N-Heterocyclic carbene copper(i), mercury(ii) and silver(i) complexes containing durene linker: Synthesis and structural studies

Article abstract of DOI:10.1039/c0ce00142b

The dibenzimidazolium salts bis[N-(alkyl)benzimidazoliumylmethyl] durene·2X (1a: alkyl = C₂H₅, X = Br; 1b: alkyl = C₂H₅, X = PF₆; 1c: alkyl = n-C ₃H₇, X = Cl; 1d: alkyl = n-C

Full text of DOI:10.1039/c0ce00142b

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PAPER
N-Heterocyclic carbene copper(I), mercury(II) and silver(I) complexes
containing durene linker: synthesis and structural studies†
*
Qing-Xiang Liu, Ai-Hui Chen, Xiao-Jun Zhao, Yan Zang, Xiu-Mei Wu, Xiu-Guang Wang and Jian-Hua Guo
Received 28th April 2010, Accepted 8th July 2010
DOI: 10.1039/c0ce00142b
The dibenzimidazolium salts bis[N-(alkyl)benzimidazoliumylmethyl]durene$2X (1a: alkyl ¼ C2H5,
X ¼ Br; 1b: alkyl ¼ C2H5, X ¼ PF6; 1c: alkyl ¼ n-C3H7, X ¼ Cl; 1d: alkyl ¼ n-C4H9, X ¼ I; 1e: alkyl ¼
1-PyCH2, X ¼ Br; durene ¼ 1,2,4,5-tetramethylbenzene) and the diimidazolium salt bis-
[N-(butyl)imidazoliumylmethyl]durene hexafluorophosphate (1f), and their seven NHC copper(I),
mercury(II) and silver(I) complexes, [durene(CH2bimyEt)2Cu2I2] (2b),
[durene(CH2bimyEt)2HgBr]$0.5[HgBr4] (2c), [durene(CH2bimynBu)2Hg2(CHCN)][HgI4] (2d),
[durene(CH2imynBu)2Ag2(CH2CN)2] (2e), [durene(CH2bimyPyCH2)2Ag2Br2] (2f),
[durene(CH2bimyEt)2Ag][PF6] (2g) and [durene(CH2bimynBu)2Ag2(OH)2] (2h), as well as one anionic
complex [durene(CH2benzimidazoliumylnPr)2][PdCl3(DMSO)]2 (2a) (bimy ¼ benzimidazol-2-ylidene,
imy ¼ imidazol-2-ylidene), have been prepared and characterized. These compounds adopt two diverse
conformations (i.e., cis- and trans-conformations). In 2d and 2e, an interesting phenomenon is that the
a-carbon atoms of deprotonated acetonitrile ([CHCN]2ꢀ for 2d and [CH2CN]ꢀ for 2e) participate in
coordination with metal ions. In the crystal packings of these complexes, 1D supramolecular chains or
2D supramolecular layers are formed via intermolecular weak interactions, including p–p interactions,
hydrogen bonds and C–H/p contacts.
In the family of NHCs, a number of functional bidentate bis-
Introduction
NHC ligands and their metal complexes have been studied.
N-Heterocyclic carbenes (NHCs) have received a burst of
Among these bidentate bis-NHC ligands, a pair of NHC moieties
attention as new ligands since the isolation of the first free stable
are connected by a bridging linker, such as alkyl,9 aryl,10
N-heterocyclic carbenes by Arduengo and coworkers.1 A variety
pyridinediyl11 and ether chain.12 This type of ligand along with
of relevant metal complexes have been synthesized through
metal ions readily form cyclic NHC-metal complexes, which may
deprotonation of N,N0-disubstituted benzimidazolium (or imi-
dazolium) salts.2 Strong electron-donating ability of NHC
have potential application in organic reactions as catalyst and in
molecular recognition as an acceptor. We are interested in
ligands leads to their metal complexes of high stability to heat,
bidentate bis-NHC ligands and their metal complexes. Recently,
moisture and air.3 NHC-metal complexes have shown to be
some silver(I) and mercury(II) complexes based on bidentate bis-
efficient catalysts for some organic reactions, such as Heck,
NHC ligands with alkyl or oligoether linkers have been reported
Suzuki and Kumada couplings, and olefin metathesis.4 Of known
by us.13 We report herein the synthesis, structures and fluorescent
NHC-metal complexes, the NHC copper(I),5 mercury(II)6 and
emission spectra of NHC-metal complexes containing durene
silver(I)7 complexes have played important roles in the
linker, [durene(CH2bimyEt)2Cu2I2] (2b), [durene(CH2bimyEt)2
HgBr]$0.5[HgBr4] (2c), [durene(CH2bimynBu)2Hg2(CHCN)]
[HgI4] (2d), [durene(CH2imynBu)2Ag2(CH2CN)2] (2e), [dure-
development of N-heterocyclic carbene chemistry. Particularly,
N-heterocyclic carbene silver(I) complexes can be used as carbene
transfer reagents for the synthesis of Ni, Pd, Pt, Cu, Au, Rh, Ir
ne(CH2bimyPyCH2)2Ag2Br2] (2f), [durene(CH2bimyEt)2Ag]
[PF6] (2g) and [durene(CH2bimynBu)2Ag2(OH)2] (2h), and one
anionic complex [durene(CH2benzimidazoliumylnPr)2][PdCl3
and Ru carbene complexes, which affords a convenient method
for the preparation of these metal carbene complexes.8
(DMSO)]2 (2a) (bimy ¼ benzimidazol-2-ylidene, imy ¼ imidazol-
Tianjin Key Laboratory of Structure and Performance for Functional
Molecule, College of Chemistry, Tianjin Normal University, Tianjin,
300387, P. R. China. E-mail: qxliu@eyou.com
2-ylidene, durene ¼ 1,2,4,5-tetramethylbenzene) is also described
in the paper. In addition, we also report two diverse conforma-
tions (i.e., cis- and trans-conformations) of the dibenzimidazo-
lium salts and their metal complexes. Moreover, the a-carbon
atoms of deprotonated acetonitrile in 2d and 2e participate in
† CCDC reference numbers 757348–757355 and 775637. For
crystallographic data in CIF or other electronic format see DOI:
10.1039/c0ce00142b
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Scheme 1 Preparation of precursors 1a–1e.
coordination with metal ions, and this observation is also inter-
esting in organometallic chemistry.
Results and discussion
Synthesis and general characterization of precursors 1a–1f and
complexes 2a–2h
The dibenzimidazolium salts, bis[N-(alkyl)benzimidazoliumylme-
thyl]durene halogenide (1a: alkyl ¼ Et, halogenide ¼ Br; 1c: alkyl ¼
nPr, halogenide ¼ Cl; 1e: alkyl ¼ 1-PyCH2, halogenide ¼ Br) were
prepared from benzimidazole by alkylation with 1-bromoethane
or 2-chloromethylpyridine followed by quarterization with bis-
(bromomethyl)durene in sequence (method 1, Scheme 1). The bis-
[N-(ethyl)benzimidazoliumylmethyl]durene hexafluorophosphate
(1b) and the bis[N-(n-butyl)benzimidazoliumylmethyl]durene
iodide (1d) were obtained in two steps. The first step is in
a manner similar to that of 1a, and the second step is through an
anionic exchange with ammonium hexafluorophosphate in
methanol for 1b and with sodium iodide in acetone for 1d
(method 2, Scheme 1). The diimidazolium salt bis[N-(n-butyl)i-
midazoliumylmethyl]durene hexafluorophosphate (1f) was
prepared in a manner similar to that for 1b (Scheme 2). Precur-
sors 1a–1f are stable towards air and moisture, soluble in polar
organic solvents such as dichloromethane, acetonitrile and
methanol, and scarcely soluble in benzene, diethyl ether and
1
petroleum ether. In the H NMR spectra of 1a–1f, the benzimi-
dazolium (or imidazolium) proton signals (NCHN) appear at d ¼
9.90–10.60 ppm, which are consistent with the chemical shifts of
reported benzimidazolium (or imidazolium) salts.2
Synthetic methods of complexes 2a–2h are shown in Scheme 3.
The reaction of 1c with [PdCl2(CH3CN)2] afford an anionic
complex [durene(CH2benzimidazoliumylnPr)2][PdCl3(DMSO)]2
(2a) (Scheme 3(1)). 1b was treated with copper(I) iodide and silver
oxide,
respectively,
to
afford
complexes
[durene-
(CH2bimyEt)2Cu2I2] (2b) and [durene(CH2bimyEt)2Ag][PF6]
Scheme 3 Preparation of complexes 2a–2h.
(2g) (Scheme 3(2) and (7)). Complex [durene(CH2bi-
myEt)2HgBr]0.5[HgBr4] (2c) was prepared by the reaction of 1a
with anhydrous mercury(II) bromide (Scheme 3(3)). 1d was
treated with anhydrous mercury(II) iodide and silver
Scheme 2 Preparation of precursor 1f.
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acetate, respectively, to afford complexes [durene-
(CH2bimynBu)2Hg2(CHCN)][HgI4] (2d) and [durene(CH2bi-
mynBu)2Ag2(OH)2] (2h) (Scheme 3(4) and (8)). Complex
[durene(CH2imynBu)2Ag2(CH2CN)2] (2e) was prepared via
reaction of 1f with silver oxide (Scheme 3(5)). Complex [dure-
ne(CH2bimyPyCH2)2Ag2Br2] (2f) was prepared via reaction of 1e
with silver oxide (Scheme 3 (6)). Complexes 2a–2h are stable
towards air and moisture, soluble in DMSO and insoluble in
diethyl ether and hydrocarbon solvents. In the 1H NMR spectra
of 2b–2h, the disappearance of the resonances for the benzimi-
dazolium (or imidazolium) protons (NCHN) shows the forma-
tion of the expected metal carbene complexes, and the chemical
shifts of other hydrogens are similar to those of corresponding
1
precursors. The H NMR spectrum of anionic complex 2a is
similar to that of corresponding precursor 1c. In 13C NMR
spectra, the signals for the carbene carbon of 2b–2d and 2f–2h
appear at 174.4–187.3 ppm, which are similar to known metal
carbene complexes.5–7 The signal of carbene carbon in 2e was not
observed. Similar results have been reported for some carbene-
silver(I) complexes, which may result from the fluxional behavior
of the NHC complexes.14 For complexes 2d and 2e containing
deprotonated acetonitriles, the signals of carbon of cyano group
(CN) appear at 113.4 ppm for 2d and 112.7 ppm for 2e, and the
signals of a-carbon atom of acetonitrile appear at 30.3 ppm for
2d and 31.2 ppm for 2e. IR spectra contain the characteristic
bands of cyano groups at 2191 cmꢀ1 for 2d and 2166 cmꢀ1 for 2e.
These values are comparable to those of the reported complexes
containing cyano groups.15
Structures of dibenzimidazolium salt 1e and complexes 2a–2h
Molecular structures of precursor 1e and complexes 2a–2h were
demonstrated by X-ray analysis. The crystals of 1e$CH3CN, 2a,
2b$0.5CH3CN, 2c$0.5DMSO, 2d$CH3CN, 2e, 2f$DMSO,
2g$0.5H2O and 2h suitable for X-ray diffraction were obtained
by slow diffusion of diethyl ether into their DMSO/CH3CN
solution. In complexes 2c and 2g, each cation contains a mono-
nuclear macrometallocycle formed by one bidentate chelate
carbene ligand and one metal atom, whereas complexes 2b, 2d, 2e
and 2f possess dinuclear macrometallocyclic structures as shown
in Fig. 1(a), Fig. 2(a) and Fig. 6(a)–Fig. 9(a). In each of 1e and
2b–2g, two Rbimi (or Rimi) arms lie in the same side of durene
plane to adopt a cis-conformation. The two benzimidazole (or
imidazole) rings within each molecule form the dihedral angles
varying from 5.1ꢁ to 56.0ꢁ, and they form the dihedral angles in
the ranges of 76.4–91.9ꢁ and 81.7–96.9ꢁ with the centric durene
Fig. 1 (a) Perspective view of 2b and anisotropic displacement param-
eters depicting 30% probability. All hydrogen atoms were omitted for
ꢁ
ꢀ
clarity. Selected bond lengths (A) and angles ( ): Cu(1)–I(1) 2.660(1),
Cu(1)–I(2) 2.600(1), Cu(1)–Cu(2) 2.668(1); I(1)–Cu(1)–Cu(2) 57.8(4),
N(1)–C(7)–N(2) 106.7(7), N(3)–C(22)–N(4) 105.6(6). (b) The 2D supra-
molecular layers by the p–p interactions and C–H/p contacts in 2b. All
hydrogen atoms except those participating in the C–H/p contacts were
omitted for clarity.
plane, respectively (the related data being given in Table 1). In
contrast, the molecular structures of complexes 2a and 2h are
different from those of above-mentioned compounds, and two
Rbimi arms within each molecule in 2a and 2h lie in the opposite
sides of durene plane to adopt an open trans-conformation as
shown in Fig. 3(a) and Fig. 4(a). The X-ray crystal structural
analyses of 2a and 2h show that there are inversion centers in the
complexes. Additionally, two benzimidazole rings within each
molecule are parallel, and they form the dihedral angles 82.3(5)ꢁ
for 2a and 88.8(2)ꢁ for 2h with the centric durene plane, respec-
tively. In 2b–2h, the internal ring angles (N–C–N) at the carbene
centers are in the range of 102.8–107.5ꢁ, which are comparable to
those of the known NHC-metal complexes,2 but these values are
smaller than the corresponding values (110.9–111.1ꢁ) of
precursor 1e and anionic complex 2a.
Table 1 Dihedral angles (ꢁ) between two benzimidazole (or imidazole)
rings (A), and dihedral angles (ꢁ) between two benzimidazole (or imid-
azole) rings and durene plane (B) for precursor 1e and complexes 2b–2g
Compounds
A
B
1e
2b
2c
2d
2e
2f
9.5(1)
5.1(3)
6.6(1)
56.0(2)
9.0(1)
6.4(2)
18.6(1)
86.4(1), 81.8(1)
82.0(2), 86.4(1)
88.1(1), 84.3(4)
76.4(2), 81.7(1)
81.7(1), 90.5(1)
91.9(2), 92.9(3)
78.7(1), 96.9(2)
In precursor 1e, one bromine atom and four hydrogen atoms
on two PyCH2bimi arms form four C–H/Br hydrogen bonds16
as shown in Fig. 5(a) (the data of hydrogen bonds being given in
Table 2). Anionic complex 2a is different from precursor 1e, one
2g
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Fig.
2 (a) Perspective view of 2g and anisotropic displacement
parameters depicting 30% probability. All hydrogen atoms and anioꢁns
ꢀ
ꢀ
2PF6 were omitted for clarity. Selected bond lengths (A) and angles ( ):
Ag(1)–C(7) 2.121(2), Ag(1)–C(28) 2.100(2); N(1)–C(7)–N(2) 105.5(4),
N(3)–C(28)–N(4) 106.1(4). (b) The 2D supramolecular layers by the both
types of p–p interactions in 2g. All hydrogen atoms were omitted for
clarity.
oxygen atom from DMSO of anionic [PdCl3(DMSO)] and two
n
hydrogen atoms on one Prbimi arm in 2a form two C–H/O
Fig. 3 (a) Perspective view of 2a and anisotropic displacement param-
eters depicting 30% probability. All hydrogen atoms except those
participating in the C–H/O hydrogen bonds were omitted for clarity.
hydrogen bonds17 as shown in Fig. 3(a) (Table 2). In anionic unit
[PdCl3(DMSO)], the center Pd is coordinated to three chlorine
atoms and one sulfur atom of DMSO to adopt a planar square
array. The bond distances of Pd–Cl are in the range of 2.328–
ꢁ
ꢀ
Selected bond lengths (A) and angles ( ): N(1)–C(10) 1.332(8), Pd(1)–S(1)
2.239(1), Pd(1)–Cl(1) 2.341(1), Pd(1)–Cl(2) 2.328(1), Pd(1)–Cl(3)
2.348(1); Cl(1)–Pd(1)–Cl(2) 92.1(6), Cl(1)–Pd(1)–Cl(3) 89.0(6), Cl(2)–
Pd(1)–Cl(3) 176.9 (7), S(1)–Pd(1)–Cl(2) 88.6(6), S(1)–Pd(1)–Cl(3) 90.2(6),
N(1)–C(10)–N(2) 111.0(6). (b) The 2D supramolecular layers by the p–p
interactions, C–H/O hydrogen bonds and C–H/Cl hydrogen bonds in
2a. All hydrogen atoms except those participating in the hydrogen bonds
were omitted for clarity.
ꢀ
2.348 A.
In NHC-copper(I) complex 2b (Fig. 1(a)), each copper(I) atom
is tetra-coordinated with one carbene carbon atom (C(carbene)),
two iodine atoms and another copper(I) atom. Two copper(I)
atoms are linked by two bridging iodine atoms to form a dis-
torted Cu2I2 quadrangular arrangement. In the Cu2I2 core, the
dihedral angle between the Cu(1)–I(1)–Cu(2) plane and Cu(1)–
I(2)–Cu(2) plane is 44.3(1)ꢁ. The Cu(1)–Cu(2) distance of
ꢀ
ꢀ
2.082(8) A to 2.101(6) A, which are similar to those of known
NHC-mercury(II) complexes.6 The anionic units of 2c and 2d are
tetrahedral [HgBr4]2ꢀ and [HgI4]2ꢀ, respectively, in which the
values of bond lengths and bond angles fall in regular range.20 In
2c, the mercury(II) atom within the cationic macrometallocycle is
tri-coordinated with two carbene carbons and one bromine
atom. The C(1)–Hg(1)–C(22) array is nearly linear with the bond
angle of 173.7(3)ꢁ. The two ethyl chains and one bromine atom in
the cation are stretching in the same direction. In the cationic
unit of 2d, the Hg(2) and Hg(3) are dicoordinated with one
ꢀ
ꢀ
2.668(1) A (van der Waals radii of copper ¼ 1.86 A) indicates
a strong metal–metal interaction.18 The bond angles of two Cu–
ꢁ
ꢁ
ꢀ
I–Cu are 61.3(4) and 61.5(3) . The Cu–I distance of 2.57–2.66 A
falls in the regular range.19 Additionally, the distances of two
ꢀ
ꢀ
Cu–C bonds are 1.962(8) A and 1.929(1) A, and the bond angles
of two C–Cu–Cu are 159.4(3)ꢁ and 161.5(1)ꢁ. These values are
comparable to those of the reported NHC copper(I) complexes.8
In two NHC-mercury(II) complexes 2c and 2d (Fig. 6(a) and
Fig. 7(a)), the bond distances of Hg–C(carbene) vary from
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a
Table 2 H-Bonding geometry (A, ꢁ) for 1e, 2a, 2d and 2e
ꢀ
D–H/A
D–H
H/A
D/A
D–H/A
1e C(6)–H(6A)/Br(2)
C(13)–H(13)/Br(2)
C(33)–H(33B)/Br(2)
C(32)–H(32)/Br(2)
2a C(3)–H(3)/O(1)i
C(10)–H(10)/O(1)i
0.97(4) 2.781(5) 3.654(3) 150.0(2)
0.93(3) 2.814(5) 3.572(4) 139.4(2)
0.97(4) 3.135(6) 3.974(4) 145.5(2)
0.93(3) 3.155(7) 3.723(4) 121.2(4)
0.97(8) 2.668(8) 3.463(1) 139.4(4)
0.93(7) 2.679(8) 3.227(1) 118.4(4)
C(11)–H(11B)/Cl(2)ii 0.97(8) 2.721(1) 3.608(7) 152.3(5)
C(17)–H(17B)/Cl(1)ii 0.96(9) 2.829(2) 3.518(1) 129.5(6)
2d C(35)–H(35)/I(1)i
C(12)–H(12)/I(4)
0.98(1) 3.189(1) 3.923(3) 133.1(1)
0.97(1) 3.010(2) 3.689(1) 128.0(3)
0.93(1) 2.334(1) 3.219(1) 158.9(3)
2e C(21)–H(21)/N(6)i
a
Symmetry code: i ¼ 1 ꢀ x, 1 ꢀ y, 1 ꢀ z; ii ¼ ꢀ1 + x, 2 + y, 2 + z for 2a.
i ¼ x, ꢀ1 + y, z for 2d. i ¼ 1 + x, y, z for 2e.
ꢀ
longer than those of two Ag–C(a) (1.913(1) A and 1.975(7) A).
ꢀ
ꢀ
The Ag/Ag separation of 3.304(1) A (van der Waals Radii of
silver ¼ 1.72 A) indicates a weak metal–metal interaction.22 The
ꢀ
two n-butyl groups on the nitrogen atoms are stretching in the
Fig. 4 (a) Perspective view of 2h and anisotropic displacement param-
eters depicting 30% probability. All hydrogen atoms except those in tꢁhe
ꢀ
OH were omitted for clarity. Selected bond lengths (A) and angles ( ):
Ag(1A)–C(1A) 2.101(3), O(1A)–H(1A) 0.820(1); N(1A)–C(1A)–N(2A)
105.7(3). (b) The 2D supramolecular layers by the p–p interactions and
C–H/p contacts in 2h. All hydrogen atoms except those participating in
the C–H/p contacts and in the OH, and all butyl groups on the nitrogen
atoms were omitted for clarity.
carbene carbon atom and one a-carbon atom (C(a)) of depro-
tonated acetonitrile. The bond distances of two Hg–C(carbene)
ꢀ
(2.082(8) A and 2.084(8) A) are slightly shorter than those of Hg–
ꢀ
ꢀ
ꢀ
C(a) (2.090(8) A and 2.112(8) A). The Hg(2)/Hg(3) separation
ꢀ
ꢀ
of 3.338(5) A (van der Waals Radii of mercury ¼ 1.70 A) indi-
cates a weak metal–metal interaction.20 Two C(carbene)–Hg–
C(a) arrays are nearly linear with the bond angles of 172.8(4)ꢁ
and 176.9(3)ꢁ. The bond angles of two Hg–C(35)–C(36) are
113.5(6)ꢁ and 114.7(7)ꢁ, and the bond angle of Hg(2)–C(35)–
Hg(3) is 105.2(3)ꢁ. Notably, the cyanomethyl moiety (C(35)–
C(36)–N(5)) is nearly linear with a bond angle of 177.9(1)ꢁ. The
ꢀ
C(35)–C(36) bond distance (1.398(1) A) is shorter than that of
ꢀ
the regular C–C single bond (1.54–1.59 A), and it has partial
double-bond character. The C(36)–N(5) bond distance (1.167(1)
ꢀ
A) is similar to that of other complexes containing cyano groups,
and this value is expected for a triple bond with a small amount
of double bond character.21 The two butyl chains on the nitrogen
atoms are stretching in the opposite directions.
In four NHC-silver(I) complexes 2e–2h, each silver(I) atom
possesses a dicoordinated geometry, and the bond distances of
Fig. 5 (a) Perspective view of 1e and anisotropic displacement parame-
ters depicting 30% probability. All hydrogen atoms except those partici-
pating in the C–H/Br hydrogꢁen bonds were omitted for clarity. Selected
ꢀ
ꢀ
Ag–C(carbene) vary from 2.058(7) A to 2.121(2) A. These values
are comparable to known NHC-silver(I) complexes.5 As for 2e,
the data of all bond lengths and angles in the [CH2CN]ꢀ unit are
comparable to the corresponding values in [CHCN]2ꢀ unit of 2d.
The two C(carbene)–Ag–C(a) arrays are nearly linear with the
bond angles of 173.0(3)ꢁ and 173.6(3)ꢁ. The bond distances of
ꢀ
bond lengths (A) and angles ( ): C(13)–N(2) 1.317(4); N(2)–C(13)–N(3)
111.1(3), N(4)–C(32)–N(5) 110.9(2). (b) The 2D supramolecular layers by
the p–p interactions and C–H/p contacts in 1e. All hydrogen atoms
except those participating in the C–H/p contacts, all methyl groups on
the durenes and all bromine atoms were omitted for clarity.
ꢀ
two Ag–C(carbene) (2.058(7) A and 2.066(7) A) are slightly
ꢀ
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Fig. 7 (a) Perspective view of 2d and anisotropic displacement param-
eters depicting 30% probability. All hydrogen atoms except that in the
[CHCN]2ꢀ were omitted for clarity. Selected bond lengths (A) and angles
ꢀ
(ꢁ): N(5)–C(36) 1.167(1), C(35)–C(36) 1.398(1), Hg(3)–C(11) 2.084(8);
N(5)–C(36)–C(35) 177.9(1), C(30)–Hg(2)–C(35) 176.9(3), C(36)–C(35)–
Hg(3) 113.5(6), C(36)–C(35)–Hg(2) 114.7(7), N(1)–C(11)–N(2) 107.5(7),
N(3)–C(30)–N(4) 106.9(7). (b) The 1D supramolecular chains by the C–
H/I hydrogen bonds in 2d. All hydrogen atoms except those partici-
pating in the C–H/I hydrogen bonds were omitted for clarity.
Fig. 6 (a)Perspectiveviewof 2candanisotropicdisplacementparameters
depicting 30% probability. All hydrogen atoms and anion 0.5[HgBr4]2ꢀ
placed in the opposite sides of the durene plane. An n-butyl group
and a AgOH part on same benzimidazole ring are stretched along
the benzimidazole ring plane in the same direction, but they point
to the opposite directions as compared with the corresponding
parts on another benzimidazole ring. The angles of two C–Ag–O
ꢁ
ꢀ
were omitted for clarity. Selected bond lengths (A) and angles ( ):
Hg(1)–C(1) 2.097(6), Hg(1)–Br(1) 3.076(1); C(1)–Hg(1)–C(22) 173.7(3),
C(1)–Hg(1)–Br(1) 90.4(2), N(1)–C(1)–N(2) 107.5(5), N(3)–C(22)–N(4)
108.2(6). (b) The 2D supramolecular layers by the weak Hg/Br bonds, p–
p interactions and C–H/p contacts in 2c. All hydrogen atoms except
those participating in the C–H/p contacts were omitted for clarity.
ꢁ
ꢀ
(177.1(1) ) and the bond distances of two Ag–O (2.274(3) A) are
the same, respectively, and they fall into the regular range.23
same direction, whereas the two [CH2CN]ꢀ units are stretching in
the opposite directions.
The conformations of the dibenzimidazole salts and their metal
complexes
The macrometallocycle of 2f is analogous to that of 2e,
ꢀ
however, the Ag/Ag separation of 3.113(7) A in 2f is shorter
ꢀ
than that of 3.304(1) A in 2e. The bond distances of two Ag–Br in
As shown in Scheme 4, the dibenzimidazole salts containing
durene linker adopt two diverse conformations (i.e., cis-confor-
mation I and trans-conformation II) according to the different
arrangements of two Rbimi arms. The conformations I and II
can converse each other in the solution, and their ratio are mostly
relative to two factors: (1) the weak interactions between anions
and two Rbimi arms; (2) the steric hindrance between two Rbimi
arms. The former may have larger effect on the ratio of
conformation than the latter. When there exist strong interac-
tions between one anion and two Rbimi arms at the same time in
a compound, the two arms lie in same side of durene plane, and
the compound adopts mainly cis-conformation (e.g., 1e). When
there exist strong interactions between one anion and only one
Rbimi arm in a compound, the two arms lie in opposite sides of
ꢀ
ꢀ
2f are 2.492(6) A and 2.437(7) A, and the bond angles of two C–
Ag–Br are 159.6(1)ꢁ and 166.9(1)ꢁ. The two bromine atoms are
stretching in the opposite directions. The dihedron angle between
pyridine ring and adjacent benzimidazole is 88.2(1)ꢁ (73.3(1)ꢁ for
the corresponding precursor 1e), and the dehedral angle between
two pyridine rings is 64.3(1)ꢁ (37.5(2)ꢁ for 1e). Compared to 1e,
some relevant bond lengths and angles of complex 2f occur
relatively large changes due to the introduction of metal silver(I)
atom. As for 2g, the C(7)–Ag(1)–C(28) array is almost linear with
the bond angle of 175.8(6)ꢁ. The two ethyl chains on the nitrogen
atoms are stretching in the opposite directions.
In the trans structure of 2h, the hydroxy groups linked on sil-
ver(I) atoms come from KOH. Two [nBubimyAg(OH)] units are
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deprotonated acetonitrile ([CHCN]2ꢀ) for 2d and singly depro-
tonated acetonitrile ([CH2CN]ꢀ) for 2e. The a-carbon atom
(C(a)) of these deprotonated acetonitrile along with didentate
carbene ligands are coordinated to metal atoms to form
complexes 2d and 2e, respectively. A distinction is that the a-
carbon atom of [CHCN]2ꢀ in 2d is bonded to two mercury(II),
whereas the a-carbon atom of [CH2CN]ꢀ in 2e is bonded to one
silver(I). From the structures of complexes 2d and 2e, as well
as reported compounds containing deprotonated acetonitrile,
such as (Me3Ge)2CHCN,21a [Pt(CH2CN)(PMe2Ph)3]PF6,21b
21c
PdCl(CH2CN)(PPh3)2 and Fe3(Cp)3(m-CO)3[m3-CCN],21d we
know that three a-hydrogen atoms of acetonitrile may be
deprotonated one by one in the presence of base to form singly,
doubly and triply deprotonated acetonitrile (i.e., [CH2CN]ꢀ,
[CHCN]2ꢀ and [CCN]3ꢀ), respectively. The different formulae
of deprotonated acetonitriles probably are relative to the
amount of base and the type of coordinated metal ions in the
system of reaction.
The crystal packings of precursor 1e and complexes 2a–2h
Scheme 4 The diverse conformations of dibenzimidazole and their metal
Analyses of the crystal packings of 1e and 2a–2h reveal that 2D
supramolecular layers of 1e, 2a, 2b, 2c and 2f–2h, as well as 1D
supramolecular chains of 2d and 2e are formed via intermolec-
ular weak interactions, including p–p stacking interactions,
hydrogen bonds, C–H/p contacts and weak Hg/Br bonds (the
data of hydrogen bonds being given in Table 2, and the related
data of p–p interactions and C–H/p contacts being given in
Table 3).
complexes
durene plane due to steric hindrance, and the compound adopts
mainly trans-conformation (e.g., 2a).
Similarly, NHC metal complexes formed via dibenzimidazole
salts and metal compounds possess both cis-conformations III or
IV (e.g., 2b–2g) and trans-conformation V (e.g., 2h), and their
conformations may depend mainly on the conformations of the
corresponding precursors. Additionally, NHC metal complexes
possessing cis-conformation have usually two different struc-
tures, namely, single nuclear macrocycle complexes III (e.g., 2c
and 2g) and dinuclear macrocycle complexes IV (e.g., 2b, 2d, 2e
and 2f). In dinuclear macrocycle complexes, metal–metal inter-
actions are observed.
In 1e, the intermolecular weak interactions involve the
C–H/p contacts24 (the hydrogen atoms being from pyridine
rings) and two types of aromatic p–p stacking interactions.25
In these two types of p–p interactions, one is from intermo-
lecular benzene rings of durenes, and another is from inter-
molecular benzimidazole rings (Fig. 5(b)). An interesting
feature in the crystal packing of 2a is that 1D supramolecular
chains are formed by the p–p stacking interactions from
intermolecular benzimidazole rings. In addition, an anionic
2ꢀ
dimer with a 12-membered ring [PdCl3(DMSO)]2 are formed
The different formulae of deprotonated acetonitrile
by two anions [PdCl3(DMSO)]ꢀ via two C–H/Cl hydrogen
bonds (C(17)–H(17B)/Cl(1)).26 These anionic dimeric units
([PdCl3(DMSO)]2) are packed between the 1D chains to
extend 1D chains into 2D supramolecular layers via new
An interesting phenomenon during the preparation of 2d or 2e is
that a-hydrogen atoms of acetonitrile are deprotonated due to
the presence of strong base KOtBu to generate doubly
ꢁ
ꢀ
ꢀ
Table 3 Distances (A) of p–p interactions, and distances (A) and angles ( ) of C–H/p contacts for 1e, 2a–2c and 2e–2h
p–p
C–H/p
Compounds
Face-to-face
Center-to-center
H/p
C–H/p
1e
3.748(3) (benzene) 3.444(2)
(benzimidazole)
3.790(1) (benzene) 3.644(2)
(benzimidazole)
2.908(2)
138.7(3)
2a
2b
2c
2e
2f
3.651(3) (benzimidazole)
3.375(2) (benzimidazole)
3.393(1) (benzimidazole)
3.521(3) (imidazole)
3.463(1) (benzimidazole)
3.686(2) (benzene) 3.530(4)
(benzimidazole)
3.440(1) (benzimidazole)
3.760(3) (benzimidazole)
3.564(2) (benzimidazole)
4.424(1) (imidazole)
3.776(3) (benzimidazole)
3.757(1) (benzene) 3.736(1)
(benzimidazole)
_
_
2.768(2)
2.968(1)
_
3.033(1)
_
119.4(1)
139.0(4)
_
143.7(2)
_
2g
2h
3.534(2) (benzimidazole)
3.732(1) (benzimidazole)
3.002(2)
123.7(1)
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Fig. 9 (a) Perspective view of 2e and anisotropic displacement param-
eters depicting 30% probability. All hydrogenꢁatoms were omitted for
ꢀ
clarity. Selected bond lengths (A) and angles ( ): C(27)–C(28) 1.259(5),
Fig. 8 (a) Perspective view of 2f and anisotropic displacement
N(5)–C(28) 1.071(9), Ag(1)–C(7) 2.058(7), C(29)–C(30) 1.276(5), N(6)–
C(30) 1.092(5); Ag(2)–C(22) 2.066(7); N(5)–C(28)–C(27) 178.2(1), C(28)–
C(27)–Ag(1) 165.7(6), C(30)–C(29)–Ag(2) 158.9(1), N(3)–C(22)–N(4)
103.3(6), N(6)–C(30)–C(29) 169.1(1), N(1)–C(7)–N(2) 102.8(6). (b) The
1D double-strand supramolecular chains by the p–p interactions and C–
H/N hydrogen bonds in 2e. All hydrogen atoms except those partici-
pating in the C–H/N hydrogen bonds, all methyl groups on durenes and
all butyl groups on the nitrogen atoms were omitted for clarity.
parameters depicting 30% probability. All hydrogen atoms were
ꢁ
ꢀ
omitted for clarity. Selected bond lengths (A) and angles ( ): Ag(1)–
C(14) 2.115(4), Ag(2)–C(33) 2.081(4); C(14)–Ag(1)–Br(1) 159.6(1),
C(33)–Ag(2)–Br(2) 166.9 (1), N(1)–C(14)–N(2) 105.2(3). (b) The 2D
supramolecular layers by the p–p interactions and C–H/p contacts
in 2f. All hydrogen atoms except those participating in the C–H/p
contacts and all methyl groups on the durenes were omitted for
clarity.
C–H/Cl hydrogen bonds (C(11)–H(11B)/Cl(2)) as shown in
Fig. 3(b).
In 2b, 2f and 2h, there exist the p–p stacking interactions
from intermolecular benzimidazole rings and C–H/p contacts
(the hydrogen atoms being from ethyl groups on nitrogen
atoms for 2b, from pyridine rings for 2f, and from methyl
groups of durenes for 2h) (Fig. 1(b) for 2b, Fig. 8(b) for 2f and
Fig. 4(b) for 2h). In 2c, the intermolecular weak interactions
include the p–p stacking interactions from intermolecular
benzimidazole rings, C–H/p contacts (the hydrogen atoms
being from methyl groups of durenes) and weak Hg/Br bonds
20
ꢀ
(Hg/Br distance ¼ 3.602(2) A) (Fig. 6(b)). In 2g, both types
of aromatic p–p stacking interactions are observed (Fig. 2(b)).
One type is formed via intermolecular benzene rings of
durenes, and another is formed via intermolecular benzimid-
azole rings.
Fig. 10 Emission spectra of 1a (—), 1e (/), 1f (—), 2b (/), 2d (/), 2e
(—) and 2f (/) at 298 K in CH2Cl2 (5.0 ꢂ 10ꢀ6 M) solution.
Different from the compounds above-mentioned, the adjacent
cationic units in 2d are held together by anionic units [HgI4]2ꢀ via
C–H/I hydrogen bonds27 to form 1D supramolecular chains
(Fig. 7(b)). The double-strand 1D supramolecular chains in 2e
are formed via C–H/N hydrogen bonds28 (the hydrogen atoms
being from imidazole rings, and nitrogen atoms being from
cyano groups) and p–p stacking interactions from intermolec-
ular imidazole rings (Fig. 9(b)).
Fluorescent emission spectra of precursors 1a, 1e and 1f, and
complexes 2b and 2d–2f
As shown in Fig. 10, the fluorescent emission spectra of
precursors 1a, 1e and 1f and complexes 2b and 2d–2f in
dichloromethane at room temperature are obtained upon
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excitation at 230 nm (the fluorescent emission spectra of 1b–1d
and 2a are similar to that of 1a; the fluorescent emission spectra
of 2c, 2g and 2h are similar to that of 2b). Precursors 1a, 1e and 1f
exhibit double emission bands in the region of 330–345 nm,
corresponding to intraligand transitions. Complex 2b exhibits
a broad and intense emission band in the region of 325–350 nm.
Complexes 2d–2f show double emission bands in the range of
330–345 nm. The fluorescence emissions of these complexes are
stronger than those of their corresponding precursors, which
may be assigned to the incorporation of metal–ligand coordi-
nation interactions.29 The results show that these metal
complexes might be candidates for potential photoactive
materials.
sodium hydride (0.480 g, 20.3 mmol) in THF (50 mL) and stirred
ꢁ
for 1 h at 60 C. Then THF (40 mL) solution of ethyl bromide
(2.029 g, 18.6 mmol) was dropwise added to above solution. The
mixture was continued to stir for 48 h at 60 ꢁC, and a yellow
solution was obtained. The solvent was removed with a rotary
evaporator, and H2O (100 mL) was added to the residue. Then
the solution was extracted with CH2Cl2 (3 ꢂ 30 mL), and the
extracting solution was dried over anhydrous MgSO4. After
removing CH2Cl2, a pale yellow liquid 1-ethylbenzimidazole was
obtained. Yield: 2.220 g (90%).
A solution of 1-ethylbenzimidazole (2.013 g, 14.0 mmol) and
bis(bromomethyl)durene (2.000 g, 6.25 mmol) in THF (150 mL)
was stirred for three days under reflux, and a precipitate was
formed. The product was filtered and washed with THF. The
white powder of bis[N-(ethyl)benzimidazoliumylmethyl]durene
bromide (1a) was obtained by recrystallization from methanol–
diethyl ether. Yield: 3.300 g (86%). Mp: 170–172 ꢁC. Anal. Calcd
for C30H36N4Br2: C, 58.83; H, 5.92; N, 9.15%. Found: C, 58.66;
H, 5.96; N, 9.43%. 1H NMR (400 MHz, DMSO-d6): d 1.62 (t, J ¼
7.2, 6H, CH3), 2.31 (s, 12H, CH3), 4.84 (q, J ¼ 7.2, 4H, CH2),
5.90 (s, 4H, CH2), 7.75 (m, 6H, PhH), 8.52 (d, J ¼ 8.1, 2H, PhH),
10.40 (s, 2H, 2-bimiH) (bimi: benzimidazole).
Conclusions
In summary, a series of new NHC copper(I), mercury(II) and
silver(I) complexes have been synthesized and characterized.
Precursor 1e and complexes 2b–2g adopt cis-conformations, and
complexes 2a and 2h adopt open trans-conformations. Addi-
tionally, complexes 2b–2g possess a macrometallocycle, respec-
tively, formed by a didentate chelate carbene ligand and one/two
metal ions. During the preparation of 2d or 2e, the acetonitrile
are deprotonated in the presence of strong base KOtBu to form
deprotonated acetonitrile ([CHCN]2ꢀ for 2d and [CH2CN]ꢀ for
2e). Then the a-carbon atom of deprotonated acetonitrile
participates in coordination with metal atoms. In crystal pack-
ings, 2D supramolecular layers of 1e, 2b, 2c and 2f–2h, as well as
1D supramolecular chains of 2d and 2e are formed via inter-
molecular weak interactions, including p–p interactions,
hydrogen bonds, C–H/p contacts and weak Hg/Br bonds.
Further studies on new organometallic compounds from
precursors 1a–1f and analogous ligands are under way.
NH4PF6 (1.171 g, 7.2 mmol) was added to a methanol solution
(100 mL) of 1a (2.000 g, 3.3 mmol) whilst stirring and a white
precipitate formed immediately. The product was collected by
filtration, washed with small portions of cold methanol,
and ꢁdried in vacuum to give 1b. Yield: 1.980 g (82%). Mp: 292–
296 C. Anal. Calcd for C30H36F12N4P2: C, 48.52; H, 4.89; N,
7.55%. Found: C, 48.85; H, 5.22; N, 7.81%. 1H NMR (400 MHz,
DMSO-d6): d 1.66 (t, J ¼ 7.2, 6H, CH3), 2.44 (s, 12H, CH3), 4.89
(q, J ¼ 7.2, 4H, CH2), 5.95 (s, 4H, CH2), 7.67 (m, 6H, PhH), 8.55
(d, J ¼ 8.3, 2H, PhH), 10.60 (s, 2H, 2-bimiH).
The following dibenzimidazolium (or diimidazolium) salts 1c
and 1e were prepared in a manner analogous to that for 1a, and
1d and 1f were prepared in a manner analogous to that for 1b.
Experimental
General procedures
Preparation of bis[N-(propyl)benzimidazoliumylmethyl]durene
chloride (1c). Yield: 4.009 g (84%). Mp: 282–284 ꢁC. Anal. Calcd
for C32H40N4Cl2: C, 69.26; H, 7.31; N, 10.16%. Found: C, 69.12;
Bis(bromomethyl)durene was prepared according to the litera-
ture method.30 All manipulations were performed using Schlenk
techniques, and solvents were purified by standard procedures.
All the reagents for synthesis and analyses were of analytical
grade and used without further purification. Melting points were
determined with a Boetius Block apparatus. IR spectra were
measured on a Bruker IR Equinox-55 infrared spectrophotom-
1
H, 7.44; N, 10.52%. H NMR (400 MHz, DMSO-d6): d 1.65 (t,
J ¼ 7.2, 6H, CH3), 1.74 (m, 4H, CH2), 2.34 (s, 12H, CH3), 4.84 (t,
J ¼ 7.2, 4H, CH2), 5.93 (s, 4H, CH2), 7.75 (m, 6H, PhH), 8.57 (d,
J ¼ 8.1, 2H, PhH), 10.43 (s, 2H, 2-bimiH) (bimi: benzimidazole).
1
eter. H and 13C{1H} NMR spectra were recorded on a Varian
Preparation of bis[N-(butyl)benzimidazoliumylmethyl]durene
ꢁ
iodide (1d). Yield: 1.919 g (80%). Mp: 320–322 C. Anal. Calcd
Mercury Vx 400 spectrometer at 400 MHz and 100 MHz,
for C34H44N4I2: C, 53.55; H, 5.82; N, 7.35%. Found: C, 53.84; H,
1
respectively. Chemical shifts, d, are reported in ppm relative to
1
the internal standard TMS for both H and 13C NMR. J values
5.48; N, 7.64%. H NMR (400 MHz, DMSO-d6): d 0.94 (t, J ¼
7.3, 6H, CH3), 1.44 (m, 4H, CH2), 1.95 (m, 4H, CH2), 2.31 (s,
12H, CH3), 4.85 (t, J ¼ 7.3, 4H, CH2), 5.95 (s, 4H, CH2), 7.81 (m,
6H, PhH), 8.67 (d, J ¼ 8.3, 2H, PhH), 10.41 (s, 2H, 2-bimiH).
are given in Hz. Elemental analyses were measured using
a Perkin-Elmer 2400C Elemental Analyzer. The luminescent
spectra were conducted on
spectrophotometer.
a Cary Eclipse fluorescence
Preparation of bis[N-(1-pyridinylmethyl)benzimidazoliumyl-
methyl]durene bromide (1e). Yield: 3.200 g (73%). Mp: 324–
326 ꢁC. Anal. Calcd for C38H38N6Br2: C, 61.80; H, 5.19; N,
11.38%. Found: 61.44; H, 5.53; N, 11.65%. 1H NMR (400 MHz,
DMSO-d6): d 2.31 (s, 12H, CH3), 5.90 (s, 4H, CH2), 5.94 (s, 4H,
CH2), 7.36 (m, 2H, PhH), 7.66 (m, 6H, PhH), 7.95 (m, 4H, PhH),
8.14 (m, 2H, PhH), 8.42 (d, J ¼ 4.8, 2H, PhH), 9.98 (s, 2H, 2-bimiH).
Preparation of dibenzimidazolium (or diimidazolium) salts
Preparation of bis[N-(ethyl)benzimidazoliumylmethyl]durene
bromide (1a) and bis[N-(ethyl)benzimidazoliumylmethyl]durene
hexafluorophosphate (1b). A THF solution of benzimidazole
(2.000 g, 16.9 mmol) was added to a suspension of oil-free
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Preparation of bis[N-(n-butyl)imidazoliumylmethyl]durene hexa-
fluorophosphate (1f). Yield: 2.100 g (86%). Mp: 286–288 ꢁC. Anal.
Calcd for C26H40F12N4P2: C, 44.70; H, 5.77; N, 8.02%. Found:
125.8 (PhC), 46.8 (NCH2Ph), 33.6 (NCH2C), 15.1 (PhCH3), 10.0
(CCH3).
1
C, 44.71; H, 6.23; N, 7.74%. H NMR (400 MHz, DMSO-d6):
Preparation of [durene(CH2benzimynBu)2Hg2(CHCN)][HgI4]
(2d). Yield: 0.230 g (54%). Mp: 276–278 ꢁC. Anal. Calcd for
C36H43Hg3I4N5: C, 26.12; H, 2.62; N, 4.23%. Found: C, 26.57;
H, 2.32; N, 4.65%. 1H NMR (400 MHz, DMSO-d6): d 0.88 (t, J ¼
7.4, 6H, CH3), 1.29 (m, 4H, CH2), 1.83 (m, 4H, CH2), 2.07 (s, 1H,
CH), 2.27 (s, 12H, CH3), 4.48 (t, J ¼ 7.2, 2H, CH2), 5.81 (s, 2H,
CH2), 7.76 (m, 4H, PhH), 8.12–8.19 (m, 4H, PhH). 13C NMR
(100 MHZ, DMSO-d6): d 187.3 (Ccarbene), 137.0, 136.2, 133.2,
132.7, 132.3, 126.3 and 126.0 (PhC), 113.4 (CN), 48.3 (NCH2Ph),
31.5 (NCH2C), 30.3 (HgCHHg), 19.2 (CCH2C), 17.3 (CCH2C),
d 0.91 (t, J ¼ 5.3, 6H, CH3), 1.37 (m, 4H, CH2), 1.86 (t, J ¼ 5.3,
4H, CH2), 2.15 (s, 12H, CH3), 4.40 (t, J ¼ 5.3, 4H, CH2), 5.83 (s,
4H, CH2), 7.36 (s, 2H, imiH), 8.58 (s, 2H, imiH), 9.90 (s, 2H,
2-imiH) (imi: imidazole).
Preparation of [durene(CH2BimynPr)2][PdCl3(DMSO)]2 (2a).
A suspension of bis[N-(n-propyl)benzimidazoliumylmethyl]dur-
ene chloride (1c) (0.200 g, 0.36 mmol), PdCl2(CH3CN)2 (0.187 g,
0.72 mmol) in acetonitrile (10 mL) and DMSO (5 mL) was
refluxed for 24 h. A brown solution was formed, and the aceto-
nitrile were removed with a rotary evaporator. The water
(30 mL) was added to the residue, and the solution extracted with
CH2Cl2 (3 ꢂ 20 mL). The extracting solution was dried over
anhydrous MgSO4, then the solution was concentrated to 10 mL
and hexane (4 mL) was added. 2a was obtained as a pale yellow
powder. Yield: 0.167 g (57%). Mp: > 320 ꢁC. Anal. Calcd for
C36H52Cl6N4O2Pd2S2: C, 40.69; H, 4.93; N, 5.27%. Found: C,
40.33; H, 4.72; N, 5.56%. 1H NMR (400 MHz, DMSO-d6): d 1.67
(t, J ¼ 6.8, 6H, CH3), 1.74 (m, 4H, CH2), 2.37 (s, 12H, CH3), 4.89
(t, J ¼ 5.6, 4H, CH2), 5.96 (s, 4H, CH2), 7.78 (m, 6H, PhH),
8.60 (d, J ¼ 8.1, 2H, PhH), 10.02 (s, 2H, 2-bimiH) (bimi: benz-
imidazole). 13C NMR (100 MHZ, DMSO-d6): d 138.3, 136.2,
132.8, 132.1, 127.1, 126.0 and 125.1 (PhC or imiC), 46.9
(NCH2Ph), 31.8 (NCH2C), 17.3 (CCH2C), 16.8 (PhCH3), 12.0
(CH2CH3).
16.2 (PhCH3), 13.4 (CCH3). IR (KBr): n CN, 2191 cmꢀ1
.
Preparation of [durene(CH2imynBu)2Ag2(CH2CN)2] (2e). Silver
oxide (0.089 g, 0.4 mmol) and KOtBu (0.146 g, 1.3 mmol) was
added to a solution of bis[N-(n-butyl)imidazoliumylmethyl]dur-
ene hexafluorophosphate (1f) (0.200 g, 0.3 mmol) in CH3CN–
CH2Cl2 (30 mL), and the suspension solution was stirred for 24 h
at refluxing. The resulting solution was filtered and concentrated
to 10 mL, and Et2O (5 mL) was added to precipitate a white
powder. Isolation by filtration yielded 2e. Yield: 0.101 g (50%),
Mp: 164–166 ꢁC. Anal. Calcd for C30H42Ag2N6: C, 51.30; H,
6.03; N, 11.96%. Found: C, 51.71; H, 6.46; N, 11.66%. 1H NMR
(400 MHz, DMSO-d6): d 0.87 (t, J ¼ 7.2, 6H, CH3), 1.20 (m, 4H,
CH2), 1.70 (m, 4H, CH2), 2.20 (s, 12H, CH3), 2.23 (s, 2H, CH2),
4.01 (t, J ¼ 6.0, 4H, CH2), 5.35 (s, 4H, CH2), 7.39 (s, 2H, imiH),
7.48 (s, 2H, imiH) (imi: imidazole). 13C NMR (100 MHZ,
DMSO-d6): d 135.4, 133.0, 123.1 and 122.1 (PhC or imiC), 112.7
(CN), 52.0 (NCH2CH2), 50.0 (NCH2Ph), 33.6 (AgCH2C), 31.2
(CCH2C), 19.7 (CCH2C), 17.4 (PhCH3), 14.2 (CCH3). IR (KBr):
n CN, 2166 cmꢀ1. The signal of carbene carbon was not observed.
Preparation of [durene(CH2BimyEt)2Cu2I2] (2b). A suspension
of KOtBu (0.146 g, 1.3 mmol), bis[N-(ethyl)benzimidazoliumyl-
methyl]durene hexafluorophosphate (1b) (0.200 g, 0.3 mmol) and
copper(I) iodide (0.100 g, 0.5 mmol) in acetonitrile (30 mL) was
refluxed for 24 h. A brown solution was formed, and the solvent
was removed with a rotary evaporator. The water (30 mL) was
added to the residue, and the solution extracted with CH2Cl2 (3 ꢂ
20mL). TheextractingsolutionwasdriedoveranhydrousMgSO4,
then the solution was concentrated to 10 mL and hexane (4 mL)
was added. As a result, a pale yellow powder was obtained. Yield:
0.126 g (56%). Mp: 352–354 ꢁC. Anal. Calcd for C30H34Cu2I2N4:
C, 43.33;H, 4.12; N, 6.74%. Found:C, 43.72;H, 4.50; N, 6.33%. 1H
NMR (400 MHz, DMSO-d6): d 1.41 (t, J ¼ 5.1, 6H, CH3), 2.36 (s,
12H, CH3), 4.40 (q, J ¼ 5.1, 4H, CH2), 5.49 (s, 4H, CH2), 7.49 (m,
4H, PhH), 7.80 (d, J ¼ 5.4, 2H, PhH), 8.3 (d, J ¼ 5.4, 2H, PhH). 13C
NMR (100 MHZ, DMSO-d6): d 174.4 (Ccarbene), 138.2, 135.3,
132.8, 132.0, 127.2, 126.1 and 124.3 (PhC), 47.4 (NCH2Ph), 32.5
(NCH2C), 17.1 (PhCH3), 12.1 (CCH3).
Preparation of [durene(CH2BimyPymethyl)2Ag2Br2] (2f). Silver
oxide (0.070 g, 0.3 mmol) was added to a solution of bis-
[N-(1-pyridinylmethly)imidazoliumylmethyl]durene
bromide
(1e) (0.200 g, 0.3 mmol) in dichloromethane (30 mL) and the
suspension solution was stirred for 24 h at refluxing. The
resulting solution was filtered and concentrated to 10 mL, and
Et2O (5 mL) was added to precipitate a white powder. Isolatꢁion
by filtration yielded 2f. Yield: 0.156 g (60%), Mp: 288–290 C.
Anal. Calcd for C38H36Ag2Br2N6: C, 47.93; H, 3.81; N, 8.83%.
Found: C, 47.58; H, 3.44; N, 8.62%. 1H NMR (400 MHz,
DMSO-d6): d 2.30 (s, 12H, CH3), 5.91 (s, 4H, CH2), 5.95 (s, 4H,
CH2), 7.34 (m, 2H, PhH or PyH), 7.61 (m, 6H, PhH or PyH),
7.92 (m, 4H, PhH or PyH), 8.13 (m, 2H, PhH or PyH), 8.44 (d,
J ¼ 4.8, 2H, PhH or PyH). 13C NMR (100 MHZ, DMSO-d6):
d 182.0 (Ccarbene), 155.8, 150.2, 138.5, 136.2, 133.8, 132.8, 132.1,
124.1, 123.0, 118.9 and 116.8 (PhC or PyC), 50.4 (NCH2Py), 40.6
(NCH2Ph), 13.1 (PhCH3).
The following two NHC mercury(II) complexes 2c and 2d were
prepared in a manner analogous to that for 2b.
Preparation of [durene(CH2BimyEt)2HgBr]$0.5[HgBr4] (2c).
Yield: 0.178 g (55%). Mp: 306–308 ꢁC. Anal. Calcd for
C30H34Br3Hg1.5N4: C, 36.35; H, 3.46; N, 5.65%. Found: C, 36.78;
H, 3.74; N, 5.33%. 1H NMR (400 MHz, DMSO-d6): d 1.59 (t, J ¼
7.2, 6H, CH3), 2.27 (s, 12H, CH3), 4.62 (q, J ¼ 7.2, 4H, CH2),
5.82 (s, 4H, CH2), 7.72 (s, 4H, PhH), 8.02 (d, J ¼ 6.2, 2H, PhH),
8.28 (d, J ¼ 6.2, 2H, PhH). 13C NMR (100 MHZ, DMSO-d6):
d 180.1 (Ccarbene), 137.2, 135.1, 132.9, 132.0, 131.3, 126.3 and
The following two NHC silver(I) complexes 2g and 2h were
prepared in a manner analogous to that for 2f.
Preparation of [durenꢁe(CH2BimyEt)Ag](PF6) (2g). Yield: 0.098
g (52%). Mp: 256–260 C. Anal. Calcd for C30H34AgF6N4P: C,
51.22; H, 4.87; N, 7.96%. Found: C, 51.61; H, 4.48; N, 7.68%. 1H
NMR (400 MHz, DMSO-d6): d 1.50 (t, J ¼ 5.2, 6H, CH3), 2.43
(s, 12H, CH3), 4.46 (q, J ¼ 5.2, 4H, CH2), 5.53 (s, 4H, CH2), 7.51
302 | CrystEngComm, 2011, 13, 293–305
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Table 4 Summary of crystallographic data for 1e, 2a and 2b
1e$CH3CN
2a
2b$0.5CH3CN
Chemical formula
Fw
C38H38N6$Br2$CH3CN
[C32H40N4]$2[PdCl3DMSO]
1062.46
Triclinic
C30H34Cu2I2N4$0.5CH3CN
852.02
Triclinic
ꢁ
P1
9.709(1)
17.216(3)
19.642(4)
72.8 (3)
86.3 (3)
88.6 (3)
3131.2(1)
2
779.62
Monoclinic
P21/c
14.781(7)
14.678(7)
18.540(9)
90
111.032(1)
90
3754.4(3)
4
1.379
Crystal system
Space group
ꢁ
P1
ꢀ
a/A
8.885(1)
10.627(1)
13.042(1)
78.793(2)
80.799(2)
66.276(2)
1101.3(2)
2
ꢀ
b/A
ꢀ
c/A
a/ꢁ
b/ꢁ
g/ꢁ
V/A
Z
3
ꢀ
Dc/Mg mꢀ3
m/mmꢀ1
F(000)
1.602
1.311
538
1.807
3.358
1668
2.197
1600
Crystal size/mm
qmin, qmax (ꢁ)
T/K
0.22 ꢂ 0.21 ꢂ 0.14
1.82, 25.01
296(2)
0.28 ꢂ 0.22 ꢂ 0.20
2.12, 25.02
296(2)
0.14 ꢂ 0.12 ꢂ 0.10
1.39, 25.02
113(2)
No. of data collected
No. of unique data
No. of refined params
18 776
6616
447
5682
3868
240
1.061
10 999
10 999
725
1.077
a
Goodness-of-fit on F2
1.032
Final R indicesb [I > 2s(I)]
R1
wR2
R indices (all data)
0.0405
0.1205
0.0559
0.1756
0.0689
0.1383
R1
wR2
0.0675
0.1358
0.0637
0.1845
0.0921
0.1524
P
P
P
a
b
2
2
Goof ¼ [ w(Fo ꢀ Fc )2/(n ꢀ p)]1/2, where n is the number of reflections and p is the number of parameters refined. R1 ¼ (kFo| ꢀ |Fck)/ |Fo|; wR2 ¼
1/[s2(Fo2) + (0.0691P) + 1.4100P] where P ¼ (Fo2 + 2Fc )/3.
2
Table 5 Summary of crystallographic data for 2c–2e
2c$0.5DMSO
2d$CH3CN
36H43Hg3I4N5$CH3CN
2e
Chemical formula
C30H34BrHgN4
$0.5HgBr4$0.5DMSO
1030.29
Triclinic
ꢁ
P1
14.017(1)
16.221(2)
18.554(2)
89.7 (2)
69.7 (2)
72.1 (2)
3745.0(8)
2
C
C30H42Ag2N6
Fw
Crystal system
Space group
1696.18
Triclinic
ꢁ
P1
702.43
Triclinic
ꢁ
P1
ꢀ
a/A
12.212(8)
13.311(8)
16.692(1)
71.1 (1)
75.7 (1)
62.9 (1)
2271.9(2)
2
10.950(6)
14.822 (7)
19.4 (9)
98.1 (1)
95.9 (1)
107.0 (1)
2955.6(3)
2
ꢀ
b/A
ꢀ
c/A
a/ꢁ
b/ꢁ
g/ꢁ
V/A
Z
3
ꢀ
Dc/Mg mꢀ3
m/mmꢀ1
F(000)
1.826
9.403
1950
2.479
12.862
1536
1.579
1.355
1432
Crystal size/mm
qmin, qmax (ꢁ)
T/K
0.24 ꢂ 0.20 ꢂ 0.16
1.63, 26.00
296(2)
0.24 ꢂ 0.20 ꢂ 0.18
1.77, 25.03
296(2)
0.28 ꢂ 0.26 ꢂ 0.20
1.07, 25.03
296(2)
No. of data collected
No. of unique data
No. of refined params
14 562
14 562
783
1.029
11 724
7972
466
1.030
15 297
10 382
690
1.020
a
Goodness-of-fit on F2
Final R indicesb [I > 2s(I)]
R1
wR2
R indices (all data)
0.0412
0.1001
0.0383
0.0978
0.0488
0.1413
R1
wR2
0.0657
0.1063
0.0481
0.1043
0.0823
0.1698
P
P
P
a
b
Goof ¼ [ w(Fo ꢀ Fc )2/(n ꢀ p)]1/2, where n is the number of reflections and p is the number of parameters refined. R1 ¼ (kFo| ꢀ |Fck)/ |Fo |; wR2 ¼
2
2
1/[s2(Fo2) + (0.0691P) + 1.4100P] where P ¼ (Fo2 + 2Fc )/3.
This journal is ª The Royal Society of Chemistry 2011
2
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Table 6 Summary of crystallographic data for 2f–2h
2f$DMSO
2g$0.5H2O
2h
Chemical formula
Fw
C38H36Ag2Br2N6$DMSO
1030.42
Triclinic
C30H34AgN4$PF6$0.5H2O
712.46
Triclinic
C34H43.88Ag2I0.1N4O1.88
768.56
Monoclinic
C2/c
3.133(4)
18.772(4)
20.002(2)
90
15.8 (5)
90
3784.7(2)
4
1.349
Crystal system
Space group
ꢁ
P1
ꢁ
P1
ꢀ
a/A
10.097(2)
13.533(3)
15.4 (3)
104.0 (3)
97.6 (3)
94.5 (4)
2010.4(7)
2
9.368(1)
13.897(2)
14.595(2)
103.6 (2)
102.9 (2)
104.9 (2)
1699.1(4)
2
ꢀ
b/A
ꢀ
c/A
a/ꢁ
b/ꢁ
g/ꢁ
V/A
Z
3
ꢀ
Dc/Mg mꢀ3
m/mmꢀ1
F(000)
1.699
3.051
1024
1.393
0.699
726
1.155
1563
Crystal size/mm
qmin, qmax (ꢁ)
T/K
0.28 ꢂ 0.22 ꢂ 0.20
1.56, 25.03
296(2)
10 282
7035
0.34 ꢂ 0.32 ꢂ 0.30
2.38, 25.01
296(2)
8589
5920
0.22 ꢂ 0.20 ꢂ 0.18
1.94, 25.01
296(2)
3344
3344
197
1.150
No. of data collected
No. of unique data
No. of refined params
510
1.032
431
1.071
a
Goodness-of-fit on F2
Final R indicesb [I > 2s(I)]
R1
0.0357
0.0962
0.0473
0.1486
0.0352
0.1164
wR2
R indices (all data)
R1
wR2
0.0525
0.1072
0.0543
0.1573
0.0400
0.1192
P
P
P
a
b
Goof ¼ [ w(Fo ꢀ Fc )2/(n ꢀ p)]1/2, where n is the number of reflections and p is the number of parameters refined. R1¼ (kFo| ꢀ |Fck)/ |Fo|; wR2 ¼
2
2
1/[s2(Fo2) + (0.0691P) + 1.4100P] where P ¼ (Fo2 + 2Fc )/3.
2
ꢀ
geometrically (C–H bond lengths fixed at 0.96 A), assigned
(m, 4H, PhH), 7.84 (d, J ¼ 5.5, 2H, PhH), 8.33 (d, J ¼ 5.5, 2H,
PhH). 13C NMR (100 MHZ, DMSO-d6): d 175.0 (Ccarbene), 138.3,
133.1, 128.4, 118.1 and 112.2 (PhC), 50.1 (NCH2Ph), 48.2
(NCH2C), 14.8 (PhCH3), 10.8 (CCH3).
appropriated isotropic thermal parameters and included in the
final calculations. Crystallographic data are summarized in
Tables 4–Table 6 for 1e and 2a–2h.
Preparation of [durene(CH2BimynBu)2Ag2(OH)2] (2h). Yield:
(50%). Mp: 150–152 ꢁC. Anal. Calcd for
Acknowledgements
0.146
g
C34H43.88 0.1
I
N4O1.88Ag2: C, 53.23; H, 5.77; N, 7.30%. Found: C,
This work was financially supported by the National Science
Foundation of China (Project Grant No. 20872111) and the
Natural Science Foundation of Tianjin (07JCYBJC00300).
53.67; H, 5.32; N, 7.72%. 1H NMR (400 MHz, DMSO-d6): d 0.92
(t, J ¼ 7.0,6H, CH3), 1.37(m, 4H, CH2), 1.87(m, 4H, CH2), 2.19(s,
12H, CH3), 4.44 (t, J ¼ 7.0, 4H, CH2), 5.57 (s, 4H, CH2), 7.56 (m,
4H, PhH), 7.86 (d, J ¼ 7.8, 2H, PhH), 8.13 (d, J ¼ 7.8, 2H, PhH).
13C NMR (100 MHZ, DMSO-d6): d 181.3 (Ccarbene), 138.3, 133.1,
129.4, 119.9 and 115.3 (PhC), 53.2 (NCH2Ph), 48.3 (NCH2C), 33.7
(CCH2C), 25.6 (CCH2C), 14.2 (CCH3), 9.2 (PhCH3).
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