μ₃-Chlorido-tris­(bis­{1-[2-(dimethyl­amino)­eth­yl]-3-methyl­imidazol-2-yl­idene}silver(I)) dichloride

In the crystal structure of the title compound, [Ag₃Cl(C₈H₁₅N₃)₆]Cl₂, the Ag^I ion, which is located on a twofold rotation axis, exists in a T-shape coordination environment. Two carbene C atoms of the N-heterocyclic carbene (NHC) ligands are bonded tightly forming a slightly bent [Ag(NHC)₂]⁺ cation [C—Ag—C angle = 162.80 (18)°]. Three of these complex cations are further aggregated by one bridging chloride anion, which is lying on a threefold rotoinversion axis and is only loosely binding to the Ag⁺ ions. The N atom of the amine group is not engaged in any coordinative bond.

Key indicators

• Single-crystal X-ray study
• T = 200 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.034
• wR factor = 0.095
• Data-to-parameter ratio = 16.5

checkCIF/PLATON results

No syntax errors found



Alert level B
            Crystal system given = trigonal
PLAT220_ALERT_2_B Large Non-Solvent    C     Ueq(max)/Ueq(min) ...        4.5 Ratio

Alert level C
PLAT042_ALERT_1_C Calc. and Reported MoietyFormula Strings  Differ          ?
PLAT094_ALERT_2_C Ratio of Maximum / Minimum Residual Density ....       2.78
PLAT222_ALERT_3_C Large Non-Solvent    H    Uiso(max)/Uiso(min) ..        4.2 Ratio
PLAT230_ALERT_2_C Hirshfeld Test Diff for    N3     --  C5      ..        5.7 su
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C4     --  C5      ..        5.7 su
PLAT242_ALERT_2_C Check Low       Ueq as Compared to Neighbors for         N3
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          3
PLAT913_ALERT_3_C Missing # of Very Strong Reflections in FCF ....          1

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details in CIF ....          ?
PLAT083_ALERT_2_G SHELXL Second Parameter in WGHT Unusually Large.      47.43
PLAT194_ALERT_1_G Missing _cell_measurement_reflns_used datum ....          ?
PLAT195_ALERT_1_G Missing _cell_measurement_theta_max   datum ....          ?
PLAT196_ALERT_1_G Missing _cell_measurement_theta_min   datum ....          ?
PLAT909_ALERT_3_G Percentage of Observed Data at Theta(Max) still          74 Perc.

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

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

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S1. Comment

In the course of our studies on gold- and silver-complexes bearing functionalized N-heterocyclic carbenes (NHCs), we became interested in examples with amino groups containing side arms at a nitrogen atom of the NHC ligands (Topf, Hirtenlehner, Fleck et al. (2011); Topf, Hirtenlehner & Monkowius (2011); Leitner et al., 2011; Hirtenlehner et al., 2011). Just recently, we published the multifarious coordination patterns of such silver complexes (Topf, Hirtenlehner, Zabel et al., 2011): E.g., in the ionic compound [(C₈H₁₅N₃)₂Ag][AgCl₂], which is formed from the respective imidazolium chloride and Ag₂O in dichloromethane, the ions are aggregated to infinite chains with short silver-silver contacts. Treatment of this complex with HBF₄ yields the cluster (C₈H₁₅N₃)₄Ag₁₀Cl₁₀ with the carbene carbon atom binding in a unusual µ₂-fashion to two silver atoms. In an attempt to prepare this cluster, crystals of the title compound were formed representing the third silver chloride complex in the series of this ligand. The formation of this complex is easily rationalized by the precipitation of AgCl from [(C₈H₁₅N₃)₂Ag][AgCl₂] in solution.

The silver atom is in a slightly bent linear coordination with an Ag1—C1 bond length of 2.099 (3) Å and an angle C1—Ag1—C1ⁱ of 162.8 (2)°. Perpendicular to the C1—Ag1—C1ⁱ vector, a chloride anion is loosely binding with an Ag1—Cl1 bond length of 2.981 (1) Å. The chloride Cl1 is linking three [(C₈H₁₅N₃)₂Ag]⁺ units in a µ₃-fashion forming a D₃ symmteric trimeric aggregate. The net 2+ charge is balanced by two non-interacting chloride ions. Within other cationic species of the type [(NHC)₂Ag]⁺, the imidazole ring planes are usually found in a coplanar arrangement due to a higher π-backbonding contribution compared to a perpendicular orientation. Presumably because of steric reasons, the [(C₈H₁₅N₃)₂Ag]⁺ moiety features an arrangement with both imidazole ring planes approaching a perpendicular orientation [N1—C1—C1ⁱ—N1ⁱ 89.8°]. The distance between two silver atoms within the trimer is 5.164 Å, which is well beyond the range of argentophilic interactions. It should be noted, that this aggregation pattern is very rare and to the best of our knowledge reported only for {[(NHC)₂Ag]₃(µ₃-I)}I₂ (NHC = 1-methyl-3-picolyl-imidazol-2-ylidene) (Wang et al., 2006) and {[(NHC)₂Au]₃(µ₃-Br)}Br₂ (NHC= 1-methyl-3-benzyl-imidazol-2-ylidene) (Hirtenlehner et al., 2011).

Related literature

For related literature, see: Topf, Hirtenlehner, Fleck et al. (2011); Topf, Hirtenlehner & Monkowius (2011); Leitner et al. (2011). For related structures, see: Hirtenlehner et al. (2011); Wang et al. (2006). For details of the preparation, see: Topf, Hirtenlehner, Zabel et al. (2011).

S2. Experimental

Crystals of the title compound were formed in an attempt to synthesize the silver cluster (C₈H₁₅N₃)₄Ag₁₀Cl₁₀ according to a literature procedure (Topf, Hirtenlehner, Zabel et al., 2011).

S3. Refinement

The hydrogen atoms were placed in calculated positions with C—H = 0.95–0.99 Å and refined using a riding model with U_iso(H) = 1.5 U_eq(C) for methyl groups and U_iso(H) = 1.2 U_eq(C) for methylen and aromatic hydrogen atoms. The highest residual electron density peak is located 1.28 Å from H9A and the deepest hole is located 0.53 Å from C9.

Computing details

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

	Fig. 1. View of the title compound with the atom numbering scheme (symmetry code: (i) x-y + 1/3, -y + 2/3, -z + 1/6). Displacement ellipsoids for non-H atoms are drawn at the 50% probability level.
	Fig. 2. [Ag3Cl]^2+ cation in the crystals of the title compound. The H atoms and the methyl and 2-dimethyl-amino-ethyl groups are omitted for the sake of clarity (symmetry codes: (ii) -y + 1, x-y, z; (iv) y + 1/3, x - 1/3, -z + 1/6).

µ₃-Chlorido-tris(bis{1-[2-(dimethylamino)ethyl]-3-methylimidazol-2- ylidene}silver(I)) dichloride

Crystal data

[Ag3Cl(C8H15N3)2]Cl2	F(000) = 4176
Mr = 1349.34	Dx = 1.434 Mg m^−3
Trigonal, R3c	Mo Kα radiation, λ = 0.71073 Å
a = 12.7300 (16) Å	µ = 1.11 mm^−1
c = 66.789 (12) Å	T = 200 K
V = 9373 (2) Å^3	Prism, colourless
Z = 6	0.50 × 0.36 × 0.31 mm

Data collection

Bruker SMART X2S diffractometer	1859 independent reflections
Radiation source: sealed MicroFocus tube	1590 reflections with I > 2σ(I)
Doubly curved silicon crystal monochromator	Rint = 0.060
ω scans	θmax = 25.1°, θmin = 3.1°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −15→14
Tmin = 0.61, Tmax = 0.73	k = −15→15
18593 measured reflections	l = −79→79

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.034	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.095	H-atom parameters constrained
S = 1.03	w = 1/[σ^2(Fo^2) + (0.0504P)^2 + 47.4314P] where P = (Fo^2 + 2Fc^2)/3
1859 reflections	(Δ/σ)max = 0.001
113 parameters	Δρmax = 1.28 e Å^−3
0 restraints	Δρmin = −0.46 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
Ag1	0.90085 (3)	0.3333	0.0833	0.03038 (16)
C6	1.1504 (3)	0.5164 (4)	0.05466 (6)	0.0422 (9)
H6A	1.1374	0.5764	0.0617	0.063*
H6B	1.2184	0.558	0.0453	0.063*
H6C	1.1689	0.4703	0.0644	0.063*
C1	0.9354 (3)	0.3530 (3)	0.05243 (5)	0.0257 (7)
N2	0.8610 (3)	0.2965 (3)	0.03679 (4)	0.0284 (6)
C5	0.7252 (4)	0.0798 (4)	0.03044 (7)	0.0543 (11)
H5A	0.6394	0.0146	0.0315	0.065*
H5B	0.7471	0.0909	0.0161	0.065*
N1	1.0411 (2)	0.4340 (2)	0.04359 (4)	0.0271 (6)
C4	0.7366 (3)	0.1961 (4)	0.03843 (6)	0.0388 (9)
H4A	0.682	0.2158	0.0308	0.047*
H4B	0.7112	0.1848	0.0526	0.047*
C3	0.9192 (3)	0.3417 (3)	0.01870 (6)	0.0358 (9)
H3	0.8853	0.3163	0.0057	0.043*
C2	1.0327 (3)	0.4284 (3)	0.02306 (5)	0.0341 (8)
H2	1.095	0.4766	0.0138	0.041*
N3	0.8016 (3)	0.0410 (3)	0.04089 (6)	0.0475 (9)
C8	0.7953 (7)	−0.0580 (6)	0.02927 (11)	0.101 (2)
H8A	0.842	−0.0898	0.036	0.151*
H8B	0.829	−0.0286	0.0159	0.151*
H8C	0.7104	−0.1226	0.028	0.151*
C9	0.7645 (7)	0.0065 (6)	0.06074 (11)	0.114 (3)
H9A	0.772	0.0761	0.0682	0.172*
H9B	0.8157	−0.0217	0.067	0.172*
H9C	0.6797	−0.0591	0.0609	0.172*
Cl1	0.6667	0.3333	0.0833	0.0307 (4)
Cl2	0.3333	0.6667	0.00857 (2)	0.0344 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ag1	0.0353 (2)	0.0290 (2)	0.0247 (2)	0.01451 (11)	0.00056 (7)	0.00112 (14)
C6	0.032 (2)	0.035 (2)	0.048 (2)	0.0078 (17)	−0.0022 (17)	−0.0035 (17)
C1	0.0288 (17)	0.0288 (17)	0.0267 (18)	0.0197 (15)	−0.0005 (14)	0.0007 (13)
N2	0.0256 (14)	0.0345 (16)	0.0289 (16)	0.0180 (13)	0.0007 (12)	−0.0018 (12)
C5	0.040 (2)	0.053 (3)	0.057 (3)	0.013 (2)	−0.003 (2)	−0.005 (2)
N1	0.0246 (14)	0.0259 (14)	0.0314 (15)	0.0131 (12)	0.0013 (11)	0.0016 (12)
C4	0.0238 (18)	0.046 (2)	0.044 (2)	0.0161 (17)	−0.0016 (15)	−0.0062 (18)
C3	0.040 (2)	0.048 (2)	0.0245 (19)	0.0255 (18)	0.0000 (15)	0.0000 (15)
C2	0.039 (2)	0.039 (2)	0.0290 (19)	0.0233 (17)	0.0095 (15)	0.0072 (15)
N3	0.0411 (19)	0.0327 (18)	0.061 (2)	0.0126 (15)	−0.0096 (17)	−0.0030 (16)
C8	0.108 (5)	0.066 (4)	0.121 (6)	0.039 (4)	0.011 (4)	−0.010 (4)
C9	0.132 (7)	0.081 (5)	0.069 (4)	0.007 (4)	−0.034 (4)	0.012 (3)
Cl1	0.0299 (6)	0.0299 (6)	0.0323 (10)	0.0150 (3)	0	0
Cl2	0.0356 (5)	0.0356 (5)	0.0319 (7)	0.0178 (3)	0	0

Geometric parameters (Å, º)

Ag1—C1^i	2.099 (3)	N1—C2	1.374 (5)
Ag1—C1	2.099 (3)	C4—H4A	0.99
C6—N1	1.458 (5)	C4—H4B	0.99
C6—H6A	0.98	C3—C2	1.340 (5)
C6—H6B	0.98	C3—H3	0.95
C6—H6C	0.98	C2—H2	0.95
C1—N2	1.350 (5)	N3—C9	1.402 (8)
C1—N1	1.355 (4)	N3—C8	1.447 (7)
N2—C3	1.383 (5)	C8—H8A	0.98
N2—C4	1.459 (5)	C8—H8B	0.98
C5—N3	1.469 (6)	C8—H8C	0.98
C5—C4	1.511 (6)	C9—H9A	0.98
C5—H5A	0.99	C9—H9B	0.98
C5—H5B	0.99	C9—H9C	0.98
C1^i—Ag1—C1	162.80 (18)	N2—C4—H4B	109.4
N1—C6—H6A	109.5	C5—C4—H4B	109.4
N1—C6—H6B	109.5	H4A—C4—H4B	108.0
H6A—C6—H6B	109.5	C2—C3—N2	106.6 (3)
N1—C6—H6C	109.5	C2—C3—H3	126.7
H6A—C6—H6C	109.5	N2—C3—H3	126.7
H6B—C6—H6C	109.5	C3—C2—N1	106.5 (3)
N2—C1—N1	103.5 (3)	C3—C2—H2	126.8
N2—C1—Ag1	130.4 (3)	N1—C2—H2	126.8
N1—C1—Ag1	126.0 (2)	C9—N3—C8	111.8 (5)
C1—N2—C3	111.5 (3)	C9—N3—C5	112.2 (5)
C1—N2—C4	125.0 (3)	C8—N3—C5	106.3 (4)
C3—N2—C4	123.4 (3)	N3—C8—H8A	109.5
N3—C5—C4	114.0 (3)	N3—C8—H8B	109.5
N3—C5—H5A	108.8	H8A—C8—H8B	109.5
C4—C5—H5A	108.8	N3—C8—H8C	109.5
N3—C5—H5B	108.8	H8A—C8—H8C	109.5
C4—C5—H5B	108.8	H8B—C8—H8C	109.5
H5A—C5—H5B	107.7	N3—C9—H9A	109.5
C1—N1—C2	111.9 (3)	N3—C9—H9B	109.5
C1—N1—C6	123.7 (3)	H9A—C9—H9B	109.5
C2—N1—C6	124.4 (3)	N3—C9—H9C	109.5
N2—C4—C5	111.3 (3)	H9A—C9—H9C	109.5
N2—C4—H4A	109.4	H9B—C9—H9C	109.5
C5—C4—H4A	109.4

Symmetry code: (i) x−y+1/3, −y+2/3, −z+1/6.