Dipraseodymium(III) pyroborate molybdate(VI), Pr₂(B₂O₅)(MoO₄)

Single crystals of triclinic Pr₂(B₂O₅)(MoO₄) were prepared from an incongruently melting flux in the system Pr₂O₃-MoO₃-B₂O₃ in a platinum crucible in an atmosphere of air. In the crystal structure, distorted edge-sharing [PrO₈] square anti­prisms form a three-dimensional framework. These are further linked by isolated [MoO₄] tetra­hedra and isolated pyroborate groups [B₂O₅], the latter consisting of two independent trigonal [BO₃] groups sharing one O atom. The [MoO₄] tetra­hedra and the [B₂O₅] groups are arranged in alternating layers parallel to the ab plane.

Key indicators

• Single-crystal X-ray study
• T = 291 K
• Mean [sigma](O-B) = 0.007 Å
• R factor = 0.031
• wR factor = 0.083
• Data-to-parameter ratio = 17.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT062_ALERT_4_C Rescale T(min) & T(max) by .....................       0.16

Alert level G
ABSTM02_ALERT_3_G  When printed, the submitted absorption T values will be
            replaced by the scaled T values. Since the ratio of scaled T's
            is identical to the ratio of reported T values, the scaling
            does not imply a change to the absorption corrections used in
            the study.
            Ratio of Tmax expected/reported      0.162
            Tmax scaled      0.161 Tmin scaled      0.048
PLAT804_ALERT_5_G ARU-Pack Problem in PLATON Analysis ............         12 Times

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   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
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S1. Comment

The existence of several compounds in the systems RE₂O₃— B₂O₃—MoO₃ (RE = rare earth element) has been studied by Lysanova et al. (1983) by means of X-ray powder diffraction data and was partly corroborated by Dzhurinskii & Lysanova (1998). Among these pseudo-ternary compounds, rare earth pyroborate molybdates of the type RE₂(B₂O₅)(MoO₄) were reported for RE = Pr - Tb (excluding Pm) (Lysanova et al., 1983), all with incongruent melting behaviour. However, no structural information about these compounds has been given so far. In the course of our investigations of the systems RE₂O₃—B₂O₃—MO₃ (M = Mo, W) we grew single crystals of the Pr-compound Pr₂(B₂O₅)(MoO₄), (I), as a representative of the rare earth pyroborate molybdate series.

In the crystal structure of (I) the two symmetrically non-equivalent Pr atoms show a distinct eightfold coordination by oxygen atoms, both with a slightly distorted square antiprismatic coordination polyhedron, and with Pr—O bond lengths ranging from 2.370 (3) Å to 2.610 (3) Å for Pr1, and from 2.364 (3) Å to 2.645 (4) Å for Pr2 (Fig. 2). The [PrO₈] polyhedra are connected via common edges, where Pr2 is connected to six neighbouring [PrO₈] polyhedra with Pr—Pr distances ranging from 3.9237 (5) Å to 4.1242 (5) Å, while Pr1 is connected to only four [PrO₈] polyhedra with Pr—Pr distances between 3.9702 (6) Å and 4.1583 (6) Å. From the different connection schemes of the two Pr atoms a three-dimensional framework of [PrO₈] polyhedra with interstitial voids results (Fig. 1). In these voids nearly undistorted and isolated [MoO₄] tetrahedra, that are arranged in layers parallel to the ab plane are positioned (Fig. 1).

The two crystallographically different B atoms are threefold coordinated by O atoms. The two [BO₃] groups are linked by a common oxygen ligand O9 (see Fig. 2), thus forming isolated pyroborate groups [B₂O₅]. The pyroborate groups are bent with an angle (B1— O9— B2) of 125.1 (4)°, while the individual [BO₃] groups show no unusual distortions (Zobetz, 1982). The oxygen ligands of the pyroborate group (apart from the bridging oxygen O9, see Fig. 2) each belong either to two different [PrO₈] polyhedra (being simultaneously ligands of B1) or to three different [PrO₈] polyhedra (being simultaneously ligands of B2). All [B₂O₅] groups are arranged in double layers that extend parallel to the ab-plane and alternate with layers of [MoO₄] tetrahedra (see Fig. 1).

Related literature

A rough investigation of the ternary systems RE₂O₃—B₂O₃—MoO₃ (RE = rare earth element) has been reported by Lysanova et al. (1983) and Dzhurinskii & Lysanova (1998). X-ray powder diffraction data of RE₂(B₂O₅)(MoO₄) compounds with RE = Pr, Nd, Sm, Eu, Gd and Tb are given by Lysanova et al. (1983). Geometric parameters of [BO₃] groups were reviewed by Zobetz (1982).

S2. Experimental

Single crystals of (I) were obtained by growth from the melt. A homogenized powder mixture of Pr₄O₁₁ (99.9%, Alfa Aesar), B₂O₃ (99.98%, Alfa Aesar) and MoO₃ (99.95%, Alfa Aesar) in a molar ratio of 1: 3.33: 7 was heated in a covered platinum crucible in air atmosphere to 1423 K and subsequently cooled at a rate of 3 K h^-1 to 1173 K. Transparent, light-green prismatic single crystals of the title compound were separated mechanically from the fine-grained praseodymium borate molybdate matrix.

S3. Refinement

The final difference Fourier map indicated a positive maximum at a distance of 0.76 Å from Pr1 and a negative maximum at a distance of 0.85 Å from the same atom.

Computing details

Data collection: MACH3 (Enraf–Nonius, 1993); cell refinement: MACH3 (Enraf–Nonius, 1993); data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS (Dowty, 2002); software used to prepare material for publication: publCIF (Westrip, 2008).

Figures

Fig. 1. : View of the structure of (I) approximately along the a-axis, emphasizing coordination surroundings of the cations. Pr atoms are shown as large red spheres, Mo atoms as smaller orange spheres, and B atoms as small green spheres. O atoms are indicated by the corners of the coordination polyhedra and are not drawn.

Fig. 2. : Fraction of the structure of (I) with atomic labelling scheme in a projection approximately along the a-axis. The atoms are drawn as displacement ellipsoids at the 50% probability level. [Symmetry codes: (i) x, y + 1, z; (ii) -x + 1, -y + 1, -z - 1; (iii) -x + 1, -y, (iv) x, y - 1, z; -z - 1; (x) -x, -y, -z; (xii) x + 1, y, z; (xiii) x + 1, y + 1, z; (xiv) -x + 1, -y - 1, -z; (xv) x + 1, y - 1, z.]

Dipraseodymium(III) pyroborate molybdate(VI)

Crystal data

Pr2(B2O5)(MoO4)	Z = 2
Mr = 543.38	F(000) = 484
Triclinic, P1	Dx = 5.059 Mg m^−3
a = 5.2806 (5) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.0278 (5) Å	Cell parameters from 25 reflections
c = 10.5824 (9) Å	θ = 20.8–24.2°
α = 74.557 (6)°	µ = 15.20 mm^−1
β = 76.307 (7)°	T = 291 K
γ = 73.065 (6)°	Prism, light green
V = 356.69 (5) Å^3	0.20 × 0.15 × 0.12 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	1983 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.019
Graphite monochromator	θmax = 30.4°, θmin = 3.1°
ω/2θ scans	h = −7→7
Absorption correction: ψ scan (MolEN; Fair, 1990)	k = −10→10
Tmin = 0.296, Tmax = 0.999	l = −15→15
4733 measured reflections	3 standard reflections every 100 reflections
2155 independent reflections	intensity decay: 1.7%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.031	w = 1/[σ^2(Fo^2) + (0.0533P)^2 + 1.1726P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.082	(Δ/σ)max < 0.001
S = 1.13	Δρmax = 2.55 e Å^−3
2155 reflections	Δρmin = −1.73 e Å^−3
127 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0319 (13)

Special details

Experimental. A suitable single-crystal was carefully selected under a polarizing microscope and mounted in a glass capillary.

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.

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

	x	y	z	Uiso*/Ueq
Pr1	0.37016 (5)	0.07689 (4)	−0.31461 (2)	0.00706 (11)
Pr2	0.15410 (5)	−0.79427 (4)	0.04666 (2)	0.00693 (11)
Mo	0.03514 (8)	0.70782 (6)	−0.41958 (4)	0.00758 (12)
O7	0.1449 (8)	0.4427 (5)	−0.3778 (4)	0.0144 (7)
O5	0.2335 (7)	0.7903 (6)	−0.5706 (3)	0.0152 (7)
O6	0.0805 (7)	0.8248 (6)	−0.2991 (4)	0.0141 (7)
O2	0.3079 (7)	0.1829 (5)	−0.5554 (3)	0.0111 (6)
B1	0.4573 (10)	−0.4118 (7)	−0.1373 (5)	0.0077 (8)
O4	0.4775 (7)	−0.2184 (5)	−0.1465 (3)	0.0114 (6)
O8	0.2350 (7)	−0.4758 (5)	−0.0732 (3)	0.0114 (6)
O9	0.6870 (7)	−0.5435 (5)	−0.1886 (4)	0.0121 (7)
B2	−0.2634 (10)	−0.7520 (8)	−0.1570 (5)	0.0091 (8)
O1	0.5437 (7)	−0.8575 (5)	−0.1392 (3)	0.0094 (6)
O3	−0.0094 (7)	−0.8664 (5)	−0.1355 (3)	0.0086 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pr1	0.00931 (15)	0.00715 (15)	0.00456 (15)	−0.00225 (10)	−0.00160 (10)	−0.00032 (10)
Pr2	0.00839 (16)	0.00662 (15)	0.00584 (15)	−0.00215 (10)	−0.00193 (10)	−0.00046 (9)
Mo	0.0094 (2)	0.0072 (2)	0.00587 (19)	−0.00159 (14)	−0.00209 (14)	−0.00082 (13)
O7	0.0190 (18)	0.0082 (15)	0.0112 (15)	−0.0002 (12)	−0.0023 (14)	0.0025 (12)
O5	0.0167 (17)	0.0188 (17)	0.0100 (15)	−0.0069 (14)	0.0023 (13)	−0.0039 (13)
O6	0.0165 (17)	0.0179 (17)	0.0109 (15)	−0.0060 (13)	−0.0036 (13)	−0.0052 (13)
O2	0.0110 (15)	0.0136 (16)	0.0096 (15)	−0.0016 (12)	−0.0034 (12)	−0.0038 (12)
B1	0.011 (2)	0.008 (2)	0.0034 (19)	−0.0022 (16)	−0.0003 (16)	−0.0011 (15)
O4	0.0159 (16)	0.0096 (15)	0.0101 (15)	−0.0046 (12)	−0.0044 (13)	−0.0008 (11)
O8	0.0093 (15)	0.0086 (14)	0.0130 (16)	−0.0015 (11)	0.0004 (13)	0.0005 (12)
O9	0.0120 (16)	0.0075 (15)	0.0142 (17)	−0.0020 (12)	0.0011 (13)	−0.0012 (12)
B2	0.009 (2)	0.009 (2)	0.008	−0.0028 (16)	−0.0004 (17)	−0.0010 (16)
O1	0.0099 (15)	0.0107 (15)	0.0088 (14)	−0.0036 (12)	−0.0030 (12)	−0.0017 (11)
O3	0.0076 (14)	0.0106 (15)	0.0071 (14)	−0.0025 (11)	0.0007 (11)	−0.0024 (11)

Geometric parameters (Å, º)

Pr1—O4	2.370 (3)	Pr2—O1^ix	2.585 (3)
Pr1—O3^i	2.430 (3)	Pr2—O6^x	2.645 (4)
Pr1—O1^i	2.450 (3)	Pr2—B2^viii	3.021 (5)
Pr1—O5^ii	2.461 (3)	Pr2—Pr2^vii	3.9237 (6)
Pr1—O7	2.480 (3)	Pr2—Pr1^vi	3.9702 (5)
Pr1—O2	2.529 (3)	Pr2—Pr1^iv	3.9893 (5)
Pr1—O2^iii	2.557 (3)	Mo—O5	1.748 (3)
Pr1—O6^iv	2.610 (3)	Mo—O7	1.748 (3)
Pr1—Mo^v	3.6714 (6)	Mo—O6	1.782 (4)
Pr1—Pr2^vi	3.9702 (5)	Mo—O2^v	1.803 (3)
Pr1—Pr2^i	3.9893 (5)	Mo—Pr1^v	3.6714 (6)
Pr1—Pr2^vii	4.0171 (5)	B1—O8	1.345 (6)
Pr2—O8	2.364 (3)	B1—O4	1.370 (6)
Pr2—O8^vii	2.375 (3)	B1—O9	1.387 (6)
Pr2—O4^vi	2.456 (3)	B2—O9^xi	1.373 (6)
Pr2—O3	2.506 (3)	B2—O1^xi	1.378 (6)
Pr2—O1	2.513 (3)	B2—O3	1.384 (6)
Pr2—O3^viii	2.585 (3)	B2—Pr2^viii	3.021 (5)
O4—Pr1—O3^i	77.59 (12)	O4^vi—Pr2—O1^ix	64.22 (10)
O4—Pr1—O1^i	67.58 (11)	O3—Pr2—O1^ix	102.94 (11)
O3^i—Pr1—O1^i	73.79 (11)	O1—Pr2—O1^ix	75.10 (12)
O4—Pr1—O5^ii	112.06 (12)	O3^viii—Pr2—O1^ix	54.11 (11)
O3^i—Pr1—O5^ii	139.81 (11)	O8—Pr2—O6^x	117.87 (11)
O1^i—Pr1—O5^ii	74.69 (11)	O8^vii—Pr2—O6^x	68.69 (12)
O4—Pr1—O7	149.37 (12)	O4^vi—Pr2—O6^x	79.69 (11)
O3^i—Pr1—O7	75.46 (11)	O3—Pr2—O6^x	126.73 (10)
O1^i—Pr1—O7	90.93 (12)	O1—Pr2—O6^x	154.52 (11)
O5^ii—Pr1—O7	80.77 (12)	O3^viii—Pr2—O6^x	69.74 (10)
O4—Pr1—O2	141.05 (11)	O1^ix—Pr2—O6^x	82.67 (11)
O3^i—Pr1—O2	121.14 (11)	O8—Pr2—Pr2^vii	34.21 (8)
O1^i—Pr1—O2	146.59 (11)	O8^vii—Pr2—Pr2^vii	34.03 (8)
O5^ii—Pr1—O2	76.77 (11)	O4^vi—Pr2—Pr2^vii	97.53 (8)
O7—Pr1—O2	67.53 (11)	O3—Pr2—Pr2^vii	93.69 (8)
O4—Pr1—O2^iii	76.63 (11)	O1—Pr2—Pr2^vii	103.65 (8)
O3^i—Pr1—O2^iii	145.67 (11)	O3^viii—Pr2—Pr2^vii	140.80 (7)
O1^i—Pr1—O2^iii	115.72 (11)	O1^ix—Pr2—Pr2^vii	161.72 (7)
O5^ii—Pr1—O2^iii	71.93 (11)	O6^x—Pr2—Pr2^vii	93.54 (8)
O7—Pr1—O2^iii	133.79 (11)	B2^viii—Pr2—Pr2^vii	166.65 (10)
O2—Pr1—O2^iii	70.32 (12)	O8—Pr2—Pr1^vi	113.11 (9)
O4—Pr1—O6^iv	69.35 (11)	O8^vii—Pr2—Pr1^vi	125.58 (9)
O3^i—Pr1—O6^iv	72.69 (11)	O4^vi—Pr2—Pr1^vi	33.96 (8)
O1^i—Pr1—O6^iv	129.69 (11)	O3—Pr2—Pr1^vi	139.70 (8)
O5^ii—Pr1—O6^iv	147.48 (12)	O1—Pr2—Pr1^vi	90.73 (8)
O7—Pr1—O6^iv	115.17 (12)	O3^viii—Pr2—Pr1^vi	79.17 (7)
O2—Pr1—O6^iv	83.51 (11)	O1^ix—Pr2—Pr1^vi	36.78 (7)
O2^iii—Pr1—O6^iv	77.21 (11)	O6^x—Pr2—Pr1^vi	63.84 (8)
O4—Pr1—Pr2^vi	35.36 (8)	B2^viii—Pr2—Pr1^vi	57.28 (10)
O3^i—Pr1—Pr2^vi	89.53 (8)	Pr2^vii—Pr2—Pr1^vi	126.063 (11)
O1^i—Pr1—Pr2^vi	39.18 (8)	O8—Pr2—Pr1^iv	82.46 (9)
O5^ii—Pr1—Pr2^vi	81.40 (9)	O8^vii—Pr2—Pr1^iv	115.15 (9)
O7—Pr1—Pr2^vi	129.95 (9)	O4^vi—Pr2—Pr1^iv	115.41 (8)
O2—Pr1—Pr2^vi	149.14 (8)	O3—Pr2—Pr1^iv	35.45 (7)
O2^iii—Pr1—Pr2^vi	82.37 (8)	O1—Pr2—Pr1^iv	35.98 (7)
O6^iv—Pr1—Pr2^vi	104.66 (8)	O3^viii—Pr2—Pr1^iv	88.62 (7)
Mo^v—Pr1—Pr2^vi	173.822 (12)	O1^ix—Pr2—Pr1^iv	89.26 (7)
O4—Pr1—Pr2^i	68.51 (8)	O6^x—Pr2—Pr1^iv	157.63 (7)
O3^i—Pr1—Pr2^i	36.74 (8)	B2^viii—Pr2—Pr1^iv	87.02 (10)
O1^i—Pr1—Pr2^i	37.06 (8)	Pr2^vii—Pr2—Pr1^iv	100.262 (11)
O5^ii—Pr1—Pr2^i	108.19 (8)	Pr1^vi—Pr2—Pr1^iv	118.956 (9)
O7—Pr1—Pr2^i	81.16 (8)	O5—Mo—O7	107.10 (17)
O2—Pr1—Pr2^i	147.30 (8)	O5—Mo—O6	107.70 (16)
O2^iii—Pr1—Pr2^i	142.36 (8)	O7—Mo—O6	111.77 (17)
O6^iv—Pr1—Pr2^i	102.41 (8)	O5—Mo—O2^v	105.62 (17)
Mo^v—Pr1—Pr2^i	124.637 (12)	O7—Mo—O2^v	118.20 (16)
Pr2^vi—Pr1—Pr2^i	61.044 (9)	O6—Mo—O2^v	105.89 (16)
O4—Pr1—Pr2^vii	53.61 (8)	Pr1^i—O6—Pr2^x	99.70 (12)
O3^i—Pr1—Pr2^vii	38.13 (7)	Mo^v—O2—Pr1	114.85 (15)
O1^i—Pr1—Pr2^vii	91.90 (8)	Mo^v—O2—Pr1^iii	122.00 (16)
O5^ii—Pr1—Pr2^vii	164.08 (9)	Pr1—O2—Pr1^iii	109.68 (12)
O7—Pr1—Pr2^vii	108.49 (8)	O8—B1—O4	122.1 (4)
O2—Pr1—Pr2^vii	118.48 (8)	O8—B1—O9	121.5 (4)
O2^iii—Pr1—Pr2^vii	107.57 (8)	O4—B1—O9	116.2 (4)
O6^iv—Pr1—Pr2^vii	40.47 (8)	B1—O4—Pr1	129.0 (3)
Mo^v—Pr1—Pr2^vii	97.798 (12)	B1—O4—Pr2^vi	113.9 (3)
Pr2^vi—Pr1—Pr2^vii	82.769 (10)	Pr1—O4—Pr2^vi	110.68 (12)
Pr2^i—Pr1—Pr2^vii	62.010 (9)	B1—O8—Pr2	134.1 (3)
O8—Pr2—O8^vii	68.24 (13)	B1—O8—Pr2^vii	113.4 (3)
O8—Pr2—O4^vi	79.16 (11)	Pr2—O8—Pr2^vii	111.76 (13)
O8^vii—Pr2—O4^vi	113.81 (11)	B2^xii—O9—B1	125.1 (4)
O8—Pr2—O3	95.79 (11)	O9^xi—B2—O1^xi	123.8 (4)
O8^vii—Pr2—O3	90.33 (12)	O9^xi—B2—O3	119.3 (4)
O4^vi—Pr2—O3	150.59 (11)	O1^xi—B2—O3	116.8 (4)
O8—Pr2—O1	72.10 (11)	Pr1^iv—O1—Pr2	106.97 (12)
O8^vii—Pr2—O1	134.09 (11)	B2^xii—O1—Pr2^ix	94.4 (3)
O4^vi—Pr2—O1	79.52 (11)	Pr1^iv—O1—Pr2^ix	104.05 (12)
O3—Pr2—O1	71.43 (11)	Pr2—O1—Pr2^ix	104.90 (12)
O8—Pr2—O3^viii	167.27 (12)	B2—O3—Pr1^iv	123.2 (3)
O8^vii—Pr2—O3^viii	108.01 (11)	B2—O3—Pr2	114.9 (3)
O4^vi—Pr2—O3^viii	113.02 (11)	Pr1^iv—O3—Pr2	107.81 (12)
O3—Pr2—O3^viii	71.81 (12)	B2—O3—Pr2^viii	94.2 (3)
O1—Pr2—O3^viii	105.54 (10)	Pr1^iv—O3—Pr2^viii	106.39 (12)
O8—Pr2—O1^ix	134.34 (11)	Pr2—O3—Pr2^viii	108.19 (12)
O8^vii—Pr2—O1^ix	150.80 (11)

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