inorganic compounds
The matlockite-type praseodymium(III) oxide bromide PrOBr
aInstitut für Anorganische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
*Correspondence e-mail: schleid@iac.uni-stuttgart.de
The 4Br4]9−. These slabs are stacked along the c axis and linked via two different secondary contacts between Pr3+ and Br−. The Pr3+ cations occupy the Wyckoff site 2c with 4mm symmetry and carry four O2− anions as well as four primary Br− anions, yielding a of 8. While the Br− anions exhibit the same as the Pr3+ cations, the oxide anions are located at the 2a with m2 and have four Pr3+ cations as neighbours, defining a tetrahedron.
of the praseodymium(III) oxide bromide, PrOBr, can be best described with layers of agglomerated square antiprisms [PrORelated literature
For prototypic PbFCl (mineral name: matlockite), see: Nieuwenkamp & Bijvoet (1932) and for an early powder study, see: Mayer et al. (1965). For other PrOX structures, see: Baenziger et al. (1950) for X = F, Zachariasen (1949) for X = Cl, and Potapova et al. (1977) for X = I. For data used for a comparison of the unit-cell dimensions, see: Shannon (1976) for ionic radii and Biltz (1934) for volume increments. For a proper classification of primary and secondary contacts, see: MAPLE (Hoppe, 1975) and for the bond-valence method, see: Brown (2002). For a comparison of intended synthesis attempts, see: Mattausch & Simon (1996); Lulei (1998).
Experimental
Crystal data
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Refinement
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Data collection: COLLECT (Nonius, 1998); cell SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: SHELXL97.
Supporting information
https://doi.org/10.1107/S1600536811048227/fi2117sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536811048227/fi2117Isup2.hkl
Pale green, transparent, plate-shaped single crystals of PrOBr were obtained as by-product from a mixture of 0.06 g Pr, 0.38 g PrBr3 and 0.01 g NaN3, along with 0.30 g NaBr added as a
The mixture was kept at 800 °C for 7 days in an evacuated, sealed fused-silica vessel designed to produce the praseodymium(III) nitride bromide Pr3NBr6 in analogy with La3NBr6 (Lulei, 1998) and Ce3NBr6 (Mattausch & Simon, 1996).The highest peak and the deepest hole in the final difference Fourier map are 95 pm and 84 pm apart from Pr.
With the exception of PrOF (Baenziger et al. 1950) all praseodymium(III) oxide halides of the general composition PrOX (X = Cl – I; Zachariasen 1949, Potapova et al. 1977) crystallize with the matlockite-type structure (Nieuwenkamp & Bijvoet, 1932). The tetragonal 4m2. Bond-Valence and MAPLE calculations support the interpretation of one important (d(Pr3+···Br-) = 360.8 (1) pm) and one less important secondary contact (d(Pr3+···Br-) = 385.9 (1) pm): The valency and ECoN for the first bond amounts to values of about 0.08 (with R0 = 267 pm, b = 37 pm; Brown, 2002) and 0.12 (Hoppe, 1975), but almost nil for the second one, since this next nearest contact to bromide has only very low influence on the effective coordination sphere of the Pr3+ cations (ECoN = 0.03).
of the here presented praseodymium(III) oxide bromide PrOBr can be best described with layers of agglomerated square antiprisms [PrO4Br4]9– (d(Pr3+–O2-) = 234.96 (4) pm, d(Pr3+–Br-) = 324.57 (8) pm, d(Pr3+···Br-) = 360.8 (1) and 385.9 (1) pm; Figure 1). These slabs are stacked along the c-axis and linked via two different secondary contacts between Pr3+ and Br- (Figure 2). According to the ionic radii (rCl = 180 pm, rBr = 195 pm, rI = 220 pm; Shannon, 1976) of the halide anions involved the expansion of the unit-cell dimensions occurs in quite an usual range, but the c-axes become significantly longer than the a-axes (a-axes: from 405.3 pm to 408.6 pm; c-axes: from 679.9 pm to 916.2 pm) along the Cl-–Br-–I- track. The lattice parameters of single crystalline PrOBr (a = 406.71 pm, c = 746.69 pm) fit almost perfectly with that from a previous powder diffraction study (a = 407.1 pm, c = 748.7 pm; Mayer et al. 1965). Differences in the molar volumes of the PbFCl-type praseodymium(III) oxide halides (Vm(PrOCl) = 33.6 cm3/mol, Vm(PrOBr) = 37.2 cm3/mol, Vm(PrOI) = 46.1 cm3/mol) correspond well with the differences of the molar volumes of the respective halide anions (Vm(Cl-) = 16.3 cm3/mol, Vm(Br-) = 19.2 cm3/mol, Vm(I-) = 24.5 cm3/mol; Biltz 1934). However, the Pr3+ cations occupy the Wyckoff site 2c (symmetry: 4mm) and bond four O2- anions as well as four+one+one Br- anions ending up with a total of 8+1+1 (Figure 1). While the Br- anions exhibit the same as the Pr3+ cations, the oxide anions are located at position 2a with theFor prototypic PbFCl (mineral name: matlockite) see Nieuwenkamp & Bijvoet (1932) and for an early powder study, see: Mayer et al. (1965). For other PrOX structures, see: Baenziger et al. (1950) for X = F, Zachariasen (1949) for X = Cl, and Potapova et al. (1977) for X = I. For data used for a comparison of the unit-cell dimensions, see: Shannon (1976) for ionic radii and Biltz (1934) for volume increments. For a proper classification of primary and secondary contacts, see: MAPLE (Hoppe, 1975) andfor the bond-valence method, see: Brown (2002). For a comparison of intended synthesis attempts, see: Mattausch & Simon (1996); Lulei (1998).
Data collection: COLLECT (Nonius, 1998); cell
SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).PrBrO | Dx = 6.368 Mg m−3 |
Mr = 236.82 | Mo Kα radiation, λ = 0.71069 Å |
Tetragonal, P4/nmm | Cell parameters from 3957 reflections |
Hall symbol: -P 4a 2a | θ = 0.4–27.9° |
a = 4.0671 (3) Å | µ = 35.52 mm−1 |
c = 7.4669 (5) Å | T = 293 K |
V = 123.51 (2) Å3 | Plate, pale green |
Z = 2 | 0.11 × 0.07 × 0.02 mm |
F(000) = 204 |
Bruker–Nonius KappaCCD diffractometer | 113 independent reflections |
Radiation source: fine-focus sealed tube | 111 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.082 |
ω and φ scans | θmax = 27.9°, θmin = 5.5° |
Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1999) | h = −5→5 |
Tmin = 0.049, Tmax = 0.535 | k = −5→5 |
1621 measured reflections | l = −9→9 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.026 | w = 1/[σ2(Fo2) + (0.0378P)2] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.059 | (Δ/σ)max < 0.001 |
S = 1.20 | Δρmax = 1.14 e Å−3 |
113 reflections | Δρmin = −2.52 e Å−3 |
10 parameters | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.032 (5) |
PrBrO | Z = 2 |
Mr = 236.82 | Mo Kα radiation |
Tetragonal, P4/nmm | µ = 35.52 mm−1 |
a = 4.0671 (3) Å | T = 293 K |
c = 7.4669 (5) Å | 0.11 × 0.07 × 0.02 mm |
V = 123.51 (2) Å3 |
Bruker–Nonius KappaCCD diffractometer | 113 independent reflections |
Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1999) | 111 reflections with I > 2σ(I) |
Tmin = 0.049, Tmax = 0.535 | Rint = 0.082 |
1621 measured reflections |
R[F2 > 2σ(F2)] = 0.026 | 10 parameters |
wR(F2) = 0.059 | 0 restraints |
S = 1.20 | Δρmax = 1.14 e Å−3 |
113 reflections | Δρmin = −2.52 e Å−3 |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
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 > 2sigma(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. |
x | y | z | Uiso*/Ueq | ||
Pr | 0.2500 | 0.2500 | 0.15763 (8) | 0.0106 (4) | |
O | 0.7500 | 0.2500 | 0.0000 | 0.0129 (13) | |
Br | 0.2500 | 0.2500 | 0.64087 (17) | 0.0153 (4) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Pr | 0.0084 (4) | 0.0084 (4) | 0.0148 (6) | 0.000 | 0.000 | 0.000 |
O | 0.0114 (17) | 0.0114 (17) | 0.016 (3) | 0.000 | 0.000 | 0.000 |
Br | 0.0149 (5) | 0.0149 (5) | 0.0160 (7) | 0.000 | 0.000 | 0.000 |
Pr—Oi | 2.3496 (3) | Pr—Pri | 3.7165 (8) |
Pr—Oii | 2.3496 (3) | Pr—Prx | 3.7165 (8) |
Pr—Oiii | 2.3496 (3) | Pr—Priii | 3.7165 (8) |
Pr—O | 2.3496 (3) | O—Pri | 2.3496 (3) |
Pr—Briv | 3.2457 (8) | O—Prxi | 2.3496 (3) |
Pr—Brv | 3.2457 (8) | O—Priii | 2.3496 (3) |
Pr—Brvi | 3.2457 (8) | Br—Priv | 3.2457 (8) |
Pr—Brvii | 3.2457 (8) | Br—Prv | 3.2457 (8) |
Pr—Br | 3.6083 (14) | Br—Prvii | 3.2457 (8) |
Pr—Brviii | 3.8586 (14) | Br—Prvi | 3.2457 (8) |
Pr—Prix | 3.7165 (8) | ||
Oi—Pr—Oii | 75.466 (11) | O—Pr—Pri | 37.733 (6) |
Oi—Pr—Oiii | 119.87 (3) | Briv—Pr—Pri | 107.075 (12) |
Oii—Pr—Oiii | 75.466 (11) | Brv—Pr—Pri | 107.075 (12) |
Oi—Pr—O | 75.466 (11) | Brvi—Pr—Pri | 168.31 (4) |
Oii—Pr—O | 119.87 (3) | Brvii—Pr—Pri | 66.920 (18) |
Oiii—Pr—O | 75.466 (11) | Prix—Pr—Pri | 66.346 (15) |
Oi—Pr—Briv | 140.758 (5) | Oi—Pr—Prx | 98.99 (2) |
Oii—Pr—Briv | 140.758 (5) | Oii—Pr—Prx | 37.733 (6) |
Oiii—Pr—Briv | 71.938 (15) | Oiii—Pr—Prx | 37.733 (6) |
O—Pr—Briv | 71.938 (15) | O—Pr—Prx | 98.99 (2) |
Oi—Pr—Brv | 71.938 (15) | Briv—Pr—Prx | 107.075 (12) |
Oii—Pr—Brv | 71.938 (15) | Brv—Pr—Prx | 107.075 (12) |
Oiii—Pr—Brv | 140.758 (5) | Brvi—Pr—Prx | 66.920 (18) |
O—Pr—Brv | 140.758 (5) | Brvii—Pr—Prx | 168.31 (4) |
Briv—Pr—Brv | 124.77 (5) | Prix—Pr—Prx | 66.346 (15) |
Oi—Pr—Brvi | 140.758 (5) | Pri—Pr—Prx | 101.39 (3) |
Oii—Pr—Brvi | 71.938 (15) | Oi—Pr—Priii | 98.99 (2) |
Oiii—Pr—Brvi | 71.938 (15) | Oii—Pr—Priii | 98.99 (2) |
O—Pr—Brvi | 140.758 (5) | Oiii—Pr—Priii | 37.733 (6) |
Briv—Pr—Brvi | 77.59 (2) | O—Pr—Priii | 37.733 (6) |
Brv—Pr—Brvi | 77.59 (2) | Briv—Pr—Priii | 66.920 (19) |
Oi—Pr—Brvii | 71.938 (15) | Brv—Pr—Priii | 168.31 (4) |
Oii—Pr—Brvii | 140.758 (5) | Brvi—Pr—Priii | 107.075 (12) |
Oiii—Pr—Brvii | 140.758 (6) | Brvii—Pr—Priii | 107.075 (12) |
O—Pr—Brvii | 71.938 (15) | Prix—Pr—Priii | 101.39 (3) |
Briv—Pr—Brvii | 77.59 (2) | Pri—Pr—Priii | 66.346 (15) |
Brv—Pr—Brvii | 77.59 (2) | Prx—Pr—Priii | 66.346 (15) |
Brvi—Pr—Brvii | 124.77 (5) | Pr—O—Pri | 104.534 (11) |
Oi—Pr—Prix | 37.733 (6) | Pr—O—Prxi | 119.87 (3) |
Oii—Pr—Prix | 37.733 (6) | Pri—O—Prxi | 104.534 (11) |
Oiii—Pr—Prix | 98.99 (2) | Pr—O—Priii | 104.534 (11) |
O—Pr—Prix | 98.99 (2) | Pri—O—Priii | 119.87 (3) |
Briv—Pr—Prix | 168.31 (4) | Prxi—O—Priii | 104.534 (11) |
Brv—Pr—Prix | 66.920 (19) | Priv—Br—Prv | 124.77 (5) |
Brvi—Pr—Prix | 107.075 (12) | Priv—Br—Prvii | 77.59 (2) |
Brvii—Pr—Prix | 107.075 (12) | Prv—Br—Prvii | 77.59 (2) |
Oi—Pr—Pri | 37.733 (6) | Priv—Br—Prvi | 77.59 (2) |
Oii—Pr—Pri | 98.99 (2) | Prv—Br—Prvi | 77.59 (2) |
Oiii—Pr—Pri | 98.99 (2) | Prvii—Br—Prvi | 124.77 (5) |
Symmetry codes: (i) −x+1, −y, −z; (ii) x−1, y, z; (iii) −x+1, −y+1, −z; (iv) −x+1, −y+1, −z+1; (v) −x, −y, −z+1; (vi) −x, −y+1, −z+1; (vii) −x+1, −y, −z+1; (viii) x, y, z−1; (ix) −x, −y, −z; (x) −x, −y+1, −z; (xi) x+1, y, z. |
Experimental details
Crystal data | |
Chemical formula | PrBrO |
Mr | 236.82 |
Crystal system, space group | Tetragonal, P4/nmm |
Temperature (K) | 293 |
a, c (Å) | 4.0671 (3), 7.4669 (5) |
V (Å3) | 123.51 (2) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 35.52 |
Crystal size (mm) | 0.11 × 0.07 × 0.02 |
Data collection | |
Diffractometer | Bruker–Nonius KappaCCD |
Absorption correction | Numerical (X-SHAPE; Stoe & Cie, 1999) |
Tmin, Tmax | 0.049, 0.535 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1621, 113, 111 |
Rint | 0.082 |
(sin θ/λ)max (Å−1) | 0.658 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.026, 0.059, 1.20 |
No. of reflections | 113 |
No. of parameters | 10 |
Δρmax, Δρmin (e Å−3) | 1.14, −2.52 |
Computer programs: COLLECT (Nonius, 1998), SCALEPACK (Otwinowski & Minor, 1997), SCALEPACK and DENZO (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2006).
Pr—Oi | 2.3496 (3) | Pr—Brv | 3.2457 (8) |
Pr—Oii | 2.3496 (3) | Pr—Brvi | 3.2457 (8) |
Pr—Oiii | 2.3496 (3) | Pr—Brvii | 3.2457 (8) |
Pr—O | 2.3496 (3) | Pr—Br | 3.6083 (14) |
Pr—Briv | 3.2457 (8) | Pr—Brviii | 3.8586 (14) |
Symmetry codes: (i) −x+1, −y, −z; (ii) x−1, y, z; (iii) −x+1, −y+1, −z; (iv) −x+1, −y+1, −z+1; (v) −x, −y, −z+1; (vi) −x, −y+1, −z+1; (vii) −x+1, −y, −z+1; (viii) x, y, z−1. |
Acknowledgements
This work was supported by the State of Baden-Württemberg (Stuttgart) and the German Research Foundation (DFG, Bonn) within the funding programme Open Access Publishing. We thank Dr Sabine Strobel for the data collection.
References
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With the exception of PrOF (Baenziger et al. 1950) all praseodymium(III) oxide halides of the general composition PrOX (X = Cl – I; Zachariasen 1949, Potapova et al. 1977) crystallize with the matlockite-type structure (Nieuwenkamp & Bijvoet, 1932). The tetragonal crystal structure of the here presented praseodymium(III) oxide bromide PrOBr can be best described with layers of agglomerated square antiprisms [PrO4Br4]9– (d(Pr3+–O2-) = 234.96 (4) pm, d(Pr3+–Br-) = 324.57 (8) pm, d(Pr3+···Br-) = 360.8 (1) and 385.9 (1) pm; Figure 1). These slabs are stacked along the c-axis and linked via two different secondary contacts between Pr3+ and Br- (Figure 2). According to the ionic radii (rCl = 180 pm, rBr = 195 pm, rI = 220 pm; Shannon, 1976) of the halide anions involved the expansion of the unit-cell dimensions occurs in quite an usual range, but the c-axes become significantly longer than the a-axes (a-axes: from 405.3 pm to 408.6 pm; c-axes: from 679.9 pm to 916.2 pm) along the Cl-–Br-–I- track. The lattice parameters of single crystalline PrOBr (a = 406.71 pm, c = 746.69 pm) fit almost perfectly with that from a previous powder diffraction study (a = 407.1 pm, c = 748.7 pm; Mayer et al. 1965). Differences in the molar volumes of the PbFCl-type praseodymium(III) oxide halides (Vm(PrOCl) = 33.6 cm3/mol, Vm(PrOBr) = 37.2 cm3/mol, Vm(PrOI) = 46.1 cm3/mol) correspond well with the differences of the molar volumes of the respective halide anions (Vm(Cl-) = 16.3 cm3/mol, Vm(Br-) = 19.2 cm3/mol, Vm(I-) = 24.5 cm3/mol; Biltz 1934). However, the Pr3+ cations occupy the Wyckoff site 2c (symmetry: 4mm) and bond four O2- anions as well as four+one+one Br- anions ending up with a total coordination number of 8+1+1 (Figure 1). While the Br- anions exhibit the same site symmetry as the Pr3+ cations, the oxide anions are located at Wyckoff position 2a with the site symmetry 4m2. Bond-Valence and MAPLE calculations support the interpretation of one important (d(Pr3+···Br-) = 360.8 (1) pm) and one less important secondary contact (d(Pr3+···Br-) = 385.9 (1) pm): The valency and ECoN for the first bond amounts to values of about 0.08 (with R0 = 267 pm, b = 37 pm; Brown, 2002) and 0.12 (Hoppe, 1975), but almost nil for the second one, since this next nearest contact to bromide has only very low influence on the effective coordination sphere of the Pr3+ cations (ECoN = 0.03).