Neodymium(III) molybdenum(VI) borate, NdBO2MoO4

Peter Held; Benjamin van der Wolf; Ladislav Bohatý; Petra Becker

doi:10.1107/S1600536811017806

. 2011 May 20;67(Pt 6):i36. doi: 10.1107/S1600536811017806

Neodymium(III) molybdenum(VI) borate, NdBO₂MoO₄

Peter Held ^a,^*, Benjamin van der Wolf ^a, Ladislav Bohatý ^a, Petra Becker ^a

PMCID: PMC3120577 PMID: 21754565

Abstract

Single crystals of NdBO₂MoO₄ were obtained from a molybdenum oxide–boron oxide flux under an air atmosphere. The structure features double chains of edge- and face-sharing distorted [NdO₁₀] bicapped square-antiprisms, which are linked by rows of isolated [MoO₄] tetrahedra and by zigzag chains of corner-sharing [BO₃] groups, all of them running along the b axis. The chains of [NdO₁₀], chains of [BO₃] and rows of [MoO₄] groups are arranged in layers parallel to the bc plane.

Related literature

A rough investigation of subsolidus phase relations in the pseudo-ternary system Nd₂O₃ – B₂O₃ – MoO₃ has been reported by Lysanova et al. (1983 ▶) and Dzhurinskii & Lysanova (1998 ▶). X-ray powder diffraction data of LnBO₂MoO₄ (Ln = La, Ce, Pr, Nd) are given by Lysanova et al. (1983 ▶). The occurrence of a structural phase transition of LaBO₂MoO₄ was reported by Becker et al. (2008 ▶). For determinations of related structures, see: Palkina et al. (1979 ▶); Zhao et al. (2008 ▶, 2009 ▶) for LaBO₂MoO₄; Zhao et al. (2008 ▶) for CeBO₂MoO₄.

Experimental

Crystal data

NdMoBO₆
M _r = 346.99
Monoclinic,
a = 10.1218 (19) Å
b = 4.1420 (5) Å
c = 11.896 (3) Å
β = 116.897 (14)°
V = 444.78 (16) Å³
Z = 4
Mo Kα radiation
μ = 14.30 mm⁻¹
T = 292 K
0.30 × 0.20 × 0.15 mm

Data collection

Enraf–Nonius CAD-4/MACH3 diffractometer
Absorption correction: ψ scan (MolEN; Fair, 1990 ▶) T _min = 0.487, T _max = 0.998
5004 measured reflections
1344 independent reflections
1268 reflections with I > 2σ(I)
R _int = 0.035
3 standard reflections every 100 reflections intensity decay: 2.1%

Refinement

R[F ² > 2σ(F ²)] = 0.025
wR(F ²) = 0.063
S = 1.22
1344 reflections
83 parameters
Δρ_max = 2.24 e Å⁻³
Δρ_min = −1.61 e Å⁻³

Data collection: MACH3 (Enraf–Nonius, 1993 ▶); cell refinement: MACH3; data reduction: MolEN (Fair, 1990 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ATOMS (Dowty, 2002 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811017806/fi2107sup1.cif

e-67-00i36-sup1.cif^{(16.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811017806/fi2107Isup2.hkl

e-67-00i36-Isup2.hkl^{(66.4KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

This work was supported by the Deutsche Forschungsgemeinschaft (DFG) under projects BO 1017/5–2 and BE 2147/6–2.

supplementary crystallographic information

Comment

In the family of lanthanide compounds LnBO₂MoO₄ the crystal structure of LaBO₂MoO₄ was first described by Palkina et al. (1979), giving the polar space group P2₁ and lattice constants a = 5.964 (1) Å, b = 4.147 (1) Å, c = 9.373 (3) Å, β = 99.28 (2)°. On the basis of X-ray powder diffraction data, Lysanova et al. (1983) claimed the isomorphism of the compounds LnBO₂MoO₄ with Ln = La, Ce, Pr, Nd. The structure of LaBO₂MoO₄ was redetermined by Zhao et al. (2008), who reported a centrosymmetric structure with space group symmetry P2₁/c with lattice constants a = 10.2968 (8) Å, b = 4.1636 (3) Å, c = 23.8587 (15) Å, β = 115.367 (3)°. These results were corroborated by Zhao et al. (2009), who, however, attributed this crystal structure to a high-temperature modification of LaBO₂MoO₄. The occurrence of a structural phase transition of LaBO₂MoO₄ was reported by Becker et al. (2008). Zhao et al. (2008) also presented the crystal structure of the related cerium compound, CeBO₂MoO₄, with space group P2₁/c and lattice constants a = 10.2404 (15) Å. b = 4.1495 (4) Å, c = 11.9286 (14) Å, β = 116.100 (9)°, and thus showed, that the presumed isomorphism of the lanthanum and the cerium compound is not correct. However, the crystal structures are closely related, with an unit cell of LaBO₂MoO₄ which is doubled with respect to the unit cell of CeBO₂MoO₄. The result of the present study shows, that also NdBO₂MoO₄ is not isomorphic to LaBO₂MoO₄, but is isomorphic to CeBO₂MoO₄.

The crystal structure of NdBO₂MoO₄ consists of groups [BO₃] and [MoO₄] and tenfold coordinated neodymium atoms. The [BO₃] groups are connected via common oxygen ligands to zigzag chains [B₂O₄]_∞ along the b axis, with a periodicity of two [BO₃] groups. The planar [BO₃] groups are slightly distorted with O—B—O angles of 114.4 (4)°, 117.4 (4)° and 128.1 (4)°. They are linked by the common oxygen atom O1 with a bond angle B – O1 – B of 125.6 (3)° (see Fig. 1). The O1 ligands are connected to two boron atoms and one Nd atom, each, while the O2 ligands of the [BO₃] groups are linked to three Nd atoms and one B, each. Mo atoms are tetrahedrally coordinated by the oxygen atoms O3, O4, O5 and O6 (see Fig. 1), with Mo—O distances ranging from 1.740 (4) Å (Mo—O3) to 1.816 (3) Å (Mo—O4) and angles O—Mo—O ranging from 96.3 (2)° (O4—Mo—O3) to 117.5 (2)° (O4—Mo—O6). The [MoO₄] tetrahedra are arranged in rows that run parallel the b axis. Within a single row the [MoO₄] tetrahedra are aligned with their Mo–O3 bonding directions pointing in the same direction approximately parallel to the b axis. Rows with opposite Mo–O3 bonding direction (+b and -b) alternate along the c axis, as shown in Fig. 2. Within a row the distance of a Mo atom to the O3 ligand of the neighbouring tetrahedron amounts 2.419 (3) Å. (Note that in Zhao et al. (2008) a distorted trigonal bipyramid is preferred as description of the coordination surrounding of Mo in CeBO₂MoO₄.) The oxygen atoms O3 and O5 serve as ligands of one Mo and one Nd atom, each, while the oxygen atoms O6 and O4 act as ligands for one Mo and two Nd atoms, each. The tenfold coordination of neodymium atoms in NdBO₂MoO₄ can be described as distorted bicapped square antiprism with Nd—O bonding distances ranging between 2.364 (3) Å (Nd—O2) and 2.981 (4) Å (Nd—O6). [NdO₁₀] polyhedra are connected along the b axis by sharing three common oxygen ligands, namely O2, O6 and O4 (Fig. 1), with each neighbouring polyhedron, thus forming chains along the b axis. Two parallel chains are linked via edges (formed by two common O2 atoms) of the Nd coordination polyhedra, resulting in a double chain along b, see Fig. 2.

Experimental

NdBO₂MoO₄ melts incongruently, therefore, single crystals of NdBO₂MoO₄ were grown from a melt with a composition differing from the crystal stoichiometry. A homogenized powder mixture of Nd₂O₃ (99.9%, Alfa Aesar), B₂O₃ (99.98%, Alfa Aesar) and MoO₃ (99,95%, Alfa Aesar) in a molar ratio of 1: 1.375: 2.625 was heated in a covered platinum crucible in air atmosphere to 1423 K and subsequently cooled at a rate of 3 K h^-1 to 1173 K. Transparent violet prismatic crystals of the title compound were separated mechanically from the surrounding flux. A suitable single-crystal was carefully selected using a polarizing microscope and mounted in a glass capillary.