Synthesis and catalytic activity of N-heterocyclic carbene silver complexes derived from 1-[2-(pyrazol-1-yl)phenyl]imidazole

Article abstract of DOI:10.1016/j.jorganchem.2012.12.008

Six mono- and dinuclear N-heterocyclic carbene (NHC) silver complexes based on 1-[2-(pyrazol-1-yl)phenyl]imidazole have been synthesized and characterized by elemental analysis and NMR spectroscopy, and their structures have been confirmed by single crystal X-ray diffraction. The N-functionalized carbene ligands exhibit versatile coordination modes in these silver complexes. N-[2-(3,5-Dimethylpyrazol-1-yl)phenyl]-N-benzylimidazol-2-ylidene (L) acts as a monodentate ligand through the carbene carbon in mononuclear LAgCl. While in dinuclear L₂Ag₂(PF₆)₂ and L' ₂Ag₂(PF₆)₂ (L' = N-[2-(pyrazol-1-yl)phenyl]-N-benzylimidazol-2-ylidene), L and L' act as bridging bidentate ligands through the pyrazolyl nitrogen and the carbene carbon atoms to two silver atoms. Though, these two silver atoms have different coordination environments. In the former, one silver atom coordinates with two carbene carbons, the other coordinates with two pyrazolyl nitrogen atoms. In the latter, each silver atom coordinates with one carbene carbon and one pyrazolyl nitrogen atom, respectively. A dinuclear macrocyclic structure is observed in m-xylyl bridging tetradentate bis-NHC complexes L₂Ag₂(BF ₄)₂ and (L)CH₂C₆H₄CH ₂(L)Ag₂(BF₄)₂, in which the coordination mode of carbene ligands is similar with that in L ₂Ag₂(PF₆)₂. Preliminary catalytic tests show that all these complexes exhibit highly effective catalytic activity in the three-component coupling reaction of alkyne, aldehyde and amine forming propargylamines.

Full text of DOI:10.1016/j.jorganchem.2012.12.008

Journal of Organometallic Chemistry 726 (2013) 1e8
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and catalytic activity of N-heterocyclic carbene silver
complexes derived from 1-[2-(pyrazol-1-yl)phenyl]imidazole
*
Cai-Hong Cheng, Dan-Feng Chen, Hai-Bin Song, Liang-Fu Tang
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, People’s Republic of China
a r t i c l e i n f o
a b s t r a c t
Article history:
Six mono- and dinuclear N-heterocyclic carbene (NHC) silver complexes based on 1-[2-(pyrazol-1-yl)
phenyl]imidazole have been synthesized and characterized by elemental analysis and NMR spectroscopy,
and their structures have been confirmed by single crystal X-ray diffraction. The N-functionalized
carbene ligands exhibit versatile coordination modes in these silver complexes. N-[2-(3,5-
Dimethylpyrazol-1-yl)phenyl]-N-benzylimidazol-2-ylidene (L) acts as a monodentate ligand through
the carbene carbon in mononuclear LAgCl. While in dinuclear L2Ag2(PF6)2 and L02Ag2(PF6)2 (L0 ¼ N-[2-
(pyrazol-1-yl)phenyl]-N-benzylimidazol-2-ylidene), L and L0 act as bridging bidentate ligands through
the pyrazolyl nitrogen and the carbene carbon atoms to two silver atoms. Though, these two silver atoms
have different coordination environments. In the former, one silver atom coordinates with two carbene
carbons, the other coordinates with two pyrazolyl nitrogen atoms. In the latter, each silver atom
coordinates with one carbene carbon and one pyrazolyl nitrogen atom, respectively. A dinuclear
macrocyclic structure is observed in m-xylyl bridging tetradentate bis-NHC complexes L2Ag2(BF4)2 and
(L)CH2C6H4CH2(L)Ag2(BF4)2, in which the coordination mode of carbene ligands is similar with that in
L2Ag2(PF6)2. Preliminary catalytic tests show that all these complexes exhibit highly effective catalytic
activity in the three-component coupling reaction of alkyne, aldehyde and amine forming
propargylamines.
Received 3 October 2012
Received in revised form
5 December 2012
Accepted 6 December 2012
Keywords:
N-heterocyclic carbene
Pyrazole
Silver
Catalytic activity
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
catalyze the three-component coupling reaction of aldehyde,
alkyne and amine to propargylamines [24e26]. With the afore-
Transition metal complexes of N-heterocyclic carbenes (NHCs)
have been the subject of extensive investigations because of their
successful applications in coordination chemistry and homoge-
neous and asymmetric catalyses [1e4]. Among these complexes,
NHC silver complexes have received special attention due to their
structural diversity, wide application as effective carbene transfer
agents [5e7] and prominent biological activity [8e12]. However,
despite the fact that silver complexes have been extensively used
to catalyze the formation of CeC and CeE (E ¼ heteroatom) bonds
[13e15], the utility of NHC silver complexes in chemical catalysis
remains scarcely explored, and only a few examples were re-
ported. Representative successes have demonstrated that NHC
silver complexes exhibit good catalytic activities for diboration of
alkenes [16], carbomagnesiation of terminal alkenes [17], direct
alkynylation of isatins [18], CO2 fixation [19], cyanosilylation of
mentioned progress as inspirations, the exploitation of wider
applications of NHC silver complexes in catalyzed organic trans-
formations is aspired, in view of the high catalytic activity of silver
compounds in many organic reactions [13e15] and the ease of
preparation of NHC silver complexes. In this paper, we report the
synthesis of six NHC silver complexes based on 1-[2-(pyrazol-1-yl)
phenyl]imidazole, and their catalytic activity in the three-
component coupling reaction of alkyne, aldehyde and amine
forming propargylamines.
2. Results and discussion
2.1. Synthesis of N-[2-(pyrazol-1-yl)phenyl]-N-benzylimidazol-2-
ylidene silver complexes
imines [20], and ring-opening polymerization of L-lactide [21e23].
Recently, NHC silver complexes have also been successfully used to
1-[2-(Pyrazol-1-yl)phenyl]imidazoles (3) and (4) were synthe-
sized by the copper catalyzed coupling reaction of 1-(2-iodophenyl)
pyrazoles (1) and (2) with imidazole (Scheme 1). Treatment of
these two substituted imidazoles with benzyl chloride gave the
imidazolium salts (5) and (6). The hexafluorophosphate and
* Corresponding author. Fax: þ86 22 23502458.
E-mail address: lftang@nankai.edu.cn (L.-F. Tang).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.12.008

2
C.-H. Cheng et al. / Journal of Organometallic Chemistry 726 (2013) 1e8
Scheme 1.
ꢀ
tetrafluoroborate salts (7e9) were obtained by the anion exchange
reaction of (5) and (6) with KPF6 or NH4BF4, respectively. Reaction
of these imidazolium salts with Ag2O gave the carbene complexes
(10e13) in good yields. Complexes 10e13 have been characterized
by elemental analyses and NMR spectroscopy. Compared with the
spectra of the imidazolium salts 5e9, a notable change in the 1H
NMR spectra of 10e13 was the disappearance of the characteristic
proton signal of imidazolium, indicating the formation of NHC
silver complexes along with the deprotonation of the acidic
hydrogen. At the same time, an obvious carbene carbon signal was
observed at ca. 179 ppm in the 13C NMR spectra of 11e13. In the
meanwhile, neither the signal of the carbene carbon in 10 nor the
silverecarbon coupling in 11e13 was observed, which may be
attributed to the fluxional behavior of these NHC complexes in
solution [27,28].
Ccarbene and AgeCl bond distances are 2.075(2) and 2.3228(8) A,
respectively, comparable to those in sterically demanding NHC
supported silver chlorides, such as (IDD)AgCl (AgeCcarbene 2.067(4)
ꢀ
and AgeCl 2.3200(9) A, IDD ¼ 1,3-bis(dodecyl)imidazol-2-ylidene)
ꢀ
[29], (IBp)AgCl (AgeCcarbene 2.079(2) and AgeCl 2.3440(11) A,
IBp ¼ 1,3-bis(2-phenylphenyl)imidazol-2-ylidene) [30] and (IPr*)
ꢀ
AgCl (AgeCcarbene 2.081(2) and AgeCl 2.3189(9) A, IPr* ¼ 1,3-
The molecular structures of 10e13 have been further confirmed
by X-ray structural analyses, and are presented in Figs. 1e4,
respectively. It seems that the coordination environment of silver
atoms in these complexes markedly depends on the substituents of
pyrazolyl rings and the anions. Fig. 1 shows that complex 10 has
a monomeric structure with a two-coordinate silver atom. N-
[2-(3,5-Dimethylpyrazol-1-yl)phenyl]-N-benzylimidazol-2-ylidene
acts a monodentate ligand by the carbene carbon atom, and the
pyrazolyl nitrogen atom does not take part in the coordination to
the silver center. The coordination geometry around the silver atom
is nearly linear. The angle of C(14)eAg(1)eCl(1) is 171.55(5)ꢀ, falling
within the range of values observed in other analogous monomeric
two-coordinate (NHC)AgX complexes (166e176ꢀ) [5,25]. The Age
Fig. 1. The molecular structure of 10. The thermal ellipsoids are drawn at the 30%
ꢀ
ꢀ
probability level. Selected bond distances (A) and angles ( ): Ag(1)eC(14), 2.075(2),
ꢀ
Ag(1)eCl(1) 2.3228(8), C(12)eC(13) 1.344(3), N(3)eC(14) 1.356(2) A; C(14)eAg(1)e
Cl(1) 171.55(5), N(4)eC(15)eC(16) 114.3(2), N(3)eC(14)eN(4) 104.1(2), C(11)eN(3)e
C(14) 125.2(2)ꢀ.

C.-H. Cheng et al. / Journal of Organometallic Chemistry 726 (2013) 1e8
3
Fig. 4. The molecular structure of 13. The thermal ellipsoids are drawn at the 30%
probability level. The uncoordinated solvent and BFꢁ4 anions have been deleted for
ꢀ
ꢀ
clarity. Selected bond distances (A) and angles ( ): Ag(1)eC(10) 2.077(2), Ag(1)eN(8)
ꢀ
2.131(2), Ag(2)eC(31) 2.063(2), Ag(2)eN(4) 2.104(2), Ag(1).Ag(2) 3.461(1) A; C(10)e
Ag(1)eN(8) 176.66(7), C(31)eAg(2)eN(4) 174.3(4), N(1)eC(7)eC(6) 111.3(2), N(5)e
C(28)eC(27) 109.9(2), N(1)eC(10)eN(2) 103.8(2), N(5)eC(31)eN(6) 104.1(2)ꢀ.
ligands exhibit different coordination modes in these two
complexes. In 11, two NHCs show a head (carbene)eto head (car-
bene) and a tail (nitrogen)eto tail (nitrogen) coordination modes to
two silver atoms, respectively. While in 12, the NHCs only show
a headeto tail coordination mode to two silver atoms. Obviously,
the substituents of pyrazolyl rings significantly affect the coordi-
nation modes of the NHC ligands in 11 and 12. The AgeCcarbene and
AgeNpyrazolyl bond distances are similar in these two complexes,
Fig. 2. The molecular structure of 11.CH3CN. The thermal ellipsoids are drawn at the
30% probability level. TheꢀPFꢁ6 anions have been deleted for clarity. Selected bond
ꢀ
distances (A) and angles ( ): Ag(1)eN(1) 2.227(5), Ag(1)eN(5) 2.276(5), Ag(1)eN(9)
ꢀ
2.225(7), Ag(1)eAg(2) 3.0667(8), Ag(2)eC(12) 2.091(5), Ag(2)eC(31) 2.088(5) A; N(1)e
Ag(1)eN(5) 115.5(2), C(12)eAg(2)eC(31) 178.8(2), N(3)eC(12)eN(4) 104.1(4), N(7)e
C(31)eN(8) 103.6(4), N(4)eC(13)eC(14) 112.9(5), N(8)eC(32)eC(33) 113.9(4), C(9)e
N(3)eC(12) 123.8(4), C(28)eN(7)eC(31) 123.2(4)ꢀ.
ꢀ
but the AgeAg distance (3.0667(8) A) in 11 is considerably shorter
ꢀ
than that in 12 (3.269(3) A). These values are shorter than the sum
ꢀ
of the van der Waals radii for silver (3.44) A [32], suggesting
bis(2,6-bis(diphenylmethyl)-4-methylphenyl)imidazol-2-ylidene)
[31]. These data suggest that N-[2-(3,5-dimethylpyrazol-1-yl)
phenyl]-N-benzylimidazol-2-ylidene is a considerably sterically
demanding ligand possibly owing to the rigidity of three aromatic
rings.
Figs. 2 and 3 illustrate that the NHC ligands in 11 and 12 act as
bridging bidentate ligands through the pyrazolyl nitrogen and the
carbene carbon atoms to two silver atoms. Though, these two NHC
significant silveresilver bonding in these two complexes.
Fig. 4 clarifies that the fundamental fragment of 13 is similar
ꢀ
with that in 12. However, the long AgeAg separation (3.461(1) A) in
13 suggests that the silveresilver interaction is very weak in this
complex. The C(10)eAg(1)eN(8) angle is 176.66(7)ꢀ, slightly larger
than the C(31)eAg(2)eN(4) angle of 174.3(4)ꢀ and the corre-
sponding CeAgeN angles (174.6(1) and 173.7(1)ꢀ in 12. The other
notable difference between 13 and 12 is the dihedral angles
between the phenyl plane and the pyrazolyl ring, or the imidazolyl
ring. For example, the dihedral angles of the C(11)eC(16) phenyl
plane with the N(3)eC(18) pyrazolyl ring and the N(1)eC(8) imi-
dazolyl ring in 13 are 62.4ꢀ and 59.1ꢀ, respectively. While the cor-
responding dihedral angles in 12 are 68.6ꢀ (the C(11)eC(16) phenyl
plane with the N(3)eC(18) pyrazolyl ring) and 119.3ꢀ (the C(11)e
C(16) phenyl plane with the N(1)eC(8) imidazolyl ring). These
data reflect the different degree of distortion in these two
complexes.
2.2. Synthesis of m-xylyl bridging bis-NHC silver complexes
Transition metal complexes with bis- or tris-NHC ligands have
shown higher stability and enhanced catalytic activities compared
with those with monodentate NHC ligands, which drives the rapid
development of polydentate NHCs [33e36]. Xylyl-linked bis-NHC
ligands have been extensively investigated in recent years [37e43],
and they usually acted as bidentate ligands in complexes. However,
polydentate xylyl-linked bis-NHCs are rare. Herein, upon treatment
of bis(imidazolium) salts 15 and 16 with Ag2O, two tetradentate
bis-NHC complexes 17 and 18 were obtained (Scheme 2).
Complexes 17 and 18 have also been characterized by elemental
analyses and NMR spectroscopy. The 1H NMR spectra of these two
complexes indicated the methylene protons of the m-xylyl group
were not equivalent, and an AB system was observed at room
temperature. This suggests that the macrocyclic structures of these
Fig. 3. The molecular structure of 12. The thermal ellipsoids are drawn at the 30%
probability level. The PFꢁ6 anions have been deleted for clarity. Selected bond distances
ꢀ
ꢀ
(A) and angles ( ): Ag(1)eC(31) 2.086(3), Ag(1)eN(4) 2.119(3), Ag(1)eAg(2) 3.269(1),
ꢀ
Ag(2)eC(10) 2.080(4), Ag(2)eN(8) 2.126(3) A; C(31)eAg(1)eN(4) 174.6(1), C(10)e
Ag(2)eN(8) 173.7(1), N(5)eC(31)eN(6) 105.3(3), N(1)eC(10)eN(2) 104.5(3), N(1)e
C(7)eC(6) 110.7(3), N(5)eC(28)eC(27) 111.1(3), C(10)eN(2)eC(11) 123.6(3), C(31)e
N(6)eC(32) 124.9(3)ꢀ.

4
C.-H. Cheng et al. / Journal of Organometallic Chemistry 726 (2013) 1e8
Scheme 2.
two complexes are reserved in solution, which prevents the free
rotation of the NHC ligand. The molecular structure of 18 has been
confirmed by X-ray crystallography and is presented in Fig. 5. As
shown in Fig. 5, the NHC acts as a tetradentate ligand through two
carbene carbons and two pyrazolyl nitrogen atoms to two silver
centers, leading to the formation of twisted dinuclear macrocyclic
structures. Each silver atom coordinates with one carbene carbon
and one pyrazolyl nitrogen. The coordination mode of the NHC
ligand is similar with that in 12. The key geometric parameters,
such as the AgeC and AgeN bond distances, the CeAgeN angles,
angles of the C(6)eC(11) phenyl plane with the N(1)eC(2) pyrazolyl
ring (108.3ꢀ) and the N(3)eC(14) imidazolyl ring (117.2ꢀ) as well as
the C(26)eC(31) phenyl plane with the N(7)eC(33) pyrazolyl ring
(112.0ꢀ) and the N(5)eC(23) imidazolyl ring (116.7ꢀ) reveal
considerable distortion between the phenyl plane with the pyr-
azolyl and the imidazolyl rings, respectively. It is noted that the
N(4)eC(15)eC(16) angle of 115.4(3)ꢀ deviates from the tetrahedral
geometry of the sp3-hybridized carbon, suggesting a large steric
repulsion in this complex.
ꢀ
are also similar to those in 12. The AgeAg distance is 3.3834(8) A,
slightly shorter than the sum of the van der Waals radii for silver
2.3. Catalytic activity of the NHC silver complexes
[32], suggesting a weak silveresilver interaction. The dihedral
The three-component coupling reaction of alkyne, aldehyde and
amine to propargylamines catalyzed by transition metals has
attracted considerable attention in recent years [44], due to the
wide applications of propargylamines as key intermediates in the
construction of nitrogen-containing biologically active compounds.
Although silver compounds exhibited highly effective catalytic
activity for this three-component coupling reaction [45], only
several NHCeAg systems were exploited as catalysts [24e26], and
most of them were mononuclear silver complexes. Furthermore, it
seems that the monomeric (NHC)AgX complexes showed higher
catalytic activity than the dimeric [(NHC)AgX]2 and the cationic
biscarbene silver complexes [25]. Herein, our preliminary studies
showed that all these monomeric complex 10 and dinuclear
cationic complexes 11e13 as well as 17 and 18 exhibited effective
catalytic activity in the three-component coupling reaction of
phenylacetylene, aldehyde and piperidine (Table 1). Moderate
yields were obtained when 3 mol% of 10 was used as the catalyst for
the coupling reaction of para-formaldehyde (Table 1, entry 1).
Unfortunately, this complex showed low catalytic activity for the
coupling of benzaldehyde (entry 2). However, high catalytic activity
for the coupling of cyclohexanecarboxaldehyde was observed
(entry 4). It is interesting that the catalytic activity of dinuclear
complexes 11e13 as well as 17 and 18 is almost two times that of
mononuclear complex 10 (entries 5e9), indicating that two silver
atoms in dinuclear complexes simultaneously play the catalytic
Fig. 5. The molecular structure of 18. The thermal ellipsoids are drawn at the 30%
probability level. The uncoordinated solvents and BFꢁ4 anions have been deleted for
ꢀ
ꢀ
clarity. Selected bond distances (A) and angles ( ): Ag(1)eC(25) 2.078(4), Ag(1)eN(1)
ꢀ
2.122(3), Ag(2)eC(14) 2.062(3), Ag(2)eN(8) 2.106(3), Ag(1).Ag(2) 3.3834(8) A; C(25)e
Ag(1)eN(1) 173.9(1), C(14)eAg(2)eN(8) 175.1(1), N(4)eC(15)eC(16) 115.4(3), N(5)e
C(22)eC(20) 109.2(3), N(4)eC(14)eN(3) 103.6(3), N(5)eC(25)eN(6) 103.9(3)ꢀ.

C.-H. Cheng et al. / Journal of Organometallic Chemistry 726 (2013) 1e8
5
J ¼ 2.1 Hz, 1H, H4 of pyrazole), 7.16 (dt, J ¼ 2.0 Hz, J ¼ 7.9 Hz, 1H),
7.41e7.48 (m, 2H), 7.98 (dd, J ¼ 0.9 Hz, J ¼ 8.0 Hz,1H) (C6H4), 7.73 (d,
J ¼ 2.3 Hz, 1H), 7.77 (d, J ¼ 1.4 Hz, 1H) (H3 and H5 of pyrazole) ppm.
Table 1
Catalytic activity of the NHC silver complexes.
13C NMR:
d 94.4, 106.6, 128.2, 129.0, 130.2, 131.1, 140.1, 140.8, 143.4
(C6H4 and carbons of pyrazole) ppm. HRMSeESI (m/z): 292.9547
(Calc. for C9H7IN2Na: 292.9552, [M þ Na]þ, 100%).
Entry
R
Cat.
n
t/h
Yield (%)a,b
3.2. Synthesis of 1-(2-iodophenyl)-3,5-dimethylpyrazole (2)
1
2
3
4
5
6
7
8
9
H
Ph
10
10
10
10
11
12
13
17
18
3
3
2
3
1.5
1.5
1.5
1.5
1.5
2
12
8
8
8
8
8
2
8
55
13
50
95
94
97
97
93
94
Acetylacetone (6.03 g, 60.3 mmol) was slowly added to the
solution of 2-iodophenylhydrazine (12.8 g, 54.7 mmol) in ethanol
(100 ml). The mixture was stirred and heated at reflux for 8 h.
After cooling to room temperature, the solvent was removed
under reduced pressure. The residue was dissolved in water
(100 ml), and extracted with ethyl ether (3 ꢂ 40 ml). The organic
phases were combined, washed with saturated NaHCO3 solution
(3 ꢂ 30 ml), and dried over anhydrous MgSO4. After the solvent
was removed under reduced pressure, red oil was obtained. Yield:
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
Cyclohexyl
a
Isolated yield.
Average of two runs.
b
13.1 g (80%). 1H NMR:
d
2.12, 2.33 (s, s, 3H, 3H, CH3), 6.01 (s, 1H, H4
of pyrazole), 7.17 (td, J ¼ 7.7 Hz, J ¼ 1.5 Hz, 1H) 7.36 (dd, J ¼ 7.8 Hz,
J ¼ 1.5 Hz, 1H), 7.46 (dd, J ¼ 11.1 Hz, J ¼ 4.0 Hz, 1H), 7.95 (d,
role. When complex 17 was used the catalyst, the coupling reaction
proceeded significantly faster (entry 8). In addition, the different
coordination mode of NHC has little effect on the catalytic activity
of complexes (entries 5 and 6).
In summary, six NHC silver complexes derived from 1-[2-(pyr-
azol-1-yl)phenyl]imidazole have been synthesized. The N-func-
tionalized NHC ligands exhibit versatile coordination modes in
these silver complexes. For example, the NHC acts as a mono-
J ¼ 7.9 Hz, 1H) (C6H4) ppm. 13C NMR:
d 11.7, 13.7 (CH3), 98.2, 105.6,
129.0, 129.4, 130.6, 139.5, 140.4, 142.6, 149.0 (C6H4 and carbons of
pyrazole) ppm. HRMSeESI (m/z): 320.9858 (Calc. for C11H11IN2Na:
320.9865, [M þ Na]þ, 100%).
3.3. Synthesis of 1-[2-(pyrazol-1-yl)phenyl]imidazole (3)
Compound 1 (2.7 g, 10 mmol), imidazole (0.82 g, 12 mmol),
dentate ligand in mononuclear complex 10. While
a head
K2CO3 (2.76 g, 20 mmol), L-proline (0.23 g, 2 mmol) and CuI (0.19 g,
(carbene)eto head (carbene) or head (carbene)eto tail (nitrogen)
coordination mode is found in dinuclear complexes 11 and 12,
respectively. In addition, m-xylyl bridging tetradentate bis-NHCs
are observed in complexes 17 and 18. Preliminary catalytic
studies prove that all these mononuclear and dinuclear complexes
exhibit good catalytic activity in the three-component coupling
reaction of alkyne, aldehyde and amine to propargylamines. Studies
on expanding the scope of substrates, the structural modification of
NHC and the structure-activity relationship of catalysts are ongoing
in our laboratory.
1 mmol) were added to DMSO (10 ml) under Ar atmosphere. The
mixture was stirred and heated at 90 ꢀC for 48 h. After cooling to
room temperature, saturated NaCl solution (30 ml) was added. The
aqueous solution was extracted with ethyl acetate (3 ꢂ 30 ml). The
organic phases were combined and washed again with saturated
NaCl solution (3 ꢂ 30 ml), and then dried over anhydrous Na2SO4.
After the solvent was removed under reduced pressure, the residue
was purified by column chromatography on silica using ethyl
acetate/hexane (1/1 v/v) as the eluent. The yellow eluate was
concentrated to dryness to give slightly yellow oil of 3. Yield: 1.15 g
(55%). 1H NMR:
d
6.34 (t, J ¼ 2.0 Hz, 1H, H4 of pyrazole), 6.85 (s, 1H),
3. Experimental
7.03 (d, J ¼ 2.4 Hz, 1H), 7.42 (s, 1H), 7.13 (s, 1H), 7.42e7.60 (m, 3H),
7.71 (s,1H), 7.76 (dd, J ¼ 1.4 Hz, J ¼ 7.8 Hz,1H) (protons of imidazole,
NMR (1H and 13C) were recorded on a Bruker 400 spectrometer
using CDCl3 as solvent unless otherwise noted, and the chemical
shifts were reported in ppm with respect to the reference (internal
SiMe4 for 1H and 13C NMR spectra). Element analyses were carried
out on an Elementar Vairo EL analyzer. HR mass spectra were ob-
tained on a Varian QFT-ESI spectrometer. Melting points were
measured with an X-4 digital micro melting-point apparatus and
were uncorrected. 2-Iodophenylhydrazine [46] was prepared
according to the literature method.
pyrazole and phenyl) ppm. 13C NMR:
d 108.0, 119.8, 126.7, 127.3,
129.0, 129.4, 129.9, 130.2, 130.3, 131.4, 136.9, 141.4 (C6H4, carbons of
imidazole and pyrazole) ppm. HRMSeESI (m/z): 233.0792 (Calc. for
C12H10N4Na: 233.0803, [M þ Na]þ, 100%).
3.4. Synthesisof1-[2-(3,5-dimethylpyrazol-1-yl)phenyl]imidazole(4)
This compound was obtained similarly using 2 instead of 1 as
described above for 3 as slightly yellow solids. Yield: 74%, mp 80e
82 ꢀC. 1H NMR:
d
1.70, 2.28 (s, s, 3H, 3H, CH3), 5.87 (s, 1H, H4 of
3.1. Synthesis of 1-(2-iodophenyl)pyrazole (1)
pyrazole), 6.78 (s, 1H), 7.05 (s, 1H), 7.33 (s, 1H) (protons of imid-
azole), 7.42e7.60 (m, 4H, C6H4) ppm. 13C NMR:
d 10.4, 13.5 (CH3),
Concentrated hydrochloric acid (14.5 ml, 87 mmol) was added
dropwise to the stirred mixture of 2-iodophenylhydrazine (14 g,
60 mmol) and malondialdehyde bis(dimethyl acetal) (12 g,
72 mmol) at 0 ꢀC. After the addition completed, the reaction
mixture was stirred for 2 h at room temperature, and water (20 ml)
was added. Then, the reaction mixture was neutralized with NaOH
solution (1 M). The solution was extracted with ethyl acetate
(3 ꢂ 30 ml). The organic phases were combined, and dried over
anhydrous MgSO4. After the solvent was removed under reduced
106.3 (C4 of pyrazole), 118.9, 124.8, 128.4, 130.0, 130.1, 130.2, 133.2,
134.3, 136.5, 141.8, 150.0 (C6H4, carbons of imidazole and pyrazole)
ppm. Anal. Calc. for C14H14N4: C, 70.57; H, 5.92; N, 23.51. Found: C,
70.37; H, 5.92; N, 23.49%.
3.5. Synthesis of L0HCl (5) (L0 ¼ N-[2-(pyrazol-1-yl)phenyl]-N-
benzylimidazol-2-ylidene)
The mixture of 3 (0.21 g, 1 mmol) and PhCH2Cl (0.12 ml, 1 mmol)
in CH3CN (2 ml) was stirred and heated at reflux for 24 h. After
pressure, red oil was obtained. Yield: 11.8 g (73%). 1H NMR:
d 6.49 (t,

6
C.-H. Cheng et al. / Journal of Organometallic Chemistry 726 (2013) 1e8
cooling to room temperature, the solvent was removed under
reduced pressure, the residue was washed with anhydrous ethyl
ether, and dried in vacuo to give viscous oils of 5. Yield: 0.32 g (94%).
3.9. Synthesis of LHBF4 (9)
This compound was obtained similarly using NH4BF4 instead of
1H NMR:
d
5.74 (s, 2H, CH2), 6.37 (s, br, 1H, H4 of pyrazole), 6.98 (s,
KPF6 as described above for 7 as white solids. Yield: 77%, mp 130e
1H), 7.36e7.40 (m, 4H), 7.54e7.59 (m, 5H), 7.63e7.68 (m, 1H), 7.74
(s, 1H), 7.82 (d, J ¼ 7.2 Hz, 1H) (C6H4, C6H5, protons of imidazole and
132 ꢀC. 1H NMR:
d 2.00, 2.01 (s, s, 3H, 3H, CH3), 5.39 (s, 2H, CH2),
5.87 (s,1H, H4 of pyrazole), 7.03 (t, J ¼ 1.8 Hz,1H), 7.35e7.38 (m, 6H),
7.46e7.49 (m, 1H), 7.61e7.66 (m, 2H), 7.78e7.81 (m, 1H) (C6H4, C6H5
and protons of imidazole), 8.68 (s, 1H, proton of imidazolium) ppm.
pyrazole),10.61 (s,1H, proton of imidazolium) ppm. 13C NMR:
d 53.4
(CH2), 108.3 (C4 of pyrazole), 122.1, 122.9, 126.8, 127.6, 129.3 (3 C),
129.4, 129.9, 131.2, 131.9, 133.3, 135.2, 138.3, 142.1 (C6H4, carbons of
imidazole and pyrazole) ppm. HRMSeESI (m/z): 301.1446 (Calc. for
C19H17Nþ4 : 301.1448, [M ꢁ Cl]þ, 100%).
13C NMR:
d
11.1, 13.3 (CH3), 53.7 (CH2), 107.1 (C4 of pyrazole), 122.4,
123.0, 126.7, 129.1, 129.2, 129.5, 129.6, 130.9, 131.4, 131.5, 132.7,
133.8, 135.9, 141.6, 150.7 (C6H4, C6H5, carbons of imidazole and
pyrazole) ppm. Anal. Calc. for C21H21BF4N4: C, 60.60; H, 5.09; N,
13.46. Found: C, 60.43; H, 5.09; N, 13.52%.
3.6. Synthesis of LHCl (6) (L ¼ N-[2-(3,5-dimethylpyrazol-1-yl)
phenyl]-N-benzylimidazol-2-ylidene)
3.10. Synthesis of LAgCl (10)
The mixture of 4 (0.24 g, 1 mmol) and PhCH2Cl (0.12 ml, 1 mmol)
in CH3CN (2 ml) was stirred and heated at reflux for 24 h. After
cooling to room temperature, ethyl acetate (10 ml) was added.
White solids were formed, which were filtered and washed with
dried ethyl ether to give white solids of 6. Yield: 0.33 g (90%), mp
The mixture of 6 (0.33 g, 0.9 mmol) and Ag2O (0.14 g, 0.6 mmol)
in CH2Cl2 (10 ml) was stirred at room temperature for 24 h in the
absence of light. The solution was filtered and concentrated to
dryness. A red solid was obtained. Yield: 0.42 g (99%), mp 69e71 ꢀC.
1H NMR:
d 1.93, 2.17 (s, s, 3H, 3H, CH3), 5.31 (s, 2H, CH2), 5.84 (s, 1H,
94e96 ꢀC. 1H NMR:
d 2.03, 2.06 (s, s, 3H, 3H, CH3), 5.78 (s, 2H, CH2),
H4 of pyrazole), 6.88 (s, 2H), 7.17e7.19 (m, 2H), 7.36e7.38 (m, 3H),
7.50e7.53 (m, 1H), 7.59e7.62 (m, 1H), 7.70e7.73 (m, 1H) (C6H4, C6H5
5.90 (s, 1H, H4 of pyrazole), 6.92 (s, 1H), 7.34e7.40 (m, 3H), 7.49e
7.53 (m, 4H), 7.65e7.69 (m, 2H), 7.98e8.01 (m, 1H) (C6H4, C6H5
and protons of imidazole), 10.78 (s, 1H, proton of imidazolium)
and protons of imidazole) ppm. 13C NMR:
d 9.9, 11.6 (CH3), 54.1
(CH2), 104.4 (C4 of pyrazole), 118.9, 121.7, 125.6, 125.7, 126.9, 127.3,
127.7, 128.4, 128.5, 133.1, 133.3, 134.6, 139.4, 148.1 (C6H4, C6H5,
carbons of imidazole and pyrazole) ppm. The carbene carbon was
not observed. Anal. Calc. for C21H20AgClN4: C, 53.47; H, 4.27; N,
11.88. Found: C, 53.74; H, 4.04; N, 11.74%.
ppm. 13C NMR:
d
11.4, 13.3 (CH3), 53.5 (CH2), 107.1 (C4 of pyrazole),
122.1, 122.4, 126.7, 129.1, 129.3, 129.4, 129.5, 131.0, 131.4, 131.5, 133.2,
133.6, 137.7, 141.6, 150.7 (C6H4, C6H5, carbons of imidazole and
pyrazole) ppm. Anal. Calc. for C21H21ClN4: C, 69.13; H, 5.80; N,15.36.
Found: C, 69.43; H, 5.98; N, 15.24%.
In addition, when heating 10 in dioxane at 80 ꢀC for 1 h under Ar
atmosphere, no obvious change was observed. After removing the
solvent, the residue was monitored by 1H NMR. The result indicated
that the 1H NMR spectrum of the residue was the same as that of 10,
suggesting that this complex was stable in the dioxane solution at
80 ꢀC.
3.7. Synthesis of L0HPF6 (7)
Compound 5 (0.17 g, 0.5 mmol) was added to the solution of
KPF6 (0.11 g, 0.6 mmol) in H2O (30 ml). The mixture was stirred for
30 min at room temperature, a white precipitate was formed. The
reaction mixture was extracted with CH2Cl2 (3 ꢂ 10 ml), the organic
phases were combined and dried over anhydrous MgSO4. After
removing the solvent, the residue was washed with ethyl ether to
give a white and strongly hygroscopic solid of 7. Yield: 0.17 g (77%).
3.11. Synthesis of L02Ag2(PF6)2 (11)
The mixture of 7 (0.17 g, 0.38 mmol) and Ag2O (80 mg,
0.38 mmol) in CH2Cl2 (10 ml) was stirred at room temperature for
24 h in the absence of light. The solution was filtered and
concentrated to ca. 2 ml, ethyl ether (5 ml) was added to give yellow
solids of 11. Yield: 0.38 g (91%), mp 153e155 ꢀC. 1H NMR (DMSO-
1H NMR:
d
5.28 (s, 2H, CH2), 6.33 (t, J ¼ 2.2 Hz, 1H, H4 of pyrazole),
7.04 (t, J ¼ 1.7 Hz, 1H), 7.22e7.24 (m, 1H), 7.33e7.35 (m, 3H), 7.38e
7.40 (m, 3H), 7.50e7.52 (m, 2H), 7.61e7.65 (m, 3H) (C6H4, C6H5 and
protons of imidazole), 8.37 (s, 1H, proton of imidazolium) ppm. 13C
d6):
d
5.22 (s, 2H, CH2), 6.43 (t, J ¼ 2.2 Hz,1H, H4 of pyrazole), 7.07 (d,
d
53.6 (CH2), 108.3 (C4 of pyrazole), 122.2, 123.6, 126.5, 127.4,
J ¼ 6.4 Hz, 2H), 7.33e7.38 (m, 3H), 7.48 (s, 1H), 7.56e7.69 (m, 7H)
NMR:
(C6H4, C6H5 and protons of imidazole) ppm. 13C NMR (DMSO-d6):
128.8, 129.0, 129.5, 129.7, 129.8, 131.1, 132.1, 132.4, 135.2, 136.2, 142.2
(C6H4, C6H5, carbons of imidazole and pyrazole) ppm. Anal. Calc. for
C19H17F6N4P: C, 51.13; H, 3.84; N, 12.55. Found: C, 51.41; H, 3.68; N,
12.22%.
d
52.9 (CH2), 106.5 (C4 of pyrazole), 121.5, 123.1, 125.9, 126.1, 126.8,
127.1, 127.6, 129.0, 129.5, 131.3, 133.3, 134.3, 135.6, 141.0 (C6H4, C6H5,
carbons of imidazole and pyrazole), 179.0 (CCarbene) ppm. Anal. Calc.
for C38H32Ag2F12N8P2: C, 41.25; H, 2.92; N, 10.13. Found: C, 41.44; H,
2.65; N, 10.21%.
3.8. Synthesis of LHPF6 (8)
3.12. Synthesis of L2Ag2(PF6)2 (12)
This compound was obtained similarly using 6 instead of 5 as
described above for 7 as white solids. Yield: 75%, mp 116e118 ꢀC. 1H
This compound was obtained similarly using 8 instead of 7 as
described above for 11 as colorless solids. Yield: 90%, mp 116e
NMR: d
2.03, 2.06 (s, s, 3H, 3H, CH3), 5.36 (s, 2H, CH2), 5.91 (s, 1H, H4
of pyrazole), 7.10 (s, 1H), 7.28 (s, 1H), 7.34e7.36 (m, 2H), 7.42e7.44
(m, 3H), 7.50 (d, J ¼ 7.5 Hz, 1H), 7.63e7.71 (m, 2H), 7.77 (d,
J ¼ 7.1 Hz, 1H) (C6H4, C6H5 and protons of imidazole), 8.40 (s, 1H,
118 ꢀC. 1H NMR (DMSO-d6):
d 1.97, 2.05 (s, s, 3H, 3H, CH3), 5.23 (s,
2H, CH2), 6.19 (s, 1H, H4 of pyrazole), 6.99 (s, br, 2H), 7.29e7.42 (m,
3H), 7.48 (s, 1H), 7.56e7.75 (m, 5H) (C6H4, C6H5 and protons of
proton of imidazolium) ppm. 13C NMR:
d
11.1, 13.3 (CH3), 53.9 (CH2),
imidazole) ppm. 13C NMR (DMSO-d6):
d 11.2, 13.5 (CH3), 53.9 (CH2),
107.2 (C4 of pyrazole), 122.4, 123.2, 126.7, 129.1, 129.2, 129.6, 129.8,
130.9, 131.3, 131.7, 132.2, 133.8, 135.5, 141.7, 150.8 (C6H4, C6H5,
carbons of imidazole and pyrazole) ppm. Anal. Calc. for
C21H21F6N4P: C, 53.17; H, 4.46; N, 11.81. Found: C, 53.13; H, 4.51; N,
11.74%.
106.8 (C4 of pyrazole), 123.4, 123.6, 126.7, 127.9, 128.3, 128.7, 129.1,
131.0, 132.3, 132.8, 136.2, 136.6, 144.3, 150.6 (C6H4, C6H5, carbons of
imidazole and pyrazole), 178.7 (CCarbene) ppm. Anal. Calc. for
C42H40Ag2F12N8P2: C, 43.39; H, 3.47; N, 9.64. Found: C, 43.33; H,
3.82; N, 9.65%.

C.-H. Cheng et al. / Journal of Organometallic Chemistry 726 (2013) 1e8
7
3.13. Synthesis of L2Ag2(BF4)2 (13)
NMR (DMSO-d6): d 1.85, 2.15 (s, s, 6H, 6H, CH3), 5.48 (s, 4H, CH2),
5.99 (s, 2H, H4 of pyrazole), 7.28 (d, J ¼ 7.4 Hz, 2H), 7.52e7.58 (m,
2H), 7.68 (s, 2H), 7.74e7.91 (m, 10H) (C6H4 and protons of imid-
azole), 9.43 (s, 2H, protons of imidazolium) ppm. 13C NMR (DMSO-
This compound was obtained similarly using 9 instead of 7 as
described above for 11 as yellow solids. Yield: 86%, mp 114e117 ꢀC.
1H NMR (DMSO-d6):
d
1.98, 2.08 (s, s, 3H, 3H, CH3), 5.25 (s, 2H, CH2),
d6): d
11.0, 12.9 (CH3), 51.8 (CH2), 106.5 (C4 of pyrazole), 122.4, 124.0,
6.23 (s,1H, H4 of pyrazole), 7.01 (s, br, 2H), 7.31e7.44 (m, 3H), 7.51 (s,
1H), 7.58e7.79 (m, 5H) (C6H4, C6H5 and protons of imidazole) ppm.
127.5, 128.2, 128.4, 128.6, 129.9, 130.0, 131.2, 131.6, 134.1, 135.1, 137.3,
141.1, 149.1 (C6H4, carbons of imidazole and pyrazole) ppm. Anal.
Calc. for C36H36F12N8P2: C, 49.66; H, 4.17; N, 12.87. Found: C, 49.63;
H, 4.17; N, 12.81%.
13C NMR (DMSO-d6):
d
11.3, 13.5 (CH3), 54.0 (CH2), 106.9 (C4 of
pyrazole), 123.4, 123.7, 126.8, 128.0, 128.4, 128.8, 129.1, 131.1, 132.4,
132.8, 136.3, 136.7, 144.4, 150.7 (C6H4, C6H5, carbons of imidazole
and pyrazole), 178.6 (CCarbene
C42H40Ag2B2F8N8: C, 48.22; H, 3.85; N, 10.71. Found: C, 48.46; H,
4.07; N, 10.77%.
)
ppm. Anal. Calc. for
3.16. Synthesis of (LH)CH2C6H4CH2(LH)(BF4)2 (16)
This compound was obtained similarly using NH4BF4 instead of
KPF6 as described above for 15 as colorless solids. Yield: 83%, mp
3.14. Synthesis of (LH)CH2C6H4CH2(LH)Br2 (14)
54e56 ꢀC. 1H NMR:
d 2.03, 2.04 (s, s, 6H, 6H, CH3), 5.40 (s, 4H, CH2),
5.92 (s, 2H, H4 of pyrazole), 6.92 (s, 2H), 7.28e7.30 (m, 1H), 7.43e
7.50 (m, 4H), 7.59 (s, 2H), 7.63e7.68 (m, 4H), 7.56e7.80 (m, 3H)
(C6H4, C6H5 and protons of imidazole), 8.96 (s, 2H, protons of imi-
The mixture of 4 (0.48 g, 2 mmol) and 1,3-bis(bromomethyl)
benzene (0.26 g, 1 mmol) in CH3CN (5 ml) was stirred and heated at
reflux 24 h. After cooling to room temperature, the resulting solu-
tion was concentrated to ca. 2 ml. Ethyl acetate (10 ml) was added
to give a slightly yellow and strongly hygroscopic solid of 14. Yield:
dazolium) ppm. 13C NMR:
d
11.1, 13.3 (CH3), 53.0 (CH2), 107.3 (C4 of
pyrazole), 122.9, 123.2, 126.7, 129.2, 129.9, 130.3, 130.4, 130.8, 131.3,
131.5, 133.7, 134.2, 135.9, 141.6, 150.8 (C6H4, C6H5, carbons of imid-
azole and pyrazole) ppm. Anal. Calc. for C36H36B2F8N8: C, 57.32; H,
4.81; N, 14.85. Found: C, 56.82; H, 5.26; N, 14.78%.
0.62 g (84%). 1H NMR:
d 2.02, 2.05 (s, s, 6H, 6H, CH3), 5.76 (s, 4H,
CH2), 5.91 (s, 2H, H4 of pyrazole), 6.78 (s, 1H), 7.18e7.21 (m, 1H),
7.48e7.50 (m, 2H), 7.64e7.71 (m, 6H), 7.99e8.02 (m, 2H), 8.28 (s,
2H), 8.49 (s, 1H) (C6H4, C6H5 and protons of imidazole), 10.57 (s, 2H,
3.17. Synthesis of (L)CH2C6H4CH2(L)Ag2(PF6)2 (17)
protons of imidazolium) ppm. 13C NMR:
d 11.5, 13.4 (CH3), 52.4
(CH2), 107.3 (C4 of pyrazole), 122.4, 123.6, 126.7, 129.5, 130.0, 130.1,
130.9, 131.3, 131.4, 131.5, 133.5, 134.4, 136.6, 141.4, 150.8 (C6H4, C6H5,
carbons of imidazole and pyrazole) ppm. Anal. Calc. for
C36H36Br2N8: C, 58.39; H, 4.90; N, 15.13. Found: C, 57.92; H, 4.48; N,
14.84%.
This compound was obtained similarly using 15 instead of 7 as
described above for 11 as colorless solids. The reaction was 48 h.
Yield: 51%, mp 167e169 ꢀC. 1H NMR (DMSO-d6):
d 1.96, 2.30 (s, s,
6H, 6H, CH3), 5.34 (d, J ¼ 14.9 Hz, 2H), 5.53 (d, J ¼ 14.9 Hz, 2H) (CH2),
6.35 (s, 2H, H4 of pyrazole), 6.89 (s, 2H), 7.46e7.55 (m, 6H), 7.64e
7.71 (m, 6H), 7.74e7.78 (m, 2H) (C6H4 and protons of imidazole)
3.15. Synthesis of (LH)CH2C6H4CH2(LH)(PF6)2 (15)
ppm. 13C NMR (DMSO-d6): 11.6, 13.8 (CH3), 54.3 (CH2), 107.0 (C4 of
d
pyrazole), 121.7, 124.7, 126.9, 127.2, 128.0, 129.0, 130.1, 131.1, 131.4,
132.0, 136.1, 136.8, 145.5, 151.9 (C6H4, carbons of imidazole and
pyrazole) ppm. The carbene carbon was not observed. Anal. Calc. for
C36H36Ag2F12N8P2.CH2Cl2: C, 38.01; H, 3.10; N, 9.58. Found: C,
38.07; H, 3.05; N, 9.40%.
KPF6 (0.30 g, 1.6 mmol) was added to the solution of 14 (0.6 g,
0.8 mmol) in H2O (20 ml). The reaction mixture was stirred for
10 min at room temperature. A white solid was formed, which was
filtered and dried in vacuo. Yield: 0.57 g (82%), mp 95e97 ꢀC. 1H
Table 2
Crystal data and refinement parameters for complexes 10e13 and 18.
Compound
10
11.CH3CN
12
13.CH3CN
18.2CH3CN
Formula
Formula weight
Crystal size (mm)
C
21H20AgClN4
C40H35Ag2F12N9P2
1147.45
0.20 ꢂ 0.18 ꢂ 0.10
293(2)
0.71073
Orthorhombic
Pbca
15.061(3)
19.088(4)
31.586(6)
90
90
90
9081(3)
8
1.679
C42H40Ag2F12N8P2
1162.50
0.20 ꢂ 0.18 ꢂ 0.12
113(2)
0.71073
Triclinic
P1
11.136(5)
11.602(4)
19.038(8)
78.25(2)
77.65(2)
75.76(2)
2299.4(17)
2
1.679
1160
1.011
1.11-27.81
23,501
10,689(0.0523)
6350
599
C44H43Ag2B2F8N9
1087.23
0.20 ꢂ 0.18 ꢂ 0.12
113(2)
0.71073
Triclinic
P1
11.985(3)
12.800(3)
16.621(5)
73.03(2)
83.53(2)
66.92(2)
2243.6(10)
2
1.609
1092
0.950
1.28-27.89
25,912
10,575 (0.0356)
8517
628
C40H40Ag2B2F8N10
1050.18
0.20 ꢂ 0.18 ꢂ 0.10
113(2)
0.71073
Triclinic
P1
9.549(3)
11.264(3)
20.471(6)
93.014(6)
98.037(7)
97.698(3)
2154.9(11)
2
1.619
1052
0.986
2.02-25.02
17,061
7600 (0.0333)
5773
565
471.73
0.20 ꢂ 0.18 ꢂ 0.12
T (K)
113(2)
ꢀ
l
(MoK
a
) (A)
0.71073
Monoclinic
P21/n
11.748(5)
13.462(6)
13.692(6)
90
114.560(5)
90
1969.4(15)
4
1.591
952
1.172
1.93-27.91
20,209
Crystal system
Space group
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
3
ꢀ
V (A)
Z
Dc (g cmꢁ3
F(000)
)
4560
1.023
2.13-26.03
72,192
8925 (0.0699)
6315
m
(mmꢁ1
Range (ꢀ)
)
q
No. of measured reflections
No. of unique reflections (Rint
No. of observed reflections with (I > 2
No. of parameters
GOF
)
4699 (0.0388)
3724
246
s(I))
698
1.053
1.012
1.001
0.974
1.046
Residuals R, Rw
0.0232, 0.0559
0.0530, 0.1315
0.0395, 0.0660
0.0289, 0.0552
0.0349, 0.0971

8
C.-H. Cheng et al. / Journal of Organometallic Chemistry 726 (2013) 1e8
3.18. Synthesis of (L)CH2C6H4CH2(L)Ag2(BF4)2 (18)
Appendix B. Supplementary data
This compound was obtained similarly using 16 instead of 7 as
described above for 11 as yellow solids. The reaction time was 48 h.
Supplementary data associated with this article can be found in
the online version, at http://dx.doi.org/10.1016/j.jorganchem.2012.
12.008. These data include MOL files and InChiKeys of the most
important compounds described in this article.
Yield: 48%, mp 142e144 ꢀC. 1H NMR (DMSO-d6):
d 1.96, 2.30 (s, s,
6H, 6H, CH3), 5.34 (d, J ¼ 14.8 Hz, 2H), 5.53 (d, J ¼ 14.8 Hz, 2H) (CH2),
6.35 (s, 2H, H4 of pyrazole), 6.89 (s, 2H), 7.46e7.54 (m, 6H), 7.64e
7.70 (m, 6H), 7.74e7.78 (m, 2H) (C6H4 and protons of imidazole)
References
ppm. 13C NMR (DMSO-d6): 11.6, 13.8 (CH3), 54.4 (CH2), 106.9 (C4 of
d
pyrazole), 121.7, 124.5, 126.8, 127.2, 128.0, 128.9, 130.4, 131.1, 131.3,
131.9, 136.1, 136.8, 145.6, 151.8 (C6H4, carbons of imidazole and
pyrazole) ppm. The carbene carbon was not observed. Anal. Calc. for
C36H34Ag2B2F8N8.0.5CH2Cl2: C, 43.38; H, 3.49; N, 11.09. Found: C,
43.76; H, 3.34; N, 10.99%.
[1] W.A. Herrmann, Angew. Chem. Int. Ed. 41 (2002) 1290e1309.
[2] F.E. Hahn, M.C. Jahnke, Angew. Chem. Int. Ed. 47 (2008) 3122e3172.
[3] S. Díez-González, N. Marion, S.P. Nolan, Chem. Rev. 109 (2009) 3612e3676.
[4] S.P. Nolan, Acc. Chem. Res. 44 (2011) 91e100.
[5] J.C. Garrison, W.J. Youngs, Chem. Rev. 105 (2005) 3978e4008.
[6] I.J.B. Lin, C.S. Vasam, Coord. Chem. Rev. 251 (2007) 642e670.
[7] J.C.Y. Lin, R.T.W. Huang, C.S. Lee, A. Bhattacharyya, W.S. Hwang, I.J.B. Lin,
Chem. Rev. 109 (2009) 3561e3598.
[8] L. Mercsa, M. Albrecht, Chem. Soc. Rev. 39 (2010) 1903e1912.
[9] A. Kascatan-Nebioglu, M.J. Panzner, C.A. Tessier, C.L. Cannonb, W.J. Youngs,
Coord. Chem. Rev. 251 (2007) 884e895.
[10] T.J. Siciliano, M.C. Deblock, K.M. Hindi, S. Durmus, M.J. Panzner, C.A. Tessier,
W.J. Youngs, J. Organomet. Chem. 696 (2011) 1066e1071.
[11] B.D. Wright, P.N. Shah, L.J. McDonald, M.L. Shaeffer, P.O. Wagers, M.J. Panzner,
J. Smolen, J. Tagaev, C.A. Tessier, C.L. Cannon, W.J. Youngs, Dalton Trans. 41
(2012) 6500e6506.
[12] D.C.F. Monteiro, R.M. Phillips, B.D. Crossley, J. Fielden, C.E. Willans, Dalton
Trans. 41 (2012) 3720e3725.
[13] M. Álvarez-Corral, M. Muñoz-Dorado, I. Rodríguez-García, Chem. Rev. 108
(2008) 3174e3198.
[14] N.T. Patil, Y. Yamamoto, Chem. Rev. 108 (2008) 3395e3442.
[15] J.-M. Weibel, A. Blanc, P. Pale, Chem. Rev. 108 (2008) 3149e3173.
[16] J. Ramírez, R. Corberán, M. Sanaú, E. Peris, E. Fernandez, Chem. Commun.
(2005) 3056e3058.
[17] Y. Fujii, J. Terao, N. Kambe, Chem. Commun. (2009) 1115e1117.
[18] X.-P. Fu, L. Liu, D. Wang, Y.-J. Chen, C.-J. Li, Green Chem. 13 (2011) 549e553.
[19] Z. Tasci, A. Kunduracioglu,I. Kani,B. Cetinkaya, ChemCatChem4 (2012)831e835.
[20] D. Wang, B. Zhang, C. He, P. Wu, C. Duan, Chem. Commun. 46 (2010) 4728e
4730.
[21] M.K. Samantaray, V. Katiyar, K. Pang, H. Nanavati, P. Ghosh, J. Organomet.
Chem. 692 (2007) 1672e1682.
[22] M.K. Samantaray, V. Katiyar, D. Roy, K. Pang, H. Nanavati, R. Stephen,
R.B. Sunoj, P. Ghosh, Eur. J. Inorg. Chem. (2006) 2975e2984.
[23] A.C. Sentman, S. Csihony, R.M. Waymouth, J.L. Hedrick, J. Org. Chem. 70 (2005)
2391e2393.
3.19. Crystal structure determinations
Crystals of 10 and 12 suitable for X-ray analyses were obtained
by slow diffusion of ethyl ether into their CH2Cl2 solutions at 4 ꢀC.
While crystals of 11, 13 and 18 suitable for X-ray analyses were
obtained by slow diffusion of ethyl ether into their CH3CN solutions
at 4 ꢀC. Crystals of 11 contained one CH3CN molecule. All fluorine
atoms in this complex were found to be disordered. Satisfactory
results were obtained when F(1)eF(6) were given occupancy
factors of 0.717 and F(1)0eF(6)0 were given occupancy factors of
0.283, as well as 0.688 for F(7)eF(12) and 0.312 for F(7)0eF(12)0,
respectively. Crystals of 13 also contained one CH3CN molecule.
The F(5)eF(8) atoms were disordered in 13. The occupancy factors
were refined to 0.826 for F(5)eF(8) and 0.174 for F(5)0eF(8)0,
respectively. In addition, crystals of 18 contained two CH3CN
molecules. All intensity data were collected on a Rigaku Saturn CCD
detector. Semi-empirical absorption corrections were applied using
the Crystalclear program [47]. The structures were solved by direct
methods and difference Fourier map using SHELXS of the SHELXTL
package and refined with SHELXL [48] by full-matrix least-squares
on F2. All non-hydrogen atoms were refined anisotropically. A
summary of the fundamental crystal data for 10e13 and 18 is listed
in Table 2.
[24] M.-T. Chen, B. Landers, O. Navarro, Org. Biomol. Chem. 10 (2012) 2206e2208.
[25] Y. Li, X. Chen, Y. Song, L. Fang, G. Zou, Dalton Trans. 40 (2011) 2046e2052.
[26] P. Li, L. Wang, Y. Zhang, M. Wang, Tetrahedron Lett. 49 (2008) 6650e6654.
[27] H.M.J. Wang, I.J.B. Lin, Organometallics 17 (1998) 972e975.
[28] H.-L. Su, L.M. Pérez, S.-J. Lee, J.H. Reibenspies, H.S. Bazzi, D.E. Bergbreiter,
Organometallics 31 (2012) 4063e4071.
[29] P. de Frémont, N.M. Scott, E.D. Stevens, T. Ramnial, O.C. Lightbody,
C.L.B. Macdonald, J.A.C. Clyburne, C.D. Abernethy, S.P. Nolan, Organometallics
24 (2005) 6301e6309.
3.20. General procedure for the AgeNHC catalyzed three-
component coupling reaction
[30] S.G. Alexander, M.L. Cole, J.C. Morris, New J. Chem. 33 (2009) 720e724.
[31] G. Berthon-Gelloz, M.A. Siegler, A.L. Spek, B. Tinant, J.N.H. Reek, I.E. Markó,
Dalton Trans. 39 (2010) 1444e1446.
In a typical experiment, the mixture of aldehyde (1 mmol),
phenylacetylene (1.5 mmol, 164.7
ml), piperidine (1.2 mmol,
[32] A. Bondi, J. Phys. Chem. 68 (1964) 441e451.
118.7 l), and NHCeAg complex (n mmol) was charged in the
m
[33] R. Corberán, E. Mas-Marzá, E. Peris, Eur. J. Inorg. Chem. (2009) 1700e1716.
[34] J.A. Mata, M. Poyatos, E. Peris, Coord. Chem. Rev. 251 (2007) 841e859.
[35] D. Pugh, A.A. Danopoulos, Coord. Chem. Rev. 251 (2007) 610e641.
[36] E. Peris, R.H. Crabtree, Coord. Chem. Rev. 248 (2004) 2239e2246.
[37] R.A. Haque, A.W. Salman, T.S. Guan, H.H. Abdallah, J. Organomet. Chem. 696
(2011) 3507e3512.
[38] S. Anezaki,Y. Yamaguchi, M. Asami, J. Organomet. Chem. 696(2011)2399e2405.
[39] S. Demir, I. Özdemir, B. Çetinkaya, Appl. Organomet. Chem. 23 (2009) 520e523.
[40] C.E. Willans, K.M. Anderson, M.J. Paterson, P.C. Junk, L.J. Barbour, J.W. Steed,
Eur. J. Inorg. Chem. (2009) 2835e2843.
reaction tube (10 ml) with 2 ml of 1,4-dioxane. After the reaction
mixture was stirred at 80 ꢀC for given time under Ar atmosphere,
the volatile materials were removed under reduced pressure, and
the products were purified by column chromatography on silica
using ethyl acetate/hexane (1/2 v/v) as the eluent to give the cor-
responding propargylic amine.
[41] M.V. Baker, D.H. Brown, P.V. Simpson, B.W. Skelton, A.H. White, C.C. Williams,
J. Organomet. Chem. 691 (2006) 5845e5855.
Acknowledgments
[42] M.V. Baker, D.H. Brown, R.A. Haque, B.W. Skelton, A.H. White, Dalton Trans.
(2004) 3756e3764.
[43] W. Chen, B. Wu, K. Matsumoto, J. Organomet. Chem. 654 (2002) 233e236.
[44] V.A. Peshkov, O.P. Pereshivko, E.V. Van der Eycken, Chem. Soc. Rev. 41 (2012)
3790e3807.
This work is supported by the National Natural Science Foun-
dation of China (No. 20972075).
[45] C. Wei, Z. Li, C.-J. Li, Org. Lett. 5 (2003) 4473e4475.
Appendix A. Supplementary material
[46] L.G. Humber, E. Ferdinandi, C.A. Demerson, S. Ahmed, U. Shah, D. Mobilio,
J. Sabatucci, B.D. Lange, F. Labbadia, P. Hughes, J. DeVirgilio, G. Neuman,
T.T. Chau, B.M. Weichm, J. Med. Chem. 31 (1988) 1712e1719.
[47] CrystalStructure 3.7.0 and Crystalclear 1.36: Crystal Structure Analysis
Package, Rigaku and Rigaku/MSC, TX, 2000.
CCDC 898717e898721 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
[48] G.M. Sheldrick, SHELXS97 and SHELXL97, University of Göttingen, Germany,
1997.