Poly[1-ethyl-3-methyl­imidazolium [tri-μ-chlorido-chromate(II)]]

Danford, J.J.; Arif, A.M.; Berreau, L.M.

doi:10.1107/S1600536809002281

metal-organic compounds

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ISSN: 2056-9890

Volume 65| Part 2| February 2009| Page m227

doi:10.1107/S1600536809002281

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Poly[1-ethyl-3-methylimidazolium [tri-μ-chlorido-chromate(II)]]

James J. Danford,^a Atta M. Arif ^b and Lisa M. Berreau ^a ^*

^aDepartment of Chemistry and Biochemistry, Utah State University, 0300 Old Main Hill, Logan, UT 84322-0300, USA, and ^bDepartment of Chemistry, University of Utah, Salt Lake City, UT 84112-0850, USA
^*Correspondence e-mail: lisa.berreau@usu.edu

(Received 12 December 2008; accepted 17 January 2009; online 28 January 2009)

The title compound, {(C₆H₁₁N₂)[CrCl₃]}_n, was generated via mixing of the ionic liquid 1-ethyl-3-methylimidazolium chloride with CrCl₂ in ethanol. Crystals were obtained by a diffusion method. In the crystal structure, the anion forms one-dimensional chains of chloride-bridged Jahn–Teller distorted chromium(II) centers extending along the [100] direction. The imidazolium cations are positioned between these chains.

Related literature

For reference to this compound as a possible catalyst for the conversion of glucose to 5-hydroxymethylfurfural (HMF), see: Zhao et al. (2007 ). For the synthesis of the ammonium and tetramethylammonium analogs [NR₄][CrCl₃] (R = H, CH₃), see Hardt & Streit (1970 ). For the crystal structures of [M][CrCl₃], see: Bellitto et al. (1984 ) [M = N(CH₃)₄]; McPherson et al. (1972 ) (M = Cs); Crama et al. (1978 ) (M = Rb, Cs); Crama et al. (1979 ) (M = Rb); Crama & Zandbergen (1981 ) (M = Cs).

Experimental

Crystal data

(C₆H₁₁N₂)[CrCl₃]
M_r = 269.52
Monoclinic, P 2₁ /a
a = 6.66150 (10) Å
b = 16.4317 (4) Å
c = 9.5258 (2) Å
β = 95.6881 (14)°
V = 1037.56 (4) Å³
Z = 4
Mo Kα radiation
μ = 1.82 mm⁻¹
T = 150 (1) K
0.25 × 0.20 × 0.15 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: multi-scan [DENZO-SMN (Otwinowski & Minor, 1997 ) with scaling algorithm from Fox & Holmes (1966 )] T_min = 0.659, T_max = 0.772
4056 measured reflections
2384 independent reflections
2082 reflections with I > 2σ(I)
R_int = 0.018

Refinement

R[F² > 2σ(F²)] = 0.026
wR(F²) = 0.064
S = 1.08
2384 reflections
154 parameters
All H-atom parameters refined
Δρ_max = 0.42 e Å⁻³
Δρ_min = −0.48 e Å⁻³

Table 1
Selected geometric parameters (Å, °)

Cr1—Cl2	2.3876 (5)
Cr1—Cl1	2.3898 (5)
Cr1—Cl3	2.4431 (5)
Cr1—Cl3ⁱ	2.4476 (5)

Cl2—Cr1—Cl1	177.976 (19)
Cl2—Cr1—Cl3	87.073 (15)
Cl1—Cr1—Cl3	91.904 (16)
Cl2—Cr1—Cl3ⁱ	91.906 (16)
Cl1—Cr1—Cl3ⁱ	89.027 (15)
Cl3—Cr1—Cl3ⁱ	176.95 (2)
Cr1—Cl3—Cr1ⁱⁱ	85.856 (13)
Symmetry codes: (i) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z]$ ; (ii) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z]$ .

Data collection: COLLECT (Nonius, 1999 ); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SIR97 (Altomare et al., 1999 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ); molecular graphics: WinGX (Farrugia, 1999 ); software used to prepare material for publication: CrystalMaker (Palmer, 2005 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809002281/si2146sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536809002281/si2146Isup2.hkl

checkCIF report

Comment top

Recently it was shown that a solution of CrCl₂in the ionic liquid 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) at 100°C will catalyze the conversion of glucose to 5-hydroxymethylfurfural (HMF) in 70% yield (Zhao et al., 2007). The proposed active catalyst in this system is a compound formulated as [EMIM]CrCl₃. While alkali metal, ammonium, and tetramethyl ammonium chromium(II) trihalides have been previously reported in the literature (Hardt & Streit, 1970), the title compound is the first structurally characterized imidazolium analog.

The structure consists of infinite linear chains of Jahn–Teller-distorted chromium centers (Fig. 1) bridged by a facial array of chloride ligands (Fig. 2). Each Cr^II has four Cr—Cl bonds of σim 2.39–2.45 Å and two longer Cr—Cl interactions (2.87–2.91 Å). The Cr···Cr distance is 3.33 Å. The Cl—Cr—Cl bond angles are in the range of 87–90°. The shortest Cr···Cr distance between chains is 9.19 Å. A number of differences are evident in the structures of [EMIM]CrCl₃ (collected at 150 (1) K) and the previously reported [N(CH₃)₄]CrCl₃ (collected at room temperature; Bellitto et al., 1984). Specifically, the chromium center in [EMIM]CrCl₃ has pseudo D₄_h site symmetry whereas [N(CH₃)₄]CrCl₃ contains trigonally distorted chromium centers (C_3v site symmetry) positioned in alternating compressed and elongated face-sharing octahedra. Similar site symmetry to that found in [N(CH₃)₄]CrCl₃ was identified in the room temperature structure of α-CsCrCl₃, see: McPherson et al. (1972) and Crama & Zandbergen (1981). This C_3v site symmetry is described as resulting from randomly distributed elongation of Cr—Cl bonds along three principal axes of the octahedron.

Related literature top

For reference to this compound as a possible catalyst for the conversion of glucose to 5-hydroxymethylfurfural (HMF), see: Zhao et al. (2007). For the synthesis of the ammonium and tetramethylammonium analogs [NR₄][CrCl₃] (R = H, CH₃), see Hardt & Streit (1970). For the X-ray crystal structures of [M][CrCl₃], see: Bellitto et al. (1984) [M = N(CH₃)₄]; McPherson et al. (1972) (M = Cs); Crama et al. (1978) (M = Rb, Cs); Crama et al. (1979) (M = Rb); Crama & Zandbergen (1981) (M = Cs).

Experimental top

Under a N₂ atmosphere, a solution of CrCl₂ (23 mg, 0.19 mmol) in ethanol (2 ml) was added to solid 1-ethyl-3-methylimidazolium chloride (23 mg, 0.16 mmol). The resulting teal colored solution was stirred at ambient temperature until all of the solid had dissolved. Addition of ethyl acetate (2 ml), followed by diffusion of Et₂O, produced pale yellow crystals suitable for X-ray analysis.

Computing details top

Data collection: COLLECT (Nonius, 1999); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: WinGX (Farrugia, 1999); software used to prepare material for publication: CrystalMaker (Palmer, 2005).

Figures top

	Fig. 1. A view of the coordination environment of the chromium center in the trichloridochromate(II) anion and the imidazolium cation with atom labelling for non-hydrogen atoms. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) x - 1/2, -y + 1/2, z; (ii) x + 1/2, -y + 1/2, z.]
	Fig. 2. A view of the one-dimensional chain structure of the trichloridochromate(II) anion extending along [100]. Included in the drawing are the four imidazolium cations within the cell. Displacement ellipsoids are drawn at the 50% probability level.

catena-Poly[1-ethyl-3-methylimidazolium [tri-µ-chlorido-chromate(II)]] top

Crystal data top

(C₆H₁₁N₂)[CrCl₃]	F(000) = 544
M_r = 269.52	D_x = 1.725 Mg m⁻³
Monoclinic, P2₁/a	Mo Kα radiation, λ = 0.71073 Å
a = 6.6615 (1) Å	Cell parameters from 8584 reflections
b = 16.4317 (4) Å	θ = 1.0–27.5°
c = 9.5258 (2) Å	µ = 1.82 mm⁻¹
β = 95.6881 (14)°	T = 150 K
V = 1037.56 (4) Å³	Prism, yellow
Z = 4	0.25 × 0.20 × 0.15 mm

Data collection top

Nonius KappaCCD diffractometer	2384 independent reflections
Radiation source: fine-focus sealed tube	2082 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.018
ϕ and ω scans	θ_max = 27.5°, θ_min = 2.5°
Absorption correction: multi-scan [DENZO-SMN (Otwinowski & Minor, 1997) with scaling algorithm from Fox & Holmes (1966)]	h = −8→8
T_min = 0.659, T_max = 0.772	k = −20→21
4056 measured reflections	l = −12→12

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.026	All H-atom parameters refined
wR(F²) = 0.064	w = 1/[σ²(F_o²) + (0.0236P)² + 0.6211P] where P = (F_o² + 2F_c²)/3
S = 1.08	(Δ/σ)_max < 0.001
2384 reflections	Δρ_max = 0.42 e Å⁻³
154 parameters	Δρ_min = −0.48 e Å⁻³
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0064 (9)

Crystal data top

(C₆H₁₁N₂)[CrCl₃]	V = 1037.56 (4) Å³
M_r = 269.52	Z = 4
Monoclinic, P2₁/a	Mo Kα radiation
a = 6.6615 (1) Å	µ = 1.82 mm⁻¹
b = 16.4317 (4) Å	T = 150 K
c = 9.5258 (2) Å	0.25 × 0.20 × 0.15 mm
β = 95.6881 (14)°

Data collection top

Nonius KappaCCD diffractometer	2384 independent reflections
Absorption correction: multi-scan [DENZO-SMN (Otwinowski & Minor, 1997) with scaling algorithm from Fox & Holmes (1966)]	2082 reflections with I > 2σ(I)
T_min = 0.659, T_max = 0.772	R_int = 0.018
4056 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.026	0 restraints
wR(F²) = 0.064	All H-atom parameters refined
S = 1.08	Δρ_max = 0.42 e Å⁻³
2384 reflections	Δρ_min = −0.48 e Å⁻³
154 parameters

Special details top

Experimental. The program DENZO-SMN (Otwinowski & Minor, 1997) uses a scaling algorithm (Fox & Holmes, 1966) which effectively corrects for absorption effects. High redundancy data were used in the scaling program hence the 'multi-scan' code word was used. No transmission coefficients are available from the program (only scale factors for each frame). The scale factors in the experimental table are calculated from the 'size' command in the SHELXL97 input file.

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 (Å²) top

	x	y	z	U_iso*/U_eq
Cr1	0.30848 (4)	0.251150 (16)	0.79201 (3)	0.01432 (10)
Cl1	0.09238 (6)	0.18418 (3)	0.61278 (4)	0.01959 (12)
Cl2	0.52336 (6)	0.31399 (3)	0.97636 (4)	0.01856 (12)
Cl3	0.55581 (5)	0.14110 (3)	0.79810 (4)	0.01695 (12)
N1	0.7020 (2)	0.05812 (10)	0.24223 (15)	0.0209 (3)
N2	0.4931 (2)	0.14965 (9)	0.30051 (15)	0.0191 (3)
C1	0.5869 (3)	0.11968 (12)	0.19414 (18)	0.0198 (4)
C2	0.6805 (3)	0.04791 (13)	0.3837 (2)	0.0301 (4)
C3	0.5517 (3)	0.10515 (13)	0.4202 (2)	0.0281 (4)
C4	0.3515 (3)	0.21791 (13)	0.2924 (2)	0.0243 (4)
C5	0.8379 (3)	0.01037 (13)	0.1611 (2)	0.0269 (4)
C6	1.0520 (3)	0.01492 (15)	0.2275 (3)	0.0339 (5)
H1	0.574 (3)	0.1415 (13)	0.104 (2)	0.022 (5)*
H2	0.748 (4)	0.0075 (16)	0.435 (3)	0.043 (7)*
H3	0.508 (4)	0.1180 (16)	0.506 (3)	0.044 (7)*
H4A	0.350 (5)	0.2419 (19)	0.206 (4)	0.071 (10)*
H4B	0.236 (5)	0.1996 (19)	0.309 (3)	0.068 (9)*
H4C	0.384 (4)	0.2545 (18)	0.356 (3)	0.059 (9)*
H5A	0.829 (4)	0.0344 (15)	0.067 (3)	0.042 (7)*
H5B	0.787 (4)	−0.0452 (16)	0.156 (2)	0.040 (6)*
H6A	1.142 (4)	−0.0168 (17)	0.176 (3)	0.047 (7)*
H6B	1.061 (3)	−0.0057 (16)	0.319 (3)	0.040 (7)*
H6C	1.099 (4)	0.0705 (19)	0.240 (3)	0.059 (8)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cr1	0.01154 (15)	0.01684 (18)	0.01412 (15)	0.00097 (10)	−0.00098 (10)	−0.00138 (10)
Cl1	0.0171 (2)	0.0254 (3)	0.0157 (2)	−0.00134 (16)	−0.00144 (15)	−0.00269 (16)
Cl2	0.0179 (2)	0.0211 (2)	0.0160 (2)	−0.00030 (15)	−0.00131 (15)	−0.00306 (16)
Cl3	0.0136 (2)	0.0164 (2)	0.0207 (2)	−0.00014 (14)	0.00140 (15)	−0.00127 (15)
N1	0.0225 (7)	0.0204 (8)	0.0203 (7)	−0.0013 (6)	0.0042 (6)	0.0004 (6)
N2	0.0186 (7)	0.0226 (8)	0.0161 (7)	−0.0017 (6)	0.0011 (5)	−0.0013 (6)
C1	0.0210 (8)	0.0225 (9)	0.0161 (8)	−0.0027 (7)	0.0021 (7)	−0.0006 (7)
C2	0.0343 (10)	0.0329 (12)	0.0234 (9)	0.0053 (9)	0.0043 (8)	0.0090 (9)
C3	0.0303 (10)	0.0373 (12)	0.0172 (9)	0.0022 (9)	0.0043 (7)	0.0039 (8)
C4	0.0195 (9)	0.0278 (11)	0.0256 (10)	0.0013 (8)	0.0027 (7)	−0.0044 (9)
C5	0.0284 (10)	0.0215 (10)	0.0321 (10)	−0.0001 (8)	0.0087 (8)	−0.0030 (8)
C6	0.0277 (11)	0.0314 (13)	0.0434 (13)	0.0049 (9)	0.0072 (9)	0.0024 (10)

Geometric parameters (Å, º) top

Cr1—Cl2	2.3876 (5)	C2—H2	0.91 (3)
Cr1—Cl1	2.3898 (5)	C3—H3	0.91 (3)
Cr1—Cl3	2.4431 (5)	C4—H4A	0.91 (3)
Cr1—Cl3ⁱ	2.4476 (5)	C4—H4B	0.86 (3)
N1—C1	1.323 (2)	C4—H4C	0.86 (3)
N1—C2	1.380 (2)	C5—C6	1.503 (3)
N1—C5	1.473 (2)	C5—H5A	0.97 (2)
N2—C1	1.336 (2)	C5—H5B	0.97 (3)
N2—C3	1.378 (2)	C6—H6A	0.96 (3)
N2—C4	1.463 (3)	C6—H6B	0.93 (3)
C1—H1	0.93 (2)	C6—H6C	0.97 (3)
C2—C3	1.342 (3)

Cl2—Cr1—Cl1	177.976 (19)	C2—C3—H3	131.2 (17)
Cl2—Cr1—Cl3	87.073 (15)	N2—C3—H3	121.7 (17)
Cl1—Cr1—Cl3	91.904 (16)	N2—C4—H4A	109 (2)
Cl2—Cr1—Cl3ⁱ	91.906 (16)	N2—C4—H4B	108 (2)
Cl1—Cr1—Cl3ⁱ	89.027 (15)	H4A—C4—H4B	113 (3)
Cl3—Cr1—Cl3ⁱ	176.95 (2)	N2—C4—H4C	112 (2)
Cr1—Cl3—Cr1ⁱⁱ	85.856 (13)	H4A—C4—H4C	108 (3)
C1—N1—C2	108.55 (16)	H4B—C4—H4C	106 (3)
C1—N1—C5	126.20 (16)	N1—C5—C6	111.08 (17)
C2—N1—C5	125.20 (17)	N1—C5—H5A	106.3 (14)
C1—N2—C3	108.45 (16)	C6—C5—H5A	109.7 (14)
C1—N2—C4	126.18 (16)	N1—C5—H5B	107.4 (14)
C3—N2—C4	125.37 (15)	C6—C5—H5B	112.2 (14)
N1—C1—N2	108.52 (15)	H5A—C5—H5B	110 (2)
N1—C1—H1	127.8 (13)	C5—C6—H6A	111.9 (15)
N2—C1—H1	123.6 (13)	C5—C6—H6B	110.2 (15)
C3—C2—N1	107.38 (18)	H6A—C6—H6B	107 (2)
C3—C2—H2	131.7 (16)	C5—C6—H6C	112.4 (17)
N1—C2—H2	121.0 (16)	H6A—C6—H6C	111 (2)
C2—C3—N2	107.08 (16)	H6B—C6—H6C	104 (2)

Cl2—Cr1—Cl3—Cr1ⁱⁱ	−48.298 (16)	C5—N1—C2—C3	176.88 (18)
Cl1—Cr1—Cl3—Cr1ⁱⁱ	133.450 (13)	N1—C2—C3—N2	0.6 (2)
C2—N1—C1—N2	0.4 (2)	C1—N2—C3—C2	−0.4 (2)
C5—N1—C1—N2	−177.10 (16)	C4—N2—C3—C2	179.39 (18)
C3—N2—C1—N1	0.0 (2)	C1—N1—C5—C6	121.0 (2)
C4—N2—C1—N1	−179.80 (17)	C2—N1—C5—C6	−56.1 (3)
C1—N1—C2—C3	−0.7 (2)

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

Experimental details

Crystal data
Chemical formula	(C₆H₁₁N₂)[CrCl₃]
M_r	269.52
Crystal system, space group	Monoclinic, P2₁/a
Temperature (K)	150
a, b, c (Å)	6.6615 (1), 16.4317 (4), 9.5258 (2)
β (°)	95.6881 (14)
V (Å³)	1037.56 (4)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	1.82
Crystal size (mm)	0.25 × 0.20 × 0.15

Data collection
Diffractometer	Nonius KappaCCD diffractometer
Absorption correction	Multi-scan [DENZO-SMN (Otwinowski & Minor, 1997) with scaling algorithm from Fox & Holmes (1966)]
T_min, T_max	0.659, 0.772
No. of measured, independent and observed [I > 2σ(I)] reflections	4056, 2384, 2082
R_int	0.018
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.026, 0.064, 1.08
No. of reflections	2384
No. of parameters	154
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.42, −0.48

Computer programs: COLLECT (Nonius, 1999), DENZO-SMN (Otwinowski & Minor, 1997), SIR97 (Altomare et al., 1999), SHELXL97 (Sheldrick, 2008), WinGX (Farrugia, 1999), CrystalMaker (Palmer, 2005).

Selected geometric parameters (Å, º) top

Cr1—Cl2	2.3876 (5)	Cr1—Cl3	2.4431 (5)
Cr1—Cl1	2.3898 (5)	Cr1—Cl3ⁱ	2.4476 (5)

Cl2—Cr1—Cl1	177.976 (19)	Cl1—Cr1—Cl3ⁱ	89.027 (15)
Cl2—Cr1—Cl3	87.073 (15)	Cl3—Cr1—Cl3ⁱ	176.95 (2)
Cl1—Cr1—Cl3	91.904 (16)	Cr1—Cl3—Cr1ⁱⁱ	85.856 (13)
Cl2—Cr1—Cl3ⁱ	91.906 (16)

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

Acknowledgements

The authors thank Utah State University for funding and Hayden Griffiths for experimental assistance.

References

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