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A new europium(III) silicophosphate, whose formula may be considered to be Eu2Si(PO4)2(P2O7), has been found to consist of phospho­silicate chains with Si-O-P-O-P-O-Si backbones extending in the a direction. The P2O7 group and the Si atom both lie on crystallographic twofold axes. Tetrahedral silicon is further bound to two monophosphate groups. This is a silicophosphate of previously unseen type.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801001519/br6001sup1.cif
Contains datablocks holt, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536801001519/br6001Isup2.hkl
Contains datablock I

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • R factor = 0.025
  • wR factor = 0.064
  • Data-to-parameter ratio = 12.8

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Yellow Alert Alert Level C:
ABSTM_02 Alert C The ratio of expected to reported Tmax/Tmin(RR') is < 0.90 Tmin and Tmax reported: 0.181 0.357 Tmin' and Tmax expected: 0.202 0.357 RR' = 0.897 Please check that your absorption correction is appropriate. General Notes
REFLT_03 From the CIF: _diffrn_reflns_theta_max 29.97 From the CIF: _reflns_number_total 1422 Count of symmetry unique reflns 1125 Completeness (_total/calc) 126.40% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 297 Fraction of Friedel pairs measured 0.264 Are heavy atom types Z>Si present yes WARNING: Large fraction of Friedel related reflns may be needed to determine absolute structure
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

The structural literature contains reports of only three silicophosphate materials with +3 charged cations. These contain two distinctly different silicophosphate moieties.

RuSiP3O11 (Fukuoka et al., 1996) may be seen to exist with Si2O7 groups sharing each of its six terminal O atoms with a different P2O7 group. Each P2O7 group is seen to share a single O atom per PO4 tetrahedron, with an Si2O7 group creating a three-dimensional network of linked tetrahedra which encapsulate Ru+3 cations. MoSiP3O11 (Leclaire & Raveau, 1987) shows the same motif, with Mo+3 encapsulated within the three-dimensional network of silicophosphates.

Mo3SiP5O19 (Wang et al., 1988) exists with isolated (PO3O)3SiOSi(OPO3)3 and (PO3O)3POP(OPO3)3 units stacked in columns parallel to the hexagonal c axis. V3SiP5O19 (Leclaire et al., 1986) appears to be isostructural with the molybedenum-containing compound of similar formula. Mo4Si2P6O25 (Leclaire et al., 1988) shows a similar motif but with (PO3O)3SiOSi(OPO3)3 groups only.

Eu2Si(PO4)2(P2O7) crystallizes with silicophosphate chains with Si—O—P—O—P—O backbones extending in the a direction (Fig. 1). Tetrahedral silicon is further bound to two monophosphate groups, whereas the P atoms of the polymeric chain are further bonded to two terminal O atoms, O21 and O23 (Fig. 1). Thus, it is a silicophosphate of a previously unseen type.

Atoms O21, O22 and O23 display a 0.455/0.545 disorder with positions O21', O22' and O23', and are related to them by a 23.3° rotation about the P2—O24 bond (Fig. 2). Atom O22 and O22' lie on a twofold axis.

Eu atoms are localized between PO3 groups and the two terminal O atoms of a P atom of the polymeric chain. Eu is within bonding distance of each of the disordered positions, O21, O21', O23 and O23'. EuIII is six coordinate [average Eu—O 2.317 (6) Å], with a seventh Eu—O distance of 2.544 (5) Å. With the inclusion of the seventh distance, the geometry at europium appears to be that of a pentagonal bipyramid. Using bond-valence calculations to ascertain the validity of the seventh distance (Brown, 1981) leads to a valence bond total of 3.065 using the six Eu—O distances of less than 2.451 (5) Å, but a significantly larger total of 3.352 Å if the seventh distance is included. Both geometry and valence-bond calculations argue that this longer distance is meaningful.

Silicon displays tetrahedral geometry, with an average Si—O distance of 1.604 (5) Å. Phosphorous tetrahedra have average P—O distances of 1.511 (11) Å.

Refinement top

The orthorhombic cell displayed absences h00, h = 2n and 0k0, k = 2n, fixing the space group as P21212. Disorder of three O atoms became apparent as refinement progressed. The P2O7 group exists with a twofold axis passing through the bridging O atom, which was seen to exist in two positions O22 and O22', both on the twofold axis. While P2 and O24 were seen in ordered positions, alternate or disordered positions were seen for terminal O atoms O21 (O21') and O23 (O23'). O21, O22, O23 and O24 form a tetrahedral array about P2 as do O21', O22' O23' and O24. The disorder may be understood in terms of an approximately 22° rotation about the P2—O24 (and the P2a—O24a bond related by the twofold axis) corresponding to the bridging O atom being `up' or `down' and resulting in a 0.59 Å displacement of each of the disordered atoms. O21 and O23 were refined with an occupancy parameter equal to x (O22 occupancy = 0.5x) whereas O21' and O23' were refined with an occupancy parameter of 1 - x [O22' occupancy = (1 - x)/2]. The refined value of x is 0.46 (3). Anisotropic displacement parameters for pairs of close atoms (O21/O21', O22/O22' and O23/O23') were constrained to identical values for each pair. The identity of the Si atom was confirmed by observing that the occupancy parameter refined to the correct value (1/2), confirming the electron density of the position, by comparing the Si—O distances with those of the literature and by observing the charge neutrality of the structure which requires a +4 cation in that position.

Computing details top

Data collection: XSCANS (Siemens, 1991); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1990); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. View of dieuropium(III) silicodimonophosphatediphosphate projected on the ab plane. Displacement ellipsoids are shown at the 50% probability level.
Dieuropium(III) silicodimonophosphatediphosphate top
Crystal data top
Eu2Si(PO4)2(P2O7)Dx = 3.581 Mg m3
Mr = 695.90Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, P21212Cell parameters from 24 reflections
a = 7.056 (1) Åθ = 5.6–16.9°
b = 16.376 (3) ŵ = 10.30 mm1
c = 5.585 (1) ÅT = 293 K
V = 645.34 (19) Å3Needle, colorless
Z = 20.15 × 0.12 × 0.1 mm
F(000) = 640
Data collection top
Syntex P4 four-circle
diffractometer
1388 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.031
Graphite monochromatorθmax = 30.0°, θmin = 2.5°
θ/2θ scansh = 19
Absorption correction: ψ scan
(XEMP; Siemens, 1990)
k = 123
Tmin = 0.181, Tmax = 0.357l = 17
1578 measured reflections3 standard reflections every 97 reflections
1422 independent reflections intensity decay: 0.0%
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)] = 0.025 w = 1/[σ2(Fo2) + (0.0334P)2 + 1.2737P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.064(Δ/σ)max = 0.012
S = 1.07Δρmax = 0.01 e Å3
1422 reflectionsΔρmin = 0.02 e Å3
111 parametersExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
1 restraintExtinction coefficient: 0.0030 (4)
Crystal data top
Eu2Si(PO4)2(P2O7)V = 645.34 (19) Å3
Mr = 695.90Z = 2
Orthorhombic, P21212Mo Kα radiation
a = 7.056 (1) ŵ = 10.30 mm1
b = 16.376 (3) ÅT = 293 K
c = 5.585 (1) Å0.15 × 0.12 × 0.1 mm
Data collection top
Syntex P4 four-circle
diffractometer
1388 reflections with I > 2σ(I)
Absorption correction: ψ scan
(XEMP; Siemens, 1990)
Rint = 0.031
Tmin = 0.181, Tmax = 0.3573 standard reflections every 97 reflections
1578 measured reflections intensity decay: 0.0%
1422 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.025111 parameters
wR(F2) = 0.0641 restraint
S = 1.07Δρmax = 0.01 e Å3
1422 reflectionsΔρmin = 0.02 e Å3
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*/UeqOcc. (<1)
Eu10.08893 (4)0.284646 (19)0.86217 (6)0.01108 (10)
Si10.00000.00001.4557 (5)0.0133 (5)
P10.0855 (2)0.16894 (9)1.3063 (3)0.0112 (3)
O110.2587 (6)0.1945 (3)1.1648 (10)0.0167 (10)
O120.0798 (6)0.2069 (3)1.1706 (9)0.0188 (10)
O130.0651 (8)0.0734 (3)1.2809 (9)0.0190 (10)
O140.0910 (9)0.1889 (3)1.5690 (9)0.0216 (10)
P20.3633 (2)0.07078 (10)1.6411 (4)0.0134 (3)
O210.378 (3)0.1316 (9)1.447 (4)0.025 (2)0.455 (12)
O21'0.407 (2)0.1026 (7)1.396 (3)0.025 (2)0.545 (12)
O220.50000.00001.589 (5)0.039 (3)0.455 (12)
O22'0.50000.00001.703 (4)0.039 (3)0.545 (12)
O230.400 (3)0.1017 (9)1.893 (3)0.026 (2)0.455 (12)
O23'0.361 (2)0.1278 (8)1.836 (2)0.026 (2)0.545 (12)
O240.1666 (7)0.0263 (3)1.6321 (11)0.0244 (11)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Eu10.00969 (13)0.01415 (14)0.00939 (14)0.00079 (12)0.00027 (12)0.00019 (13)
Si10.0139 (11)0.0104 (10)0.0155 (12)0.0008 (9)0.0000.000
P10.0109 (6)0.0115 (6)0.0110 (7)0.0013 (6)0.0004 (6)0.0010 (5)
O110.0101 (18)0.021 (2)0.019 (2)0.0008 (16)0.002 (2)0.0089 (19)
O120.0083 (17)0.025 (2)0.023 (2)0.002 (2)0.002 (2)0.008 (2)
O130.028 (3)0.0118 (19)0.017 (2)0.0018 (19)0.006 (2)0.0021 (18)
O140.025 (2)0.024 (2)0.016 (2)0.000 (2)0.000 (3)0.005 (2)
P20.0131 (7)0.0120 (6)0.0150 (7)0.0005 (5)0.0008 (7)0.0005 (7)
O210.032 (5)0.013 (6)0.030 (6)0.002 (5)0.009 (5)0.012 (5)
O21'0.032 (5)0.013 (6)0.030 (6)0.002 (5)0.009 (5)0.012 (5)
O220.045 (6)0.042 (6)0.029 (8)0.030 (5)0.0000.000
O22'0.045 (6)0.042 (6)0.029 (8)0.030 (5)0.0000.000
O230.045 (6)0.021 (6)0.011 (5)0.003 (5)0.011 (4)0.006 (4)
O23'0.045 (6)0.021 (6)0.011 (5)0.003 (5)0.011 (4)0.006 (4)
O240.020 (2)0.032 (3)0.022 (3)0.012 (2)0.006 (3)0.003 (3)
Geometric parameters (Å, º) top
Eu1—O21i2.217 (18)Si1—O131.615 (5)
Eu1—O21'i2.344 (13)P1—O111.514 (5)
Eu1—O23ii2.309 (15)P1—O121.523 (5)
Eu1—O23'ii2.240 (12)P1—O131.577 (5)
Eu1—O14iii2.267 (5)P1—O141.504 (5)
Eu1—O12iv2.349 (4)P2—O211.476 (18)
Eu1—O11v2.360 (4)P2—O21'1.496 (15)
Eu1—O122.451 (5)P2—O221.536 (5)
Eu1—O112.544 (5)P2—O22'1.547 (5)
Si1—O241.593 (6)P2—O231.520 (14)
Si1—O24vi1.593 (6)P2—O23'1.436 (12)
Si1—O13vi1.615 (5)P2—O241.568 (5)
O21i—Eu1—O14iii82.2 (5)O21'i—Eu1—O11149.4 (4)
O23'ii—Eu1—O14iii169.9 (4)O12—Eu1—O1157.32 (14)
O21i—Eu1—O23ii87.6 (5)O24—Si1—O24vi103.6 (5)
O14iii—Eu1—O23ii169.7 (4)O24—Si1—O13vi112.5 (3)
O21i—Eu1—O12iv78.4 (5)O24vi—Si1—O13vi111.4 (3)
O23'ii—Eu1—O12iv82.1 (4)O24—Si1—O13111.4 (3)
O14iii—Eu1—O12iv88.8 (2)O24vi—Si1—O13112.5 (3)
O23ii—Eu1—O12iv88.0 (5)O13vi—Si1—O13105.6 (4)
O21i—Eu1—O11v87.9 (5)O14—P1—O11115.4 (3)
O23'ii—Eu1—O11v96.4 (4)O14—P1—O12114.6 (3)
O14iii—Eu1—O11v93.5 (2)O11—P1—O12104.2 (3)
O23ii—Eu1—O11v87.4 (5)O14—P1—O13107.8 (3)
O12iv—Eu1—O11v165.72 (15)O11—P1—O13107.5 (3)
O14iii—Eu1—O21'i95.7 (4)O12—P1—O13106.8 (3)
O12iv—Eu1—O21'i83.9 (4)O21—P2—O23116.4 (8)
O11v—Eu1—O21'i81.9 (4)O21—P2—O22108.9 (10)
O21i—Eu1—O12156.9 (5)O23—P2—O22108.8 (11)
O23'ii—Eu1—O1283.2 (4)O21—P2—O24110.7 (8)
O14iii—Eu1—O1298.71 (18)O23—P2—O24109.6 (8)
O23ii—Eu1—O1291.1 (4)O22—P2—O24101.5 (2)
O12iv—Eu1—O12124.68 (12)O23'—P2—O22'109.0 (9)
O11v—Eu1—O1268.94 (15)O21'—P2—O22'109.7 (9)
O21'i—Eu1—O12148.0 (4)O23'—P2—O24108.4 (6)
O21i—Eu1—O11145.8 (5)O23'—P2—O21'118.1 (7)
O23'ii—Eu1—O1178.3 (4)O21'—P2—O24108.4 (6)
O14iii—Eu1—O1194.34 (18)O22'—P2—O24102.2 (2)
O23ii—Eu1—O1193.4 (4)P2vii—O22—P2158 (2)
O12iv—Eu1—O1167.52 (15)P2—O22'—P2vii154.1 (16)
O11v—Eu1—O11126.26 (12)
Symmetry codes: (i) x+1/2, y+1/2, z+2; (ii) x+1/2, y+1/2, z+3; (iii) x, y, z1; (iv) x+1/2, y+1/2, z+2; (v) x1/2, y+1/2, z+2; (vi) x, y, z; (vii) x+1, y, z.

Experimental details

Crystal data
Chemical formulaEu2Si(PO4)2(P2O7)
Mr695.90
Crystal system, space groupOrthorhombic, P21212
Temperature (K)293
a, b, c (Å)7.056 (1), 16.376 (3), 5.585 (1)
V3)645.34 (19)
Z2
Radiation typeMo Kα
µ (mm1)10.30
Crystal size (mm)0.15 × 0.12 × 0.1
Data collection
DiffractometerSyntex P4 four-circle
diffractometer
Absorption correctionψ scan
(XEMP; Siemens, 1990)
Tmin, Tmax0.181, 0.357
No. of measured, independent and
observed [I > 2σ(I)] reflections
1578, 1422, 1388
Rint0.031
(sin θ/λ)max1)0.703
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.025, 0.064, 1.07
No. of reflections1422
No. of parameters111
No. of restraints1
Δρmax, Δρmin (e Å3)0.01, 0.02

Computer programs: XSCANS (Siemens, 1991), XSCANS, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), XP (Siemens, 1990), SHELXL97.

Selected geometric parameters (Å, º) top
Eu1—O21i2.217 (18)Si1—O131.615 (5)
Eu1—O21'i2.344 (13)P1—O111.514 (5)
Eu1—O23ii2.309 (15)P1—O121.523 (5)
Eu1—O23'ii2.240 (12)P1—O131.577 (5)
Eu1—O14iii2.267 (5)P1—O141.504 (5)
Eu1—O12iv2.349 (4)P2—O211.476 (18)
Eu1—O11v2.360 (4)P2—O21'1.496 (15)
Eu1—O122.451 (5)P2—O221.536 (5)
Eu1—O112.544 (5)P2—O22'1.547 (5)
Si1—O241.593 (6)P2—O231.520 (14)
Si1—O24vi1.593 (6)P2—O23'1.436 (12)
Si1—O13vi1.615 (5)P2—O241.568 (5)
O21i—Eu1—O14iii82.2 (5)O21'i—Eu1—O11149.4 (4)
O23'ii—Eu1—O14iii169.9 (4)O12—Eu1—O1157.32 (14)
O21i—Eu1—O23ii87.6 (5)O24—Si1—O24vi103.6 (5)
O14iii—Eu1—O23ii169.7 (4)O24—Si1—O13vi112.5 (3)
O21i—Eu1—O12iv78.4 (5)O24vi—Si1—O13vi111.4 (3)
O23'ii—Eu1—O12iv82.1 (4)O24—Si1—O13111.4 (3)
O14iii—Eu1—O12iv88.8 (2)O24vi—Si1—O13112.5 (3)
O23ii—Eu1—O12iv88.0 (5)O13vi—Si1—O13105.6 (4)
O21i—Eu1—O11v87.9 (5)O14—P1—O11115.4 (3)
O23'ii—Eu1—O11v96.4 (4)O14—P1—O12114.6 (3)
O14iii—Eu1—O11v93.5 (2)O11—P1—O12104.2 (3)
O23ii—Eu1—O11v87.4 (5)O14—P1—O13107.8 (3)
O12iv—Eu1—O11v165.72 (15)O11—P1—O13107.5 (3)
O14iii—Eu1—O21'i95.7 (4)O12—P1—O13106.8 (3)
O12iv—Eu1—O21'i83.9 (4)O21—P2—O23116.4 (8)
O11v—Eu1—O21'i81.9 (4)O21—P2—O22108.9 (10)
O21i—Eu1—O12156.9 (5)O23—P2—O22108.8 (11)
O23'ii—Eu1—O1283.2 (4)O21—P2—O24110.7 (8)
O14iii—Eu1—O1298.71 (18)O23—P2—O24109.6 (8)
O23ii—Eu1—O1291.1 (4)O22—P2—O24101.5 (2)
O12iv—Eu1—O12124.68 (12)O23'—P2—O22'109.0 (9)
O11v—Eu1—O1268.94 (15)O21'—P2—O22'109.7 (9)
O21'i—Eu1—O12148.0 (4)O23'—P2—O24108.4 (6)
O21i—Eu1—O11145.8 (5)O23'—P2—O21'118.1 (7)
O23'ii—Eu1—O1178.3 (4)O21'—P2—O24108.4 (6)
O14iii—Eu1—O1194.34 (18)O22'—P2—O24102.2 (2)
O23ii—Eu1—O1193.4 (4)P2vii—O22—P2158 (2)
O12iv—Eu1—O1167.52 (15)P2—O22'—P2vii154.1 (16)
O11v—Eu1—O11126.26 (12)
Symmetry codes: (i) x+1/2, y+1/2, z+2; (ii) x+1/2, y+1/2, z+3; (iii) x, y, z1; (iv) x+1/2, y+1/2, z+2; (v) x1/2, y+1/2, z+2; (vi) x, y, z; (vii) x+1, y, z.
 

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