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Acta Crystallogr Sect E Struct Rep Online. 2010 August 1; 66(Pt 8): i59–i60.
Published online 2010 July 14. doi:  10.1107/S1600536810026942
PMCID: PMC3007571

KPr(PO3)4

Abstract

Single crystals of the title compound, potassium praseodymium(III) polyphosphate, were obtained by solid-state reaction. The monoclinic non-centrosymmetric structure is isotypic with all other KLn(PO3)4 analogues from Ln = La to Er, inclusive. The crystal structure of these long-chain polyphosphates is built up from infinite crenelated polyphosphate chains of corner-sharing PO4 tetra­hedra with a repeating unit of four tetra­hedra. These chains, running along [100], are arranged in a pseudo-tetra­gonal rod packing and are further linked by isolated PrO8 square anti­prisms [Pr—O = 2.3787 (9)–2.5091 (8) Å], forming a three-dimensional framework. The K+ ions reside in channels parallel to [010] and exhibit a highly distorted coordination sphere by eight O atoms at distances ranging from 2.7908 (9) to 3.1924 (11) Å.

Related literature

Long-chain polyphosphates with general formula A I B III(PO3)4 have been classified into seven structural types, labelled from I to VII (Jaoudi et al., 2003 [triangle]). All KLn(PO3)4 polyphosphates (Ln is a trivalent rare earth element) reported up to now adopt type III except for KYb(PO3)4 (Palkina et al., 1981 [triangle]). For corresponding isotypic crystal structures, see: Zhu et al. (2009 [triangle]) for Ce and Eu; Horchani-Naifer et al. (2008 [triangle]) for Y; Parreu et al. (2006 [triangle]) for Gd and Nd; Xing et al. (1987 [triangle]) for Tb; Ninghai et al. (1984 [triangle]) for Eu; Lin et al. (1983 [triangle]) for La; Krutik et al. (1980 [triangle]) for Er; Hong et al. (1975 [triangle]) for Nd. For a review of the crystal chemistry of phosphates, see: Durif (1995 [triangle]). For the cyclo­phosphate structure with the same composition, KPr(PO3)4, see: Zhou et al. (1987 [triangle]).

Experimental

Crystal data

  • KPr(PO3)4
  • M r = 495.89
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-00i59-efi3.jpg
  • a = 7.2872 (2) Å
  • b = 8.4570 (3) Å
  • c = 8.0268 (2) Å
  • β = 91.994 (1)°
  • V = 494.37 (3) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 6.06 mm−1
  • T = 296 K
  • 0.29 × 0.21 × 0.16 mm

Data collection

  • Bruker APEXII CCD diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2008 [triangle]) T min = 0.448, T max = 0.751
  • 45940 measured reflections
  • 13443 independent reflections
  • 13257 reflections with I > 2σ(I)
  • R int = 0.034

Refinement

  • R[F 2 > 2σ(F 2)] = 0.018
  • wR(F 2) = 0.043
  • S = 1.07
  • 13443 reflections
  • 164 parameters
  • 1 restraint
  • Δρmax = 2.86 e Å−3
  • Δρmin = −2.42 e Å−3
  • Absolute structure: Flack (1983 [triangle]), 6278 Friedel pairs
  • Flack parameter: 0.022 (3)

Data collection: APEX2 (Bruker, 2008 [triangle]); cell refinement: SAINT (Bruker, 2008 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: CaRine (Boudias & Monceau, 1998 [triangle]) and ORTEP-3 for Windows (Farrugia, 1997 [triangle]); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 [triangle]).

Table 1
Selected bond lengths (Å)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810026942/wm2370sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810026942/wm2370Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

Long chains polyphosphates with general formula AIBIII(PO3)4 have been classified into seven structural types, labelled from I to VII (Durif, 1995; Jaoudi et al. 2003). All long-chains polyphosphates of formula KLn(PO3)4 (Ln = rare earth elements) reported up to now (Zhu et al., 2009; Horchani-Naifer et al., 2008; Parreu et al., 2006; Xing et al., 1987; Ninghai et al., 1984; Lin et al., 1983; Krutik et al., 1980; Hong et al., 1975) adopt type III except for KYb(PO3)4 (Palkina et al. 1981) which is the only presently known member of type V. Most of these potassium polyphosphates are dimorphic and crystallize with both the type III and the type IV polymorphs. KCe(PO3)4 which has been shown to crystallize with either the type II and the type III is the first exception. The second exception is concerned with the Er member of this series presenting the type VII polymorph besides both type III and type IV polymorphs. Moreover, type III long-chain polyphosphates do not exist for monovalent cations other than K+. The structure of the title compound also fits in this type III isotypic series.

The crystal structure of the title compound is built from crenelated chains with a repeating unit of four corner-sharing tetrahedra, as displayed in Fig. 1. The chains are further linked by isolated PrO8 square antiprisms to form the three-dimensional framework. Each PrO8 polyhedron (Pr—O distances range from 2.3787 (9) to 2.5091 (8) Å) is connected through vertices to four (PO3) chains stacked in a pseudo-tetragonal rod packing as shown in Fig. 2. Figure 2 also shows that within this pseudo-tetragonal rod packing, two adjacent chains are twisted by ca. 90 ° whereas two opposite chains are parallel. The relative disposition of the chains running along the [100] direction accounts for the strong non-centrosymmetric character of the structure. Figure 3 displays details of the connections between the PrO8 square antiprisms and the four chains surrounding each antiprism. One of the four chains (labelled C1) is attached in a tridentate fashion on a triangular face of the square antiprism whereas the opposite and parallel chain (labelled C2) is connected only through a vertex (Fig. 3a). The two other chains which are adjacent to the first one are attached in a bidentate fashion. The first of these two chains (labelled C3) is linked through a bidentate diphosphate group attached on one side of one square face of the square antiprism (Fig. 3b). The second chain (labelled C4) is connected at the ends of one diagonal of the second square face of the antiprism (Fig. 3c) through corners of the terminal PO4 groups of the crenel-shaped tetraphosphate group corresponding to the repeating unit of the chain. This polyhedral linkage delimits channels running along [010] where the K+ions lie in a highly distorted environment defined by eight oxygen atoms at distances ranging from 2.7908 (9) to 3.1924 (11) Å.

For the cyclophosphate structure with the same composition KPr(PO3)4, see: (Zhou et al., 1987).

Experimental

Crystals of the title compound were synthesized by reacting Pr6O11 with (NH4)H2PO4 and K2CO3 in a platinum crucible. A mixture of these reagents in the molar ratio 14: 66: 20 was used for the synthesis. The mixture has first been heated at 473 K for 12 h and then the temperature has been increased up to 573 K and maintained for 12 h before to be raised at 853 K and kept for 24 additional hours. At the end of this heating step, the muffle furnace was cooled down first to 673 K at the rate of 2 K h-1 and subsequently to room temperature by switching the power off. Single crystals were extracted from the batch by leaching with hot water.

Refinement

The highest residual peak in the final difference Fourier map was located 0.46 Å from atom Pr and the deepest hole was located 0.47 Å from atom K.

Figures

Fig. 1.
View of the repeating unit of the (PO3)∞ chains. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (vi) -x + 1, y + 1/2, -z + 1; (vii) x, y, z - 1; (viii) -x, y + 1/2, -z + 1; (ix) x - 1, y, z.]
Fig. 2.
Projection along [100] showing the pseudo-tetragonal rod packing of the infinite (PO3) chains.
Fig. 3.
Details of the connections between the (PO3)∞ chains and the PrO8 square antiprisms: a) view showing the tridentate attachement of one chain (C1) and the connection of the second chain (C2) parallel and opposite to the first one. b) view showing ...

Crystal data

KPr(PO3)4F(000) = 468
Mr = 495.89Dx = 3.331 Mg m3
Monoclinic, P21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ybCell parameters from 9960 reflections
a = 7.2872 (2) Åθ = 2.8–57.3°
b = 8.4570 (3) ŵ = 6.06 mm1
c = 8.0268 (2) ÅT = 296 K
β = 91.994 (1)°Prism, green
V = 494.37 (3) Å30.29 × 0.21 × 0.16 mm
Z = 2

Data collection

Bruker APEXII CCD diffractometer13443 independent reflections
Radiation source: fine-focus sealed tube13257 reflections with I > 2σ(I)
graphiteRint = 0.034
Detector resolution: 8.3333 pixels mm-1θmax = 57.4°, θmin = 3.7°
ω and [var phi] scansh = −17→17
Absorption correction: multi-scan (SADABS; Bruker, 2008)k = −19→20
Tmin = 0.448, Tmax = 0.751l = −18→18
45940 measured reflections

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullw = 1/[σ2(Fo2) + (0.P)2 + 0.0715P] where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.018(Δ/σ)max = 0.004
wR(F2) = 0.043Δρmax = 2.86 e Å3
S = 1.07Δρmin = −2.41 e Å3
13443 reflectionsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
164 parametersExtinction coefficient: 0.0305 (6)
1 restraintAbsolute structure: Flack (1983), 6278 Friedel pairs
0 constraintsFlack parameter: 0.022 (3)
Primary atom site location: structure-invariant direct methods

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. 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)

xyzUiso*/Ueq
K0.77227 (5)0.31500 (7)0.72001 (4)0.02909 (8)
Pr0.265282 (4)0.119995 (8)0.757982 (4)0.00552 (1)
P10.50137 (3)0.26677 (3)0.38019 (3)0.00690 (3)
P20.93476 (3)0.24280 (3)0.09865 (3)0.00685 (3)
P30.12252 (3)0.37267 (3)0.39531 (3)0.00674 (3)
P40.60346 (3)0.04117 (3)0.10444 (3)0.00675 (3)
O11.04301 (12)0.23711 (10)0.27436 (11)0.01360 (11)
O20.81354 (11)0.08886 (10)0.12702 (13)0.01412 (12)
O3−0.03801 (11)0.02642 (9)0.65100 (11)0.01191 (10)
O40.11151 (11)0.31458 (11)0.56903 (9)0.01188 (10)
O50.33093 (10)0.38001 (9)0.34329 (10)0.01061 (9)
O60.66909 (10)0.36646 (10)0.38630 (10)0.01127 (9)
O70.18250 (12)−0.11539 (10)0.92653 (10)0.01172 (10)
O80.41427 (12)0.38104 (10)0.82424 (13)0.01527 (12)
O90.53826 (12)0.07174 (11)0.93036 (10)0.01395 (12)
O100.49263 (14)0.16280 (13)0.21526 (13)0.01754 (15)
O111.06463 (16)0.21154 (13)−0.03535 (13)0.01866 (16)
O120.46952 (13)0.16652 (11)0.52829 (11)0.01411 (12)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
K0.01717 (11)0.0542 (3)0.01579 (10)0.00955 (13)−0.00159 (8)−0.00090 (12)
Pr0.00546 (1)0.00563 (1)0.00548 (1)−0.00032 (1)0.00021 (1)0.00006 (1)
P10.00666 (7)0.00665 (7)0.00750 (7)0.00002 (5)0.00174 (5)0.00055 (5)
P20.00649 (6)0.00695 (7)0.00716 (7)−0.00010 (5)0.00069 (5)−0.00144 (5)
P30.00623 (6)0.00685 (7)0.00704 (7)0.00079 (5)−0.00105 (5)0.00031 (5)
P40.00704 (7)0.00576 (6)0.00735 (7)−0.00051 (5)−0.00141 (5)−0.00019 (5)
O10.0159 (3)0.0098 (2)0.0145 (3)0.0010 (2)−0.0082 (2)−0.00244 (18)
O20.0083 (2)0.0108 (2)0.0229 (3)−0.00354 (17)−0.0037 (2)0.0027 (2)
O30.0102 (2)0.0084 (2)0.0168 (3)−0.00284 (17)−0.00320 (19)−0.00037 (18)
O40.0114 (2)0.0160 (3)0.0082 (2)0.0013 (2)0.00038 (16)0.00301 (18)
O50.00730 (18)0.0111 (2)0.0135 (2)0.00173 (16)0.00166 (16)0.00354 (18)
O60.00779 (19)0.0116 (2)0.0145 (2)−0.00191 (17)0.00084 (16)0.00167 (19)
O70.0141 (2)0.0103 (2)0.0106 (2)−0.00433 (19)−0.00116 (18)0.00117 (17)
O80.0131 (3)0.0090 (2)0.0235 (4)0.00183 (19)−0.0015 (2)−0.0067 (2)
O90.0143 (3)0.0186 (3)0.0087 (2)0.0028 (2)−0.00406 (18)0.0001 (2)
O100.0157 (3)0.0201 (3)0.0169 (3)0.0020 (3)0.0016 (2)−0.0106 (3)
O110.0206 (4)0.0191 (3)0.0171 (3)0.0030 (3)0.0121 (3)−0.0029 (3)
O120.0141 (3)0.0144 (3)0.0142 (3)0.0033 (2)0.0059 (2)0.0074 (2)

Geometric parameters (Å, °)

K—O4i2.7908 (9)P2—O7vi1.4822 (8)
K—O62.7909 (9)P2—O11.5926 (8)
K—O82.8231 (10)P2—O21.5941 (8)
K—O3i2.8684 (10)P2—Kvii3.2805 (4)
K—O7ii2.9050 (9)P3—O3viii1.4806 (8)
K—O122.9285 (11)P3—O41.4832 (8)
K—O11iii2.9781 (13)P3—O51.5902 (8)
K—O93.1924 (11)P3—O1ix1.5980 (8)
K—P2iii3.2805 (4)P4—O8v1.4777 (8)
K—P13.3360 (4)P4—O9vii1.4829 (8)
Pr—O11iv2.3787 (9)P4—O21.5874 (8)
Pr—O92.4180 (8)P4—O101.5973 (9)
Pr—O122.4414 (8)O1—P3i1.5980 (8)
Pr—O32.4731 (7)O3—P3x1.4806 (8)
Pr—O42.4791 (8)O3—Kix2.8684 (10)
Pr—O6v2.4912 (8)O4—Kix2.7908 (9)
Pr—O72.4928 (8)O6—Prvi2.4912 (8)
Pr—O82.5091 (8)O7—P2v1.4822 (8)
P1—O61.4841 (8)O7—Kxi2.9051 (9)
P1—O121.4850 (8)O8—P4vi1.4776 (8)
P1—O51.5881 (7)O9—P4iii1.4829 (8)
P1—O101.5887 (9)O11—Prxii2.3787 (9)
P2—O111.4810 (9)O11—Kvii2.9782 (13)
O4i—K—O678.26 (2)O12—Pr—O875.38 (3)
O4i—K—O8166.08 (3)O3—Pr—O8136.89 (3)
O6—K—O891.87 (3)O4—Pr—O874.26 (3)
O4i—K—O3i58.32 (3)O6v—Pr—O8140.10 (3)
O6—K—O3i93.61 (3)O7—Pr—O8134.32 (3)
O8—K—O3i133.01 (3)O11iv—Pr—Kix48.64 (3)
O4i—K—O7ii110.62 (3)O9—Pr—Kix147.29 (2)
O6—K—O7ii157.42 (3)O12—Pr—Kix116.78 (2)
O8—K—O7ii75.23 (3)O3—Pr—Kix46.23 (2)
O3i—K—O7ii108.78 (3)O4—Pr—Kix44.44 (2)
O4i—K—O12115.71 (3)O6v—Pr—Kix120.771 (19)
O6—K—O1252.38 (2)O7—Pr—Kix97.96 (2)
O8—K—O1263.48 (3)O8—Pr—Kix91.99 (2)
O3i—K—O1283.86 (3)O11iv—Pr—K120.16 (3)
O7ii—K—O12131.14 (3)O9—Pr—K51.68 (2)
O4i—K—O11iii70.23 (2)O12—Pr—K45.47 (3)
O6—K—O11iii147.28 (3)O3—Pr—K155.08 (2)
O8—K—O11iii120.66 (3)O4—Pr—K94.44 (2)
O3i—K—O11iii62.54 (3)O6v—Pr—K97.156 (19)
O7ii—K—O11iii50.31 (2)O7—Pr—K127.02 (2)
O12—K—O11iii136.81 (3)O8—Pr—K43.25 (2)
O4i—K—O9136.58 (3)Kix—Pr—K130.558 (15)
O6—K—O9118.49 (3)O6—P1—O12116.70 (5)
O8—K—O956.95 (3)O6—P1—O5107.54 (5)
O3i—K—O979.85 (3)O12—P1—O5110.52 (5)
O7ii—K—O970.04 (3)O6—P1—O10110.55 (5)
O12—K—O966.11 (2)O12—P1—O10110.38 (6)
O11iii—K—O981.08 (3)O5—P1—O1099.78 (5)
O4i—K—P2iii96.054 (18)O6—P1—K55.97 (3)
O6—K—P2iii174.10 (2)O12—P1—K61.30 (4)
O8—K—P2iii94.00 (2)O5—P1—K121.03 (3)
O3i—K—P2iii81.93 (2)O10—P1—K138.98 (4)
O7ii—K—P2iii26.858 (16)O11—P2—O7vi115.17 (6)
O12—K—P2iii130.40 (2)O11—P2—O1109.17 (6)
O11iii—K—P2iii26.821 (17)O7vi—P2—O1114.25 (5)
O9—K—P2iii64.676 (17)O11—P2—O2109.22 (6)
O4i—K—P198.784 (19)O7vi—P2—O2111.14 (5)
O6—K—P126.147 (16)O1—P2—O296.24 (5)
O8—K—P174.92 (2)O11—P2—Kvii65.14 (5)
O3i—K—P190.78 (2)O7vi—P2—Kvii62.31 (3)
O7ii—K—P1150.12 (2)O1—P2—Kvii167.90 (4)
O12—K—P126.409 (16)O2—P2—Kvii95.76 (4)
O11iii—K—P1153.20 (3)O3viii—P3—O4119.42 (5)
O9—K—P192.400 (19)O3viii—P3—O5107.01 (5)
P2iii—K—P1156.78 (2)O4—P3—O5110.07 (4)
O4i—K—P4vi148.57 (3)O3viii—P3—O1ix109.79 (4)
O6—K—P4vi96.19 (2)O4—P3—O1ix107.65 (5)
O8—K—P4vi21.809 (17)O5—P3—O1ix101.41 (5)
O3i—K—P4vi152.95 (2)O3viii—P3—Kix90.09 (4)
O7ii—K—P4vi65.122 (18)O5—P3—Kix150.30 (3)
O12—K—P4vi82.33 (2)O1ix—P3—Kix95.04 (4)
O11iii—K—P4vi115.28 (2)O8v—P4—O9vii119.69 (6)
O9—K—P4vi73.308 (19)O8v—P4—O2106.59 (5)
P2iii—K—P4vi89.502 (11)O9vii—P4—O2109.84 (5)
P1—K—P4vi87.099 (10)O8v—P4—O10108.77 (6)
O4i—K—P3i20.271 (16)O9vii—P4—O10105.12 (6)
O6—K—P3i58.589 (17)O2—P4—O10106.09 (5)
O8—K—P3i147.16 (3)O8v—P4—Kv45.22 (4)
O3i—K—P3i68.374 (19)O9vii—P4—Kv103.55 (4)
O7ii—K—P3i126.64 (2)O2—P4—Kv145.07 (4)
O12—K—P3i102.092 (19)O10—P4—Kv73.90 (4)
O11iii—K—P3i90.45 (2)P2—O1—P3i132.40 (6)
O9—K—P3i147.36 (2)P4—O2—P2136.74 (6)
P2iii—K—P3i115.882 (11)P3x—O3—Pr136.64 (5)
P1—K—P3i81.085 (10)P3x—O3—Kix126.63 (4)
P4vi—K—P3i137.479 (17)Pr—O3—Kix95.26 (3)
O11iv—Pr—O999.75 (4)P3—O4—Pr139.19 (5)
O11iv—Pr—O12151.63 (3)P3—O4—Kix119.05 (4)
O9—Pr—O1287.04 (3)Pr—O4—Kix97.10 (3)
O11iv—Pr—O377.45 (4)P1—O5—P3132.48 (5)
O9—Pr—O3148.45 (3)P1—O6—Prvi130.14 (5)
O12—Pr—O3110.50 (3)P1—O6—K97.89 (4)
O11iv—Pr—O486.26 (3)Prvi—O6—K122.05 (3)
O9—Pr—O4143.85 (3)P2v—O7—Pr136.16 (5)
O12—Pr—O472.87 (3)P2v—O7—Kxi90.83 (4)
O3—Pr—O467.70 (3)Pr—O7—Kxi132.10 (3)
O11iv—Pr—O6v137.47 (3)P4vi—O8—Pr147.72 (6)
O9—Pr—O6v87.33 (3)P4vi—O8—K112.97 (5)
O12—Pr—O6v69.86 (3)Pr—O8—K99.24 (3)
O3—Pr—O6v75.34 (3)P4iii—O9—Pr143.02 (6)
O4—Pr—O6v112.14 (3)P4iii—O9—K116.82 (5)
O11iv—Pr—O773.45 (4)Pr—O9—K91.87 (3)
O9—Pr—O776.38 (3)P1—O10—P4144.49 (7)
O12—Pr—O7134.75 (3)P2—O11—Prxii171.29 (7)
O3—Pr—O772.70 (3)P2—O11—Kvii88.04 (5)
O4—Pr—O7138.54 (3)Prxii—O11—Kvii94.52 (4)
O6v—Pr—O767.60 (3)P1—O12—Pr144.39 (5)
O11iv—Pr—O880.66 (4)P1—O12—K92.29 (5)
O9—Pr—O871.69 (3)Pr—O12—K98.06 (3)

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

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2370).

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