Heptasodium tetra­aluminium tetra­kis­(diphosphate) orthophosphate, Na₇Al₄(P₂O₇)₄(PO₄)

The asymmetric unit of title compound contains three Na⁺, one Al³⁺, three P⁵⁺ and eight O^2- atoms, with one Na⁺ atom lying on a twofold rotation axis and one Na⁺ and one P⁵⁺ atom on fourfold rotoinversion axes. The fundamental building units of the title structure are isolated PO₄ tetra­hedra, AlO₆ octa­hedra and P₂O₇ groups, which are further inter­locked by corner-sharing O atoms, forming a three-dimensional framework structure. The Na⁺ atoms are located within the cavities of the framework, showing coordination numbers of 4, 6 and 7.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](P-O) = 0.002 Å
• R factor = 0.017
• wR factor = 0.047
• Data-to-parameter ratio = 11.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          2
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600          4

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           27.48
           From the CIF: _reflns_number_total               1347
           Count of symmetry unique reflns          816
           Completeness (_total/calc)            165.07%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       531
           Fraction of Friedel pairs measured     0.651
           Are heavy atom types Z>Si present        yes
PLAT004_ALERT_5_G Info: Polymeric Structure Found with Dimension .          1
PLAT005_ALERT_5_G No _iucr_refine_instructions_details in CIF ....          ?
PLAT152_ALERT_1_G The Supplied and Calc. Volume s.u. Differ by ...          2 Units
PLAT792_ALERT_1_G Note: The Model has Chirality at P1     (Verify)          R
PLAT792_ALERT_1_G Note: The Model has Chirality at P2     (Verify)          S
PLAT792_ALERT_1_G Note: The Model has Chirality at P3     (Verify)          R
PLAT961_ALERT_5_G Dataset Contains no Negative Intensities .......          !

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   2 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   8 ALERT level G = General information/check it is not something unexpected

   4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   3 ALERT type 5 Informative message, check

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S1. Comment

Metal phosphates possessing open-framework structures with defined tunnels have been extensively investigated for their structural diversity, properties, and potential applications in shape-selective catalysis, adsorbents, ion exchangers, and molecular sieves. Among them, a series of isotypic ortho-diphosphates Na₇(MP₂O₇)₄PO₄ (M = Al, Cr, Fe) (Rochère et al., 1985) and Na₇(InP₂O₇)₄PO₄ (Stus et al., 2001) were synthesized, and their ion exchange and conductivity properties studied. However, for compound Na₇(AlP₂O₇)₄PO₄, a detailed crystal structure analysis has not been reported so far. In this work, the synthesis and results of the crystal structure refinement of this compound is reported. In comparison with the unit cell parameters reported by Rochère from X-ray powder data (a = 14.046 (3), c = 6.169 (2) Å; Rochère et al., 1985), the determined unit cell parameters from the single crystal X-ray study are slighty larger.

As shown in Figs 1 and 2, the structure of the title compound consists of a three-dimensional framework of isolated PO₄ tetrahedra, AlO₆ octahedra and P₂O₇ groups, the conformation of the latter more eclipsed than staggered. The sodium cations are located in sites within cavities in the framework, exhibiting coordination numbers of 7 (Na1), 6 (Na2) and 4 (Na3). There are three crystallography distinct P atoms in the structure of the title compound. P1 and P2 atoms are located in general positions and their corresponding P1O₄ and P2O₄ tetrahedra are connected by the bridging O5 atom to form a P₂O₇ group, which is further linked to four AlO₆ octahedra. P3 atoms are located on 4 axes, forming isolated P3O₄ tetrahedra which are further connected to four AlO₆ octahedra. The P3O₄ tetrahedra are regular with a P—O bond length of 1.5351 (18) Å, while the P–O distances in the P₂O₇ group are irregular, showing the characteristic variance of smaller P–O_terminal bonds (1.4862 (14) to 1.5199 (14) Å) and larger P–O_bridging bonds (1.6097 (14) and 1.6284 (15) Å) as typically observed for diphosphate unit. The title structure differs in their P–O–P bridging angle of the diphosphate group and the average metal–O distances from those of the isotypic congeners. For the Al compound, the interatomic distances in the MO₆ octahedron are decreasing (Fe–O₆ 1.968–2.021 Å, InO₆ 2.091–2.146 Å, AlO₆ 1.8391 (15)–1.9278 (16) Å), as expected from the smaller ionic radius of Al³⁺ comparerd to Fe³⁺ and In³⁺. With a decrease of the unit-cell parameters a trend in a likewise decreasing P–O–P bridging angle of the diphosphate groups is observed: (Na₇(FeP₂O₇)₄PO₄: 136.6 (3)°; Na₇(InP₂O₇)₄PO₄: 136.7 (3)°, Na₇(AlP₂O₇)₄PO₄: 127.92 (9)°.

Related literature

For isotypic structures, see: Rochère et al. (1985); Stus et al. (2001).

S2. Experimental

The finely ground reagents Na₂CO₃, Al₂O₃ and NH₄H₂PO₄ were mixed in the molar ratio Na: Al: P = 2: 1: 8, were placed in a Pt crucible, and heated at 673 K for 4 h. The mixture was then re-ground and heated at 1173 K for 20 h, then cooled to 673 K at a rate of 3 K h^-1, and finally quenched to room temperature. A few colorless crystals of the title compound with prismatic shape were obtained.

S3. Refinement

The highest peak in the difference electron density map equals to 0.22 e/ų at the distance of 0.63 Šfrom O4 site while the deepest hole equals to -0.29 e/ų at the distance of 0.68 Šfrom the P3 site.

Computing details

Data collection: CrystalClear (Rigaku, 2004); cell refinement: CrystalClear (Rigaku, 2004); data reduction: CrystalClear (Rigaku, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2004); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. The expanded asymmetric unit of Na7(AlP2O7)4PO4 showing the coordination environments of the P and Al atoms. The displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (iii) -y + 1, x, -z + 1; (vii) -x + 1, -y + 1, z; (viii) -y + 1, x, -z + 2; (ix) x - 1/2, -y + 3/2, -z + 3/2; (x) y, -x + 1, -z + 1.]
	Fig. 2. View of the crystal structure of Na7(AlP2O7)4PO4. PO4 and AlO6 units are given in the polyhedral representation.

Heptasodium tetraaluminium tetrakis(diphosphate) orthophosphate

Crystal data

Na7Al4(P2O7)4(PO4)	Dx = 2.887 Mg m^−3
Mr = 1059.58	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P421c	Cell parameters from 3720 reflections
Hall symbol: P -4 2n	θ = 2.9–27.5°
a = 14.054 (3) Å	µ = 1.06 mm^−1
c = 6.1718 (16) Å	T = 296 K
V = 1219.1 (4) Å^3	Prism, colourless
Z = 2	0.15 × 0.05 × 0.05 mm
F(000) = 1040

Data collection

Rigaku Saturn70 CCD diffractometer	1347 independent reflections
Radiation source: fine-focus sealed tube	1287 reflections with I > 2σ(I)
Graphite Monochromator monochromator	Rint = 0.024
Detector resolution: 14.6306 pixels mm^-1	θmax = 27.5°, θmin = 3.2°
ω scans	h = −18→17
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −18→16
Tmin = 0.857, Tmax = 0.949	l = −7→7
5562 measured reflections

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)] = 0.017	w = 1/[σ^2(Fo^2) + (0.0297P)^2 + 0.278P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.047	(Δ/σ)max = 0.001
S = 1.08	Δρmax = 0.22 e Å^−3
1347 reflections	Δρmin = −0.29 e Å^−3
118 parameters	Absolute structure: Flack (1983), 540 Friedel pairs
0 restraints	Absolute structure parameter: −0.04 (9)

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 (Ų)

	x	y	z	Uiso*/Ueq
Na1	0.42251 (6)	0.75865 (7)	0.09314 (15)	0.0200 (2)
Na2	0.5000	1.0000	0.3156 (2)	0.0268 (3)
Na3	0.5000	0.5000	1.0000	0.0411 (6)
Al1	0.32097 (4)	0.62225 (4)	0.63747 (9)	0.00558 (13)
P1	0.62752 (3)	0.74207 (3)	0.84990 (8)	0.00573 (11)
P2	0.46166 (3)	0.79988 (3)	0.60041 (8)	0.00656 (11)
P3	0.5000	0.5000	0.5000	0.00535 (19)
O1	0.42717 (10)	0.89936 (10)	0.5600 (2)	0.0117 (3)
O2	0.54197 (10)	0.81323 (10)	0.7882 (2)	0.0109 (3)
O3	0.38751 (10)	0.73621 (10)	0.7038 (2)	0.0128 (3)
O4	0.51085 (9)	0.75581 (10)	0.4067 (2)	0.0104 (3)
O5	0.71136 (9)	0.80522 (10)	0.8791 (2)	0.0129 (3)
O6	0.59683 (10)	0.69263 (10)	1.0575 (2)	0.0113 (3)
O7	0.63718 (10)	0.66852 (9)	0.6721 (2)	0.0087 (3)
O8	0.43148 (9)	0.55247 (10)	0.6522 (2)	0.0100 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Na1	0.0224 (4)	0.0242 (5)	0.0133 (4)	−0.0060 (3)	−0.0034 (4)	0.0031 (4)
Na2	0.0280 (7)	0.0405 (9)	0.0118 (6)	−0.0216 (6)	0.000	0.000
Na3	0.0561 (9)	0.0561 (9)	0.0111 (9)	0.000	0.000	0.000
Al1	0.0049 (2)	0.0063 (3)	0.0055 (3)	0.0010 (2)	0.0002 (2)	0.0000 (2)
P1	0.0056 (2)	0.0069 (2)	0.0047 (2)	−0.00024 (16)	0.00004 (17)	0.00036 (18)
P2	0.0064 (2)	0.0068 (2)	0.0064 (2)	0.00048 (16)	−0.00085 (19)	−0.00024 (18)
P3	0.0053 (3)	0.0053 (3)	0.0054 (4)	0.000	0.000	0.000
O1	0.0133 (7)	0.0101 (6)	0.0117 (8)	0.0030 (6)	−0.0018 (6)	0.0007 (6)
O2	0.0106 (7)	0.0123 (7)	0.0097 (7)	0.0043 (5)	−0.0043 (6)	−0.0034 (6)
O3	0.0139 (7)	0.0127 (7)	0.0118 (7)	−0.0066 (6)	0.0023 (6)	−0.0033 (6)
O4	0.0086 (6)	0.0138 (7)	0.0088 (6)	0.0027 (5)	0.0000 (5)	−0.0019 (6)
O5	0.0101 (7)	0.0166 (7)	0.0121 (8)	−0.0056 (5)	−0.0004 (6)	−0.0012 (6)
O6	0.0149 (7)	0.0134 (7)	0.0055 (7)	−0.0024 (5)	0.0008 (6)	0.0021 (5)
O7	0.0119 (7)	0.0076 (7)	0.0065 (7)	0.0015 (5)	−0.0005 (5)	0.0007 (5)
O8	0.0081 (6)	0.0135 (7)	0.0084 (6)	0.0039 (5)	0.0000 (6)	−0.0014 (5)

Geometric parameters (Å, º)

Na1—O4	2.2998 (17)	P1—O7	1.5136 (14)
Na1—O1^i	2.3993 (17)	P1—O6	1.5199 (14)
Na1—O3^ii	2.4730 (18)	P1—O2	1.6097 (14)
Na1—O7^iii	2.5789 (17)	P2—O1	1.5006 (14)
Na1—O6^ii	2.6291 (18)	P2—O4	1.5134 (14)
Na1—O2^ii	2.6363 (18)	P2—O3	1.5145 (15)
Na1—O6^iii	2.9419 (18)	P2—O2	1.6284 (15)
Na2—O1^iv	2.3072 (16)	P3—O8^iii	1.5341 (14)
Na2—O1	2.3072 (17)	P3—O8^x	1.5341 (14)
Na2—O1^i	2.3532 (17)	P3—O8	1.5341 (14)
Na2—O1^v	2.3532 (17)	P3—O8^vii	1.5341 (14)
Na2—O2^i	2.6957 (15)	O1—Na2^xi	2.3532 (17)
Na2—O2^v	2.6957 (15)	O1—Na1^xii	2.3993 (17)
Na3—O8^vi	2.4655 (16)	O2—Na1^xiii	2.6363 (18)
Na3—O8	2.4655 (16)	O2—Na2^xi	2.6957 (15)
Na3—O8^vii	2.4655 (16)	O3—Na1^xiii	2.4730 (18)
Na3—O8^viii	2.4655 (16)	O4—Al1^x	1.9210 (15)
Al1—O8	1.8391 (15)	O5—Al1^xiv	1.8500 (15)
Al1—O5^ix	1.8500 (15)	O6—Al1^vi	1.9258 (16)
Al1—O3	1.8993 (16)	O6—Na1^xiii	2.6291 (18)
Al1—O4^iii	1.9210 (15)	O6—Na1^x	2.9419 (18)
Al1—O6^viii	1.9258 (16)	O7—Al1^x	1.9278 (16)
Al1—O7^iii	1.9278 (16)	O7—Na1^x	2.5789 (17)
P1—O5	1.4862 (14)
O4—Na1—O1^i	99.33 (6)	O3—Al1—O6^viii	89.69 (7)
O4—Na1—O3^ii	157.36 (7)	O4^iii—Al1—O6^viii	86.10 (7)
O1^i—Na1—O3^ii	90.92 (6)	O8—Al1—O7^iii	92.43 (7)
O4—Na1—O7^iii	77.49 (5)	O5^ix—Al1—O7^iii	87.07 (6)
O1^i—Na1—O7^iii	129.35 (6)	O3—Al1—O7^iii	94.82 (7)
O3^ii—Na1—O7^iii	111.27 (6)	O4^iii—Al1—O7^iii	89.49 (6)
O4—Na1—O6^ii	63.97 (5)	O6^viii—Al1—O7^iii	175.36 (7)
O1^i—Na1—O6^ii	117.88 (6)	O5—P1—O7	115.13 (8)
O3^ii—Na1—O6^ii	93.38 (6)	O5—P1—O6	113.31 (8)
O7^iii—Na1—O6^ii	106.00 (5)	O7—P1—O6	108.92 (9)
O4—Na1—O2^ii	105.20 (6)	O5—P1—O2	104.47 (8)
O1^i—Na1—O2^ii	74.83 (5)	O7—P1—O2	108.65 (8)
O3^ii—Na1—O2^ii	58.00 (5)	O6—P1—O2	105.76 (8)
O7^iii—Na1—O2^ii	155.46 (6)	O1—P2—O4	113.43 (9)
O6^ii—Na1—O2^ii	56.60 (5)	O1—P2—O3	113.46 (8)
O4—Na1—O6^iii	123.33 (6)	O4—P2—O3	113.91 (8)
O1^i—Na1—O6^iii	131.42 (6)	O1—P2—O2	103.58 (8)
O3^ii—Na1—O6^iii	59.00 (5)	O4—P2—O2	107.01 (8)
O7^iii—Na1—O6^iii	52.62 (5)	O3—P2—O2	104.19 (8)
O6^ii—Na1—O6^iii	102.31 (6)	O8^iii—P3—O8^x	104.48 (11)
O2^ii—Na1—O6^iii	110.46 (5)	O8^iii—P3—O8	112.02 (6)
O1^iv—Na2—O1	98.36 (9)	O8^x—P3—O8	112.02 (6)
O1^iv—Na2—O1^i	166.32 (7)	O8^iii—P3—O8^vii	112.02 (6)
O1—Na2—O1^i	84.54 (5)	O8^x—P3—O8^vii	112.02 (6)
O1^iv—Na2—O1^v	84.54 (5)	O8—P3—O8^vii	104.48 (11)
O1—Na2—O1^v	166.32 (7)	P1—O2—P2	127.92 (9)
O1^i—Na2—O1^v	95.80 (8)	P1—O2—Na1^xiii	97.23 (7)
O1^iv—Na2—O2^i	109.82 (5)	P2—O2—Na1^xiii	91.90 (7)
O1—Na2—O2^i	75.12 (5)	P1—O2—Na2^xi	138.90 (8)
O1^i—Na2—O2^i	57.84 (5)	P2—O2—Na2^xi	90.30 (6)
O1^v—Na2—O2^i	116.61 (6)	Na1^xiii—O2—Na2^xi	95.69 (5)
O1^iv—Na2—O2^v	75.12 (5)	P2—O3—Al1	138.27 (10)
O1—Na2—O2^v	109.82 (5)	P2—O3—Na1^xiii	101.37 (7)
O1^i—Na2—O2^v	116.61 (6)	Al1—O3—Na1^xiii	114.51 (7)
O1^v—Na2—O2^v	57.84 (5)	P2—O4—Al1^x	135.59 (9)
O2^i—Na2—O2^v	172.79 (8)	P2—O4—Na1	114.27 (8)
O8^vi—Na3—O8	139.29 (4)	Al1^x—O4—Na1	109.28 (7)
O8^vi—Na3—O8^vii	139.29 (4)	P1—O5—Al1^xiv	169.27 (10)
O8—Na3—O8^vii	58.94 (7)	P1—O6—Al1^vi	144.77 (10)
O8^vi—Na3—O8^viii	58.94 (7)	P1—O6—Na1^xiii	100.00 (7)
O8—Na3—O8^viii	139.29 (4)	Al1^vi—O6—Na1^xiii	97.24 (6)
O8^vii—Na3—O8^viii	139.29 (4)	P1—O6—Na1^x	76.46 (6)
O8—Al1—O5^ix	178.73 (7)	Al1^vi—O6—Na1^x	96.37 (6)
O8—Al1—O3	91.33 (7)	Na1^xiii—O6—Na1^x	160.22 (7)
O5^ix—Al1—O3	87.55 (7)	P1—O7—Al1^x	131.02 (9)
O8—Al1—O4^iii	92.68 (6)	P1—O7—Na1^x	89.48 (7)
O5^ix—Al1—O4^iii	88.48 (6)	Al1^x—O7—Na1^x	131.83 (7)
O3—Al1—O4^iii	173.98 (7)	P3—O8—Al1	139.13 (10)
O8—Al1—O6^viii	86.36 (7)	P3—O8—Na3	98.29 (7)
O5^ix—Al1—O6^viii	94.23 (6)	Al1—O8—Na3	122.17 (7)

Symmetry codes: (i) y−1/2, x+1/2, z−1/2; (ii) x, y, z−1; (iii) −y+1, x, −z+1; (iv) −x+1, −y+2, z; (v) −y+3/2, −x+3/2, z−1/2; (vi) y, −x+1, −z+2; (vii) −x+1, −y+1, z; (viii) −y+1, x, −z+2; (ix) x−1/2, −y+3/2, −z+3/2; (x) y, −x+1, −z+1; (xi) −y+3/2, −x+3/2, z+1/2; (xii) y−1/2, x+1/2, z+1/2; (xiii) x, y, z+1; (xiv) x+1/2, −y+3/2, −z+3/2.