Lithium bis­(2-methyl­lactato)borate monohydrate

Joshua L Allen; Elie Paillard; Paul D Boyle; Wesley A Henderson

doi:10.1107/S1600536812017540

. 2012 May 12;68(Pt 6):m749. doi: 10.1107/S1600536812017540

Lithium bis(2-methyllactato)borate monohydrate

Joshua L Allen ^a, Elie Paillard ^a, Paul D Boyle ^b, Wesley A Henderson ^a,^*

PMCID: PMC3379088 PMID: 22719309

Abstract

The title compound {systematic name: poly[[aqualithium]-μ-3,3,8,8-tetramethyl-1,4,6,9-tetraoxa-5λ⁴-borataspiro[4.4]nonane-2,7-dione]}, [Li(C₈H₁₂BO₆)(H₂O)]_n (LiBMLB), forms a 12-membered macrocycle, which lies across a crystallographic inversion center. The lithium cations are pseudo-tetrahedrally coordinated by three methyllactate ligands and a water molecule. The asymmetric units couple across crystallographic inversion centers, forming the 12-membered macrocycles. These macrocycles, in turn, cross-link through the Li⁺ cations, forming an infinite polymeric structure in two dimensions parallel to (101).

Related literature

For the synthesis and purification of HBMLB [BMLB is bis(2-methyllactato)borate], see: Lamande et al. (1987 ▶). For the synthesis and properties of LiBMLB and BMLB⁻-based ionic liquids, see: Xu et al. (2003 ▶). For crystallographic data of similar lithium salts, see: Zavalij et al. (2004 ▶); Allen et al. (2011 ▶). graphic file with name e-68-0m749-scheme1.jpg

Experimental

Crystal data

[Li(C₈H₁₂BO₆)(H₂O)]
M _r = 239.94
Orthorhombic,
a = 12.7034 (4) Å
b = 11.3939 (4) Å
c = 15.8258 (5) Å
V = 2290.65 (13) Å³
Z = 8
Mo Kα radiation
μ = 0.12 mm⁻¹
T = 110 K
0.34 × 0.23 × 0.18 mm

Data collection

Bruker–Nonius Kappa X8 APEXII diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2007 ▶) T _min = 0.961, T _max = 0.979
97648 measured reflections
5663 independent reflections
4436 reflections with I > 2σ(I)
R _int = 0.037

Refinement

R[F ² > 2σ(F ²)] = 0.036
wR(F ²) = 0.098
S = 1.05
5663 reflections
210 parameters
All H-atom parameters refined
Δρ_max = 0.51 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SIR92 (Altomare et al., 1994 ▶); program(s) used to refine structure: XL (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: cif2tables.py (Boyle, 2008 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812017540/vn2036sup1.cif

e-68-0m749-sup1.cif^{(18.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812017540/vn2036Isup2.hkl

e-68-0m749-Isup2.hkl^{(277.4KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Li1—O1	1.9725 (13)
Li1—O1W	1.9487 (13)
Li1—O3ⁱ	2.0059 (13)
Li1—O6ⁱⁱ	1.9155 (13)

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

This work was fully supported by the US DOE BATT Program (contract DE—AC02–05-CH11231). The authors wish to thank the Department of Chemistry of North Carolina State University and the State of North Carolina for funding the purchase of the APEXII diffractometer. JLA would like to thank the SMART Scholarship Program and the American Society for Engineering Education (ASEE) for the award of a SMART Graduate Research Fellowship.

supplementary crystallographic information

Comment

Various lithium salts for lithium-ion batteries have been proposed in recent years either as alternatives to the commonly used lithium hexafluorophosphate (LiPF₆) or as electrolyte additives. Of these salts, lithium bis(oxalato)borate [LiBOB] remains one of the most promising (Zavalij et al.). The title compound, lithium bis(2-methyllactato)borate [LiBMLB] is based on this structure, differing only by replacing the oxygen of a carbonyl group of each ligand with two methyl groups. Although this salt has previously been synthesized (Lamande et al., Xu et al.), the crystal structure and ion coordination have not yet been reported. The structure of the monohydrate solvate of this salt is reported in the present manuscript.

The Li⁺ cation coordination in the title compound is different from what has been previously reported for similar cyclic structures (Allen et al., Zavalij et al.). For salts such as LiBOB, the Li⁺ cations are exclusively coordinated by the anion carbonyl oxygen atoms. In the present structure, however, the anion ring pseudo-ether oxygen also participates in the Li⁺ cation coordination (Fig. 1). Thus, each Li⁺ cation is coordinated by two carbonyl oxygen atoms from two BMLB^- anions, one ring oxygen from a third BMLB^- anion and an oxygen from a single water molecule. The asymmetric unit couples across crystallographic inversion centers to form 12-membered macrocycles (Fig. 2). These macrocycles are cross-linked through the Li⁺ cation coordination, forming the infinite polymeric crystal structure in two dimensions parallel to (101) (Fig. 3).

Experimental

Lithium bis(2-methyllactato)borate was synthesized by dissolving 2-methyllactic acid, boric acid and lithium carbonate (mole ratio 4:2:1) in water. The aqueous solution was allowed to slowly evaporate, forming colorless crystals suitable for X-ray analysis.