Electron density distribution in tetralithium hypodiphosphate hexahydrate, Li₄P₂O₆·6H₂O

Tetralithium hypodiphosphate hexahydrate, Li₄P₂O₆·6H₂O, forms a highly symmetrical crystal structure, where hypodiphosphate anions have (D_3d) symmetry. Analysis of the charge distribution (experimental and theoretically calculated) shows that the charges of the P atoms are lower than in phosphates and phosphonates, whereas the O charges are similar. Values of both ρ_c and ∇²ρ_c suggest that the P—P bond is a weak covalent one, while the P—O one is polarized covalent, with topological parameters similar to those of P—O bonds in phosphates or phosphonates. Theoretical calculations show that the hypodiphosphate anion is relatively insensitive to its coordination environment; this is brought about by the vicinity of cationic P atoms. The localization and delocalization indices have been computed and discussed.

Computing details

Data collection: CrysAlis CCD, Oxford Diffraction Ltd., Version 1.171.33.55 (release 05-01-2010 CrysAlis171 .NET) (compiled Jan 5 2010,16:28:46); cell refinement: CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.33.55 (release 05-01-2010 CrysAlis171 .NET) (compiled Jan 5 2010,16:28:46); data reduction: CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.33.55 (release 05-01-2010 CrysAlis171 .NET) (compiled Jan 5 2010,16:28:46); program(s) used to refine structure: Volkov et al., (2006); molecular graphics: Volkov et al., (2006); software used to prepare material for publication: Volkov et al., (2006).

Figures

(I)

Crystal data

H12Li4O12P2	Mo Kα radiation, λ = 0.7107 Å
Mr = 293.80	Cell parameters from 41589 reflections
Cubic, Ia3	θ = 3.2–72.5°
a = 12.700 (3) Å	µ = 0.48 mm^−1
V = 2048.4 (8) Å^3	T = 85 K
Z = 8.0	Parallelepiped, colourless
F(000) = 1200	0.35 × 0.22 × 0.21 mm
Dx = 1.905 Mg m^−3

Data collection

Xcalibur, Onyx diffractometer	3497 independent reflections
Radiation source: Enhance (Mo) X-ray Source	3178 reflections with > 3σ(I)
Graphite monochromator	Rint = 0.039
Detector resolution: 8.1956 pixels mm^-1	θmax = 72.5°, θmin = 3.2°
ω and π scans	h = −33→34
Absorption correction: analytical CrysAlis RED, Oxford Diffraction Ltd., Version 1.171.33.66 (release 28-04-2010 CrysAlis171 .NET) (compiled Apr 28 2010,14:27:37) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. Reid. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897)	k = −34→32
Tmin = 0.885, Tmax = 0.919	l = −27→31
103877 measured reflections

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	w1 = [Fo*sqrt(w2) + sqrt(Fo^2w2^2 + sqrt(w2^2))]^2 where w2 = q/[s^2(Fo^2) + (0.00 P)^2 + 2.50 P + 0.00 + 0.00 sin(th)] where P = (0.3333 Fo^2 + 0.6667 Fc^2) q = 1.0
R[F^2 > 2σ(F^2)] = 0.014	(Δ/σ)max = 0.00001
wR(F^2) = 0.013	Δρmax = 0.32 e Å^−3
S = 1.72	Δρmin = −0.17 e Å^−3
2884 reflections	Extinction correction: Becker-Coppens type 1 Gaussian isotropic, Becker, P.J. & Coppens, P. (1974) Acta Cryst., A30, 129-153.
95 parameters	Extinction coefficient: 0.418 (18)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
P	0.200353 (3)	0.200353 (3)	0.200353 (3)	0.004
O	0.174504 (9)	0.264039 (8)	0.101346 (8)	0.006
O(W)	0.431732 (11)	0.149707 (10)	0.051172 (10)	0.008
LI(1)	0.25	0.34863 (4)	0	0.01
LI(2)	0.5	0	0	0.011
H(1)	0.405447	0.19426	−0.00944	0.026 (2)
H(2)	0.366639	0.123312	0.091399	0.024 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
P	0.003899 (19)	0.003899 (19)	0.003899 (19)	−0.000086 (6)	−0.000086 (6)	−0.000086 (6)
O	0.00747 (3)	0.00639 (3)	0.00513 (3)	0.00026 (2)	−0.00052 (2)	0.001072 (19)
O(W)	0.00742 (4)	0.00807 (4)	0.00721 (4)	0.00006 (2)	−0.00002 (2)	0.00034 (3)
LI(1)	0.01037 (17)	0.00940 (17)	0.00885 (16)	0	0.00072 (13)	0
LI(2)	0.01128 (13)	0.01128 (13)	0.01128 (13)	0.00010 (15)	−0.00010 (15)	0.00010 (15)

Geometric parameters (Å, º)

P—P^i	2.1842 (1)	O(W)—H(1)	1.0120 (1)
P—O	1.5307 (1)	O(W)—H(2)	1.0280 (1)
P^i—P—O	107.039 (5)	O^ii—P—O^iii	111.790 (4)
O—P—O^ii	111.790 (4)	H(1)—O(W)—H(2)	107.162 (12)
O—P—O^iii	111.790 (4)

Symmetry codes: (i) −x+1/2, −y+1/2, −z+1/2; (ii) z, x, y; (iii) y, z, x.