Cs0.49NbPS6

Eunsil Lee; Yonghee Lee; Hoseop Yun

doi:10.1107/S1600536810052724

. 2010 Dec 24;67(Pt 1):i4. doi: 10.1107/S1600536810052724

Cs_0.49NbPS₆

Eunsil Lee ^a, Yonghee Lee ^a, Hoseop Yun ^a,^*

PMCID: PMC3050425 PMID: 21522512

Abstract

The quaternary thiophosphate, Cs_0.49NbPS₆, caesium hexathioniobiophosphate(V), has been synthesized by the reactive halide flux method. The title compound is isotypic with Rb_0.46TaPS₆ and is made up of a bicapped trigonal–biprismatic [Nb₂S₁₂] unit and a tetrahedral [PS₄] group. The [Nb₂S₁₂] units linked by the [PS₄] tetrahedra form infinite chains, yielding a three-dimensional network with rather large van der Waals gaps along the c axis in which the disordered Cs⁺ ions reside. The electrons released by the Cs atoms are transferred to the pairwise niobium metal site and there are substantial intermetallic Nb—Nb bonding interactions. This leads to a significant decrease of the intermetallic distance in the title compound compared to that in TaPS₆. The classical charge balance of the title compound may be represented as [Cs⁺]_0.49[Nb^4.51+][P⁵⁺][S²⁻]₄[S₂ ²⁻].

Related literature

For the synthesis and structural characterization of TaPS₆, see: Fiechter et al. (1980 ▶). For the related quaternary alkali metal thiophosphates, see: K_0.38TaPS₆ and Rb_0.46TaPS₆ (Gutzmann et al., 2004a ▶) and A ₂Nb₂P₂S₁₂ (A = K, Rb, Cs; Gieck et al., 2004 ▶). Quite a few quaternary alkali metal thiophosphates having similar composition but with different structures have been reported. For compounds with layered structures, see: Gutzmann & Bensch (2003 ▶) for Rb₄Ta₄P₄S₂₄; Gutzmann et al. (2004b ▶) for Cs₄Ta₄P₄S₂₄ and Cs₂Ta₂P₂S₁₂ and Gutzmann et al. (2005) ▶ for K₄Ta₄P₄S₂₄. For Rb₂Ta₂P₂S₁₁ with a one-dimensional structure, see: Gutzmann & Bensch (2002 ▶).

Experimental

Crystal data

Cs_0.49NbPS₆
M _r = 380.95
Tetragonal,
a = 15.9477 (3) Å
c = 13.2461 (3) Å
V = 3368.88 (11) Å³
Z = 16
Mo Kα radiation
μ = 5.08 mm⁻¹
T = 290 K
0.30 × 0.08 × 0.06 mm

Data collection

Rigaku R-AXIS RAPID diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ▶) T _min = 0.751, T _max = 1.000
16125 measured reflections
1929 independent reflections
1843 reflections with I > 2σ(I)
R _int = 0.032

Refinement

R[F ² > 2σ(F ²)] = 0.020
wR(F ²) = 0.047
S = 1.06
1929 reflections
81 parameters
Δρ_max = 0.84 e Å⁻³
Δρ_min = −0.42 e Å⁻³
Absolute structure: Flack (1983 ▶), 851 Friedel pairs
Flack parameter: 0.452 (18)

Data collection: RAPID-AUTO (Rigaku, 2006 ▶); cell refinement: RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: locally modified version of ORTEP (Johnson, 1965 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810052724/si2311sup1.cif

e-67-000i4-sup1.cif^{(16.2KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810052724/si2311Isup2.hkl

e-67-000i4-Isup2.hkl^{(93.3KB, hkl)}

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

Table 1. Selected geometric parameters (Å, °).

Nb—S1ⁱ	2.5016 (9)
Nb—S6ⁱⁱ	2.5221 (9)
Nb—S1ⁱⁱⁱ	2.5238 (8)
Nb—S6^iv	2.5457 (9)
Nb—S2	2.5457 (9)
Nb—S3	2.5730 (9)
Nb—S5^v	2.5971 (9)
Nb—S4	2.6266 (9)
Nb—Nb^vi	3.1236 (5)
P1—S2ⁱ	2.0300 (11)
P1—S2	2.0300 (11)
P1—S5^vii	2.0413 (10)
P1—S5^v	2.0413 (10)
P2—S3^viii	2.0353 (10)
P2—S3^ix	2.0353 (10)
P2—S4^ix	2.0519 (11)
P2—S4^viii	2.0519 (11)
S1—S1^x	2.0302 (17)
S6—S6^xi	2.0264 (17)

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S2ⁱ—P1—S2	109.11 (7)
S2ⁱ—P1—S5^vii	102.92 (3)
S2—P1—S5^vii	113.21 (4)
S2ⁱ—P1—S5^v	113.21 (4)
S2—P1—S5^v	102.92 (3)
S5^vii—P1—S5^v	115.63 (7)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) ; (viii) ; (ix) ; (x) ; (xi) .

Acknowledgments

This work was supported by the Priority Research Centers Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2010–0029617). Use was made of the X-ray facilities supported by the Ajou University.

supplementary crystallographic information

Comment

During an effort to find a new phase in the A_xMPS₆ family (A=alkali metals; M=Ta, Nb), a new compound was isolated. Here we report the synthesis and structure of the new quaternary thiophosphates, Cs_0.49NbPS₆.

The title compound is isostructural with the previously reported Rb_0.46TaPS₆ (Gutzmann et al., 2004a). The structure of Cs_0.49NbPS₆ is also very similar to that of ANb₂P₂S₁₂ (A=K, Rb, and Cs, Gieck et al., 2004) prepared from alkali metal sulfide fluxes. The only difference between them lies in the distribution of the alkali metals. There are two crystallographically independent sites for Cs atoms in ANb₂P₂S₁₂, while we were able to find only one in Cs_0.49NbPS₆.

The structure of Cs_0.49NbPS₆ is made up of the bicapped trigonal biprismatic [Nb₂S₁₂] unit and the tetrahedral [PS₄] group. The niobium atom is coordinated by eight sulfur atoms in a distorted bicapped trigonal prismatic arrangement. Two NbS₈ prisms share a rectangular face to form the [Nb₂S₁₂] dimeric core. Four sulfur atoms sharing rectangular prism faces are in pairs with two disulfide ions, (S—S)^2-. Each one of the capping sulfur atoms and one of the sulfur atoms at the corner of the [Nb₂S₁₂] unit are bound to a phosphorous atom (Fig. 1). Additional two sulfur atoms from the neighboring [Nb₂S₁₂] units are connected to the phosphorous atoms to complete the [PS₄] tetrahedral coordination. Each [Nb₂S₁₂] unit connects four phosphorous atoms to build up left- and right-handed helices. These helices interwind to each other forming infinite channels along the [001] direction (Fig. 2). The structural array yields rather large channels, where the Cs⁺ ions reside. The size of the cations is small compared to the diameter of the large channels and the cations can therefore rattle within the channels as indicated by the high anisotropic displacement parameters.

The Nb—S and P—S distances are in good agreement with those found in other related phases (Gutzmann et al., 2004b). The interatomic Nb—Nb distance is 3.124 (1) Å which is similar to those in K_0.38TaPS₆ (3.142 (2) Å) and Rb_0.46TaPS₆ (3.1011 (5) Å). These distances are considerably shorter compared to that in TaPS₆ (3.361 (1) Å, Fiechter et al., 1980). The electrons released by the Cs atoms are transferred to pair-wise niobium metal sites and there are substantial intermetallic Nb—Nb bonding interactions. Consequently, the classical charge balance of the title compound may be represented as [Cs⁺]_0.49[M^4.51+][P⁵⁺][S^2-]₄[S₂^2-].

Experimental

Cs_0.49NbPS₆ was prepared by the reaction of elements Nb, P, and S by the reactive halide-flux technique. A combination of the pure elements, Nb powder (CERAC 99.999%), P powder (CERAC 99.5%) and S powder (Aldrich 99.999%) were mixed in a fused silica tube in molar ratio of Nb:P:S=1:1:6 in the presence of CsCl as flux. The mass ratio of the reactants and the alkali halide flux was 1:2. The tube was evacuated to 0.133 Pa, sealed, and heated gradually (60 K/h) to 973 K, where it was kept for 72 h. The tube was cooled to room temperature at the rate 4 K/h. The excess halide was removed with distilled water and shiny black needle-shaped crystals were obtained. The crystals are stable in air and water. Qualitative analysis of the crystals with an EDAX-equipped SEM indicated the presence of Cs, Nb, P, and S. The composition of the compound was determined by single-crystal X-ray diffraction.