 4606-4609.
9. Amberg, M.; Guenter, J. R.; Schmalle, H.; Blasse, G.: Preparation, crystal
structure, and luminescence of magnesium molybdate and tungstate
monohydrates, MgMoCV H2O and MgW04- H2O. J. Solid State Chem. 77
(1988) 162-169.
10. Frondel, C.: Crystal chemistry of scandium as a trace element in minerals.
Z. Kristallogr. 127 (1968) 121-138.
11.Brese, N. E.; O'Keeffe, M.: Bond-valence parameters for solids. Acta
Crystallogr. B47 (1991) 192-197.
12. Maksimov, B. A.; Mel'nikov, O. K.; Zhdanova, T. A.; Ilyukhin, V. V.:
Crystal structure of Na4Sc2SUOi3. Dokl. Akad. Nauk SSSR 251 (1980)
98-102 (in Russian).
13. Sheldrick, G. M.: SHELXS-97. Program for the Solution of Crystal Structures. University of Göttingen, Germany 1997.
14. Sheldrick, G. M.: SHELXL-97. Program for the Refinement of Crystal
Structures. University of Göttingen, Germany 1997.
15. Pennington, W. T.: DIAMOND - Visual Crystal Structure Information
System. J. Appl. Crystallogr. 32 (1999) 1028-1029.
16. Fanugia, L. J.: ORTEP-3 for Windows - a version of ORTEP-m with a
graphical user interface (GUI) I. Appl. Crystallogr. 30 (1997) 565.
Unauthenticated
Download Date | 6/19/17 3:21 AM