A new quaternary thiophosphate, RbNb₂(S₂)₃(PS₄)

The structure of the new quaternary thio­phosphate rubidium diniobium tris­(di­sulfide) tetra­thio­phosphate, RbNb₂(S₂)₃(PS₄), is made up of one-dimensional [Nb₂(S₂)₃(PS₄)^-] chains along the [101] direction, and these chains are separated from one another by Rb⁺ ions. The chain is basically built up from [Nb₂S₁₂] units and tetrahedral [PS₄] groups. The [Nb₂S₁₂] units are linked together to form a linear [Nb₂S₉] chain by sharing the S-S prism edge. Short and long Nb-Nb distances [2.888 (2) and 3.760 (2) Å, respectively] alternate along the chain, and the anionic species S₂^2- and S^2- are observed.

S1. Comment

Group 5 transition metal thiophosphates have been extensively investigated, due to the structural variety endowed by the many different P—S catenations and their interesting properties (Rouxel, 1986). In particular, their low-dimensional nature makes them of potential importance as cathode materials for high-energy-density secondary batteries (Evain et al., 1987). However, no stable intercalated product in the group 5 metal/P/S system has been well characterized. Thus, we have used alkali metal halides as reactive fluxes to find new phases (Do & Yun, 1996) and to investigate the structural features in this system.

The title compound, RbNb₂(S₂)₃(PS₄) or RbNb₂PS₁₀, has a structure similar to that of the previously reported KNb₂PS₁₀ (Do & Yun, 1996) and it is closely related to those of the other group 5 metal thiophosphates, V₂PS₁₀ (Brec, Ouvrard et al., 1983), Nb₄P₂S₂₁ (Brec, Evain et al., 1983) and Nb₂PS₁₀ (Brec, Grenouilleau et al., 1983). The structure of RbNb₂(S₂)₃(PS₄) consists of one-dimensional _∞¹[Nb₂PS₁₀^-] chains along the [101] direction (Fig. 1) and these are well separated by Rb⁺ ions (Fig. 2). There are only van der Waaals interactions between the chains. The Rb⁺ ions in this van der Waals gap stabilize the structure through ionic interactions.

As shown in other phases in the M/P/S family (M is V or Nb), each chain is made up of the typical bicapped biprismatic [Nb₂S₁₂] units and tetrahedral [PS₄] groups. Both Nb1 and Nb2 atoms are surrounded by eight S atoms in a bicapped trigonal prismatic fashion. Two prisms share a rectangular face to form the [Nb₂S₁₂] unit (Fig 3). This unit shows an approximate twofold rotation symmetry, which is also found in KNb₂PS₁₀. The rotation axis bisects the short Nb1—Nb2 distance and the (S—S)₂ sides of the rectangular face shared by each trigonal prism. One of the S atoms at the prism edge and two other capping S atoms are bound to the P atom, and an additional S atom (S9) is attached to the P atom to complete the PS₄ tetrahedral coordination. The average P—S distance within the PS₄ unit [2.042 (6) Å] is in good agreement with the P—S distances found in other related phases. Atom S9 is the only terminal atom in the compound, and this is responsible for the short P—S9 distance [1.979 (6) Å] and the large anisotropic displacement parameter of atom S9 (Do & Yun, 1996).

Along the chains, the Nb atoms associate in pairs, with Nb—Nb interactions alternating in the sequence of one short and one long distance. The short distance [2.888 (2) Å] is typical of Nb⁴⁺—Nb⁴⁺ bonding interactions (Angenault et al., 2000). However, the long distance [3.760 (2) Å] implies that there is no significant Nb—Nb interaction, and such an arrangement is consistent with the highly resistive and diamagnetic nature of the compound.

The classical charge balance of RbNb₂(S₂)₃(PS₄) may be represented as [Rb⁺][Nb⁴⁺]₂[P⁵⁺][S₂^2-]₃[S^2-]₄. Studies to solubilize this compound with highly polar solvents (Tarascon et al., 1985), to obtain an isolated polymeric _∞¹[Nb₂PS₁₀^-] chain, are underway.

S2. Experimental

The title compound was prepared by the reaction of Nb, P and S in an elemental ratio of 2:1:10 in a eutectic mixture of RbCl/LiCl. The starting materials, Nb powder (CERAC, 99.8%), P powder (CERAC, 99.5%), and S powder (Aldrich, 99.999%), were placed in a quartz tube. The mass ratio of reactants and halide fluxes was 1:2. The tube was evacuated to 10 ^-2 Torr (1 Torr = 133.322 Pa), sealed and heated to 973 K, where it was kept for 7 d. Afterwards, the tube was cooled to room temperature at a rate of 4 K hr^-1. Dark-red needle-shaped crystals of RbNb₂(S₂)₃(PS₄) were isolated from the flux with distilled water. The crystals are stable in water and in air. Electron-microprobe analysis of the crystals established their homogeneity and the presence of Rb, Nb, P and S.

Computing details

Data collection: MXC3 Software (MacScience Corporation, 1994); cell refinement: MXC3 Software; data reduction: MXC3 Software; program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Please provide missing details.

Figures

	Fig. 1. A stereoscopic view of the one-dimensional ∞^1[Nb2PS10^-] chain in RbNb2(S2)3(PS4). Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. A view of RbNb2(S2)3(PS4) down the chain axis, showing the one-dimensional nature of the compound. Large, medium and small filled circles indicate Rb, Nb and P atoms respectively; large open circles indicate S atoms.
	Fig. 3. A perspective view of the [Nb2S12] unit in RbNb2(S2)3(PS4). Small filled circles indicate Nb atoms and large open circles indicate S atoms. Nb—S bonds have been omitted for clarity, except for the capping S atoms.

Rubidium diniobium tris(disulfide) tetrathiophosphate

Crystal data

RbNb2(S2)3(PS4)	F(000) = 588
Mr = 622.86	Dx = 3.124 Mg m^−3
Monoclinic, Pn	Mo Kα radiation, λ = 0.71073 Å
a = 12.773 (3) Å	Cell parameters from 24 reflections
b = 7.529 (2) Å	θ = 10.0–15.0°
c = 7.108 (2) Å	µ = 7.03 mm^−1
β = 104.37 (2)°	T = 293 K
V = 662.2 (3) Å^3	Needle, dark red
Z = 2	0.54 × 0.04 × 0.03 mm

Data collection

MacScience MXC3 diffractometer	1169 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.031
Graphite monochromator	θmax = 25.0°, θmin = 2.7°
ω/2θ scans	h = 0→15
Absorption correction: analytical (de Meulenaer & Tompa, 1965)	k = −8→0
Tmin = 0.691, Tmax = 0.794	l = −8→8
1293 measured reflections	2 standard reflections every 100 reflections
1198 independent reflections	intensity decay: 0.0(15)

Refinement

Refinement on F^2	w = 1/[σ^2(Fo^2) + (0.0771P)^2 + 1.6949P] where P = (Fo^2 + 2Fc^2)/3
Least-squares matrix: full	(Δ/σ)max < 0.001
R[F^2 > 2σ(F^2)] = 0.039	Δρmax = 1.44 e Å^−3
wR(F^2) = 0.114	Δρmin = −1.41 e Å^−3
S = 1.10	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
1198 reflections	Extinction coefficient: 0.0073 (14)
128 parameters	Absolute structure: Flack (1983), 52 Friedel pairs
2 restraints	Absolute structure parameter: 0.04 (3)
Primary atom site location: structure-invariant direct methods

Special details

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Rb	0.0101 (2)	0.0072 (3)	−0.2556 (3)	0.0450 (6)
Nb1	−0.00311 (10)	0.43829 (17)	0.27041 (14)	0.0141 (4)
Nb2	−0.21457 (10)	0.56236 (17)	0.06501 (15)	0.0143 (4)
P	0.1698 (3)	0.0986 (5)	0.2953 (6)	0.0187 (8)
S1	−0.0934 (3)	0.3854 (6)	−0.0850 (5)	0.0200 (9)
S2	−0.1731 (4)	0.3697 (6)	0.3633 (6)	0.0246 (10)
S3	−0.0370 (3)	0.6358 (6)	−0.0172 (5)	0.0206 (9)
S4	0.1859 (3)	0.3577 (5)	0.2028 (5)	0.0166 (8)
S5	0.0990 (3)	0.4494 (5)	0.6316 (6)	0.0203 (9)
S6	−0.1280 (4)	0.6277 (6)	0.4087 (5)	0.0237 (10)
S7	0.0064 (4)	0.0928 (5)	0.2770 (7)	0.0223 (9)
S8	0.1299 (3)	0.6617 (5)	0.4718 (5)	0.0191 (8)
S9	−0.2839 (4)	0.0878 (6)	−0.3629 (7)	0.0339 (10)
S10	0.2590 (4)	0.1003 (6)	0.5767 (6)	0.0237 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Rb	0.0682 (14)	0.0336 (10)	0.0357 (9)	0.0020 (10)	0.0176 (9)	0.0058 (8)
Nb1	0.0143 (7)	0.0138 (7)	0.0157 (7)	0.0004 (5)	0.0065 (5)	0.0009 (5)
Nb2	0.0152 (7)	0.0134 (7)	0.0153 (7)	0.0006 (5)	0.0057 (5)	0.0016 (5)
P	0.0169 (19)	0.0176 (18)	0.0203 (18)	0.0004 (16)	0.0021 (15)	−0.0009 (15)
S1	0.024 (2)	0.018 (2)	0.020 (2)	0.0004 (17)	0.0100 (17)	−0.0016 (16)
S2	0.023 (2)	0.029 (3)	0.024 (2)	−0.001 (2)	0.0111 (17)	0.0103 (18)
S3	0.022 (2)	0.020 (2)	0.021 (2)	−0.0003 (18)	0.0069 (16)	0.0049 (16)
S4	0.0170 (19)	0.016 (2)	0.0177 (18)	−0.0014 (16)	0.0060 (15)	−0.0009 (15)
S5	0.021 (2)	0.022 (2)	0.0196 (18)	0.0004 (16)	0.0088 (15)	0.0012 (15)
S6	0.027 (2)	0.030 (3)	0.0166 (19)	0.0077 (19)	0.0081 (17)	−0.0019 (16)
S7	0.0155 (19)	0.0153 (18)	0.035 (2)	−0.0027 (17)	0.0034 (17)	0.0015 (18)
S8	0.0181 (18)	0.0144 (17)	0.0245 (18)	0.0004 (15)	0.0046 (15)	−0.0008 (14)
S9	0.044 (3)	0.021 (2)	0.040 (2)	−0.006 (2)	0.015 (2)	0.0092 (18)
S10	0.024 (2)	0.0164 (18)	0.0256 (19)	0.0013 (17)	−0.0037 (17)	0.0029 (17)

Geometric parameters (Å, º)

Rb—S7^i	3.372 (5)	Nb2—S5^v	2.543 (4)
Rb—S3^ii	3.400 (4)	Nb2—S8^v	2.565 (4)
Rb—S9^iii	3.403 (6)	Nb2—S10^v	2.566 (4)
Rb—S1	3.482 (5)	Nb2—S4^v	2.642 (4)
Rb—S5^i	3.669 (5)	P—S9^iii	1.979 (6)
Rb—S9	3.692 (6)	P—S10	2.042 (6)
Rb—S10^i	3.728 (5)	P—S7	2.060 (6)
Rb—S8^iv	3.786 (4)	P—S4	2.085 (6)
Rb—S7	3.852 (5)	S1—S3	2.034 (6)
Rb—S6^iv	3.857 (5)	S2—S6	2.029 (6)
Rb—P	4.001 (4)	S3—Rb^vi	3.400 (4)
Nb1—S2	2.475 (4)	S4—Nb2^vii	2.642 (4)
Nb1—S3	2.478 (4)	S5—S8	2.056 (6)
Nb1—S6	2.515 (4)	S5—Nb2^vii	2.543 (4)
Nb1—S1	2.535 (4)	S5—Rb^viii	3.669 (5)
Nb1—S8	2.561 (4)	S6—Rb^ix	3.857 (5)
Nb1—S5	2.576 (4)	S7—Rb^viii	3.372 (5)
Nb1—S7	2.604 (4)	S8—Nb2^vii	2.565 (4)
Nb1—S4	2.646 (4)	S8—Rb^ix	3.786 (4)
Nb1—Nb2	2.888 (2)	S9—P^x	1.979 (6)
Nb2—S6	2.468 (4)	S9—Rb^x	3.403 (6)
Nb2—S1	2.475 (4)	S10—Nb2^vii	2.566 (4)
Nb2—S2	2.515 (4)	S10—Rb^viii	3.728 (5)
Nb2—S3	2.540 (4)
S7^i—Rb—S3^ii	133.40 (11)	S1—Nb2—S2	91.68 (15)
S7^i—Rb—S9^iii	131.84 (14)	S6—Nb2—S3	88.75 (15)
S3^ii—Rb—S9^iii	67.33 (11)	S1—Nb2—S3	47.83 (14)
S7^i—Rb—S1	105.86 (11)	S2—Nb2—S3	107.83 (15)
S3^ii—Rb—S1	111.67 (11)	S6—Nb2—S5^v	91.88 (14)
S9^iii—Rb—S1	99.77 (11)	S1—Nb2—S5^v	140.91 (15)
S7^i—Rb—S5^i	62.69 (10)	S2—Nb2—S5^v	80.46 (14)
S3^ii—Rb—S5^i	163.27 (12)	S3—Nb2—S5^v	169.05 (15)
S9^iii—Rb—S5^i	98.74 (12)	S6—Nb2—S8^v	120.98 (14)
S1—Rb—S5^i	59.95 (10)	S1—Nb2—S8^v	93.52 (14)
S7^i—Rb—S9	90.00 (12)	S2—Nb2—S8^v	79.98 (14)
S3^ii—Rb—S9	86.64 (11)	S3—Nb2—S8^v	139.68 (14)
S9^iii—Rb—S9	138.06 (16)	S5^v—Nb2—S8^v	47.47 (13)
S1—Rb—S9	58.84 (11)	S6—Nb2—S10^v	78.51 (15)
S5^i—Rb—S9	99.19 (11)	S1—Nb2—S10^v	130.40 (16)
S7^i—Rb—S10^i	56.91 (9)	S2—Nb2—S10^v	123.05 (15)
S3^ii—Rb—S10^i	125.76 (11)	S3—Nb2—S10^v	85.65 (15)
S9^iii—Rb—S10^i	75.79 (12)	S5^v—Nb2—S10^v	83.77 (15)
S1—Rb—S10^i	112.68 (11)	S8^v—Nb2—S10^v	124.04 (14)
S5^i—Rb—S10^i	54.91 (10)	S6—Nb2—S4^v	155.23 (14)
S9—Rb—S10^i	143.85 (11)	S1—Nb2—S4^v	84.49 (13)
S7^i—Rb—S8^iv	62.34 (10)	S2—Nb2—S4^v	154.52 (15)
S3^ii—Rb—S8^iv	80.45 (10)	S3—Nb2—S4^v	88.14 (12)
S9^iii—Rb—S8^iv	86.95 (10)	S5^v—Nb2—S4^v	86.71 (13)
S1—Rb—S8^iv	167.65 (10)	S8^v—Nb2—S4^v	75.14 (12)
S5^i—Rb—S8^iv	108.98 (10)	S10^v—Nb2—S4^v	76.75 (13)
S9—Rb—S8^iv	121.79 (11)	S6—Nb2—Nb1	55.34 (11)
S10^i—Rb—S8^iv	58.70 (9)	S1—Nb2—Nb1	55.78 (10)
S7^i—Rb—S7	159.32 (14)	S2—Nb2—Nb1	54.00 (11)
S3^ii—Rb—S7	66.46 (10)	S3—Nb2—Nb1	53.85 (9)
S9^iii—Rb—S7	54.88 (11)	S5^v—Nb2—Nb1	134.14 (11)
S1—Rb—S7	54.73 (9)	S8^v—Nb2—Nb1	119.01 (10)
S5^i—Rb—S7	98.23 (10)	S10^v—Nb2—Nb1	114.69 (11)
S9—Rb—S7	85.15 (11)	S4^v—Nb2—Nb1	136.86 (9)
S10^i—Rb—S7	120.15 (12)	S9^iii—P—S10	112.9 (3)
S8^iv—Rb—S7	136.30 (10)	S9^iii—P—S7	113.0 (3)
S7^i—Rb—S6^iv	68.88 (10)	S10—P—S7	111.9 (3)
S3^ii—Rb—S6^iv	65.72 (10)	S9^iii—P—S4	114.7 (3)
S9^iii—Rb—S6^iv	119.56 (11)	S10—P—S4	103.2 (2)
S1—Rb—S6^iv	131.76 (13)	S7—P—S4	100.2 (2)
S5^i—Rb—S6^iv	130.97 (10)	S9^iii—P—Rb	58.22 (18)
S9—Rb—S6^iv	73.04 (11)	S10—P—Rb	170.1 (2)
S10^i—Rb—S6^iv	103.71 (10)	S7—P—Rb	70.85 (18)
S8^iv—Rb—S6^iv	49.88 (9)	S4—P—Rb	85.32 (15)
S7—Rb—S6^iv	128.04 (10)	S3—S1—Nb2	67.75 (17)
S7^i—Rb—P	144.16 (11)	S3—S1—Nb1	64.59 (16)
S3^ii—Rb—P	76.33 (10)	Nb2—S1—Nb1	70.39 (11)
S9^iii—Rb—P	29.62 (9)	S3—S1—Rb	134.2 (2)
S1—Rb—P	70.37 (10)	Nb2—S1—Rb	157.30 (18)
S5^i—Rb—P	87.01 (10)	Nb1—S1—Rb	110.94 (15)
S9—Rb—P	114.79 (11)	S6—S2—Nb1	67.03 (17)
S10^i—Rb—P	90.72 (10)	S6—S2—Nb2	64.78 (15)
S8^iv—Rb—P	116.51 (10)	Nb1—S2—Nb2	70.73 (11)
S7—Rb—P	30.33 (9)	S1—S3—Nb1	67.56 (16)
S6^iv—Rb—P	140.94 (10)	S1—S3—Nb2	64.42 (17)
S2—Nb1—S3	111.11 (15)	Nb1—S3—Nb2	70.28 (11)
S2—Nb1—S6	47.97 (15)	S1—S3—Rb^vi	137.8 (2)
S3—Nb1—S6	89.10 (15)	Nb1—S3—Rb^vi	152.71 (17)
S2—Nb1—S1	91.19 (15)	Nb2—S3—Rb^vi	124.92 (15)
S3—Nb1—S1	47.85 (14)	P—S4—Nb2^vii	88.12 (16)
S6—Nb1—S1	107.62 (15)	P—S4—Nb1	89.53 (17)
S2—Nb1—S8	119.48 (14)	Nb2^vii—S4—Nb1	90.63 (11)
S3—Nb1—S8	91.30 (14)	S8—S5—Nb2^vii	66.83 (16)
S6—Nb1—S8	78.83 (14)	S8—S5—Nb1	66.03 (16)
S1—Nb1—S8	137.31 (14)	Nb2^vii—S5—Nb1	94.54 (13)
S2—Nb1—S5	90.08 (14)	S8—S5—Rb^viii	159.8 (2)
S3—Nb1—S5	138.11 (14)	Nb2^vii—S5—Rb^viii	111.35 (14)
S6—Nb1—S5	78.77 (13)	Nb1—S5—Rb^viii	94.64 (13)
S1—Nb1—S5	172.27 (15)	S2—S6—Nb2	67.17 (16)
S8—Nb1—S5	47.17 (13)	S2—S6—Nb1	64.99 (17)
S2—Nb1—S7	80.02 (15)	Nb2—S6—Nb1	70.83 (11)
S3—Nb1—S7	127.75 (15)	S2—S6—Rb^ix	151.1 (2)
S6—Nb1—S7	126.20 (16)	Nb2—S6—Rb^ix	141.59 (17)
S1—Nb1—S7	82.45 (14)	Nb1—S6—Rb^ix	115.12 (16)
S8—Nb1—S7	128.65 (15)	P—S7—Nb1	91.25 (19)
S5—Nb1—S7	90.26 (14)	P—S7—Rb^viii	100.1 (2)
S2—Nb1—S4	154.23 (14)	Nb1—S7—Rb^viii	101.40 (14)
S3—Nb1—S4	88.18 (13)	P—S7—Rb	78.81 (19)
S6—Nb1—S4	153.75 (15)	Nb1—S7—Rb	99.27 (13)
S1—Nb1—S4	89.61 (12)	Rb^viii—S7—Rb	159.32 (14)
S8—Nb1—S4	75.13 (12)	S5—S8—Nb1	66.79 (16)
S5—Nb1—S4	85.95 (13)	S5—S8—Nb2^vii	65.70 (16)
S7—Nb1—S4	74.55 (13)	Nb1—S8—Nb2^vii	94.37 (13)
S2—Nb1—Nb2	55.27 (11)	S5—S8—Rb^ix	95.40 (17)
S3—Nb1—Nb2	55.87 (10)	Nb1—S8—Rb^ix	116.16 (13)
S6—Nb1—Nb2	53.83 (10)	Nb2^vii—S8—Rb^ix	134.85 (13)
S1—Nb1—Nb2	53.83 (10)	P^x—S9—Rb^x	92.2 (2)
S8—Nb1—Nb2	118.53 (10)	P^x—S9—Rb	101.4 (2)
S5—Nb1—Nb2	132.21 (10)	Rb^x—S9—Rb	132.43 (16)
S7—Nb1—Nb2	111.45 (11)	P—S10—Nb2^vii	91.2 (2)
S4—Nb1—Nb2	139.75 (9)	P—S10—Rb^viii	89.95 (18)
S6—Nb2—S1	111.08 (16)	Nb2^vii—S10—Rb^viii	109.02 (14)
S6—Nb2—S2	48.05 (15)

Symmetry codes: (i) x, y, z−1; (ii) x, y−1, z; (iii) x+1/2, −y, z+1/2; (iv) x, y−1, z−1; (v) x−1/2, −y+1, z−1/2; (vi) x, y+1, z; (vii) x+1/2, −y+1, z+1/2; (viii) x, y, z+1; (ix) x, y+1, z+1; (x) x−1/2, −y, z−1/2.