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

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.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](o-O)= 0.004 Å
• R factor = 0.014
• wR factor = 0.079
• Data-to-parameter ratio = 16.0

checkCIF/PLATON results

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S1. Comment

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

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).

S2. Experimental

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%).

Computing details

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

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)

Crystal data

K2Sm(MoO4)(PO4)	F(000) = 1768
Mr = 483.46	Dx = 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) Å^3	Prism, colourless
Z = 8	0.15 × 0.10 × 0.05 mm

Data collection

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

Refinement

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

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
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 (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
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)

K1—O4^i	2.685 (3)	Mo1—O4^ix	1.743 (3)
K1—O2	2.695 (3)	Mo1—O4	1.743 (3)
K1—O2^ii	2.768 (3)	Mo1—O3	1.784 (3)
K1—O3^ii	2.991 (4)	Mo1—O3^ix	1.784 (3)
K1—O4	3.012 (4)	P1—O2	1.533 (3)
K1—O1^iii	3.025 (3)	P1—O2^iii	1.533 (3)
K1—O4^iv	3.184 (4)	P1—O1^iii	1.549 (3)
K1—O3^v	3.191 (4)	P1—O1	1.549 (3)
Sm1—O1^ii	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—K1^iii	3.025 (3)
Sm1—O3^iii	2.399 (3)	O2—K1^iv	2.768 (3)
Sm1—O2	2.451 (3)	O3—K1^iv	2.991 (4)
Sm1—O2^iii	2.451 (3)	O3—K1^viii	3.191 (4)
Sm1—O1^vii	2.481 (3)	O4—K1^i	2.685 (3)
Sm1—O1^viii	2.481 (3)	O4—K1^ii	3.184 (4)
O4^i—K1—O2	153.25 (10)	O3^iii—Sm1—O1^vii	78.98 (10)
O4^i—K1—O2^ii	123.87 (11)	O2—Sm1—O1^vii	133.07 (9)
O2—K1—O2^ii	79.73 (9)	O2^iii—Sm1—O1^vii	145.94 (9)
O4^i—K1—O3^ii	83.90 (10)	O1^ii—Sm1—O1^viii	68.11 (13)
O2—K1—O3^ii	121.45 (10)	O1^vi—Sm1—O1^viii	126.05 (8)
O2^ii—K1—O3^ii	61.05 (10)	O3—Sm1—O1^viii	78.98 (10)
O4^i—K1—O4	79.19 (11)	O3^iii—Sm1—O1^viii	77.59 (10)
O2—K1—O4	94.69 (10)	O2—Sm1—O1^viii	145.94 (9)
O2^ii—K1—O4	79.85 (10)	O2^iii—Sm1—O1^viii	133.07 (9)
O3^ii—K1—O4	116.70 (11)	O1^vii—Sm1—O1^viii	58.14 (15)
O4^i—K1—O1^iii	146.34 (11)	O4^ix—Mo1—O4	111.8 (2)
O2—K1—O1^iii	52.27 (9)	O4^ix—Mo1—O3	107.33 (15)
O2^ii—K1—O1^iii	62.16 (9)	O4—Mo1—O3	109.46 (16)
O3^ii—K1—O1^iii	70.78 (8)	O4^ix—Mo1—O3^ix	109.46 (16)
O4—K1—O1^iii	131.75 (9)	O4—Mo1—O3^ix	107.33 (15)
O4^i—K1—O4^iv	78.43 (8)	O3—Mo1—O3^ix	111.5 (2)
O2—K1—O4^iv	77.88 (9)	O2—P1—O2^iii	106.9 (3)
O2^ii—K1—O4^iv	157.51 (9)	O2—P1—O1^iii	110.83 (15)
O3^ii—K1—O4^iv	131.29 (10)	O2^iii—P1—O1^iii	113.07 (14)
O4—K1—O4^iv	104.03 (10)	O2—P1—O1	113.08 (14)
O1^iii—K1—O4^iv	101.61 (9)	O2^iii—P1—O1	110.83 (15)
O4^i—K1—O3^v	98.70 (10)	O1^iii—P1—O1	102.3 (3)
O2—K1—O3^v	76.53 (10)	P1—O1—Sm1^vi	145.66 (18)
O2^ii—K1—O3^v	119.10 (9)	P1—O1—Sm1^x	99.81 (16)
O3^ii—K1—O3^v	86.19 (11)	Sm1^vi—O1—Sm1^x	111.05 (13)
O4—K1—O3^v	156.35 (10)	P1—O1—K1^iii	91.19 (13)
O1^iii—K1—O3^v	58.87 (8)	Sm1^vi—O1—K1^iii	90.67 (9)
O4^iv—K1—O3^v	52.93 (8)	Sm1^x—O1—K1^iii	112.46 (9)
O1^ii—Sm1—O1^vi	165.83 (15)	P1—O2—Sm1	96.39 (15)
O1^ii—Sm1—O3	88.61 (10)	P1—O2—K1	104.95 (15)
O1^vi—Sm1—O3	94.68 (10)	Sm1—O2—K1	128.43 (12)
O1^ii—Sm1—O3^iii	94.68 (10)	P1—O2—K1^iv	144.03 (15)
O1^vi—Sm1—O3^iii	88.61 (10)	Sm1—O2—K1^iv	94.74 (11)
O3—Sm1—O3^iii	153.13 (16)	K1—O2—K1^iv	94.39 (10)
O1^ii—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)
O3^iii—Sm1—O2	132.14 (11)	Mo1—O3—K1^viii	99.04 (13)
O1^ii—Sm1—O2^iii	77.48 (9)	Sm1—O3—K1^viii	109.51 (11)
O1^vi—Sm1—O2^iii	90.20 (9)	K1^iv—O3—K1^viii	86.78 (10)
O3—Sm1—O2^iii	132.14 (11)	Mo1—O4—K1^i	132.86 (18)
O3^iii—Sm1—O2^iii	74.39 (11)	Mo1—O4—K1	115.37 (15)
O2—Sm1—O2^iii	60.33 (15)	K1^i—O4—K1	94.75 (10)
O1^ii—Sm1—O1^vii	126.05 (8)	Mo1—O4—K1^ii	100.26 (13)
O1^vi—Sm1—O1^vii	68.11 (13)	K1^i—O4—K1^ii	120.73 (12)
O3—Sm1—O1^vii	77.59 (10)	K1—O4—K1^ii	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.