Dipotassium samarium(III) molybdate(VI) phosphate(V), K2Sm(MoO4)(PO4)

Zhao, D.; Li, F.; Cheng, W.; Zhang, H.

doi:10.1107/S1600536809041622

inorganic compounds

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Volume 65| Part 11| November 2009| Page i78

https://doi.org/10.1107/S1600536809041622

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Dipotassium samarium(III) molybdate(VI) phosphate(V), K₂Sm(MoO₄)(PO₄)

Dan Zhao,^a ^* Feifei Li,^a Wendan Cheng ^b and Hao Zhang ^b

^aDepartment of Physics and Chemistry, Henan Polytechnic University, Jiaozuo, Henan 454000, People's Republic of China, and ^bState Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian, 350002, People's Republic of China
^*Correspondence e-mail: iamzd@hpu.edu.cn

(Received 30 September 2009; accepted 12 October 2009; online 17 October 2009)

The title compound, K₂Sm(MoO₄)(PO₄), has been prepared under atmospheric conditions using a high temperature solution growth (HTSG) method. The structure of K₂Sm(MoO₄)(PO₄) is isotypic with other A₂M(MoO₄)(PO₄) compounds, where A = Na or K, and M = trivalent rare earth cation. It can be described as being built up from two-dimensional anionic layers with composition [Sm(MoO₄)(PO₄)]²⁻ that are stacked along the c axis and are interconnected by K⁺ cations which are in an eightfold coordination by O atoms. The SmO₈, MoO₄ and PO₄ polyhedra exhibit 2 symmetry.

Related literature

The structures and properties of other molybdate-phosphates with the general formula A₂M(MoO₄)(PO₄), where A = Na, K; M = Y, Bi, La—Nd, Sm—Lu, have been reported by Ben Amara & Dabbabi (1987 ); Komissarova et al. (2006 ); Ryumin et al. (2007 ); Zatovsky et al. (2006 ). For crystallographic background, see: Spek (2009 ).

Experimental

Crystal data

K₂Sm(MoO₄)(PO₄)
M_r = 483.46
Orthorhombic, I b c a
a = 12.345 (9) Å
b = 7.004 (5) Å
c = 19.733 (12) Å
V = 1706 (2) Å³
Z = 8
Mo Kα radiation
μ = 9.46 mm⁻¹
T = 298 K
0.15 × 0.10 × 0.05 mm

Data collection

Rigaku Saturn 70 diffractometer
Absorption correction: multi-scan (CrystalClear; Rigaku, 2000 ) T_min = 0.742, T_max = 1.000
3660 measured reflections
979 independent reflections
903 reflections with I > 2σ(I)
R_int = 0.022

Refinement

R[F² > 2σ(F²)] = 0.014
wR(F²) = 0.079
S = 1.01
979 reflections
61 parameters
Δρ_max = 0.85 e Å⁻³
Δρ_min = −0.99 e Å⁻³

Table 1
Selected bond lengths (Å)

K1—O4ⁱ	2.685 (3)
K1—O2	2.695 (3)
K1—O2ⁱⁱ	2.768 (3)
K1—O3ⁱⁱ	2.991 (4)
K1—O4	3.012 (4)
K1—O1ⁱⁱⁱ	3.025 (3)
K1—O4^iv	3.184 (4)
K1—O3^v	3.191 (4)
Sm1—O1ⁱⁱ	2.339 (3)
Sm1—O3	2.399 (3)
Sm1—O2	2.451 (3)
Sm1—O1^vi	2.481 (3)
Mo1—O4	1.743 (3)
Mo1—O3	1.784 (3)
P1—O2	1.533 (3)
P1—O1	1.549 (3)
Symmetry codes: (i) $[-x+{\script{1\over 2}}, y, -z]$ ; (ii) $[-x+{\script{1\over 2}}, y-{\script{1\over 2}}, z]$ ; (iii) $[x, -y+1, -z+{\script{1\over 2}}]$ ; (iv) $[-x+{\script{1\over 2}}, y+{\script{1\over 2}}, z]$ ; (v) $[x-{\script{1\over 2}}, -y+1, z]$ ; (vi) $[x+{\script{1\over 2}}, y, -z+{\script{1\over 2}}]$ .

Data collection: CrystalClear (Rigaku, 2000); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg & Putz, 2005 ); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536809041622/wm2263sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536809041622/wm2263Isup2.hkl

checkCIF report

Comment top

In recent years, several complex molybdate-phosphates with the general formula A₂M(MoO₄)(PO₄) (A = Na, K; M= Y, Bi, La—Nd, Sm—Lu) have been reported (Ben Amara & Dabbabi, 1987); Komissarova et al., 2006; Ryumin et al., 2007; Zatovsky et al., 2006). Herein, we present synthesis and crystal structure of the title compound, K₂Sm(MoO₄)(PO₄).

X-ray analysis revealed that the compound K₂Sm(MoO₄)(PO₄) crystallizes in the orthorhombic system with space group Ibca (Fig. 1). The asymmetric unit contains one K, one Sm, one Mo, one P and four O atoms. Each of the Mo and P atoms is tetrahedrally coordinated by four O atoms, forming nearly ideal MoO₄ and PO₄ tetrahedra with two types of Mo–O (1.743 (3) Å, 1.784 (3) Å) and P–O distances (1.533 (3) Å, 1.549 (3) Å), respectively. The Sm atom is surrounded by eight oxygen atoms in a distorted dodecahedral environment with the Sm–O bond distances in the range of 2.339 (3)–2.481 (3) Å. MoO₄, PO₄ and SmO₈ polyhedra are interconnected via corner- or edge-sharing O atoms forming a two-dimensional anionic layer of overall composition [Sm(MoO₄)(PO₄)]^2- extending parallel to the ab-plane, as shown in Fig. 2. Furthermore, the anionic framework delimits large cages in which the K⁺ cations (coordination number 8) reside to ensure the cohesion of the structure and the neutrality of the compound, resulting in a three-dimensional framework structure.

Related literature top

The structures and properties of other molybdate-phosphates with the general formula A₂M(MoO₄)(PO₄), where A = Na, K; M = Y, Bi, La—Nd, Sm—Lu, have been reported by Ben Amara & Dabbabi (1987); Komissarova et al. (2006); Ryumin et al. (2007); Zatovsky et al. (2006). For crystallographic background, see: Spek (2009).

Experimental top

Single crystals of K₂Sm(MoO₄)(PO₄) were obtained by the high temperature solution growth (HTSG) reaction of K₂CO₃ (2.253 g, 16.3 mmol), Sm₂O₃ (0.569g, 1.63 mmol), MoO₃ (0.939 g, 6.52 mmol) and NH₄H₂PO₄ (3.000 g, 26.1 mmol), with the molar ratio of 10:1:2:8 (K:Sm:Mo:P). The reaction mixture was thoroughly ground in an agate mortar and pressed into a pellet to ensure the best homogeneity and reactivity. The pellet was put into a platinum crucible and calcined at 673 K or 10 h to decompose the salts. Then the crucible was transferred to another furnace and heated at 1223 K for 48 h. Then the sample was cooled from 1173 K at a rate of 4 Kh^-1. After boiling for 24 h in water, a few prism-shaped colorless crystals were obtained in very low yield (<5%).

Structure description top

The structures and properties of other molybdate-phosphates with the general formula A₂M(MoO₄)(PO₄), where A = Na, K; M = Y, Bi, La—Nd, Sm—Lu, have been reported by Ben Amara & Dabbabi (1987); Komissarova et al. (2006); Ryumin et al. (2007); Zatovsky et al. (2006). For crystallographic background, see: Spek (2009).

Computing details top

Data collection: CrystalClear (Rigaku, 2000); cell refinement: CrystalClear (Rigaku, 2000); data reduction: CrystalClear (Rigaku, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

Fig. 1. Part of the structure of the title compound, showing the labelling of the atoms. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (a) - X, 1/2 - Y, Z (b) X, - Y, 1/2 – Z (c) - X, 1/2 + Y, 1/2 – Z (e) X, 1/2 + Y, - Z (f) - X, Y, 1/2 + Z (l) 1/2 + X, Y, 1/2 – z.]

Dipotassium samarium(III) molybdate(VI) phosphate(V) top

Crystal data top

K₂Sm(MoO₄)(PO₄)	F(000) = 1768
M_r = 483.46	D_x = 3.764 Mg m⁻³
Orthorhombic, Ibca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -I 2b 2c	Cell parameters from 369 reflections
a = 12.345 (9) Å	θ = 3.1–27.4°
b = 7.004 (5) Å	µ = 9.46 mm⁻¹
c = 19.733 (12) Å	T = 298 K
V = 1706 (2) Å³	Prism, colourless
Z = 8	0.15 × 0.10 × 0.05 mm

Data collection top

Rigaku Saturn 70 diffractometer	979 independent reflections
Radiation source: fine-focus sealed tube	903 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.022
Detector resolution: 14.6306 pixels mm^-1	θ_max = 27.5°, θ_min = 2.1°
ω scans	h = −15→15
Absorption correction: multi-scan (CrystalClear; Rigaku, 2000)	k = −9→8
T_min = 0.742, T_max = 1.000	l = −25→25
3660 measured reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F² > 2σ(F²)] = 0.014	Secondary atom site location: difference Fourier map
wR(F²) = 0.079	w = 1/[σ²(F_o²) + (0.063P)²] where P = (F_o² + 2F_c²)/3
S = 1.01	(Δ/σ)_max < 0.001
979 reflections	Δρ_max = 0.85 e Å⁻³
61 parameters	Δρ_min = −0.99 e Å⁻³

Crystal data top

K₂Sm(MoO₄)(PO₄)	V = 1706 (2) Å³
M_r = 483.46	Z = 8
Orthorhombic, Ibca	Mo Kα radiation
a = 12.345 (9) Å	µ = 9.46 mm⁻¹
b = 7.004 (5) Å	T = 298 K
c = 19.733 (12) Å	0.15 × 0.10 × 0.05 mm

Data collection top

Rigaku Saturn 70 diffractometer	979 independent reflections
Absorption correction: multi-scan (CrystalClear; Rigaku, 2000)	903 reflections with I > 2σ(I)
T_min = 0.742, T_max = 1.000	R_int = 0.022
3660 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.014	61 parameters
wR(F²) = 0.079	0 restraints
S = 1.01	Δρ_max = 0.85 e Å⁻³
979 reflections	Δρ_min = −0.99 e Å⁻³

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Single crystal of K₂Sm(MoO₄)(PO₄)with dimensions of 0.15 mm×0.10 mm×0.05 mm was selected for single-crystal X-ray diffraction determination. The diffraction data of K₂Sm(MoO₄)(PO₄) were collected on a Rigaku Saturn70 CCD diffractometer with graphite-monochromated Mo—Ka radiation (λ = 0.71073 Å). Intensity data were collected by the narrow frame method at 298 K. The data were corrected for Lorentz factor, polarization, air absorption and absorption due to variations in the path length through the detector faceplate. Absorption corrections based on Multi-scan technique were also applied (CrystalClear. ver. 1.3.5.,Rigaku Corp., Woodlands, TX, 1999). The single-crystal refinement was performed with the program SHELX97. The spacegroup was determined to be Ibca based on systematic absences as well as E-value statistics. The structure was solved by the direct methods and the molybdenum and phosphorus atoms were revealed. Subsequent difference-Fourier syntheses by full-matrix least-squares fitting on F² allowed localization of potassium and all oxygen atoms. The final structure refinement performed by least-square methods with atomic coordinates and anisotropic thermal parameters resulted in satisfactory residuals. In addition, the final refined solutions obtained for were checked with the ADDSYM algorithm in the program PLATON (Spek, 2009) and no higher symmetries were found.

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. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
K1	0.17099 (8)	0.28431 (16)	0.09418 (5)	0.0233 (3)
Sm1	0.42384 (2)	0.5000	0.2500	0.00627 (15)
Mo1	0.5000	0.2500	0.08208 (2)	0.01213 (17)
P1	0.17826 (12)	0.5000	0.2500	0.0066 (4)
O1	0.0995 (3)	0.6698 (4)	0.26009 (13)	0.0111 (6)
O2	0.2522 (3)	0.5240 (3)	0.18818 (14)	0.0113 (6)
O3	0.4690 (3)	0.4533 (5)	0.13294 (14)	0.0177 (6)
O4	0.3879 (3)	0.1914 (5)	0.03256 (15)	0.0292 (8)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
K1	0.0327 (6)	0.0226 (5)	0.0147 (4)	−0.0016 (4)	−0.0042 (4)	−0.0018 (4)
Sm1	0.0049 (2)	0.0050 (2)	0.0090 (2)	0.000	0.000	0.00005 (8)
Mo1	0.0142 (3)	0.0153 (3)	0.0069 (3)	0.00155 (19)	0.000	0.000
P1	0.0041 (8)	0.0042 (9)	0.0115 (8)	0.000	0.000	0.0001 (4)
O1	0.0065 (13)	0.0058 (15)	0.0212 (13)	0.0000 (12)	−0.0006 (11)	−0.0018 (11)
O2	0.0085 (14)	0.0139 (14)	0.0116 (13)	−0.0026 (11)	−0.0010 (12)	0.0021 (10)
O3	0.0228 (18)	0.0192 (15)	0.0112 (13)	0.0032 (14)	0.0029 (12)	−0.0013 (12)
O4	0.032 (2)	0.033 (2)	0.0224 (15)	−0.0012 (16)	−0.0163 (15)	0.0016 (14)

Geometric parameters (Å, º) top

K1—O4ⁱ	2.685 (3)	Mo1—O4^ix	1.743 (3)
K1—O2	2.695 (3)	Mo1—O4	1.743 (3)
K1—O2ⁱⁱ	2.768 (3)	Mo1—O3	1.784 (3)
K1—O3ⁱⁱ	2.991 (4)	Mo1—O3^ix	1.784 (3)
K1—O4	3.012 (4)	P1—O2	1.533 (3)
K1—O1ⁱⁱⁱ	3.025 (3)	P1—O2ⁱⁱⁱ	1.533 (3)
K1—O4^iv	3.184 (4)	P1—O1ⁱⁱⁱ	1.549 (3)
K1—O3^v	3.191 (4)	P1—O1	1.549 (3)
Sm1—O1ⁱⁱ	2.339 (3)	O1—Sm1^vi	2.339 (3)
Sm1—O1^vi	2.339 (3)	O1—Sm1^x	2.481 (3)
Sm1—O3	2.399 (3)	O1—K1ⁱⁱⁱ	3.025 (3)
Sm1—O3ⁱⁱⁱ	2.399 (3)	O2—K1^iv	2.768 (3)
Sm1—O2	2.451 (3)	O3—K1^iv	2.991 (4)
Sm1—O2ⁱⁱⁱ	2.451 (3)	O3—K1^viii	3.191 (4)
Sm1—O1^vii	2.481 (3)	O4—K1ⁱ	2.685 (3)
Sm1—O1^viii	2.481 (3)	O4—K1ⁱⁱ	3.184 (4)

O4ⁱ—K1—O2	153.25 (10)	O3ⁱⁱⁱ—Sm1—O1^vii	78.98 (10)
O4ⁱ—K1—O2ⁱⁱ	123.87 (11)	O2—Sm1—O1^vii	133.07 (9)
O2—K1—O2ⁱⁱ	79.73 (9)	O2ⁱⁱⁱ—Sm1—O1^vii	145.94 (9)
O4ⁱ—K1—O3ⁱⁱ	83.90 (10)	O1ⁱⁱ—Sm1—O1^viii	68.11 (13)
O2—K1—O3ⁱⁱ	121.45 (10)	O1^vi—Sm1—O1^viii	126.05 (8)
O2ⁱⁱ—K1—O3ⁱⁱ	61.05 (10)	O3—Sm1—O1^viii	78.98 (10)
O4ⁱ—K1—O4	79.19 (11)	O3ⁱⁱⁱ—Sm1—O1^viii	77.59 (10)
O2—K1—O4	94.69 (10)	O2—Sm1—O1^viii	145.94 (9)
O2ⁱⁱ—K1—O4	79.85 (10)	O2ⁱⁱⁱ—Sm1—O1^viii	133.07 (9)
O3ⁱⁱ—K1—O4	116.70 (11)	O1^vii—Sm1—O1^viii	58.14 (15)
O4ⁱ—K1—O1ⁱⁱⁱ	146.34 (11)	O4^ix—Mo1—O4	111.8 (2)
O2—K1—O1ⁱⁱⁱ	52.27 (9)	O4^ix—Mo1—O3	107.33 (15)
O2ⁱⁱ—K1—O1ⁱⁱⁱ	62.16 (9)	O4—Mo1—O3	109.46 (16)
O3ⁱⁱ—K1—O1ⁱⁱⁱ	70.78 (8)	O4^ix—Mo1—O3^ix	109.46 (16)
O4—K1—O1ⁱⁱⁱ	131.75 (9)	O4—Mo1—O3^ix	107.33 (15)
O4ⁱ—K1—O4^iv	78.43 (8)	O3—Mo1—O3^ix	111.5 (2)
O2—K1—O4^iv	77.88 (9)	O2—P1—O2ⁱⁱⁱ	106.9 (3)
O2ⁱⁱ—K1—O4^iv	157.51 (9)	O2—P1—O1ⁱⁱⁱ	110.83 (15)
O3ⁱⁱ—K1—O4^iv	131.29 (10)	O2ⁱⁱⁱ—P1—O1ⁱⁱⁱ	113.07 (14)
O4—K1—O4^iv	104.03 (10)	O2—P1—O1	113.08 (14)
O1ⁱⁱⁱ—K1—O4^iv	101.61 (9)	O2ⁱⁱⁱ—P1—O1	110.83 (15)
O4ⁱ—K1—O3^v	98.70 (10)	O1ⁱⁱⁱ—P1—O1	102.3 (3)
O2—K1—O3^v	76.53 (10)	P1—O1—Sm1^vi	145.66 (18)
O2ⁱⁱ—K1—O3^v	119.10 (9)	P1—O1—Sm1^x	99.81 (16)
O3ⁱⁱ—K1—O3^v	86.19 (11)	Sm1^vi—O1—Sm1^x	111.05 (13)
O4—K1—O3^v	156.35 (10)	P1—O1—K1ⁱⁱⁱ	91.19 (13)
O1ⁱⁱⁱ—K1—O3^v	58.87 (8)	Sm1^vi—O1—K1ⁱⁱⁱ	90.67 (9)
O4^iv—K1—O3^v	52.93 (8)	Sm1^x—O1—K1ⁱⁱⁱ	112.46 (9)
O1ⁱⁱ—Sm1—O1^vi	165.83 (15)	P1—O2—Sm1	96.39 (15)
O1ⁱⁱ—Sm1—O3	88.61 (10)	P1—O2—K1	104.95 (15)
O1^vi—Sm1—O3	94.68 (10)	Sm1—O2—K1	128.43 (12)
O1ⁱⁱ—Sm1—O3ⁱⁱⁱ	94.68 (10)	P1—O2—K1^iv	144.03 (15)
O1^vi—Sm1—O3ⁱⁱⁱ	88.61 (10)	Sm1—O2—K1^iv	94.74 (11)
O3—Sm1—O3ⁱⁱⁱ	153.13 (16)	K1—O2—K1^iv	94.39 (10)
O1ⁱⁱ—Sm1—O2	90.20 (9)	Mo1—O3—Sm1	134.48 (17)
O1^vi—Sm1—O2	77.48 (9)	Mo1—O3—K1^iv	126.79 (14)
O3—Sm1—O2	74.39 (11)	Sm1—O3—K1^iv	90.36 (10)
O3ⁱⁱⁱ—Sm1—O2	132.14 (11)	Mo1—O3—K1^viii	99.04 (13)
O1ⁱⁱ—Sm1—O2ⁱⁱⁱ	77.48 (9)	Sm1—O3—K1^viii	109.51 (11)
O1^vi—Sm1—O2ⁱⁱⁱ	90.20 (9)	K1^iv—O3—K1^viii	86.78 (10)
O3—Sm1—O2ⁱⁱⁱ	132.14 (11)	Mo1—O4—K1ⁱ	132.86 (18)
O3ⁱⁱⁱ—Sm1—O2ⁱⁱⁱ	74.39 (11)	Mo1—O4—K1	115.37 (15)
O2—Sm1—O2ⁱⁱⁱ	60.33 (15)	K1ⁱ—O4—K1	94.75 (10)
O1ⁱⁱ—Sm1—O1^vii	126.05 (8)	Mo1—O4—K1ⁱⁱ	100.26 (13)
O1^vi—Sm1—O1^vii	68.11 (13)	K1ⁱ—O4—K1ⁱⁱ	120.73 (12)
O3—Sm1—O1^vii	77.59 (10)	K1—O4—K1ⁱⁱ	80.58 (9)

Symmetry codes: (i) −x+1/2, y, −z; (ii) −x+1/2, y−1/2, z; (iii) x, −y+1, −z+1/2; (iv) −x+1/2, y+1/2, z; (v) x−1/2, −y+1, z; (vi) −x+1/2, −y+3/2, −z+1/2; (vii) x+1/2, y, −z+1/2; (viii) x+1/2, −y+1, z; (ix) −x+1, −y+1/2, z; (x) x−1/2, y, −z+1/2.

Experimental details

Crystal data
Chemical formula	K₂Sm(MoO₄)(PO₄)
M_r	483.46
Crystal system, space group	Orthorhombic, Ibca
Temperature (K)	298
a, b, c (Å)	12.345 (9), 7.004 (5), 19.733 (12)
V (Å³)	1706 (2)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	9.46
Crystal size (mm)	0.15 × 0.10 × 0.05

Data collection
Diffractometer	Rigaku Saturn 70
Absorption correction	Multi-scan (CrystalClear; Rigaku, 2000)
T_min, T_max	0.742, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	3660, 979, 903
R_int	0.022
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.014, 0.079, 1.01
No. of reflections	979
No. of parameters	61
Δρ_max, Δρ_min (e Å⁻³)	0.85, −0.99

Computer programs: CrystalClear (Rigaku, 2000), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and DIAMOND (Brandenburg & Putz, 2005), SHELXTL (Sheldrick, 2008).

Selected bond lengths (Å) top

K1—O4ⁱ	2.685 (3)	Sm1—O1ⁱⁱ	2.339 (3)
K1—O2	2.695 (3)	Sm1—O3	2.399 (3)
K1—O2ⁱⁱ	2.768 (3)	Sm1—O2	2.451 (3)
K1—O3ⁱⁱ	2.991 (4)	Sm1—O1^vi	2.481 (3)
K1—O4	3.012 (4)	Mo1—O4	1.743 (3)
K1—O1ⁱⁱⁱ	3.025 (3)	Mo1—O3	1.784 (3)
K1—O4^iv	3.184 (4)	P1—O2	1.533 (3)
K1—O3^v	3.191 (4)	P1—O1	1.549 (3)

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

Acknowledgements

We thank Dr Yougui Huang and Qingxia Yao for fruitful discussions concerning the crystal structure and for help with graphics.

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