Poly[3,3′-diethyl-1,1′-(ethane-1,2-di­yl)diimidazolium [tetra-μ-bromido-­diargentate(I)]]

Wang, Z.; Liu, S.; Zhang, N.

doi:10.1107/S160053681002146X

metal-organic compounds

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ISSN: 2056-9890

Volume 66| Part 7| July 2010| Page m845

doi:10.1107/S160053681002146X

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Poly[3,3′-diethyl-1,1′-(ethane-1,2-diyl)diimidazolium [tetra-μ-bromido-diargentate(I)]]

Zhiguo Wang,^a ^* Siman Liu ^a and Na Zhang ^a

^aDepartment of Chemistry and Chemical Engineering, Mianyang Normal University, Mianyang 621000, People's Republic of China
^*Correspondence e-mail: wangzhiguo224865@163.com

(Received 20 May 2010; accepted 4 June 2010; online 26 June 2010)

The asymmetric unit of the title salt, {(C₁₂H₂₀N₄)[Ag₂Br₄]}_n, contains one-half of a substituted imidazolium cation, one Ag⁺ and two Br⁻ ions. The cation is completed by crystallographic inversion symmetry. The crystal structure is made up from polymeric sheets of {[AgBr₂]⁻}_n anions extending parallel to (100). The basic building unit of the anion is a slightly distorted AgBr₄ tetrahedron. A four- and 12-membered ring system is formed by corner sharing of the AgBr₄ tetrahedra. The imidazolium cations are located between the anionic sheets and partly protrude into the voids defined by the 12-membered rings.

Related literature

For general background to N-heterocyclic carbenes, see: Arnold (2002 ); Lin & Vasam (2004 ). For related structures, see: Lee et al. (2002 ); Helgesson & Jagner (1990 , 1991 ); Olson et al. (1994 ).

Experimental

Crystal data

(C₁₂H₂₀N₄)[Ag₂Br₄]
M_r = 755.90
Monoclinic, P 2₁ /c
a = 9.5593 (13) Å
b = 12.9512 (17) Å
c = 8.4565 (11) Å
β = 106.294 (2)°
V = 1004.9 (2) Å³
Z = 2
Mo Kα radiation
μ = 9.90 mm⁻¹
T = 296 K
0.25 × 0.24 × 0.22 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2006 ) T_min = 0.191, T_max = 0.219
5036 measured reflections
1766 independent reflections
1533 reflections with I > 2σ(I)
R_int = 0.023

Refinement

R[F² > 2σ(F²)] = 0.031
wR(F²) = 0.077
S = 1.06
1766 reflections
101 parameters
H-atom parameters constrained
Δρ_max = 0.64 e Å⁻³
Δρ_min = −0.88 e Å⁻³

Table 1
Selected geometric parameters (Å, °)

Ag1—Br1	2.6788 (7)
Ag1—Br2ⁱ	2.6934 (8)
Ag1—Br1ⁱⁱ	2.6999 (7)
Ag1—Br2	2.7227 (8)

Br1—Ag1—Br2ⁱ	114.34 (3)
Br1—Ag1—Br1ⁱⁱ	103.92 (2)
Br2ⁱ—Ag1—Br1ⁱⁱ	116.12 (3)
Br1—Ag1—Br2	119.16 (3)
Br2ⁱ—Ag1—Br2	95.81 (2)
Br1ⁱⁱ—Ag1—Br2	107.93 (2)
Symmetry codes: (i) -x, -y+1, -z+2; (ii) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ .

Data collection: SMART (Bruker, 2006 ); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Crystal Impact, 2008 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053681002146X/wm2354sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S160053681002146X/wm2354Isup2.hkl

checkCIF report

Comment top

Silver and other transition metal N-heterocyclic carbene complexes have played an important role in the development of metal-carbene systems for transmetalation reactions. Silver oxide is the most commonly used metal base for this purposes. Recent reviews dealing with silver N-heterocyclic carbenes were published by Arnold (2002) and Lin & Vasam (2004). The products differ depending upon reaction conditions and the imidazolium salt used. The silver carbene [Ag₂(Me₂-edimy)Cl₂] has been successfully synthesized by the reaction of [Me₂-edimyH₂][PF₆]₂ with Ag₂O in CH₃CN and [NM₄]Cl (Lee et al., 2002). In an attempt to prepare a similar carbene, we obtained the title compound, [(C₁₂H₂₀N₄)]²⁺[Ag₂Br₄]^2-, instead. Synthesis and crystal structure are reported in this article.

The crystal structure of the title salt is composed of [(C₁₂H₂₀N₄)]²⁺ cations and [Ag₂Br₄]^2- anions (Fig. 1). The anion forms polymeric sheets extending parallel to (100). The cations are located between the sheets and partly reach through the voids of the anion. A characteristic feature of the polymeric {[Ag₂Br₄]^2-}_n anion is the construction of rings built up from corner-sharing of slightly distorted AgBr₄ tetrahedra. A large twelve-membered ring is formed by six alternating bromine and six silver atoms; another four-membered ring completes the building units of the polymeric anion (Fig. 2). The four-membered ring is very similar to that in the complex anion [Ag₄Br₈]^4- (Helgesson & Jagner, 1991). These anions contain tetrahedrally coordinated Ag⁺ atoms, whereas the [Ag₄I₈]^4- ion, isolated as the tetraphenylphosphonium and tetraphenylarsonium salts, contains three-coordinated and four-coordinated Ag⁺ (Helgesson & Jagner, 1990).

The average Ag—Br distance of the AgBr₄ tetrahedron in the title compound is 2.699 Å, which is considerably longer than for the [Ag₂Br₄]^2- dimer ((2.518 (2) Å; Helgesson et al., 1990). These values are comparable to other tetrahedral AgBr₄ units (Olson et al., 1994).

Related literature top

For general background to N-heterocyclic carbenes, see: Arnold (2002); Lin & Vasam (2004). For related structures, see: Lee et al. (2002); Helgesson & Jagner (1990, 1991); Olson et al. (1994).

Experimental top

Ag₂O (2.32 g, 10 mmol) was added to a solution of 1H-imidazolium, 1,1'-(1,2-ethanediyl)bis[3-ethyl] dibromide (3.78 g, 10 mmol) in DMSO. This mixture was refluxed for 30 min under stirring, resulting in a clean solution. When the solvent was removed, the residue was exatracted with acetonitrile. The remaining residue was separated by centrifugation and the resulting solution was kept at room temperature. Colourless crystals of the title compound were obtained after slow evaporation (2.64 g, 34.9 % yield). Mp: 421 K. ¹H NMR (CDCl₃): 9.48(m,1H), 9.43 (m.1H), 6.84 (s, 2H, CH), 6.87 (s, 2H, CH), 4.52 (s, 4H, CH2), 3.64(s, 4H, CH3),1.42(m, 6H) ppm. Anal. calcd.: C, 19.05 H, 2.65; N, 7.41; found: C, 19.26; H, 2.57 ; N, 7.32%.

Computing details top

Data collection: SMART (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT (Bruker, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Crystal Impact, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. The [(C₁₂H₂₀N₄)]²⁺ cation and the basic AgBr₄ building unit of the polymeric anion. Displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. The four- and twelve-membered ring system of the polymeric {[Ag₂Br₄]^2-}_n anion.

Poly[3,3'-diethyl-1,1'-(ethane-1,2-diyl)diimidazolium [tetra-µ-bromido-diargentate(I)]] top

Crystal data top

(C₁₂H₂₀N₄)[Ag₂Br₄]	F(000) = 708
M_r = 755.90	D_x = 2.498 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3112 reflections
a = 9.5593 (13) Å	θ = 2.2–27.8°
b = 12.9512 (17) Å	µ = 9.90 mm⁻¹
c = 8.4565 (11) Å	T = 296 K
β = 106.294 (2)°	Block, colourless
V = 1004.9 (2) Å³	0.25 × 0.24 × 0.22 mm
Z = 2

Data collection top

Bruker SMART CCD area-detector diffractometer	1766 independent reflections
Radiation source: fine-focus sealed tube	1533 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.023
phi and ω scans	θ_max = 25.0°, θ_min = 2.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 2006)	h = −11→11
T_min = 0.191, T_max = 0.219	k = −15→14
5036 measured reflections	l = −10→5

Refinement top

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)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.077	H-atom parameters constrained
S = 1.06	w = 1/[σ²(F_o²) + (0.0366P)² + 1.7373P] where P = (F_o² + 2F_c²)/3
1766 reflections	(Δ/σ)_max = 0.001
101 parameters	Δρ_max = 0.64 e Å⁻³
0 restraints	Δρ_min = −0.88 e Å⁻³

Crystal data top

(C₁₂H₂₀N₄)[Ag₂Br₄]	V = 1004.9 (2) Å³
M_r = 755.90	Z = 2
Monoclinic, P2₁/c	Mo Kα radiation
a = 9.5593 (13) Å	µ = 9.90 mm⁻¹
b = 12.9512 (17) Å	T = 296 K
c = 8.4565 (11) Å	0.25 × 0.24 × 0.22 mm
β = 106.294 (2)°

Data collection top

Bruker SMART CCD area-detector diffractometer	1766 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2006)	1533 reflections with I > 2σ(I)
T_min = 0.191, T_max = 0.219	R_int = 0.023
5036 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.031	0 restraints
wR(F²) = 0.077	H-atom parameters constrained
S = 1.06	Δρ_max = 0.64 e Å⁻³
1766 reflections	Δρ_min = −0.88 e Å⁻³
101 parameters

Special details top

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 > 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
Ag1	0.06806 (5)	0.63160 (3)	1.01898 (5)	0.05733 (16)
N1	0.8101 (4)	0.5496 (3)	0.4321 (5)	0.0424 (9)
N2	0.6179 (5)	0.6042 (4)	0.2519 (6)	0.0575 (12)
Br1	0.13558 (8)	0.75994 (4)	0.80302 (6)	0.0632 (2)
Br2	0.20441 (6)	0.44528 (4)	1.08097 (7)	0.05774 (18)
C1	0.6983 (6)	0.4833 (5)	0.4277 (8)	0.0646 (16)
H1	0.7040	0.4239	0.4911	0.078*
C2	0.5809 (6)	0.5178 (5)	0.3180 (8)	0.0650 (16)
H2	0.4889	0.4877	0.2912	0.078*
C3	0.7579 (6)	0.6221 (5)	0.3208 (7)	0.0584 (14)
H3	0.8110	0.6766	0.2952	0.070*
C4	0.5147 (8)	0.6630 (6)	0.1169 (10)	0.095 (3)
H4A	0.4988	0.6241	0.0153	0.114*
H4B	0.4219	0.6683	0.1417	0.114*
C5	0.5611 (12)	0.7605 (6)	0.0923 (13)	0.121 (4)
H5A	0.5711	0.8012	0.1898	0.182*
H5B	0.4911	0.7923	0.0012	0.182*
H5C	0.6535	0.7563	0.0688	0.182*
C6	0.9600 (5)	0.5390 (4)	0.5370 (6)	0.0432 (11)
H6A	0.9594	0.5169	0.6464	0.052*
H6B	1.0093	0.6052	0.5469	0.052*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ag1	0.0590 (3)	0.0526 (3)	0.0561 (3)	−0.0056 (2)	0.0091 (2)	0.00076 (18)
N1	0.031 (2)	0.048 (2)	0.045 (2)	−0.0008 (18)	0.0046 (17)	0.0031 (18)
N2	0.039 (3)	0.074 (3)	0.053 (3)	0.005 (2)	0.002 (2)	0.013 (2)
Br1	0.1030 (5)	0.0489 (3)	0.0362 (3)	−0.0160 (3)	0.0171 (3)	0.0008 (2)
Br2	0.0326 (3)	0.0547 (3)	0.0783 (4)	0.0051 (2)	0.0029 (2)	−0.0090 (3)
C1	0.039 (3)	0.058 (3)	0.088 (4)	−0.008 (3)	0.002 (3)	0.023 (3)
C2	0.035 (3)	0.068 (4)	0.083 (4)	−0.006 (3)	0.002 (3)	0.014 (3)
C3	0.045 (3)	0.068 (4)	0.061 (4)	−0.005 (3)	0.013 (3)	0.017 (3)
C4	0.064 (5)	0.106 (6)	0.096 (6)	0.003 (4)	−0.007 (4)	0.043 (5)
C5	0.135 (9)	0.067 (5)	0.125 (8)	0.012 (5)	−0.026 (6)	0.003 (5)
C6	0.035 (3)	0.051 (3)	0.040 (3)	−0.004 (2)	0.005 (2)	−0.008 (2)

Geometric parameters (Å, º) top

Ag1—Br1	2.6788 (7)	C2—H2	0.9300
Ag1—Br2ⁱ	2.6934 (8)	C3—H3	0.9300
Ag1—Br1ⁱⁱ	2.6999 (7)	C4—C5	1.374 (10)
Ag1—Br2	2.7227 (8)	C4—H4A	0.9700
N1—C3	1.324 (6)	C4—H4B	0.9700
N1—C1	1.363 (7)	C5—H5A	0.9600
N1—C6	1.466 (6)	C5—H5B	0.9600
N2—C3	1.321 (7)	C5—H5C	0.9600
N2—C2	1.341 (7)	C6—C6ⁱⁱⁱ	1.506 (9)
N2—C4	1.491 (8)	C6—H6A	0.9700
C1—C2	1.317 (8)	C6—H6B	0.9700
C1—H1	0.9300

Br1—Ag1—Br2ⁱ	114.34 (3)	N2—C3—H3	125.6
Br1—Ag1—Br1ⁱⁱ	103.92 (2)	N1—C3—H3	125.6
Br2ⁱ—Ag1—Br1ⁱⁱ	116.12 (3)	C5—C4—N2	114.4 (7)
Br1—Ag1—Br2	119.16 (3)	C5—C4—H4A	108.7
Br2ⁱ—Ag1—Br2	95.81 (2)	N2—C4—H4A	108.7
Br1ⁱⁱ—Ag1—Br2	107.93 (2)	C5—C4—H4B	108.7
C3—N1—C1	106.9 (4)	N2—C4—H4B	108.7
C3—N1—C6	127.3 (4)	H4A—C4—H4B	107.6
C1—N1—C6	125.7 (4)	C4—C5—H5A	109.5
C3—N2—C2	108.4 (5)	C4—C5—H5B	109.5
C3—N2—C4	128.2 (5)	H5A—C5—H5B	109.5
C2—N2—C4	123.4 (5)	C4—C5—H5C	109.5
Ag1—Br1—Ag1^iv	152.39 (4)	H5A—C5—H5C	109.5
Ag1ⁱ—Br2—Ag1	84.19 (2)	H5B—C5—H5C	109.5
C2—C1—N1	108.1 (5)	N1—C6—C6ⁱⁱⁱ	109.6 (5)
C2—C1—H1	125.9	N1—C6—H6A	109.8
N1—C1—H1	125.9	C6ⁱⁱⁱ—C6—H6A	109.8
C1—C2—N2	107.8 (5)	N1—C6—H6B	109.8
C1—C2—H2	126.1	C6ⁱⁱⁱ—C6—H6B	109.8
N2—C2—H2	126.1	H6A—C6—H6B	108.2
N2—C3—N1	108.8 (5)

Br2ⁱ—Ag1—Br1—Ag1^iv	4.51 (7)	C4—N2—C2—C1	177.1 (7)
Br1ⁱⁱ—Ag1—Br1—Ag1^iv	−123.08 (5)	C2—N2—C3—N1	−1.2 (7)
Br2—Ag1—Br1—Ag1^iv	116.83 (6)	C4—N2—C3—N1	−177.9 (7)
Br1—Ag1—Br2—Ag1ⁱ	−122.09 (3)	C1—N1—C3—N2	1.7 (7)
Br2ⁱ—Ag1—Br2—Ag1ⁱ	0.0	C6—N1—C3—N2	179.7 (5)
Br1ⁱⁱ—Ag1—Br2—Ag1ⁱ	119.87 (3)	C3—N2—C4—C5	−18.3 (12)
C3—N1—C1—C2	−1.5 (7)	C2—N2—C4—C5	165.6 (8)
C6—N1—C1—C2	−179.6 (5)	C3—N1—C6—C6ⁱⁱⁱ	−98.5 (7)
N1—C1—C2—N2	0.8 (8)	C1—N1—C6—C6ⁱⁱⁱ	79.1 (7)
C3—N2—C2—C1	0.2 (8)

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

Experimental details

Crystal data
Chemical formula	(C₁₂H₂₀N₄)[Ag₂Br₄]
M_r	755.90
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	296
a, b, c (Å)	9.5593 (13), 12.9512 (17), 8.4565 (11)
β (°)	106.294 (2)
V (Å³)	1004.9 (2)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	9.90
Crystal size (mm)	0.25 × 0.24 × 0.22

Data collection
Diffractometer	Bruker SMART CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 2006)
T_min, T_max	0.191, 0.219
No. of measured, independent and observed [I > 2σ(I)] reflections	5036, 1766, 1533
R_int	0.023
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.031, 0.077, 1.06
No. of reflections	1766
No. of parameters	101
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.64, −0.88

Computer programs: SMART (Bruker, 2006), SAINT (Bruker, 2006), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Crystal Impact, 2008).

Selected geometric parameters (Å, º) top

Ag1—Br1	2.6788 (7)	Ag1—Br1ⁱⁱ	2.6999 (7)
Ag1—Br2ⁱ	2.6934 (8)	Ag1—Br2	2.7227 (8)

Br1—Ag1—Br2ⁱ	114.34 (3)	Br1—Ag1—Br2	119.16 (3)
Br1—Ag1—Br1ⁱⁱ	103.92 (2)	Br2ⁱ—Ag1—Br2	95.81 (2)
Br2ⁱ—Ag1—Br1ⁱⁱ	116.12 (3)	Br1ⁱⁱ—Ag1—Br2	107.93 (2)

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

Acknowledgements

The authors thank the Sichuan Province Youth Foundation of Science and Technology (09 J J0088) for financial support.

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