Tetra­aqua­lithium(I) bis­(tropolonato-κ²O,O′)lithate(I)

The title salt, [Li(H₂O)₄][Li(C₇H₅O₂)₂], which was synthesized by reacting equimolar quanti­ties of lithium hydroxide and tropolone in water, consists of a hydrated lithium cation whose charge is balanced by a ditropolonatolithate. Both Li atoms exist in a tetra­hedral geometry (the cation and anion lie on different sites of 222 symmetry). Hydrogen bonds link the cation and anion into a layer structure; π–π stacking [centroid–centroid distance 3.313 (2) Å] is observed with the tropolonate rings, the stacking allowing the formation of channels that facilitate the packing of the cations within them.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.055
• wR factor = 0.157
• Data-to-parameter ratio = 13.0

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PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical .          ?
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       2.05
PLAT720_ALERT_4_C Number of Unusual/Non-Standard Label(s) ........          3
PLAT764_ALERT_4_C Overcomplete CIF Bond List Detected (Rep/Expd) .       2.57 Ratio

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S1. Comment

The title compound, (I), is a novel example of a diketonato and lithium atom complex. To date very little data exist with lithium cation interactions with α- or β-diketones (Filatov et al., 2006; Gonçalves et al., 1996; Teixidor et al., 1985). The title compound is particularly interesting since the expected 1:1 ratio of an anion to cation as observed for the sodium derivative (Shiono, 1961) has been disrupted. This effect might be due to the smaller ionic radius of the lithium ion. The Li···O bond distances in both the independent units are nearly similar, with the Li···O(H₂) and Li···O(trop), 1.9356 (12) and 1.9278 (12) Å, respectively.

The cationic and anionic parts of the title compound are linked together through O—H···O hydrogen bonds, see Table 2. The effect of this hydrogen bond in ordering the solid state can be observed as sheets perpendicular to the c axis, Figure 2. The tropolonato moieties form π-π stacking units (3.313 (2) Å) in the solid state creating channels in which the solvated lithium cations can pack.

Related literature

Diketonato–lithium compounds have only one diketonate group for each lithium. See, for example: Filatov et al. (2006); Gonçalves et al. (1996); Teixidor et al. (1985); Shiono (1961).

S2. Experimental

The title compound was obtained by mixing Tropolone (100 mg, 0.8 mmol) and LiOH (19 mg, 0.8 mmol) in 10 ml of water. The solution was stored at 4 ° C for 2 weeks, during which crystals grew suitable for X-ray crystallography. (Yield: 132 mg, 50%) NMR data: ¹H 6.83 (t, 9 Hz); 7.06 (d, 11 Hz); 7.31 (t, 11 Hz); ⁷Li 0.344 (s).

S3. Refinement

H atoms bonded to O atoms were located in a difference map and refined with distance restraints of O—H = 0.84 (2) Å, and with U_iso(H) = 1.2U_eq(O). Other H atoms were positioned geometrically and refined using a riding model, with C—H = 0.95 Å and with U_iso(H) = 1.2 times U_eq(C).

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-Plus (Bruker, 2004); data reduction: SAINT-Plus and XPREP (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg & Putz, 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

	Fig. 1. The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms.
	Fig. 2. The packing of (I), viewed down the c-axis, showing one layer of molecules connected by O—H···O hydrogen bonds (dashed lines). H atoms not involved in hydrogen bonding have been omitted.

Tetraaqualithium(I) bis(tropolonato-κ²O,O')lithate(I)

Crystal data

[Li(H2O)4][Li(C7H5O2)2]	F(000) = 1376
Mr = 328.16	Dx = 1.415 Mg m^−3
Orthorhombic, Fddd	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -F 2uv 2vw	Cell parameters from 2008 reflections
a = 9.4452 (7) Å	θ = 2.5–28.0°
b = 10.0151 (7) Å	µ = 0.11 mm^−1
c = 32.566 (2) Å	T = 100 K
V = 3080.6 (4) Å^3	Cuboid, white
Z = 8	0.13 × 0.08 × 0.06 mm

Data collection

Bruker SMART 1K CCD area-detector diffractometer	844 independent reflections
Radiation source: fine-focus sealed tube	715 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.078
Detector resolution: 512 pixels mm^-1	θmax = 27.0°, θmin = 2.5°
φ and ω scans	h = −12→12
Absorption correction: multi-scan (SADABS; Bruker, 1998)	k = −12→12
Tmin = 0.985, Tmax = 0.993	l = −41→41
6210 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)] = 0.055	Hydrogen site location: mixed
wR(F^2) = 0.157	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ^2(Fo^2) + (0.1125P)^2 + 2.5701P] where P = (Fo^2 + 2Fc^2)/3
844 reflections	(Δ/σ)max < 0.001
65 parameters	Δρmax = 0.51 e Å^−3
3 restraints	Δρmin = −0.25 e Å^−3

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
O01	0.50030 (13)	0.24879 (12)	0.15285 (4)	0.0186 (4)
Li2	0.6250	0.1250	0.1250	0.0170 (11)
H011	0.520 (3)	0.3295 (18)	0.1582 (7)	0.036 (7)*
H012	0.4138 (19)	0.241 (2)	0.1578 (8)	0.039 (7)*
O1	0.54310 (12)	0.52151 (11)	0.16890 (4)	0.0150 (4)
C2	0.54144 (18)	0.49237 (18)	0.23993 (5)	0.0176 (5)
H2	0.4936	0.4110	0.2343	0.021*
C1	0.58113 (16)	0.56432 (16)	0.20457 (5)	0.0130 (4)
C3	0.5595 (2)	0.5186 (2)	0.28138 (5)	0.0231 (5)
H3	0.5209	0.4535	0.2994	0.028*
C4	0.6250	0.6250	0.30048 (7)	0.0254 (7)
H4	0.6250	0.6250	0.3296	0.030*
Li1	0.6250	0.6250	0.1250	0.0175 (11)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O01	0.0155 (7)	0.0139 (7)	0.0264 (7)	−0.0014 (5)	0.0042 (5)	−0.0034 (5)
Li2	0.013 (2)	0.017 (3)	0.021 (3)	0.000	0.000	0.000
O1	0.0148 (7)	0.0154 (7)	0.0147 (7)	−0.0023 (5)	−0.0014 (4)	−0.0006 (4)
C2	0.0144 (9)	0.0183 (9)	0.0201 (10)	0.0029 (6)	0.0033 (6)	0.0053 (7)
C1	0.0104 (7)	0.0156 (9)	0.0130 (8)	0.0036 (6)	−0.0003 (5)	−0.0003 (6)
C3	0.0213 (10)	0.0304 (11)	0.0175 (9)	0.0113 (8)	0.0056 (7)	0.0092 (7)
C4	0.0275 (13)	0.0371 (16)	0.0116 (11)	0.0182 (12)	0.000	0.000
Li1	0.022 (3)	0.014 (3)	0.016 (3)	0.000	0.000	0.000

Geometric parameters (Å, º)

O01—Li2	1.9356 (12)	C1—Li1	2.6938 (15)
O01—H011	0.847 (17)	C3—C4	1.380 (2)
O01—H012	0.837 (17)	C3—H3	0.9500
Li2—O01^i	1.9356 (12)	C4—C3^iv	1.380 (2)
Li2—O01^ii	1.9356 (12)	C4—H4	0.9500
Li2—O01^iii	1.9356 (12)	Li1—O1^iv	1.9278 (12)
O1—C1	1.2894 (19)	Li1—O1^v	1.9278 (12)
O1—Li1	1.9278 (12)	Li1—O1^ii	1.9278 (12)
C2—C3	1.386 (2)	Li1—C1^iv	2.6938 (15)
C2—C1	1.409 (2)	Li1—C1^v	2.6938 (15)
C2—H2	0.9500	Li1—C1^ii	2.6938 (15)
C1—C1^iv	1.471 (3)
Li2—O01—H011	125.2 (17)	O1^iv—Li1—O1^v	114.95 (7)
Li2—O01—H012	128.4 (17)	O1—Li1—O1^ii	114.95 (7)
H011—O01—H012	105 (2)	O1^iv—Li1—O1^ii	132.68 (7)
O01^i—Li2—O01	105.04 (8)	O1^v—Li1—O1^ii	84.27 (7)
O01^i—Li2—O01^ii	124.13 (8)	O1—Li1—C1	26.31 (5)
O01—Li2—O01^ii	100.34 (7)	O1^iv—Li1—C1	57.97 (5)
O01^i—Li2—O01^iii	100.34 (7)	O1^v—Li1—C1	140.62 (5)
O01—Li2—O01^iii	124.13 (8)	O1^ii—Li1—C1	130.83 (5)
O01^ii—Li2—O01^iii	105.04 (8)	O1—Li1—C1^iv	57.97 (5)
C1—O1—Li1	112.18 (10)	O1^iv—Li1—C1^iv	26.31 (5)
C3—C2—C1	131.78 (17)	O1^v—Li1—C1^iv	130.83 (5)
C3—C2—H2	114.1	O1^ii—Li1—C1^iv	140.62 (5)
C1—C2—H2	114.1	C1—Li1—C1^iv	31.69 (7)
O1—C1—C2	119.48 (15)	O1—Li1—C1^v	140.62 (5)
O1—C1—C1^iv	115.57 (9)	O1^iv—Li1—C1^v	130.83 (5)
C2—C1—C1^iv	124.91 (10)	O1^v—Li1—C1^v	26.31 (5)
C2—C1—Li1	160.46 (13)	O1^ii—Li1—C1^v	57.97 (5)
C1^iv—C1—Li1	74.15 (3)	C1—Li1—C1^v	162.30 (7)
C4—C3—C2	129.83 (18)	C1^iv—Li1—C1^v	153.92 (7)
C4—C3—H3	115.1	O1—Li1—C1^ii	130.83 (5)
C2—C3—H3	115.1	O1^iv—Li1—C1^ii	140.62 (5)
C3—C4—C3^iv	126.4 (2)	O1^v—Li1—C1^ii	57.97 (5)
C3—C4—H4	116.8	O1^ii—Li1—C1^ii	26.31 (5)
C3^iv—C4—H4	116.8	C1—Li1—C1^ii	153.92 (7)
O1—Li1—O1^iv	84.27 (7)	C1^iv—Li1—C1^ii	162.30 (7)
O1—Li1—O1^v	132.68 (7)	C1^v—Li1—C1^ii	31.69 (7)
Li1—O1—C1—C2	−174.11 (12)	C2—C1—Li1—O1^iv	−166.3 (4)
Li1—O1—C1—C1^iv	4.0 (2)	C1^iv—C1—Li1—O1^iv	1.94 (10)
C3—C2—C1—O1	−175.48 (17)	O1—C1—Li1—O1^v	86.96 (15)
C3—C2—C1—C1^iv	6.7 (3)	C2—C1—Li1—O1^v	102.4 (4)
C3—C2—C1—Li1	172.8 (2)	C1^iv—C1—Li1—O1^v	−89.34 (13)
C1—C2—C3—C4	−1.0 (3)	O1—C1—Li1—O1^ii	−60.69 (15)
C2—C3—C4—C3^iv	−0.82 (15)	C2—C1—Li1—O1^ii	−45.2 (4)
C1—O1—Li1—O1^iv	−1.51 (8)	C1^iv—C1—Li1—O1^ii	123.02 (11)
C1—O1—Li1—O1^v	−120.47 (11)	O1—C1—Li1—C1^iv	176.3 (2)
C1—O1—Li1—O1^ii	133.31 (11)	C2—C1—Li1—C1^iv	−168.2 (5)
C1—O1—Li1—C1^iv	−2.30 (12)	O1—C1—Li1—C1^v	53.03 (10)
C1—O1—Li1—C1^v	−157.49 (10)	C2—C1—Li1—C1^v	68.5 (4)
C1—O1—Li1—C1^ii	158.54 (8)	C1^iv—C1—Li1—C1^v	−123.26 (12)
C2—C1—Li1—O1	15.5 (3)	O1—C1—Li1—C1^ii	−39.04 (10)
C1^iv—C1—Li1—O1	−176.3 (2)	C2—C1—Li1—C1^ii	−23.5 (3)
O1—C1—Li1—O1^iv	178.23 (9)	C1^iv—C1—Li1—C1^ii	144.67 (12)

Symmetry codes: (i) x, −y+1/4, −z+1/4; (ii) −x+5/4, y, −z+1/4; (iii) −x+5/4, −y+1/4, z; (iv) −x+5/4, −y+5/4, z; (v) x, −y+5/4, −z+1/4.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O01—H011···O1	0.85 (2)	1.97 (2)	2.8101 (16)	174 (2)