supplementary materials


zs2262 scheme

Acta Cryst. (2013). E69, m411    [ doi:10.1107/S1600536813016875 ]

catena-Poly[di-[mu]3-bromido-bis[(1-ethyl-1H-imidazole-[kappa]N3)disilver(I)]]

Z. Wang, Q. Bian and Y. Guo

Abstract top

The asymmetric unit of the title coordination complex, [Ag2Br2(C5H8N2)2]n, comprises a monodentate 1-ethylimidazole ligand, an Ag+ cation and a [mu]3-bridging Br- anion, giving a distorted tetrahedral AgNBr3 stereochemistry about the Ag+ cation [Ag-N = 2.247 (2) Å and Ag-Br = 2.7372 (4)-2.7523 (4) Å]. Two bridging bromide anions generate the dimeric [Ag2Br2(C5H8N)2] repeat unit [Ag...Ag = 3.0028 (5) Å], while a third Br- anion links the units through corner sharing in an inversion-related Ag2Br2 association [Ag...Ag = 3.0407 (4) Å], generating a one-dimensional ribbon step-polymer structure, extending along the c axis.

Comment top

Silver and other transition metal N-heterocyclic carbene complexes have played an important role in development of metal-carbene systems for transmetalation reactions. 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. Deprotonation by use of Ag2O has been the most widely used method in the syntheses of N-heterocyclic carbene complexes of silver. The procedure can be accomplished using the reaction of Ag2O with the imidazolium salt in CH2Cl2 solution. The 3-diethylbenzole N-heterocyclic carbene complexes of silver have been successfully synthesized by the reaction of the 1,3-diethylbenzolium salt with Ag2O in CH2Cl2 (Wang & Lin, 1998). In an attempt to prepare similar N-heterocyclic carbene complexes of silver by the reaction of Ag2O with 1,2-dibromocyclohexane and 1-ethylimidazole in DMSO solution, we obtained the title compound, [(C5H8N)2Ag2Br2]n, instead and the synthesis and crystal structure are reported herein. Although the stair polymers of [(C5H5N)4Ag4I4]n (Liu et al., 2003) and 1-allyl-3-methylimidazole carbine silver iodide (Chen & Liu, 2003) have recently been reported, their structural features are different from that of the title complex being formed through triple and quadruple halide bridges with Ag···Ag interactions.

In the title complex the asymmetric unit comprises one monodentate 1-ethylimidazole ligand, an Ag+ cation and a doubly bridging Br- anion, giving a distorted tetrahedral AgNBr3stereochemistry about silver [Ag—N, 2.247 (2) Å; Ag—Br, 2.7372 (4)–2.7752 (3) Å and bond angle range about Ag of 106.78 (6)–113.55 (5)°] (Fig. 1). These Ag—Br bond distances are considerably longer than those found in the [Ag2Br4]2- complex anion [2.518 (2) Å] (Helgesson & Jagner, 1990). The Ag1—N1 bond [2.247 (2) Å] is somewhat shorter than 2.335 Å found in the pyridine silver iodide polymer [(C5H5N)4Ag4I4]n (Liu et al., 2003). The dimeric Ag2Br2 repeating core unit in the title complex is generated through a double Br bridge, giving an Ag···Agi separation of 3.0028(r) Å [for symmetry code (i): -x + 1, y, -z) + 1/2]. The four-membered core ring so formed is very similar to that in the complex anion [Ag4Br8]4-(Helgesson & Jagner, 1991).

The basic coomplex is extended into a one-dimensional step-polymer ribbon structure through centrosymmetric Ag—Br and Br—Ag bonds along the c axial direction (Fig. 2). Within these cyclic Ag2Br2 linkages, the Ag···Agiii separation is 3.0407 (4) Å [for symmetry code (iii): -x + 1, -y + 1, -z].

Related literature top

For general background to N-heterocyclic carbenes, see: Arnold (2002); Lin & Vasam (2004). For related structures, see: Wang & Lin (1998); Liu et al. (2003); Helgesson & Jagner (1990, 1991); Chen & Liu (2003).

Experimental top

1,2-Dibromocyclohexane (2.42 g, 10 mmol) was added to a solution of 1-ethylimidazole (1.92 g, 20 mmol) in DMSO (100 ml) at room temperature and stirred for 2 h, after which Ag2O (2.32 g, 10 mmol) was added and the mixture was refluxed for 3 h with stirring. The volume of the solution was reduced to 50 ml under vacuum, the residue was removed by filtration and the filtrate was kept at room temperature for a few days. Colorless crystals of the title compound were obtained after slow evaporation (1.74 g, 30% yield). (mp: 335 K). 1H NMR(CDCl3): 9.42(m,1H), 6.88(s, 1H, CH), 6.84 (s, 1H, CH), 4.54(s, 2H, CH2), 3.65 (s, 3H, CH3)p.p.m. Anal. calcd.: C, 21.12; H, 2.82; N, 9.86%; found: C, 21.05; H, 2.76; N, 9.75%.

Refinement top

The H atoms attached to C atoms of the imidazole ring were positioned geometrically and allowed to ride on their parent atoms, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C). Methylene and methyl H atoms were likewise positioned geometrically (C—H = 0.99 and 0.98 Å, respectively) and also refined as riding atoms, and Uiso(H) = 1.2Ueq(C)

Computing details top

Data collection: APEX2 (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: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The atom numbering scheme for the contents of the asymmetric unit in the title complex. Displacement ellipsoids are drawn at the 30% probability level. For symmetry codes: (i) -x + 1, y, -z) - 1/2]; (ii) x, -y, z) + 1/2.
[Figure 2] Fig. 2. The step-polymeric structure of the title complex, extending along the c axial direction.
catena-Poly[di-µ3-bromido-bis[(1-ethyl-1H-imidazole-κN3)disilver(I)] top
Crystal data top
[Ag2Br2(C5H8N2)2]F(000) = 1072
Mr = 567.80Dx = 2.434 Mg m3
Monoclinic, C2/cMelting point: 335 K
Hall symbol: -C 2ycMo Kα radiation, λ = 0.71073 Å
a = 15.2489 (15) ÅCell parameters from 3344 reflections
b = 13.9888 (13) Åθ = 2.8–28.4°
c = 7.7198 (7) ŵ = 7.67 mm1
β = 109.809 (1)°T = 173 K
V = 1549.3 (3) Å3Block, colourless
Z = 40.17 × 0.16 × 0.15 mm
Data collection top
Bruker APEXII CCD
diffractometer
1362 independent reflections
Radiation source: fine-focus sealed tube1315 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.024
φ and ω scansθmax = 25.0°, θmin = 2.9°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 1618
Tmin = 0.355, Tmax = 0.392k = 1614
3840 measured reflectionsl = 69
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.019Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.048H-atom parameters constrained
S = 1.05 w = 1/[σ2(Fo2) + (0.025P)2 + 1.7996P]
where P = (Fo2 + 2Fc2)/3
1362 reflections(Δ/σ)max < 0.001
83 parametersΔρmax = 0.38 e Å3
0 restraintsΔρmin = 0.68 e Å3
Crystal data top
[Ag2Br2(C5H8N2)2]V = 1549.3 (3) Å3
Mr = 567.80Z = 4
Monoclinic, C2/cMo Kα radiation
a = 15.2489 (15) ŵ = 7.67 mm1
b = 13.9888 (13) ÅT = 173 K
c = 7.7198 (7) Å0.17 × 0.16 × 0.15 mm
β = 109.809 (1)°
Data collection top
Bruker APEXII CCD
diffractometer
1362 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1315 reflections with I > 2σ(I)
Tmin = 0.355, Tmax = 0.392Rint = 0.024
3840 measured reflectionsθmax = 25.0°
Refinement top
R[F2 > 2σ(F2)] = 0.019H-atom parameters constrained
wR(F2) = 0.048Δρmax = 0.38 e Å3
S = 1.05Δρmin = 0.68 e Å3
1362 reflectionsAbsolute structure: ?
83 parametersAbsolute structure parameter: ?
0 restraintsRogers parameter: ?
Special details top

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
xyzUiso*/Ueq
Ag10.445475 (14)0.080848 (14)0.12049 (3)0.02369 (10)
Br10.363999 (18)0.066857 (18)0.49464 (4)0.01975 (10)
N10.39450 (15)0.21798 (15)0.0362 (3)0.0183 (5)
N20.34342 (14)0.31681 (15)0.1304 (3)0.0204 (5)
C10.38660 (17)0.23374 (18)0.1262 (4)0.0182 (5)
H10.40880.19140.22800.022*
C20.32148 (18)0.35730 (18)0.0411 (4)0.0236 (6)
H20.29030.41630.08080.028*
C30.35336 (18)0.29593 (19)0.1426 (4)0.0216 (6)
H30.34820.30520.26760.026*
C40.3277 (2)0.3578 (2)0.2924 (4)0.0307 (7)
H4A0.31010.30610.36180.037*
H4B0.27510.40360.25140.037*
C50.4122 (2)0.4081 (2)0.4169 (4)0.0295 (7)
H5A0.46480.36350.45550.044*
H5B0.39960.43180.52560.044*
H5C0.42750.46200.35120.044*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ag10.02308 (14)0.02533 (14)0.02428 (15)0.00355 (7)0.01013 (10)0.00298 (8)
Br10.01675 (15)0.02566 (16)0.01700 (17)0.00117 (9)0.00595 (12)0.00022 (10)
N10.0171 (11)0.0193 (10)0.0203 (12)0.0016 (9)0.0089 (9)0.0010 (9)
N20.0145 (10)0.0223 (11)0.0242 (12)0.0017 (9)0.0064 (9)0.0064 (9)
C10.0148 (12)0.0213 (13)0.0179 (13)0.0015 (10)0.0046 (10)0.0001 (10)
C20.0193 (13)0.0171 (13)0.0312 (15)0.0016 (10)0.0043 (11)0.0014 (11)
C30.0201 (13)0.0219 (13)0.0215 (14)0.0036 (10)0.0053 (11)0.0047 (11)
C40.0247 (15)0.0373 (17)0.0332 (17)0.0033 (12)0.0138 (13)0.0189 (13)
C50.0228 (15)0.0343 (15)0.0287 (17)0.0016 (12)0.0050 (13)0.0108 (13)
Geometric parameters (Å, º) top
Ag1—N12.247 (2)N2—C41.467 (3)
Ag1—Br12.7372 (4)C1—H10.9500
Ag1—Br1i2.7420 (4)C2—C31.358 (4)
Ag1—Br1ii2.7523 (4)C2—H20.9500
Ag1—Ag1i3.0028 (5)C3—H30.9500
Ag1—Ag1iii3.0407 (4)C4—C51.497 (4)
Br1—Ag1i2.7420 (4)C4—H4A0.9900
Br1—Ag1iv2.7522 (4)C4—H4B0.9900
N1—C11.318 (3)C5—H5A0.9800
N1—C31.381 (3)C5—H5B0.9800
N2—C11.342 (3)C5—H5C0.9800
N2—C21.374 (4)
N1—Ag1—Br1106.78 (6)C2—N2—C4127.2 (2)
N1—Ag1—Br1i113.55 (5)N1—C1—N2111.8 (2)
Br1—Ag1—Br1i112.899 (9)N1—C1—H1124.1
N1—Ag1—Br1ii107.26 (5)N2—C1—H1124.1
Br1—Ag1—Br1ii102.771 (10)C3—C2—N2106.1 (2)
Br1i—Ag1—Br1ii112.797 (10)C3—C2—H2126.9
N1—Ag1—Ag1i121.11 (5)N2—C2—H2126.9
Br1—Ag1—Ag1i56.845 (11)C2—C3—N1109.6 (2)
Br1i—Ag1—Ag1i56.690 (10)C2—C3—H3125.2
Br1ii—Ag1—Ag1i130.781 (8)N1—C3—H3125.2
N1—Ag1—Ag1iii128.97 (6)N2—C4—C5112.2 (2)
Br1—Ag1—Ag1iii123.435 (12)N2—C4—H4A109.2
Br1i—Ag1—Ag1iii56.559 (9)C5—C4—H4A109.2
Br1ii—Ag1—Ag1iii56.238 (11)N2—C4—H4B109.2
Ag1i—Ag1—Ag1iii95.508 (11)C5—C4—H4B109.2
Ag1—Br1—Ag1i66.464 (9)H4A—C4—H4B107.9
Ag1—Br1—Ag1iv109.172 (11)C4—C5—H5A109.5
Ag1i—Br1—Ag1iv67.204 (10)C4—C5—H5B109.5
C1—N1—C3105.3 (2)H5A—C5—H5B109.5
C1—N1—Ag1124.76 (17)C4—C5—H5C109.5
C3—N1—Ag1129.32 (18)H5A—C5—H5C109.5
C1—N2—C2107.1 (2)H5B—C5—H5C109.5
C1—N2—C4125.6 (2)
N1—Ag1—Br1—Ag1i116.60 (6)Br1i—Ag1—N1—C3107.5 (2)
Br1i—Ag1—Br1—Ag1i8.881 (15)Br1ii—Ag1—N1—C3127.1 (2)
Br1ii—Ag1—Br1—Ag1i130.686 (9)Ag1i—Ag1—N1—C343.4 (2)
Ag1iii—Ag1—Br1—Ag1i72.907 (15)Ag1iii—Ag1—N1—C3172.66 (18)
N1—Ag1—Br1—Ag1iv169.81 (6)C3—N1—C1—N20.2 (3)
Br1i—Ag1—Br1—Ag1iv44.330 (16)Ag1—N1—C1—N2172.05 (16)
Br1ii—Ag1—Br1—Ag1iv77.474 (18)C2—N2—C1—N10.3 (3)
Ag1i—Ag1—Br1—Ag1iv53.212 (9)C4—N2—C1—N1176.8 (2)
Ag1iii—Ag1—Br1—Ag1iv19.696 (19)C1—N2—C2—C30.3 (3)
Br1—Ag1—N1—C1152.24 (18)C4—N2—C2—C3176.8 (2)
Br1i—Ag1—N1—C182.7 (2)N2—C2—C3—N10.1 (3)
Br1ii—Ag1—N1—C142.6 (2)C1—N1—C3—C20.0 (3)
Ag1i—Ag1—N1—C1146.79 (17)Ag1—N1—C3—C2171.36 (17)
Ag1iii—Ag1—N1—C117.6 (2)C1—N2—C4—C580.9 (3)
Br1—Ag1—N1—C317.5 (2)C2—N2—C4—C595.7 (3)
Symmetry codes: (i) x+1, y, z1/2; (ii) x, y, z+1/2; (iii) x+1, y, z; (iv) x, y, z1/2.

Experimental details

Crystal data
Chemical formula[Ag2Br2(C5H8N2)2]
Mr567.80
Crystal system, space groupMonoclinic, C2/c
Temperature (K)173
a, b, c (Å)15.2489 (15), 13.9888 (13), 7.7198 (7)
β (°) 109.809 (1)
V3)1549.3 (3)
Z4
Radiation typeMo Kα
µ (mm1)7.67
Crystal size (mm)0.17 × 0.16 × 0.15
Data collection
DiffractometerBruker APEXII CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.355, 0.392
No. of measured, independent and
observed [I > 2σ(I)] reflections
3840, 1362, 1315
Rint0.024
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.019, 0.048, 1.05
No. of reflections1362
No. of parameters83
No. of restraints0
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.38, 0.68

Computer programs: APEX2 (Bruker, 2006), SAINT (Bruker, 2006), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Acknowledgements top

The authors thank the Quality Engineering of Higher Education in Chemical Specialty Construction from Sichuan Province (Sc-mnu1111; Sc-mnu1115; Mnu-JY1104) for financial support.

references
References top

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Helgesson, G. & Jagner, S. (1990). J. Chem. Soc. Dalton Trans. pp. 2414–2420.

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