Poly[[(acetonitrile)­lithium(I)]-μ₃-tetra­fluoridoborato]

Abstract

The structure of the title compound, [Li(BF₄)(CH₃CN)]_n, consists of a layered arrangement parallel to (100) in which the Li⁺ cations are coordinated by three F atoms from three tetra­fluoridoborate (BF₄ ⁻) anions and an N atom from an acetonitrile mol­ecule. The BF₄ ⁻ anion is coordinated to three different Li⁺ cations though three F atoms. The structure can be described as being built from vertex-shared BF₄ and LiF₃(NCCH₃) tetra­hedra. These tetra­hedra reside around a crystallographic inversion center and form 8-membered rings.

Related literature

For related compounds containing Li(BF₄), see: Andreev et al. (2005 ▶); Henderson et al. (2003a ▶,b ▶); Ramirez et al. (2003 ▶); Francisco & Williams (1990 ▶). For the structures of related Li salts with CH₃CN , see: Klapötke et al. (2006 ▶); Brooks et al. (2002 ▶); Yokota et al. (1999 ▶); Raston et al. (1989 ▶).

Experimental

Crystal data

• [Li(BF₄)(C₂H₃N)]

• M _r = 134.80

• Monoclinic,

• a = 7.8248 (6) Å

• b = 8.8187 (7) Å

• c = 8.2932 (6) Å

• β = 95.5708 (18)°

• V = 569.57 (8) ų

• Z = 4

• Mo Kα radiation

• μ = 0.18 mm⁻¹

• T = 110 K

• 0.34 × 0.26 × 0.16 mm

Data collection

• Bruker–Nonius Kappa X8 APEXII diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.941, T _max = 0.971

• 13920 measured reflections

• 2650 independent reflections

• 2001 reflections with I > 2σ(I)

• R _int = 0.037

Refinement

• R[F ² > 2σ(F ²)] = 0.045

• wR(F ²) = 0.118

• S = 1.05

• 2650 reflections

• 94 parameters

• All H-atom parameters refined

• Δρ_max = 0.43 e Å⁻³

• Δρ_min = −0.18 e Å⁻³

Data collection: APEX2 (Bruker, 2009 ▶); cell refinement: SAINT (Bruker, 2009 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 (Farrugia, 1997 ▶); software used to prepare material for publication: cif2tables.py (Boyle, 2008 ▶).

Supplementary Material

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

supplementary crystallographic information

Comment

In this structure, atoms F1 and F2 are endocyclic linking the boron atom to the lithium atom while F3 and F4 are exocyclic. Neighboring rings are linked through a Li1—F3 bond to form an infinite two dimensional network which orients parallel to (1 0 0). The interface between the two dimensional networks is occupied by the aliphatic ends of the acetonitrile molecules and the F4 atoms and is largely at van der Waal contact distances. There is, however, a close intermolecular contact of 3.1601 (11) Å between the nitrile carbon atom, C1, and F4 (1 - x, 1 - y, 2 - z).

Solvate structures provide significant insight into the species which may exist in electrolytes solutions. Solvates based upon acetonitrile and lithium salts are particularly noteworthy as dinitrile solvents gain increasing interest as high-voltage solvents for lithium battery electrolytes. The phase diagram for (CH₃CN)_n—LiBF₄ mixtures indicates that at least three different solvates may form with 4/1 (T_m = -12°C), 2/1 (T_m = 25°C) and 1/1 (T_m = 63°C) AN/Li compositions. The 4/1 solvate may resemble that for LiClO₄ in which the Li⁺ cations are fully solvated by four acetonitrile molecules and the anions are uncoordinated. The 2/1 solvate, in turn, may resemble that for LiBr in which the Li⁺ cations are solvated by two acetonitrile molecules and two anions to form aggregated dimer solvates. The 1/1 solvate structure is reported here.

Experimental

LiBF₄ (99.998%) was purchased from Sigma-Aldrich and used as-received. Anhydrous acetonitrile (Sigma Aldrich, 99.8%) was used as-received. In a Vacuum Atmospheres inert atmosphere (N₂) glove box (< 5 p.p.m. H₂O), LiBF₄ (1 mmol) and acetonitrile (1.5 mmol) were sealed in a vial and the mixture heated on a hot plate to form a homogeneous solution. Upon standing at ambient temperature, colorless plate single crystals suitable for analysis formed.

Refinement

The structure was solved by direct methods using the XS program. All non-hydrogen atoms were obtained from the initial solution. The hydrogen atoms were introduced at idealized positions and were allowed to refine isotropically. The structural model was fit to the data using full matrix least-squares based on F². The calculated structure factors included corrections for anomalous dispersion from the usual tabulation. The structure was refined using the XL program from SHELXTL, and graphic plots were produced using the ORTEP-3 program.

Figures

Fig. 1.

Molecular structure of the title compound. The thermal ellipsoids are shown at a 50% probability level. (Symmetric codes: (i) x, -y + 3/2, z - 1/2; (ii) -x, -y + 1, -z + 2; (iii) x, -y + 3/2, z + 1/2.)

Fig. 2.

Packing diagram for the title compound.

Crystal data

[Li(BF4)(C2H3N)]	F(000) = 264
Mr = 134.80	Dx = 1.572 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2729 reflections
a = 7.8248 (6) Å	θ = 2.6–29.5°
b = 8.8187 (7) Å	µ = 0.18 mm−1
c = 8.2932 (6) Å	T = 110 K
β = 95.5708 (18)°	Prism, colourless
V = 569.57 (8) Å3	0.34 × 0.26 × 0.16 mm
Z = 4

Data collection

Bruker–Nonius Kappa X8 APEXII diffractometer	2650 independent reflections
Radiation source: fine-focus sealed tube	2001 reflections with I > 2σ(I)
graphite	Rint = 0.037
ω and φ scans	θmax = 36.5°, θmin = 2.6°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −13→12
Tmin = 0.941, Tmax = 0.971	k = −14→14
13920 measured reflections	l = −13→13

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.118	All H-atom parameters refined
S = 1.05	w = 1/[σ2(Fo2) + (0.0588P)2 + 0.0555P] where P = (Fo2 + 2Fc2)/3
2650 reflections	(Δ/σ)max = 0.001
94 parameters	Δρmax = 0.43 e Å−3
0 restraints	Δρmin = −0.18 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
Li1	0.0962 (2)	0.60760 (19)	0.7753 (2)	0.0207 (3)
N1	0.21544 (11)	0.47042 (10)	0.62923 (10)	0.02471 (18)
C1	0.28947 (11)	0.38756 (11)	0.55611 (11)	0.01953 (17)
C2	0.38544 (13)	0.28199 (12)	0.46485 (13)	0.02381 (19)
H2A	0.447 (3)	0.336 (2)	0.392 (2)	0.058 (5)*
H2B	0.309 (2)	0.211 (2)	0.408 (2)	0.049 (5)*
H2C	0.461 (3)	0.223 (2)	0.533 (2)	0.059 (5)*
B1	0.19662 (13)	0.58984 (12)	1.14638 (12)	0.01831 (18)
F1	0.21991 (8)	0.59642 (7)	0.98110 (7)	0.02477 (14)
F2	0.12648 (7)	0.44806 (6)	1.17989 (8)	0.02285 (14)
F3	0.07681 (9)	0.70149 (7)	1.17969 (9)	0.03087 (16)
F4	0.34930 (8)	0.61145 (9)	1.23724 (8)	0.03467 (19)

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Li1	0.0227 (7)	0.0198 (7)	0.0202 (8)	0.0011 (6)	0.0048 (6)	0.0011 (6)
N1	0.0279 (4)	0.0250 (4)	0.0220 (4)	0.0037 (3)	0.0060 (3)	0.0003 (3)
C1	0.0205 (4)	0.0204 (4)	0.0176 (4)	−0.0002 (3)	0.0016 (3)	0.0005 (3)
C2	0.0252 (4)	0.0239 (4)	0.0227 (4)	0.0038 (3)	0.0045 (3)	−0.0062 (4)
B1	0.0195 (4)	0.0181 (4)	0.0175 (4)	−0.0047 (3)	0.0030 (3)	−0.0010 (3)
F1	0.0258 (3)	0.0324 (3)	0.0164 (3)	−0.0019 (2)	0.0035 (2)	0.0009 (2)
F2	0.0219 (3)	0.0168 (3)	0.0304 (3)	−0.00237 (19)	0.0056 (2)	0.0023 (2)
F3	0.0368 (3)	0.0182 (3)	0.0399 (4)	−0.0010 (2)	0.0154 (3)	−0.0065 (2)
F4	0.0272 (3)	0.0515 (4)	0.0238 (3)	−0.0175 (3)	−0.0052 (2)	0.0047 (3)

Geometric parameters (Å, °)

Li1—F3i	1.8609 (18)	C2—H2B	0.956 (18)
Li1—F1	1.8810 (18)	C2—H2C	0.935 (19)
Li1—F2ii	1.8820 (18)	B1—F4	1.3626 (11)
Li1—N1	2.0051 (19)	B1—F1	1.4013 (12)
N1—C1	1.1426 (12)	B1—F2	1.4041 (11)
C1—C2	1.4539 (13)	B1—F3	1.4053 (12)
C2—H2A	0.94 (2)
F3i—Li1—F1	116.59 (9)	H2A—C2—H2C	109.8 (16)
F3i—Li1—F2ii	106.33 (9)	H2B—C2—H2C	105.1 (16)
F1—Li1—F2ii	102.23 (8)	F4—B1—F1	110.18 (8)
F3i—Li1—N1	108.18 (9)	F4—B1—F2	110.71 (8)
F1—Li1—N1	106.74 (8)	F1—B1—F2	108.72 (8)
F2ii—Li1—N1	117.12 (9)	F4—B1—F3	111.05 (8)
C1—N1—Li1	174.92 (10)	F1—B1—F3	108.41 (8)
N1—C1—C2	179.24 (10)	F2—B1—F3	107.69 (7)
C1—C2—H2A	109.4 (12)	B1—F1—Li1	141.75 (8)
C1—C2—H2B	110.4 (11)	B1—F2—Li1ii	131.19 (7)
H2A—C2—H2B	110.3 (16)	B1—F3—Li1iii	133.56 (8)
C1—C2—H2C	111.7 (11)
F4—B1—F1—Li1	−168.69 (11)	F4—B1—F2—Li1ii	132.27 (10)
F2—B1—F1—Li1	69.82 (15)	F1—B1—F2—Li1ii	−106.58 (11)
F3—B1—F1—Li1	−46.99 (15)	F3—B1—F2—Li1ii	10.69 (13)
F3i—Li1—F1—B1	99.32 (14)	F4—B1—F3—Li1iii	18.68 (14)
F2ii—Li1—F1—B1	−16.17 (16)	F1—B1—F3—Li1iii	−102.49 (12)
N1—Li1—F1—B1	−139.69 (11)	F2—B1—F3—Li1iii	140.04 (10)

Symmetry codes: (i) x, −y+3/2, z−1/2; (ii) −x, −y+1, −z+2; (iii) x, −y+3/2, z+1/2.