inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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A quaternary germanium(II) phosphate, Na[Ge4(PO4)3]

aDepartment of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001 Ta-Hsueh Rd, Hsinchu 30010, Taiwan
*Correspondence e-mail: chishen@mail.nctu.edu.tw

(Received 22 November 2007; accepted 29 January 2008; online 6 February 2008)

A new germanium(II) phosphate, sodium tetra­germanium tris­(phosphate), Na[Ge4(PO4)3], has been synthesized by a solid-state reaction. The compound is isotypic with A[Sn4(PO4)3] (A = Na, K, NH4). It features a [Ge4(PO4)3] framework made up of GeO3 pyramids and PO4 tetra­hedra, which are linked by shared corners, yielding a three-dimensional structure. The crystal studied showed partial inversion twinning.

Related literature

Open–framework series of isotypic tin(II) phosphates with general formula A[Sn4(PO4)3] (A = Na, K, NH4) were synthesized by hydro­thermal methods (Ayyappan et al., 2000[Ayyappan, S., Chang, J. S., Stock, N., Hatfield, R., Rao, C. N. R. & Cheetham, A. K. (2000). Int. J. Inorg. Mater. 2, 21-27.]; Bontchev & Moore, 2004[Bontchev, R. P. & Moore, R. C. (2004). Solid State Sci. 6, 867-873.]; Deng et al., 2004[Deng, J.-F., Kang, Y.-J., Mi, J.-X., Li, M.-R., Zhao, J.-T. & Mao, S.-Y. (2004). Acta Cryst. E60, i116-i117.]; Mao et al., 2004[Mao, S. Y., Deng, J. F., Li, M. R., Mi, J. X., Chen, H. H. & Zhao, J. T. (2004). Z. Kristallogr. 219, 205-206.]). For related literature, see: Brown & Altermatt (1985[Brown, I. D. & Altermatt, D. (1985). Acta Cryst. B41, 244-247.]); Cheetham et al. (1999[Cheetham, A. K., Férey, G. & Loiseau, T. (1999). Angew. Chem. Int. Ed. 38, 3268-3292.]); Weakley & Watt (1979[Weakley, T. J. R. & Watt, W. W. L. (1979). Acta Cryst. B35, 3023-3024.]).

Experimental

Crystal data
  • Na[Ge4(PO4)3]

  • Mr = 598.26

  • Trigonal, R 3c

  • a = 9.377 (8) Å

  • c = 23.48 (3) Å

  • V = 1788 (3) Å3

  • Z = 6

  • Mo Kα radiation

  • μ = 10.49 mm−1

  • T = 298 (2) K

  • 0.2 × 0.13 × 0.1 mm

Data collection
  • Bruker SMART CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2000[Bruker (2000). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.488, Tmax = 1 (expected range = 0.171–0.350)

  • 2164 measured reflections

  • 639 independent reflections

  • 567 reflections with I > 2σ(I)

  • Rint = 0.068

Refinement
  • R[F2 > 2σ(F2)] = 0.058

  • wR(F2) = 0.133

  • S = 1.09

  • 639 reflections

  • 62 parameters

  • 1 restraint

  • Δρmax = 1.71 e Å−3

  • Δρmin = −1.06 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 146 Friedel pairs

  • Flack parameter: 0.23 (8)

Data collection: SMART (Bruker, 2000[Bruker (2000). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2000[Bruker (2000). SMART, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: ATOMS (Dowty, 2005[Dowty, E. (2005). ATOMS. Shape Software, Kingsport, TN, USA.]); software used to prepare material for publication: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]).

Supporting information


Comment top

Open-framework metal phosphates exhibit interesting structural types and physical properties that have been the subject of intensive research due to their potential applications in the areas of catalysis, ion–exchange and phase separation (Cheetham et al., 1999). Among these compounds, germanium phosphates are rare compared to other phosphate compounds. Most of reported germanophosphate contain germanium (IV) with octahedral coordination environment to oxygen atoms. To the best of our knowledge, germanophosphate with Ge(II) are very rare. Our group has demonstrated that A2HPO4 and metal can serve as reducing and oxidizing reagents to synthesize metal phosphates. In an attempt to synthesize compounds in the system using A2HPO4 as the precursor, we obtained a new quaternary compound Na[Ge4(PO4)3]. As confirmed by measurements on single crystals, the synthesis of Na[Ge4(PO4)3] is presented as follows:

4Na2HPO4+17Ge+15GeO2+10P2O58Na[Ge4(PO4)3]+2H2

The structure of Na[Ge4(PO4)3] is shown in Figure 1. The asymmetric unit contains two germanium, one phosphorus, four oxygen and one sodium atom (Figure 2). The Ge atoms occupy two different crystallographic sites and each site being coordinated by three O atoms to form distorted pyramids with Ge—O distances ranging from 1.87 (1) to 1.92 (1) Å, which agrees well with bond valence sum calculations (Brown & Altermatt, 1985). Similar Ge—O distances are reported in GeCl(H2PO2) (Weakley & Watt, 1979). The coordination environment of the Ge2+ atoms is similar to Sn2+ in A[Sn4(PO4)3] (A=Na, K, NH4) (Ayyappan et al., 2000, Bontchev & Moore, 2004, Deng et al., 2004, Mao et al., 2004).. The phosphorus atoms is tetrahedrally coordinated with P—O distances in a range 1.53 (1) to 1.54 (1) Å, which agrees with literature values. The structure of the title compound contains [PO4]3- layers stacked along the c–axis with a repeat sequence of six layers. The [PO4]3- units on the ab plane form 6 membered–ring with corner–shared [PO4] and Ge(2)O3 units, which are connected by Ge(1)O3 pyramids to construct the two–dimensional framework. The two-dimensional layers are additionally connected to each other by out of planeGe(1)O3 groups to form a three–dimensional framework. Each sodium atom is coordinated by nine oxygen atoms with Na—O distances ranging between 2.46 (1) and 2.71 (1) Å in a basket–like cage.

Related literature top

Open–framework series of isotypic tin(II) phosphates with general formula A[Sn4(PO4)3] (A=Na, K, NH4) were synthesized by hydrothermal methods (Ayyappan et al., 2000, Bontchev & Moore, 2004, Deng et al., 2004, Mao et al., 2004).

For related literature, see: Brown & Altermatt (1985); Cheetham et al. (1999); Weakley & Watt (1979).

Experimental top

Na[Ge4(PO4)3] were synthesized from mixtures of Na2HPO4 (99%, Riedel-de Haën), Ge (99.999%, Alfa), GeO2 (99.999%, Cerac), and P2O5 (99.999%, J.T.Baker) in stoichiometric proportions according to the solid state method. Initially, all reagents were mixed in an Ar-filled glove box (total weight0.5 g), placed in a silica tube, sealed under vacuum (P10-4 torr), and heated slowly to 600 °C over 48 h, followed by furnace cooling to room temperature on simply terminating the power. The length of the reaction tube was kept about 7~8 cm to avoid the prospective explosion due to the formation of gaseous hydrogen. The product contains hydrogen gas and brittle, colorless, transparent rod-shape crystals. The crystalline product was confirmed to be pure Na[Ge4(PO4)3] by powder X-ray diffraction. Attempts to synthesize the analogue K[Ge4(PO4)3] with the precursor K2HPO4 failed.

Refinement top

The structures were solved by direct methods and refined by full matrix least–squares techniques with the SHELXTL software package. Analysis of single-crystal X–ray diffraction data revealed four unique sites for Na, Ge and P and four unique sites for O atoms. The structural analysis yielded a charge–balanced formula Na[Ge4(PO4)3]. All atomic positions were refined with anisotropic displacement parameters. The highest peak in the difference map is 1.67 e/Å3 and 0.96 Å from Ge1, while the minimum peak is -1.08 e/Å3 and 1.51 Å from O3.

Computing details top

Data collection: SMART (Bruker, 2000); cell refinement: SMART (Bruker, 2000); data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ATOMS (Dowty, 2005); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The framework of Na[Ge4(PO4)3] [Symmetry codes: (i)-y,x-y,z (ii)-x + y, -x, z (ix)-y + 2/3, -x + 1/3, z + 5/6 (x)-x + y+2/3, y + 1/3, z + 5/6. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. The alternating full/empty sequence of channels running parallel to the a– and b–axes.
sodium tetragermanium tris(phosphate) top
Crystal data top
Na[Ge4(PO4)3]Dx = 3.334 Mg m3
Mr = 598.26Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3cCell parameters from 2164 reflections
Hall symbol: R 3 -2" cθ = 3.1–28.3°
a = 9.377 (8) ŵ = 10.49 mm1
c = 23.48 (3) ÅT = 298 K
V = 1788 (3) Å3Rod, colourless
Z = 60.2 × 0.13 × 0.1 mm
F(000) = 1680
Data collection top
Bruker SMART CCD area-detector
diffractometer
639 independent reflections
Radiation source: fine-focus sealed tube567 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.068
ϕ and ω scansθmax = 28.3°, θmin = 3.1°
Absorption correction: multi-scan
(SADABS; Bruker, 2000)
h = 116
Tmin = 0.488, Tmax = 1k = 1210
2164 measured reflectionsl = 1431
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.058 w = 1/[σ2(Fo2) + (0.08P)2]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.133(Δ/σ)max = 0.017
S = 1.09Δρmax = 1.71 e Å3
639 reflectionsΔρmin = 1.06 e Å3
62 parametersAbsolute structure: Flack (1983), 146 Friedel pairs
1 restraintAbsolute structure parameter: 0.23 (8)
Crystal data top
Na[Ge4(PO4)3]Z = 6
Mr = 598.26Mo Kα radiation
Trigonal, R3cµ = 10.49 mm1
a = 9.377 (8) ÅT = 298 K
c = 23.48 (3) Å0.2 × 0.13 × 0.1 mm
V = 1788 (3) Å3
Data collection top
Bruker SMART CCD area-detector
diffractometer
639 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2000)
567 reflections with I > 2σ(I)
Tmin = 0.488, Tmax = 1Rint = 0.068
2164 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0581 restraint
wR(F2) = 0.133Δρmax = 1.71 e Å3
S = 1.09Δρmin = 1.06 e Å3
639 reflectionsAbsolute structure: Flack (1983), 146 Friedel pairs
62 parametersAbsolute structure parameter: 0.23 (8)
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. 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
xyzUiso*/Ueq
Ge11.00001.00000.07489 (10)0.0243 (6)
Ge21.41201 (19)1.47337 (17)0.10322 (6)0.0214 (4)
P11.3317 (4)1.1233 (4)0.14139 (17)0.0190 (7)
Na10.66670.33330.0506 (4)0.025 (2)
O11.4071 (13)1.2667 (13)0.0985 (4)0.024 (2)
O21.1603 (13)0.9917 (13)0.1226 (5)0.032 (2)
O31.6040 (13)1.5600 (13)0.1466 (4)0.027 (2)
O41.5371 (12)1.5216 (13)0.0335 (4)0.026 (2)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ge10.0271 (9)0.0271 (9)0.0187 (11)0.0136 (4)0.0000.000
Ge20.0170 (8)0.0212 (8)0.0242 (6)0.0083 (6)0.0022 (5)0.0022 (6)
P10.0169 (17)0.0186 (17)0.0205 (14)0.0082 (14)0.0026 (12)0.0008 (12)
Na10.025 (3)0.025 (3)0.026 (5)0.0125 (16)0.0000.000
O10.025 (5)0.027 (6)0.019 (4)0.012 (5)0.005 (4)0.000 (4)
O20.019 (5)0.031 (6)0.050 (6)0.016 (5)0.002 (4)0.010 (5)
O30.027 (6)0.028 (5)0.020 (4)0.009 (5)0.000 (4)0.004 (4)
O40.018 (5)0.024 (6)0.019 (4)0.001 (4)0.002 (4)0.008 (4)
Geometric parameters (Å, º) top
Ge1—O21.908 (10)Na1—O1viii2.462 (11)
Ge1—O2i1.908 (10)Na1—O4vii2.627 (11)
Ge1—O2ii1.908 (10)Na1—O4ii2.627 (11)
Ge1—Na1iii3.343 (11)Na1—O4viii2.627 (11)
Ge2—O31.864 (10)Na1—O2ix2.705 (13)
Ge2—O11.918 (11)Na1—O2x2.705 (13)
Ge2—O41.931 (10)Na1—O2xi2.705 (13)
Ge2—Na1iv3.477 (5)Na1—P1ix3.254 (7)
P1—O21.522 (12)Na1—P1x3.254 (7)
P1—O3v1.534 (11)Na1—P1xi3.254 (7)
P1—O11.540 (11)O1—Na1iv2.462 (11)
P1—O4vi1.540 (9)O2—Na1iii2.705 (13)
P1—Na1iii3.254 (7)O3—P1xii1.534 (11)
Na1—O1vii2.462 (11)O4—P1xiii1.540 (9)
Na1—O1ii2.462 (11)O4—Na1iv2.627 (11)
O2—Ge1—O2i89.0 (5)O2ix—Na1—O2x59.2 (4)
O2—Ge1—O2ii89.0 (5)O1vii—Na1—O2xi135.5 (4)
O2i—Ge1—O2ii89.0 (5)O1ii—Na1—O2xi122.3 (4)
O2—Ge1—Na1iii54.0 (3)O1viii—Na1—O2xi83.0 (3)
O2i—Ge1—Na1iii54.0 (3)O4vii—Na1—O2xi77.9 (4)
O2ii—Ge1—Na1iii54.0 (3)O4ii—Na1—O2xi113.5 (4)
O3—Ge2—O190.1 (5)O4viii—Na1—O2xi55.5 (3)
O3—Ge2—O491.2 (4)O2ix—Na1—O2xi59.2 (4)
O1—Ge2—O483.8 (4)O2x—Na1—O2xi59.2 (4)
O3—Ge2—Na1iv70.3 (3)O1vii—Na1—P1ix69.3 (2)
O1—Ge2—Na1iv43.3 (3)O1ii—Na1—P1ix158.4 (3)
O4—Ge2—Na1iv48.4 (3)O1viii—Na1—P1ix100.0 (3)
O2—P1—O3v108.5 (6)O4vii—Na1—P1ix27.8 (2)
O2—P1—O1110.8 (6)O4ii—Na1—P1ix97.9 (3)
O3v—P1—O1110.5 (6)O4viii—Na1—P1ix119.8 (3)
O2—P1—O4vi108.4 (6)O2ix—Na1—P1ix27.7 (2)
O3v—P1—O4vi109.1 (6)O2x—Na1—P1ix86.4 (3)
O1—P1—O4vi109.5 (6)O2xi—Na1—P1ix66.4 (3)
O2—P1—Na1iii55.7 (4)O1vii—Na1—P1x100.0 (3)
O3v—P1—Na1iii122.1 (4)O1ii—Na1—P1x69.3 (2)
O1—P1—Na1iii127.4 (4)O1viii—Na1—P1x158.4 (3)
O4vi—P1—Na1iii52.8 (4)O4vii—Na1—P1x119.8 (3)
O1vii—Na1—O1ii100.8 (4)O4ii—Na1—P1x27.8 (2)
O1vii—Na1—O1viii100.8 (4)O4viii—Na1—P1x97.9 (3)
O1ii—Na1—O1viii100.8 (4)O2ix—Na1—P1x66.4 (3)
O1vii—Na1—O4vii60.6 (3)O2x—Na1—P1x27.7 (2)
O1ii—Na1—O4vii159.5 (5)O2xi—Na1—P1x86.4 (3)
O1viii—Na1—O4vii76.3 (3)P1ix—Na1—P1x92.9 (2)
O1vii—Na1—O4ii76.3 (3)O1vii—Na1—P1xi158.4 (3)
O1ii—Na1—O4ii60.6 (3)O1ii—Na1—P1xi100.0 (3)
O1viii—Na1—O4ii159.5 (5)O1viii—Na1—P1xi69.3 (2)
O4vii—Na1—O4ii117.71 (15)O4vii—Na1—P1xi97.9 (3)
O1vii—Na1—O4viii159.5 (5)O4ii—Na1—P1xi119.8 (3)
O1ii—Na1—O4viii76.3 (3)O4viii—Na1—P1xi27.8 (2)
O1viii—Na1—O4viii60.6 (3)O2ix—Na1—P1xi86.4 (3)
O4vii—Na1—O4viii117.71 (15)O2x—Na1—P1xi66.4 (3)
O4ii—Na1—O4viii117.71 (15)O2xi—Na1—P1xi27.7 (2)
O1vii—Na1—O2ix83.0 (3)P1ix—Na1—P1xi92.9 (2)
O1ii—Na1—O2ix135.5 (4)P1x—Na1—P1xi92.9 (2)
O1viii—Na1—O2ix122.3 (4)P1—O1—Ge2127.8 (6)
O4vii—Na1—O2ix55.5 (3)P1—O1—Na1iv118.9 (6)
O4ii—Na1—O2ix77.9 (4)Ge2—O1—Na1iv104.4 (5)
O4viii—Na1—O2ix113.5 (4)P1—O2—Ge1132.2 (6)
O1vii—Na1—O2x122.3 (4)P1—O2—Na1iii96.7 (5)
O1ii—Na1—O2x83.0 (3)Ge1—O2—Na1iii91.2 (4)
O1viii—Na1—O2x135.5 (4)P1xii—O3—Ge2141.5 (7)
O4vii—Na1—O2x113.5 (4)P1xiii—O4—Ge2123.5 (6)
O4ii—Na1—O2x55.5 (3)P1xiii—O4—Na1iv99.4 (6)
O4viii—Na1—O2x77.9 (4)Ge2—O4—Na1iv98.3 (4)
Symmetry codes: (i) y+2, xy+1, z; (ii) x+y+1, x+2, z; (iii) y+4/3, x+5/3, z+1/6; (iv) x+1, y+1, z; (v) y+3, xy+1, z; (vi) x+y+4/3, y1/3, z+1/6; (vii) y+2, xy, z; (viii) x1, y1, z; (ix) y+5/3, x+4/3, z1/6; (x) x1/3, xy+1/3, z1/6; (xi) x+y+2/3, y2/3, z1/6; (xii) x+y+2, x+3, z; (xiii) x+y+5/3, y+1/3, z1/6.

Experimental details

Crystal data
Chemical formulaNa[Ge4(PO4)3]
Mr598.26
Crystal system, space groupTrigonal, R3c
Temperature (K)298
a, c (Å)9.377 (8), 23.48 (3)
V3)1788 (3)
Z6
Radiation typeMo Kα
µ (mm1)10.49
Crystal size (mm)0.2 × 0.13 × 0.1
Data collection
DiffractometerBruker SMART CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2000)
Tmin, Tmax0.488, 1
No. of measured, independent and
observed [I > 2σ(I)] reflections
2164, 639, 567
Rint0.068
(sin θ/λ)max1)0.667
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.058, 0.133, 1.09
No. of reflections639
No. of parameters62
No. of restraints1
Δρmax, Δρmin (e Å3)1.71, 1.06
Absolute structureFlack (1983), 146 Friedel pairs
Absolute structure parameter0.23 (8)

Computer programs: SMART (Bruker, 2000), SAINT (Bruker, 2000), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ATOMS (Dowty, 2005), SHELXTL (Sheldrick, 2008).

 

Acknowledgements

This work was supported by the National Science Council (NSC94–2113–M–009–012, 94–2120–M–009–014) and the Institute of Nuclear Energy Research, Atomic Energy Council, Taiwan (NL940251).

References

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