Tetra­yttrium difluoride disilicate orthosilicate, Y4F2[Si2O7][SiO4]

Marion C Schäfer; Ingo Hartenbach; Thomas Schleid

doi:10.1107/S1600536813026391

. 2013 Sep 28;69(Pt 10):i71. doi: 10.1107/S1600536813026391

Tetrayttrium difluoride disilicate orthosilicate, Y₄F₂[Si₂O₇][SiO₄]

Marion C Schäfer ^a,^b, Ingo Hartenbach ^b, Thomas Schleid ^b,^*

PMCID: PMC3790338 PMID: 24098160

Abstract

In the crystal structure of Y₄F₂[Si₂O₇][SiO₄], three fundamental building blocks are present, viz. anionic disilicate and orthosilicate units ([Si₂O₇]⁶⁻ and [SiO₄]⁴⁻) and cationic [F₂Y₄]¹⁰⁺ entities. The latter are built up by two [FY₃]⁸⁺ triangles sharing a common edge. The four crystallographically independent Y³⁺ cations display coordination numbers of eight for one and of seven for the other three cations, provided by oxide and fluoride anions. The overall arrangement of the building blocks can be considered as layer-like parallel to the ac plane.

Related literature

For isotypic Er₄F₂[Si₂O₇][SiO₄], see: Müller-Bunz & Schleid (2001 ▶). For the minor by-product phase Y₃F[Si₃O₁₀], see: Müller-Bunz & Schleid (1998 ▶). For the crystal structure of allanite (old name orthite), see: Rumanova & Nikoleva (1959 ▶).

Experimental

Crystal data

Y₄F₂[Si₂O₇][SiO₄]
M _r = 653.91
Triclinic,
a = 6.4987 (5) Å
b = 6.6196 (5) Å
c = 13.2978 (9) Å
α = 87.418 (4)°
β = 85.702 (4)°
γ = 60.854 (3)°
V = 498.19 (6) Å³
Z = 2
Mo Kα radiation
μ = 23.52 mm⁻¹
T = 293 K
0.10 × 0.06 × 0.03 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1995 ▶) T _min = 0.104, T _max = 0.463
12473 measured reflections
2427 independent reflections
1475 reflections with I > 2σ(I)
R _int = 0.120

Refinement

R[F ² > 2σ(F ²)] = 0.055
wR(F ²) = 0.107
S = 0.98
2427 reflections
182 parameters
Δρ_max = 1.56 e Å⁻³
Δρ_min = −1.49 e Å⁻³

Data collection: COLLECT (Nonius, 1998 ▶); cell refinement: SCALEPACK (Otwinowski & Minor, 1997 ▶); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 2006 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablock(s) I, publication_text. DOI: 10.1107/S1600536813026391/wm2768sup1.cif

e-69-00i71-sup1.cif^{(18.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813026391/wm2768Isup2.hkl

e-69-00i71-Isup2.hkl^{(119.2KB, hkl)}

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

Acknowledgments

This work was supported by the State of Baden-Württemberg (Stuttgart) and the Deutsche Forschungsgemeinschaft (DFG, Frankfurt/Main) within the funding program Open Access Publishing.

supplementary crystallographic information

1. Comment

Y₄F₂[Si₂O₇][SiO₄] crystallizes isotypically with the already known erbium analogue Er₄F₂[Si₂O₇][SiO₄] (Müller-Bunz & Schleid, 2001). The crystal structure comprises two different oxidosilicate anions, namely a pyroanionic bitetrahedral disilicate unit [Si₂O₇]^6– with eclipsed conformation (Fig. 1, top left) and an orthosilicate tetrahedron [SiO₄]^4– (Fig. 1, top right), just like in the mineral allanite (old name orthite) (Rumanova & Nikoleva, 1959). Together with these two anionic building blocks, discrete cationic [F₂Y₄]¹⁰⁺ entities (Fig. 1, bottom) complete the crystal structure of Y₄F₂[Si₂O₇][SiO₄]. For the formation of the latter, two almost planar [FY₃]⁸⁺ triangles are fused together via one common edge, resulting in a butterfly-shaped [F₂Y₄]¹⁰⁺ unit comprising an angle between the two triangular planes of 161.65 (5)°. Two of the four crystallographically distinct Y³⁺ cations (Y2, Y3) display just one fluoride anion in their coordination sphere, while the other two (F1, F4) have contact with two F^– anions each. O^2– anions complete the coordination environments of the yttrium cations resulting in distorted bi- (Y1) or monocapped (Y2-4) trigonal prisms. The cationic [F₂Y₄]¹⁰⁺ as well as the anionic [Si₂O₇]^6– and [SiO₄]^4– building blocks are arranged layer-like parallel to the ac plane in the crystal structure of the title compound (Fig. 2).

2. Experimental

Colourless lath-shaped single crystals of Y₄F₂[Si₂O₇][SiO₄] were obtained by the reaction of yttrium sesquioxide (Y₂O₃), yttrium trifluoride (YF₃), and silicon dioxide (SiO₂) in the molar ratio 2:5:3 and an excess of cesium chloride (CsCl) as flux in evacuated silica ampoules within nine days at 973 K and a cooling rate of 10 Kh^-1. Due to the stability of the product against air and moisture, the excess flux can the removed by washing with water. Besides the title compound, single crystals of thalenite-type Y₃F[Si₃O₁₀] (Müller-Bunz & Schleid, 1998) were also found in the product mixture as minor by-product.