2-Bromo-1,3-diisopropyl-4,5-dimethyl-1H-imidazol-3-ium dicyanidoargentate

The title structure, (C₁₁H₂₀BrN₂)[Ag(CN)₂)], is built up from an approximately C_2v-symmetric imidazolium cation and a nearly linear dicyanidoargentate anion [N—Ag—N = 176.6 (9)° and Ag—C—N = 178.8 (9) and 177.2 (11)°]. These two constituents are linked by a remarkably short inter­action between the Br atom of the imidazolium cation [C—Br = 1.85 (3) Å] and one N atom of the cyanidoargentate anion [Br...N = 2.96 (2) Å], which is much less than the sum of the van der Waals radii (3.40 Å). The crystal studied was twinned by merohedry.

Key indicators

• Single-crystal X-ray study
• T = 291 K
• Mean [sigma](C-C) = 0.012 Å
• R factor = 0.052
• wR factor = 0.082
• Data-to-parameter ratio = 19.3

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT431_ALERT_2_B Short Inter HL..A Contact  Br1    ..  N12     ..       2.96 Ang.

Alert level C
STRVA01_ALERT_4_C           Flack test results are ambiguous.
           From the CIF: _refine_ls_abs_structure_Flack    0.474
           From the CIF: _refine_ls_abs_structure_Flack_su    0.017
PLAT033_ALERT_4_C Flack x Parameter Value Deviates from Zero .....      0.474
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for        C51
PLAT342_ALERT_3_C Low Bond Precision on  C-C Bonds ...............     0.0116 Ang
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          3
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600          2

Alert level G
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           26.37
           From the CIF: _reflns_number_total               3475
           Count of symmetry unique reflns         2028
           Completeness (_total/calc)            171.35%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured      1447
           Fraction of Friedel pairs measured     0.714
           Are heavy atom types Z>Si present        yes
PLAT005_ALERT_5_G No _iucr_refine_instructions_details in CIF ....          ?
PLAT710_ALERT_4_G Delete 1-2-3 or 2-3-4 Linear Torsion Angle ... #         21
            C12 -AG1 -C11 -N11    10.00  0.00   1.555   1.555   1.555   1.555
PLAT710_ALERT_4_G Delete 1-2-3 or 2-3-4 Linear Torsion Angle ... #         22
            C11 -AG1 -C12 -N12    -5.00 30.00   1.555   1.555   1.555   1.555

   0 ALERT level A = Most likely a serious problem - resolve or explain
   1 ALERT level B = A potentially serious problem, consider carefully
   6 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   4 ALERT level G = General information/check it is not something unexpected

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   2 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   5 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

N-heterocyclic carbenes can form stable coordination compounds with main group elements by using their strongly basic character. Kuhn et al. (2004) showed that weak interionic halogen contacts between 2-haloimidazolium cations and halogen containing counter anions do exist in the solid state. Results of related investigations were reported by Kuhn et al. (2009), Mallah et al. (2009), and Potocenak & Chomic (2006). The reaction of 2-bromo-1,3-diisopropyl-4,5-dimethylimidazolium bromide with silver cyanide gives the title compound as stable crystalline solid in a good yield. The structure contains an approximately C_2v imidazolium cation (Fig. 1), similar to the crystal structure of the 2-chloroimidazolium analogue (Mallah et al., 2011), where the C—Cl bond (1.677 (5) Å) is shorter than the C—Br bond of the title compound (1.848 (6) Å). The title structure contains a cation-anion pair (Fig. 1) with a short N(12)(x-1,y,z)···Br(1) interaction of 2.96 (2) Å, by ca. 0.4 Å shorther than the sum of the van der Waals radii. Mascal et al. (1996) found for a s-triazine–dibromine cocrystal a N···Br contact distance as short as 2.515 Å.

Related literature

For similar structures, see: Mallah et al. (2009, 2011); Kuhn et al. (2009); Potocenak & Chomic (2006); Mascal et al. (1996). For the synthesis of the starting material, see: Kuhn et al. (2004).

S2. Experimental

The title compound was prepared by addition of silver cyanide (1.3 g, 9.7 mmol) to a solution of 2-bromo-1,3-diisopropyl-4,5-dimethylimidazoliumbromide, see: Kuhn et al. (2004), (1.1 g, 3.2 mmol) in 30 ml of acetonitrile. The mixture was stirred for 48 hr at room temperature, then the solvent was removed in vacuo and 20 ml of dichloromethane was added. The resulting solution was filtered off and solvent was removed in vacuo. Yield after recrystallisation from dichloromethane/diethyl ether 0.98 g (73 %), as colorless crystals.

S3. Refinement

There are no Friedel pairs because only the minimal data set was measured with the CAD4 instrument (±h, +k, +l). Hydrogen atoms were included at calculated positions with C—H = 0.95–1.00 Å and 1.5U_eq(aliphatic C), using a riding-model approximation.

Computing details

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CELDIM (Enraf–Nonius, 1989); data reduction: HELENA/PLATON (Spek, 2009),; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

Fig. 1. The molecular structure the cation-anion pair of the title compound showing 20% probability displacement ellipsoids for non-H atoms. The symmetry transformation for the depicted dicyanoargentate anion is x-1, y, z.

2-Bromo-1,3-diisopropyl-4,5-dimethyl-1H-imidazol-3-ium dicyanidoargentate

Crystal data

(C11H20BrN2)[Ag(CN)2)]	F(000) = 832
Mr = 420.11	Dx = 1.635 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 25 reflections
a = 6.6986 (15) Å	θ = 6.7–13.0°
b = 10.6222 (14) Å	µ = 3.52 mm^−1
c = 23.989 (4) Å	T = 291 K
V = 1706.9 (5) Å^3	Block, colourless
Z = 4	0.40 × 0.20 × 0.20 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	1781 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.052
Graphite monochromator	θmax = 26.4°, θmin = 3.2°
ω scans	h = −8→8
Absorption correction: part of the refinement model (ΔF) (DIFABS; Walker & Stuart, 1983)	k = −1→13
Tmin = 0.40, Tmax = 1.00	l = −1→29
4327 measured reflections	3 standard reflections every 300 reflections
3475 independent reflections	intensity decay: 1.5%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.052	H-atom parameters constrained
wR(F^2) = 0.082	w = 1/[σ^2(Fo^2) + (0.0199P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 0.98	(Δ/σ)max = 0.001
3475 reflections	Δρmax = 0.33 e Å^−3
180 parameters	Δρmin = −0.46 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.00128 (16)

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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
Ag1	0.71941 (9)	0.98742 (7)	0.12744 (3)	0.0718 (2)
C1	0.6144 (9)	0.5300 (5)	0.1252 (3)	0.0411 (16)
N2	0.7155 (9)	0.5116 (6)	0.0780 (2)	0.0417 (16)
C3	0.8807 (12)	0.4401 (6)	0.0898 (3)	0.045 (2)
C4	0.8812 (11)	0.4187 (7)	0.1450 (3)	0.048 (2)
N5	0.7109 (9)	0.4757 (6)	0.1669 (2)	0.0470 (16)
C11	0.5572 (13)	1.1454 (10)	0.1123 (4)	0.072 (3)
C12	0.8919 (14)	0.8303 (9)	0.1400 (4)	0.073 (3)
C21	0.6467 (13)	0.5572 (8)	0.0225 (3)	0.059 (2)
H21	0.5233	0.6041	0.0296	0.071*
C22	0.7867 (15)	0.6484 (9)	−0.0028 (3)	0.092 (3)
H22A	0.8289	0.7079	0.0249	0.138*
H22B	0.7212	0.6921	−0.0327	0.138*
H22C	0.9010	0.6044	−0.0171	0.138*
C23	0.5874 (13)	0.4462 (9)	−0.0143 (3)	0.087 (3)
H23A	0.7051	0.4020	−0.0260	0.131*
H23B	0.5170	0.4766	−0.0465	0.131*
H23C	0.5027	0.3902	0.0063	0.131*
C31	1.0326 (11)	0.3991 (9)	0.0475 (3)	0.076 (3)
H31A	1.1349	0.3508	0.0656	0.115*
H31B	1.0910	0.4719	0.0303	0.115*
H31C	0.9689	0.3484	0.0196	0.115*
C41	1.0252 (11)	0.3428 (9)	0.1781 (3)	0.085 (3)
H41A	1.1237	0.3072	0.1537	0.128*
H41B	0.9553	0.2763	0.1969	0.128*
H41C	1.0896	0.3957	0.2051	0.128*
C51	0.6523 (12)	0.4807 (8)	0.2263 (3)	0.056 (2)
H51	0.5282	0.5296	0.2266	0.067*
C52	0.5934 (14)	0.3535 (9)	0.2481 (3)	0.089 (3)
H52A	0.5176	0.3096	0.2202	0.133*
H52B	0.5138	0.3635	0.2811	0.133*
H52C	0.7112	0.3060	0.2569	0.133*
C53	0.7912 (14)	0.5544 (8)	0.2608 (3)	0.086 (3)
H53A	0.9073	0.5047	0.2688	0.129*
H53B	0.7267	0.5776	0.2950	0.129*
H53C	0.8301	0.6290	0.2410	0.129*
N11	0.4683 (10)	1.2343 (8)	0.1047 (3)	0.076 (2)
N12	0.9891 (11)	0.7474 (8)	0.1450 (4)	0.090 (3)
Br1	0.37724 (11)	0.61731 (7)	0.13261 (3)	0.0596 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ag1	0.0664 (4)	0.0772 (5)	0.0718 (4)	0.0139 (4)	0.0084 (4)	0.0021 (5)
C1	0.040 (4)	0.032 (4)	0.051 (4)	−0.001 (3)	0.002 (5)	−0.007 (5)
N2	0.040 (3)	0.053 (4)	0.033 (3)	0.010 (4)	−0.003 (3)	−0.001 (4)
C3	0.050 (5)	0.043 (5)	0.042 (5)	0.008 (4)	−0.005 (4)	−0.004 (4)
C4	0.037 (4)	0.052 (5)	0.054 (5)	0.003 (4)	−0.007 (4)	0.010 (4)
N5	0.046 (3)	0.053 (4)	0.042 (3)	0.003 (4)	−0.001 (3)	0.009 (4)
C11	0.070 (7)	0.077 (8)	0.069 (7)	0.017 (5)	0.009 (5)	−0.001 (6)
C12	0.077 (6)	0.069 (7)	0.072 (7)	−0.005 (5)	0.015 (6)	−0.009 (6)
C21	0.057 (5)	0.070 (6)	0.050 (5)	0.016 (5)	−0.005 (4)	0.010 (5)
C22	0.106 (8)	0.100 (9)	0.070 (6)	−0.029 (7)	−0.004 (6)	0.030 (6)
C23	0.081 (6)	0.108 (9)	0.073 (6)	0.010 (6)	−0.026 (6)	−0.013 (6)
C31	0.061 (5)	0.104 (8)	0.063 (5)	0.024 (6)	0.003 (4)	−0.011 (6)
C41	0.072 (6)	0.112 (9)	0.072 (6)	0.031 (6)	−0.012 (5)	0.023 (6)
C51	0.063 (6)	0.062 (6)	0.042 (4)	0.007 (6)	0.003 (4)	0.006 (5)
C52	0.104 (8)	0.100 (9)	0.061 (6)	−0.016 (7)	0.022 (6)	0.010 (6)
C53	0.112 (8)	0.094 (8)	0.052 (5)	−0.028 (7)	−0.008 (5)	−0.013 (5)
N11	0.069 (5)	0.079 (6)	0.079 (5)	0.009 (5)	0.001 (4)	−0.006 (5)
N12	0.082 (6)	0.071 (6)	0.117 (8)	0.005 (5)	0.002 (5)	−0.001 (6)
Br1	0.0552 (5)	0.0610 (5)	0.0624 (5)	0.0161 (4)	0.0033 (5)	−0.0025 (6)

Geometric parameters (Å, º)

Ag1—C11	2.032 (10)	C22—H22C	0.9600
Ag1—C12	2.053 (10)	C23—H23A	0.9600
C1—N5	1.325 (7)	C23—H23B	0.9600
C1—N2	1.332 (7)	C23—H23C	0.9600
C1—Br1	1.848 (6)	C31—H31A	0.9600
N2—C3	1.371 (8)	C31—H31B	0.9600
N2—C21	1.490 (8)	C31—H31C	0.9600
C3—C4	1.344 (8)	C41—H41A	0.9600
C3—C31	1.501 (10)	C41—H41B	0.9600
C4—N5	1.394 (8)	C41—H41C	0.9600
C4—C41	1.486 (9)	C51—C53	1.471 (11)
N5—C51	1.478 (8)	C51—C52	1.502 (11)
C11—N11	1.131 (10)	C51—H51	0.9800
C12—N12	1.102 (10)	C52—H52A	0.9600
C21—C22	1.479 (10)	C52—H52B	0.9600
C21—C23	1.526 (10)	C52—H52C	0.9600
C21—H21	0.9800	C53—H53A	0.9600
C22—H22A	0.9600	C53—H53B	0.9600
C22—H22B	0.9600	C53—H53C	0.9600
C11—Ag1—C12	177.5 (4)	C21—C23—H23C	109.5
N5—C1—N2	109.2 (5)	H23A—C23—H23C	109.5
N5—C1—Br1	124.4 (6)	H23B—C23—H23C	109.5
N2—C1—Br1	126.4 (6)	C3—C31—H31A	109.5
C1—N2—C3	108.5 (5)	C3—C31—H31B	109.5
C1—N2—C21	123.6 (6)	H31A—C31—H31B	109.5
C3—N2—C21	127.9 (6)	C3—C31—H31C	109.5
C4—C3—N2	107.4 (7)	H31A—C31—H31C	109.5
C4—C3—C31	127.9 (8)	H31B—C31—H31C	109.5
N2—C3—C31	124.6 (6)	C4—C41—H41A	109.5
C3—C4—N5	107.2 (7)	C4—C41—H41B	109.5
C3—C4—C41	128.3 (8)	H41A—C41—H41B	109.5
N5—C4—C41	124.4 (6)	C4—C41—H41C	109.5
C1—N5—C4	107.7 (5)	H41A—C41—H41C	109.5
C1—N5—C51	125.7 (6)	H41B—C41—H41C	109.5
C4—N5—C51	126.6 (6)	C53—C51—N5	113.2 (7)
N11—C11—Ag1	178.8 (9)	C53—C51—C52	116.7 (7)
N12—C12—Ag1	177.2 (11)	N5—C51—C52	111.9 (7)
C22—C21—N2	112.6 (7)	C53—C51—H51	104.5
C22—C21—C23	115.7 (7)	N5—C51—H51	104.5
N2—C21—C23	110.3 (6)	C52—C51—H51	104.5
C22—C21—H21	105.8	C51—C52—H52A	109.5
N2—C21—H21	105.8	C51—C52—H52B	109.5
C23—C21—H21	105.8	H52A—C52—H52B	109.5
C21—C22—H22A	109.5	C51—C52—H52C	109.5
C21—C22—H22B	109.5	H52A—C52—H52C	109.5
H22A—C22—H22B	109.5	H52B—C52—H52C	109.5
C21—C22—H22C	109.5	C51—C53—H53A	109.5
H22A—C22—H22C	109.5	C51—C53—H53B	109.5
H22B—C22—H22C	109.5	H53A—C53—H53B	109.5
C21—C23—H23A	109.5	C51—C53—H53C	109.5
C21—C23—H23B	109.5	H53A—C53—H53C	109.5
H23A—C23—H23B	109.5	H53B—C53—H53C	109.5
N5—C1—N2—C3	1.5 (7)	Br1—C1—N5—C51	−3.3 (10)
Br1—C1—N2—C3	−178.6 (5)	C3—C4—N5—C1	−0.5 (8)
N5—C1—N2—C21	178.3 (6)	C41—C4—N5—C1	−177.2 (7)
Br1—C1—N2—C21	−1.8 (9)	C3—C4—N5—C51	−177.7 (7)
C1—N2—C3—C4	−1.8 (8)	C41—C4—N5—C51	5.7 (12)
C21—N2—C3—C4	−178.5 (7)	C12—Ag1—C11—N11	−100 (52)
C1—N2—C3—C31	180.0 (7)	C11—Ag1—C12—N12	−5 (30)
C21—N2—C3—C31	3.3 (12)	C1—N2—C21—C22	118.1 (8)
N2—C3—C4—N5	1.4 (8)	C3—N2—C21—C22	−65.7 (10)
C31—C3—C4—N5	179.5 (7)	C1—N2—C21—C23	−111.1 (8)
N2—C3—C4—C41	177.9 (7)	C3—N2—C21—C23	65.2 (10)
C31—C3—C4—C41	−4.0 (14)	C1—N5—C51—C53	−111.4 (8)
N2—C1—N5—C4	−0.6 (8)	C4—N5—C51—C53	65.2 (11)
Br1—C1—N5—C4	179.5 (5)	C1—N5—C51—C52	114.3 (9)
N2—C1—N5—C51	176.6 (7)	C4—N5—C51—C52	−69.0 (10)