Dipotassium dialuminium cyclo-octa-phosphate.

Single crystals of the title compound, K(2)Al(2)P(8)O(24), were obtained by solid-state reaction. The monoclinic structure is isotypic with that of the Ga(III) analogue and is built of eight-membered phosphate ring anions P(8)O(24) (8-) (2/m symmetry) isolated from each other and further linked by isolated AlO(6) octa-hedra ( symmetry) by sharing corners. Each AlO(6) octa-hedron is linked to four P(8)O(24) (8-) rings in such a way that two rings are linked through bidentate diphosphate groups attached in the cis positions on two opposite parallel edges of the octa-hedron. The two other rings are linked via corner-sharing to the two remaining corners in the trans positions of the AlO(6) octa-hedron. Each P(8)O(24) (8-) ring anion is linked to eight AlO(6) octa-hedra. More accurately, each ring anion is linked to four AlO(6) octa-hedra through bidentate diphosphate groups attached in the cis positions to the AlO(6) octa-hedron and to the four remaining octa-hedra by sharing corners. This three-dimensional linkage delimits channels running parallel to [001] in which the ten-coordinated K(+) cations (2 symmetry) are distributed over two columns. These columns alternate with empty octa-gonally-shaped channels expanding through the P(8)O(24) (8-) ring anions.

Related literature

The synthesis and an approximate unit cell with a slightly smaller β angle were reported for the title compound more than a quarter of a century ago (Grunze et al., 1983 ▶). The crystal structures of isotypic compounds determined from single-crystal data have been reported for K2Ga2P8O24 (Palkina et al., 1979 ▶) and K2Mn2P8O24 (Murashova & Chudinova, 1999 ▶). The isostructural potassium-containing cyclo­octa­phosphates K2V2P8O24 (Lavrov et al., 1981 ▶), K2Fe2P8O24 (Grunze et al., 1983 ▶) and K2Cr2P8O24 (Grunze & Chudinova, 1988 ▶) were reported without detailed structure analyses. For a review of the crystal chemistry of cyclo­octa­phosphates, see: Durif (1995 ▶, 2005 ▶). For potential applications of aluminophosphates, see: Cheetham et al. (1999 ▶); Hartmann & Kevan (1999 ▶). For background to distortion indices, see: Momma & Izumi (2008 ▶).

Experimental

Crystal data

K2Al2P8O24

M = 763.92

Monoclinic,

a = 16.598 (2) Å

b = 12.2150 (17) Å

c = 5.0705 (7) Å

β = 100.315 (4)°

V = 1011.4 (2) Å3

Z = 2

Mo Kα radiation

μ = 1.31 mm−1

T = 296 K

0.30 × 0.10 × 0.08 mm

Data collection

Bruker APEXII CCD diffractometer

Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T min = 0.562, T max = 0.748

9643 measured reflections

2844 independent reflections

2252 reflections with I > 2σ(I)

R int = 0.047

Refinement

R[F 2 > 2σ(F 2)] = 0.042

wR(F 2) = 0.124

S = 1.07

2844 reflections

87 parameters

Δρmax = 1.40 e Å−3

Δρmin = −1.04 e Å−3

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 1999 ▶), CaRine (Boudias & Monceau, 1998 ▶) and ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶).

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810020751/wm2355sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810020751/wm2355Isup2.hkl

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

K2Al2P8O24	F(000) = 752
Mr = 763.92	Dx = 2.508 Mg m−3
Monoclinic, C2/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2y	Cell parameters from 3017 reflections
a = 16.598 (2) Å	θ = 3.3–37.7°
b = 12.2150 (17) Å	µ = 1.31 mm−1
c = 5.0705 (7) Å	T = 296 K
β = 100.315 (4)°	Needle, colourless
V = 1011.4 (2) Å3	0.30 × 0.10 × 0.08 mm
Z = 2

Bruker APEXII CCD diffractometer	2844 independent reflections
Radiation source: fine-focus sealed tube	2252 reflections with I > 2σ(I)
graphite	Rint = 0.047
Detector resolution: 8.3333 pixels mm-1	θmax = 38.7°, θmin = 4.1°
ω and φ scans	h = −29→28
Absorption correction: multi-scan (SADABS; Bruker, 2008)	k = −18→20
Tmin = 0.562, Tmax = 0.748	l = −8→8
9643 measured reflections

Refinement on F2	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.042	Secondary atom site location: difference Fourier map
wR(F2) = 0.124	w = 1/[σ2(Fo2) + (0.0738P)2 + 0.0398P] where P = (Fo2 + 2Fc2)/3
S = 1.07	(Δ/σ)max < 0.001
2844 reflections	Δρmax = 1.40 e Å−3
87 parameters	Δρmin = −1.04 e Å−3

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.

	x	y	z	Uiso*/Ueq
K	−0.09371 (4)	0.5000	0.25194 (13)	0.02290 (13)
Al	0.2500	0.2500	0.0000	0.00771 (13)
P1	0.19023 (2)	0.12098 (3)	0.46962 (8)	0.00720 (9)
P2	0.07782 (2)	0.27631 (3)	0.16477 (8)	0.00835 (9)
O1	0.28060 (8)	0.36965 (10)	0.2366 (2)	0.0118 (2)
O2	0.14059 (7)	0.28394 (11)	−0.0132 (2)	0.0132 (2)
O3	0.24968 (7)	0.15349 (10)	0.2942 (2)	0.0105 (2)
O4	0.10711 (7)	0.18408 (11)	0.3873 (2)	0.0122 (2)
O5	0.05469 (9)	0.37739 (12)	0.2866 (3)	0.0184 (3)
O6	0.0000	0.21471 (15)	0.0000	0.0140 (3)
O7	0.16028 (11)	0.0000	0.3993 (3)	0.0125 (3)

	U11	U22	U33	U12	U13	U23
K	0.0299 (3)	0.0147 (3)	0.0240 (3)	0.000	0.0046 (2)	0.000
Al	0.0085 (3)	0.0083 (3)	0.0064 (3)	0.0001 (2)	0.0016 (2)	0.0006 (2)
P1	0.00956 (16)	0.00518 (17)	0.00672 (15)	0.00032 (12)	0.00110 (11)	0.00033 (11)
P2	0.00850 (17)	0.00632 (18)	0.01023 (16)	0.00094 (12)	0.00164 (12)	0.00031 (12)
O1	0.0186 (5)	0.0084 (5)	0.0078 (4)	−0.0009 (4)	0.0006 (4)	−0.0006 (3)
O2	0.0095 (5)	0.0177 (6)	0.0130 (5)	0.0020 (4)	0.0033 (4)	0.0049 (4)
O3	0.0104 (5)	0.0111 (5)	0.0105 (5)	0.0011 (4)	0.0037 (3)	0.0033 (4)
O4	0.0108 (5)	0.0125 (6)	0.0138 (5)	0.0033 (4)	0.0034 (4)	0.0051 (4)
O5	0.0247 (6)	0.0105 (6)	0.0198 (6)	0.0053 (5)	0.0030 (5)	−0.0045 (5)
O6	0.0096 (7)	0.0092 (8)	0.0217 (8)	0.000	−0.0011 (6)	0.000
O7	0.0177 (7)	0.0051 (7)	0.0129 (7)	0.000	−0.0021 (5)	0.000

K—O5i	2.7559 (15)	Al—O3	1.9021 (11)
K—O5ii	2.7559 (15)	P1—O1ix	1.4861 (12)
K—O5	2.8612 (15)	P1—O3	1.4956 (12)
K—O5iii	2.8612 (15)	P1—O4	1.5701 (13)
K—O2iv	2.9493 (14)	P1—O7	1.5794 (8)
K—O2v	2.9493 (13)	P2—O5	1.4622 (14)
K—O3vi	3.2431 (13)	P2—O2	1.4983 (12)
K—O3vii	3.2431 (13)	P2—O6	1.5957 (10)
K—O5iv	3.2790 (17)	P2—O4	1.6070 (13)
K—O5v	3.2790 (17)	P2—Kv	3.4928 (7)
K—P2iv	3.4927 (7)	O1—P1ix	1.4861 (12)
K—P2v	3.4927 (7)	O2—Kv	2.9494 (13)
Al—O2viii	1.8523 (12)	O3—Kx	3.2431 (13)
Al—O2	1.8523 (12)	O5—Ki	2.7559 (15)
Al—O1viii	1.9013 (12)	O5—Kv	3.2790 (17)
Al—O1	1.9013 (12)	O6—P2iv	1.5957 (10)
Al—O3viii	1.9021 (11)	O7—P1xi	1.5793 (8)
O5i—K—O5ii	65.84 (6)	O5—K—P2v	106.81 (4)
O5i—K—O5	99.41 (4)	O5iii—K—P2v	58.01 (3)
O5ii—K—O5	66.08 (6)	O2iv—K—P2v	119.65 (3)
O5i—K—O5iii	66.08 (6)	O2v—K—P2v	25.13 (2)
O5ii—K—O5iii	99.41 (4)	O3vi—K—P2v	129.83 (3)
O5—K—O5iii	63.13 (6)	O3vii—K—P2v	74.69 (2)
O5i—K—O2iv	147.08 (5)	O5iv—K—P2v	78.81 (3)
O5ii—K—O2iv	82.35 (4)	O5v—K—P2v	24.68 (2)
O5—K—O2iv	73.61 (4)	P2iv—K—P2v	102.94 (2)
O5iii—K—O2iv	130.89 (4)	O2viii—Al—O2	180.0
O5i—K—O2v	82.35 (4)	O2viii—Al—O1viii	90.00 (6)
O5ii—K—O2v	147.08 (5)	O2—Al—O1viii	89.99 (6)
O5—K—O2v	130.89 (4)	O2viii—Al—O1	89.99 (6)
O5iii—K—O2v	73.61 (4)	O2—Al—O1	90.01 (6)
O2iv—K—O2v	126.97 (6)	O1viii—Al—O1	180.00 (5)
O5i—K—O3vi	109.11 (4)	O2viii—Al—O3viii	91.53 (5)
O5ii—K—O3vi	72.48 (4)	O2—Al—O3viii	88.47 (5)
O5—K—O3vi	112.63 (4)	O1viii—Al—O3viii	91.12 (5)
O5iii—K—O3vi	171.88 (4)	O1—Al—O3viii	88.88 (5)
O2iv—K—O3vi	49.77 (3)	O2viii—Al—O3	88.47 (5)
O2v—K—O3vi	112.88 (4)	O2—Al—O3	91.52 (5)
O5i—K—O3vii	72.48 (4)	O1viii—Al—O3	88.88 (5)
O5ii—K—O3vii	109.11 (4)	O1—Al—O3	91.12 (5)
O5—K—O3vii	171.88 (4)	O3viii—Al—O3	180.0
O5iii—K—O3vii	112.63 (4)	O1ix—P1—O3	116.38 (7)
O2iv—K—O3vii	112.88 (4)	O1ix—P1—O4	109.98 (7)
O2v—K—O3vii	49.77 (3)	O3—P1—O4	110.70 (7)
O3vi—K—O3vii	70.64 (5)	O1ix—P1—O7	109.34 (8)
O5i—K—O5iv	154.67 (6)	O3—P1—O7	109.20 (8)
O5ii—K—O5iv	114.04 (5)	O4—P1—O7	99.98 (8)
O5—K—O5iv	61.04 (5)	O5—P2—O2	117.73 (9)
O5iii—K—O5iv	89.66 (4)	O5—P2—O6	111.73 (8)
O2iv—K—O5iv	47.65 (3)	O2—P2—O6	107.39 (6)
O2v—K—O5iv	98.27 (4)	O5—P2—O4	111.39 (8)
O3vi—K—O5iv	94.08 (3)	O2—P2—O4	108.11 (7)
O3vii—K—O5iv	126.82 (4)	O6—P2—O4	98.73 (7)
O5i—K—O5v	114.04 (5)	O5—P2—Kv	69.45 (6)
O5ii—K—O5v	154.67 (6)	O2—P2—Kv	56.71 (5)
O5—K—O5v	89.66 (4)	O6—P2—Kv	101.18 (5)
O5iii—K—O5v	61.04 (5)	O4—P2—Kv	157.99 (5)
O2iv—K—O5v	98.27 (4)	P1ix—O1—Al	133.95 (8)
O2v—K—O5v	47.65 (3)	P2—O2—Al	138.36 (8)
O3vi—K—O5v	126.82 (4)	P2—O2—Kv	98.17 (6)
O3vii—K—O5v	94.08 (3)	Al—O2—Kv	113.58 (5)
O5iv—K—O5v	54.36 (5)	P1—O3—Al	136.54 (8)
O5i—K—P2iv	155.10 (4)	P1—O3—Kx	120.51 (6)
O5ii—K—P2iv	93.25 (3)	Al—O3—Kx	101.05 (4)
O5—K—P2iv	58.01 (3)	P1—O4—P2	132.20 (8)
O5iii—K—P2iv	106.81 (4)	P2—O5—Ki	141.08 (8)
O2iv—K—P2iv	25.13 (2)	P2—O5—K	134.77 (8)
O2v—K—P2iv	119.65 (3)	Ki—O5—K	80.59 (4)
O3vi—K—P2iv	74.69 (2)	P2—O5—Kv	85.87 (6)
O3vii—K—P2iv	129.83 (3)	Ki—O5—Kv	114.04 (5)
O5iv—K—P2iv	24.68 (2)	K—O5—Kv	90.34 (4)
O5v—K—P2iv	78.81 (3)	P2—O6—P2iv	123.73 (12)
O5i—K—P2v	93.25 (3)	P1xi—O7—P1	138.66 (12)
O5ii—K—P2v	155.10 (4)

Table 1

Selected bond lengths (Å)

P1—O1i	1.4861 (12)
P1—O3	1.4956 (12)
P1—O4	1.5701 (13)
P1—O7	1.5794 (8)
P2—O5	1.4622 (14)
P2—O2	1.4983 (12)
P2—O6	1.5957 (10)
P2—O4	1.6070 (13)

Symmetry code: (i) .