Hg(II), Ag(I) and Au(I) complexes with aniline or pyridine-functionalized N-heterocyclic carbene

Article abstract of DOI:10.1016/j.poly.2012.12.026

[Hg(L_a)₂](PF₆)₂ (1), [Hg(L _b)₂](PF₆)₂ (2), [Hg(L _c)₂](PF₆)₂ (3), [Ag(L _a)₂]I (4) and Au(L_a)Cl (5) (L_a, L_b, and L_c are aniline or pyridine N-functionalized imidazol-2-ylidene) have been synthesized and characterized. Single crystals of 1·MeOH, 3 and 5 are obtained and their crystal structures are determined by X-ray diffraction analysis. The molecular structure of 1·MeOH shows that Hg(II) center is coordinated to two carbene ligands, one nitrogen atom from aniline group and one oxygen atom from methanol. The anions are embedded between two cations layers and linked the cations through the intermolecular hydrogen bonding. The Hg(II) center of 3 is coordinated to two carbene ligands and two nitrogen atoms from pyridine group. The PF₆^- anions of 3 hold two adjacent cations through Hg?F interactions and H?F hydrogen bonding and the crystal packing consists of alternating anion and cation layers. The Au atom of 5 is linearly coordinated with a carbenoic carbon and a chloro ligand, and the molecules are neatly arranged to a one-dimensional hole through weak hydrogen bonding interactions. For 1·MeOH and 5, the -NH₂ group of aniline plays an important role in stabilizing the crystal structure through intramolecular and intermolecular hydrogen bonding interactions.

Full text of DOI:10.1016/j.poly.2012.12.026

Polyhedron 51 (2013) 132–141
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Polyhedron
journal homepage: www.elsevier.com/locate/poly
Hg(II), Ag(I) and Au(I) complexes with aniline or pyridine-functionalized
N-heterocyclic carbene
⇑
Ren-Tai Zhuang, Wan-Jung Lin, Rui Rui Zhuang, Wen-Shu Hwang
Department of Chemistry, National Dong Hwa University, Hualien 974, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
Article history:
[Hg(La)2](PF6)2 (1), [Hg(Lb)2](PF6)2 (2), [Hg(Lc)2](PF6)2 (3), [Ag(La)2]I (4) and Au(La)Cl (5) (La, Lb, and Lc are
aniline or pyridine N-functionalized imidazol-2-ylidene) have been synthesized and characterized. Single
crystals of 1ꢀMeOH, 3 and 5 are obtained and their crystal structures are determined by X-ray diffraction
analysis. The molecular structure of 1ꢀMeOH shows that Hg(II) center is coordinated to two carbene
ligands, one nitrogen atom from aniline group and one oxygen atom from methanol. The anions are
embedded between two cations layers and linked the cations through the intermolecular hydrogen bond-
ing. The Hg(II) ꢁcenter of 3 is coordinated to two carbene ligands and two nitrogen atoms from pyridine
group. The PF6 anions of 3 hold two adjacent cations through Hgꢀ ꢀ ꢀF interactions and Hꢀ ꢀ ꢀF hydrogen
bonding and the crystal packing consists of alternating anion and cation layers. The Au atom of 5 is lin-
early coordinated with a carbenoic carbon and a chloro ligand, and the molecules are neatly arranged to a
one-dimensional hole through weak hydrogen bonding interactions. For 1ꢀMeOH and 5, the –NH2 group
of aniline plays an important role in stabilizing the crystal structure through intramolecular and intermo-
lecular hydrogen bonding interactions.
Received 30 October 2012
Accepted 21 December 2012
Available online 8 January 2013
Keywords:
N-Heterocyclic carbene
Aniline
Pyridine
Mercury
Silver
Gold
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
groups can dynamically dissociate to generate coordinatively
unsaturated active species [13].
Metal complexes of carbenes based on imidazol-2-ylidene have
received much attention in the past years. A major reason is that
these N-heterocyclic carbene (NHC) ligands can stabilize both high
as well as low oxidation metal ions and form stable carbene com-
plexes with a wide range of metal ions [1]. Moreover, NHC ligands
can be easily modified by changing the substituent on the nitrogen
atom or the backbone in order to provide diverse organometallic
materials [2]. In recent years, much attention has been attracted
for the design and synthesis of carbene hybrid ligands containing
N-heterocyclic donor groups, such as pyridine [3], pyrazine [4],
pyrimidine [3a,3f,5], quinoline [6], benzimidazole [7], oxazoline
[8], phenanthroline [9], and N-amido such as acetamide [4a] . The
transition metal complexes have been stabilized by the weaker do-
nor groups functionalized NHC ligands and found to be good cata-
lysts for C–C coupling reactions. However, only symmetric CNC
[10] and NCN [11] type pincer ligands with one or two NHC donors
were well studied, and there are few reports concerning the prepa-
ration and use of dissymmetric pincer ligands [12]. An asymmetric
ligand containing a carbene and side weaker ancillary groups would
be useful in homogeneous catalysis since the strong carbene donor
facilitates the electronic density of metal, and the weaker donor
The aniline and pyridine groups have lone pair electrons on the
nitrogen atom, such that formation of supramolecules is possible
through extended H-bonds. Furthermore, aniline and pyridine are
potential donor ligands, which together with the carbene donor
site form interesting multidentate ligands suitable for the study
of supramolecular chemistry. So we lay our interests in the design
and synthesis of metal complexes containing aniline- or pyridine-
functionalized NHC ligands (Scheme 1). In this report we describe
the synthesis and structural characterization of stable Hg(II), Ag(I)
and Au(I) complexes with aniline–/pyridine–NHC ligands.
2. Results and discussion
2.1. Synthesis
Carbene ligand precursors, [LaH]I, [LaH]PF6, [LbH]I, [LbH]PF6, [Lc-
H]I, [LcH]PF6, were synthesized by reacting the corresponding het-
erocyclic linkers with imidazole (Scheme 2). Ligand precursors
with iodine anion have very poor solubility in common organic sol-
vents and are therefore difficult to use to prepare metal complexes.
Ligand precursors with PF6ꢁ anion were obtained from their corre-
ꢁ
sponding iodine salts by metathesis in water. These PF6 salts are
⇑
soluble in methanol and acetone and are used for the synthesis of
metal–carbene complexes.
Corresponding author. Tel.: +886 3 8633577; fax: +886 3 8633570.
E-mail address: hws@mail.ndhu.edu.tw (W.-S. Hwang).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.12.026

R.-T. Zhuang et al. / Polyhedron 51 (2013) 132–141
133
+
+
+
in dichloromethane at room temperature for 5 min (Scheme 2).
The disappearance of the acidic NCHN proton signals in their 1H
NMR spectra and the appearance of the characteristic carbenoic
carbon signals (170–180 ppm) in their 13C NMR spectra confirmed
the formation of complexes 4 and 5. The substantial up field shift of
the –NH2 1H NMR signals from 5.49 ppm in the ligand precursor
[LaH]I salt to 4.77 ppm in 4 and 4.66 ppm in 5 showing that the
–NH2 groups do not coordinate to the metal centers in both com-
plexes. These two complexes are tolerant of air and moisture.
NH2
NH2
N
N
N
N
N
N
N
[LaH]+
[LcH]+
[LbH]+
Scheme 1.
Synthesis of [Hg(La)2](PF6)2 (1), [Hg(Lb)2](PF6)2 (2) and
[Hg(Lc)2](PF6)2 (3) complexes were carried out by treating
Hg(OAc)2 with the NHC precursors [LaH]PF6, [LbH]PF6, and [LcH]PF6,
respectively, in an 1:1.5 M ratio in refluxing methanol for 14 h
(Scheme 2). The success of the formation of the Hg–NHC com-
plexes was confirmed by the disappearance of the acidic NCHN
proton in their 1H NMR spectra and the appearance of the charac-
teristic carbenoic carbon signal (ꢂ175 ppm) in their 13C NMR spec-
tra. The –NH2 groups in 1 and 2 complexes show signals at 5.30
and 5.27 ppm, respectivly, in their 1H NMR spectra, which are
down field shifted by 0.21 and 0.16 ppm, respectively, relative to
their ligand precursors [LaH]PF6 and [LbH]PF6, indicating that the
–NH2 groups might coordinate to the Hg centers in both com-
plexes. Complexes 1–3 were readily soluble in DMSO, DMF, ace-
tone, and acetonitrile, and insoluble in methanol. The silver
complex [Ag(La)2]I (4) was synthesized via reaction of the ligand
precursor [LaH]I salt with Ag2O carried out in acetonitrile at room
temperature in the dark for 5 h. The gold complex Au(La)Cl (5) was
synthesized by the commonly used silver carbene transfer route
from the silver complex [Ag(La)2]I, by treating with AuCl(SMe2)
2.2. Crystal structure analysis
Single crystals of 1ꢀMeOH suitable for X-ray diffraction studies
were obtained by slow diffusion of methanol into an acetone
solution of 1. Complex 3 was crystallized in acetonitrile by slow
evaporation of the solvent. Complex 5 was crystallized in dichloro-
methane by slow evaporation of the solvent and diffusion of meth-
ylbenzene into this solution. Details of the relevant data collection
and refinement are summarized in Table 1.
2.2.1. Structure of [Hg(La)2(MeOH)](PF6)2 (1ꢀMeOH)
The molecular structure of 1ꢀMeOH is illustrated in Fig. 1. Se-
lected geometric characteristics of the structure are tabulated in
Table 2. In the cation, Hg(II) center is coordinated by two carbene
ligands, one nitrogen atom from aniline group and one oxygen
atom from methanol. The two NHC carbon atoms are almost
+
NO2
N
I
I
N
100 o
12 h
C
NO2
NO2
N
1
K2CO3
oC
N
HN
+
N
0
12
MeI
THF,r.t.
24 h
+
NO2
N
h
36
I
N
2
+
I
+
NH2
NH2
N
Zn, NH4Cl
-
PF6
1
N
N
N
NH4PF6
MeOH, reflux
30 min
[LaH]I
[LaH]PF6
2+
N
N
H2N
Hg(OAc)2
-
2PF6
[LaH]PF6
Hg
NH2
MeOH, reflux,
14 h
N
N
[Hg(La)2](PF6)2
+
I
H2N
N
Ag
N
Ag2O
N
N
AuCl(SMe2)
[LaH]I
NH
2 Au
Cl
CH3CN, dark, rt, 5 h
N
NH2
N
DCM, dark, rt, 5 min
[Ag(La)2]I
Au(La)Cl
2+
+
+
PF6
MeOH, reflux
14 h
NH2
N
NH2
Hg(OAc)2
Zn, NH4Cl
N
H2N
I
2
2PF6
N
N
Hg
MeOH, reflux
N
N
NH4PF6
NH2
30 min
N
N
[LbH]I
[LbH]PF6
[Hg(Lb)2](PF6)2
2+
2PF6
+
PF6
N
+
N
N
MeI
N
N
N
N
Hg(OAc)2
NH4PF6
H2O, r.t, 10 min
I
Hg
N
N
N
N
N
THF, rt
24 h
MeOH, reflux,
14 h
N
N
N
[LcH]I
[LcH]PF6
[Hg(Lc)2](PF6)2
Scheme 2. Synthesis of ligand precursors and complexes.

134
R.-T. Zhuang et al. / Polyhedron 51 (2013) 132–141
Table 1
Crystal data and refinement parameters for complexes 1ꢀMeOH, 3, and 5.
Complex
[Hg(La)2(MeOH)](PF6)2
[Hg(Lc)2](PF6)2
[AuLaCl]
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C
25H34F12HgN6OP2
C18H18F12HgN6P2
808.91
296(2)
0.71073
triclinic
C12H15AuClN3
433.69
296(2)
0.71073
orthorhombic
Pca21
20.3224(12)
7.9911(5)
17.1777(10)
90
925.11
296(2)
0.71073
monoclinic
P21/n
10.7199(10)
20.6199(19)
15.4726(15)
90
Pı
¯
7.5091 (14)
8.8506(16)
9.8948(17)
84.727(3)
b (Å)
c (Å)
a
(°)
b (°)
93.124(2)
75.150(3)
90
c
(°)
90
3415.0(6)
75.421(3)
614.91(19)
90
2789.6(3)
V (Å3)
Z
4
1
8
dcalc (Mg mꢁ3
)
1.799
4.697
2.184
6.501
2.065
10.721
Absorption coefficient (mmꢁ1
)
F(000)
1808
386
1632
Theta range for data collection (°)
1.65–26.48
2.13–25.29
1.00–26.55
Limiting indices
ꢁ12 6 h 6 13,
ꢁ25 6 k 6 25,
ꢁ19 6 l 6 19
ꢁ9 6 h 6 8,
ꢁ25 6 h 6 25,
ꢁ10 6 k 6 10,
ꢁ21 6 l 6 21
37512/5737 [Rint = 0.0429]
99.1
ꢁ9 6 k 6 10,
ꢁ11 6 l 6 11
4270/2176 [Rint = 0.0459]
97.7
Reflections collected/unique
Completeness (%)
Refinement method
26679/7032 [Rint = 0.0772]
99.4
full-matrix least-squares on F2
7032/0/447
0.925
full-matrix least-squares on F2
2176/0/179
full-matrix least-squares on F2
5737/1/312
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
0.945
1.016
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0460, wR2 = 0.1206
R1 = 0.1066, wR2 = 0.1592
1.140 and ꢁ0.809
R1 = 0.0399, wR2 = 0.1151
R1 = 0.0407, wR2 = 0.1183
1.788 and ꢁ2.299
R1 = 0.0203, wR2 = 0.0433
R1 = 0.0251, wR2 = 0.0451
0.619 and -0.372
Largest difference in peak and hole (e Åꢁ3
)
(2.75 Å) [17], [C6Cl2F4Hg2ꢀ(
[C6Cl2F4Hg2( 2-THF)] (2.80 Å) [19], and slightly longer than those
measured in[C6Cl2F4Hg2( 2-acetone)] (2.73 Å) [20], [C6Cl2F4Hg2
2-DMF)] (2.70 Å) [20], and [C6Cl2F4Hg2( 2-DMSO)2] (2.70 Å)
l2-propylene oxide)] (2.74 Å) [18], and
l
l
(l
l
[21]. Bond angles around the Hg(II) center are C(9)–Hg(1)–C(21)
170.8(3)°, O(1)–Hg(1)–N(4) 94.4(6)°, C(21)–Hg(1)–N(4) 75.9(3)°
and C(9)–Hg(1)–O(1) 87.8(3)°. The two imidazole rings and the
mercury atom are almost coplanar with a dihedral angle of 7.15°
between two rings. The coordinated aniline plane [N(4)–C(13)–
C(14)–C(15)–C(16)–C(17)–C(18)] forms a dihedral angle of 47.84°
witꢁh imidazole ring [N(5)–C(19)–C(20)–N(6)–C(21)]. The two
PF6 anions are in the external for charge balance.
The –NH2 of the aniline group form intramolecular hydrogen
bonding with a imidazol nitrogen, with the donor–acceptor dis-
tance of 2.821(16) Å for N(1)–H(1N)ꢀ ꢀ ꢀN(2) and 2.860(11) Å for
N(4)–H(4N)ꢀ ꢀ ꢀN(5), and several intermolecular hydrogen bonding
ꢁ
with PF6 anions, e.g. with the donor–acceptor distance of
2.962(18) Å for N(1)–H(1N)ꢀ ꢀ ꢀF(11), 3.130(13) Å for N(4)–
H(4N)ꢀ ꢀ ꢀF(1) (Fig. 2). There are also weak intermolecular O–Hꢀ ꢀ ꢀF
and C–Hꢀ ꢀ ꢀF hydrogen bonding as summarized in Table 2. There
are five types of C–Hꢀ ꢀ ꢀ
p
and P–Fꢀ ꢀ ꢀ
p
interactions in the crystal lat-
Fig. 1. Molecular structure of the cation in 1ꢀMeOH showing the atom labeling
tice (Table 2). There is also one
p–p stacking interaction between
scheme. Anions are omitted.
the adjacent phenyl rings [C(13)–C(14)–C(15)–C(16)–C(17)–
C(18)] and [C(13)#–C(14)#–C(15)#–C(16)#–C(17)#–C(18)#]. The
center-to-center distance is 3.674(6) Å and the shortest interplanar
distance is 3.563 Å. Viewed along the b-axis, the crystal packing
consists of alternating anions and cations. The anions are embed-
ded between two cation layers, and linked the cations through
the intermolecular hydrogen bonding (Fig. 3). In the solid state,
all the above mentioned intermolecular interactions in this struc-
ture have stabilized the crystal structure.
linearly coordinated to the Hg(II) (170.8(3)°) with normal Hg–C
bond lengths (2.059(9) and 2.073(8) Å). The Hg–N distance
(2.755(9) Å) is significantly shorter than the sum of the van der
Waals radii of nitrogen (1.60 Å) [14] and mercury (1.73–2.00 Å)
[15], which is consistent with the similar structure reported earlier
[4a]. Interestingly, the oxygen atom from methanol is also coordi-
nated to mercury center. The resulting Hg–O bond is approxi-
mately perpendicular to the C(9)–Hg(1)–C(21). The Hg(1)–O(1)
distance (2.735(9) Å) is shorter than the sum of the van der Waals
radii of oxygen (1.54 Å) [14] and mercury (1.73–2.00 Å) [15,16],
and is comparable to those measured in [C6Cl2F4Hg2ꢀDMF]
2.2.2. Structure of [Hg(Lc)2](PF6)2 (3)
The molecular structure of 3 with the atomic numbering
scheme is shown in Fig. 4. Selected geometric characteristics of
the structure are tabulated in Table 3. The mercury atom on this

R.-T. Zhuang et al. / Polyhedron 51 (2013) 132–141
135
Table 2
occasion is disposed on a crystallographic inversion center. The
Hg(II) center is coordinated with two carbene ligands and two pyr-
idyl nitrogen atoms. The geometry about the Hg atom is planar,
and this atom also lies close to co-planarity with both coordinating
carbene ligands. The Ccarbene–Hg–Ccarbene axis is constrained exactly
to linearity by crystallographic symmetry with Hg(1)–C(1) dis-
tance of 2.047(9) Å, in close agreement with values reported previ-
ously for (ArC,N)2Hg [22] and other diarylmercury compounds [23].
The Hg(1)–N(3) distance (2.896(8) Å) is comparable to those mea-
sured in (ArC,N)2Hg (2.89(1) Å) [22], and is still in the range of
bonding interaction [15a,24]. Bond angles around the Hg center
are C(1)–Hg(1)–N(3) 66.6(3)°, C(1)–Hg(1)–C(1A) 180.00°, N(3)–
Hg(1)–N(3A) 179.98°, and N(3)–Hg(1)–C(1A) 113.4(3)°.
Selected geometric characteristics of crystal 1ꢀMeOH.
0
Bond lengths (ÅA)
Hg(1)–C(9)
Hg(1)–N(4)
2.059(9) Hg(1)–C(21)
2.755(9) Hg(1)–O(1)
2.073(8)
2.735(9)
Bond angles (°)
C(21)–Hg(1)–N(4)
C(9)–Hg(1)–C(21A)
75.9(3)
C(9)–Hg(1)–O(1) 87.8(3)
170.8(3) N(3)–Hg(1)–
N(3A)
179.98(1)
0
Hgꢀ ꢀ ꢀF distance(ÅA)
Hg(1)ꢀ ꢀ ꢀF(4)
Hydrogen bonding
D–Hꢀ ꢀ ꢀA
2.971(7) Hg(1)ꢀ ꢀ ꢀF(6)
3.150(9)
0
0
0
<DHA (°)
The PF6ꢁ anions hold two adjacent cations through Hgꢀ ꢀ ꢀF inter-
actions and Hꢀ ꢀ ꢀF hydrogen bonding (Fig. 5). Weak contact of
2.971(7) and 3.150(9) Å between the fluorine atoms (F(4) and
D–H (ÅA) Hꢀ ꢀ ꢀA (AÅ)
Dꢀ ꢀ ꢀA (AÅ)
N(1)–H(1N)ꢀ ꢀ ꢀN(2)a
N(4)–H(4N)ꢀ ꢀ ꢀN(5)a
N(1)–H(1N)ꢀ ꢀ ꢀF(11)b
N(4)–H(4N)ꢀ ꢀ ꢀF(1)b
N(4)–H(4N)ꢀ ꢀ ꢀF(5)b
N(4)–H(4N)ꢀ ꢀ ꢀF(4)b
N(4)–H(3N)ꢀ ꢀ ꢀF(10)b
O(1)–H(1W)ꢀ ꢀ ꢀF(8)b
O(1)–H(1W)ꢀ ꢀ ꢀF(11)b
C(4)–H(4)ꢀ ꢀ ꢀF(2)b
0.89
0.85
0.89
0.85
0.85
0.85
0.86
0.98
0.98
0.93
0.93
0.93
0.93
0.93
0.96
2.80
2.77
2.11
2.52
2.45
2.60
2.55
2.42
2.54
2.64
2.56
2.55
2.48
2.60
2.58
2.821(16) 82
2.860(11) 75
2.962(18) 158
3.130(13) 130
3.288(15) 173
3.291(19) 140
3.321(15) 150
3.096(18) 126
ꢁ
F(6)) of PF6 anion and Hg(1) atom are observed. These value are
shorter than the sum of the van der Waals radii of fluorine
ꢁ
(1.47 Å) [14] and mercury (1.73–2.00 Å) [15,16]. The PF6 anion
forms hydrogen bonding with neighboring atoms of the cations,
with the donor–acceptor distance of 3.393(15) Å for C(2)–
H(2)ꢀ ꢀ ꢀF(1) and 3.221(13) Å for C(9)–H(9)ꢀ ꢀ ꢀF(4), respectively.
3.39(2)
3.54(2)
145
165
C(14)–H(14)ꢀ ꢀ ꢀF(10)b
C(17)–H(17)ꢀ ꢀ ꢀF(11)b
C(7)–H(7)ꢀ ꢀ ꢀF(2)b
3.332(16) 141
3.275(15) 135
3.134(17) 127
3.268(17) 130
3.493(17) 159
There is also one type of P–Fꢀ ꢀ ꢀ
p halogen bond interaction in the
crystal lattice. The distance between F(1) and the imidazole ring
[N(1)–C(1)–N(2)–C(3)–C(2)] is 3.461(9) Å. Viewed along the a-axis,
the crystal packing consists of alternating PF6ꢁ anions and complex
cations. The anions and cations are arranged in layers, and the an-
ions are embedded between two cation layers (Fig. 6).
C(20)–H(20)ꢀ ꢀ ꢀF(6)b
C(11)–H(11C)ꢀ ꢀ ꢀF(12)b
Y–Xꢀ ꢀ ꢀ
Y–Xꢀ ꢀ ꢀ
p interaction
0
0
0
p
Y–Xꢀ ꢀ ꢀ
p
Xꢀ ꢀ ꢀp
(AÅ) Xꢀ ꢀ ꢀ
p
(\) (ÅA)d
Yꢀ ꢀ ꢀ
p
(ÅA)
(°)
C(22)–H(22)ꢀ ꢀ ꢀph ring(4)c 2.83
2.807
2.672
152
159
3.727(12)
3.588(15)
2.2.3. Structure of [AuLa]Cl
C(25)–H(25A)ꢀ ꢀ ꢀph
2.67
ring(5)c
The molecular structure of 5 with the atomic numbering
scheme is shown in Fig. 7. Selective geometric characteristics of
the structure are tabulated in Table 4. The Au atom is linearly coor-
dinated with a carbene and a chloro ligands with a Cl(1)–Au(1)–
C(1) angle of 177.89(15)°. Au–Cl and Au–C bond lengths are
2.288(1) and 1.969(5) Å, respectively, which are consistent with
the similar structures reported earlier [25]. Different from that in
1ꢀMeOH, the –NH2 group of aniline in 5 does not coordinate to
the gold center. The gold atom and the imidazole ring are almost
coplanar, while the dihedral angle between imidazole ring and ani-
line ring is 75.99°, which is also different from that of 1ꢀMeOH.
C(25)–H(25B)ꢀ ꢀ ꢀim
ring(2)c
2.96
2.942
144
3.780(15)
P(2)–F(5)ꢀ ꢀ ꢀim ring(2)c
3.425(15) 3.337
3.314(17) 3.261
136.9(8) 4.681(5)
152.2(10) 4.662(6)
P(1)–F(9)ꢀ ꢀ ꢀim ring(1)c
0
0
Phenyl–phenyl
pꢀ ꢀ ꢀ
p
interaction: d
= 3.563 ÅA, dcenter–center = 3.674(6) ÅA
ꢀ ꢀ ꢀp
p
a
b
c
Intramolecular hydrogen bonding.
Intermolecular hydrogen bonding.
Stacking parameters taken into account is the perpendicular distance between
the X and ring plane.
d
Here the ring (n) represents the phenyl or imidazol ring defined in Fig. 1.
Fig. 2. Hydrogen bonding in 1ꢀMeOH.

136
R.-T. Zhuang et al. / Polyhedron 51 (2013) 132–141
Fig. 3. Crystal packing drawing of 1ꢀMeOH viewed along the b-axis.
Table 3
Selected geometric characteristics of crystal 3.
0
Bond lengths (ÅA)
Hg(1)–C(1)
2.047(9) Hg(1)–N(3)
2.896(8)
Bond angles (°)
C(1)–Hg(1)–N(3)
C(1)–Hg(1)–C(1A)
66.6(3)
180.00
C(1A)–Hg(1)–N(3) 113.4(3)
N(3)–Hg(1)–
N(3A)
179.98(1)
3.150(9)
0
Hgꢀ ꢀ ꢀF distance(ÅA)
Hg(1)ꢀ ꢀ ꢀF(4)
Hydrogen bonding
D–Hꢀ ꢀ ꢀA
2.971(7) Hg(1)ꢀ ꢀ ꢀF(6)
0
0
0
<DHA (°)
D–H (AÅ) Hꢀ ꢀ ꢀA (ÅA)
Dꢀ ꢀ ꢀA (ÅA)
C(2)–H(2)ꢀ ꢀ ꢀF(1)
C(9)–H(9)ꢀ ꢀ ꢀF(4)
0.93
0.93
2.50
2.54
3.393(15)
3.221(13)
162
130
P–Fꢀ ꢀ ꢀ
p interaction
0
0
0
P–Fꢀ ꢀ ꢀ
p
P–Fꢀ ꢀ ꢀ
115.4(5)
p (°)
Fꢀ ꢀ ꢀ
p
(AÅ) Fꢀ ꢀ ꢀ
p
(\) (AÅ)a
Pꢀ ꢀ ꢀ
p (ÅA)
4.376(5)
P(1)–F(1)ꢀ ꢀ ꢀring
3.461(9) 3.380
(1)b
a
Stacking parameters taken into account is the perpendicular distance between
Fig. 4. Molecular structure of the cation in 3 showing the atom labeling scheme.
Anions are omitted.
the F and ring plane.
b
Here the ring (1) represent the five-membered N(1)–C(1)–N(2)–C(3)–C(2)
imidazol ring.
There may be a correlation between the uncoordinated aniline and
the difference of dihedral angles.
H(6N)ꢀ ꢀ ꢀCl(1). There are two types of C–Hꢀ ꢀ ꢀ
p
and Au–Clꢀ ꢀ ꢀ
p supra-
molecular interactions in the crystal lattice. The distances between
C(8) and the benzene ring is 3.814(7) Å. The distances between
Au(1), Au(2) and the imidazole ring are 4.171(2) and 4.212(2) Å,
respectively. The molecules are neatly arranged and stacked to a
one-dimensional hole through these weak interactions (Fig. 8
right). Viewed along the b-axis, a notable feature in the crystal
packing of 5 is that one-dimensional polymeric chains are formed
by the intermolecular interactions (Fig. 9).
As shown in Fig. 8, the –NH2 group of aniline forms intramolec-
ular hydrogen bonding with the imidazol nitrogen atom, with the
donor–acceptor distance of 2.808(7) Å for N(3)–H(3N)ꢀ ꢀ ꢀN(2) and
2.797(8) Å for N(6)–H(6N)ꢀ ꢀ ꢀN(4). The intermolecular hydrogen
bonding between the –NH2 group and the chloro ligand of the adja-
cent molecule (N–Hꢀ ꢀ ꢀCl) leads to the formation of a stable sixteen-
member ring (Fig. 8left), with the donor–acceptor distance of
3.527(7) Å for N(3)–H(3N)ꢀ ꢀ ꢀCl(2) and 3.513(7) Å for N(6)–

R.-T. Zhuang et al. / Polyhedron 51 (2013) 132–141
137
Fig. 5. Hydrogen bonding in 3.
Fig. 6. Crystal packing drawing of 3 viewed along the a-axis.
Fig. 7. Molecular structure of 5 showing the atom labeling scheme.

138
R.-T. Zhuang et al. / Polyhedron 51 (2013) 132–141
Table 4
4. Experimental
Selected geometric characteristic of crystal 5.
0
4.1. General procedures, materials and physical measurements
Bond lengths (ÅA)
Au(1)–C(1)
1.969(5)
Au(1)–Cl(1) 2.288(1)
The solvents and reagents were purchased from general sources
and were used without further purification. The NMR spectra were
recorded on a Bruker DPX-300 spectrometer (1H, 299.96 MHz; 13C,
75.43 MHz) with tetramethylsilane as an internal standard. Mass
Spectra were measured on a Micromass Platform II spectrometer.
Elemental microanalyses were performed by the Taiwan Instru-
mentation Center. G.C. analyses were performed with a GC9800
gas chromatography (Shanghai Kechuang Chromatograph Instru-
ment Co.) equipped with a flame ionization detector and a 10 m
Bond angles (°)
C(1)–Au(1)–Cl(1)
177.89(15)
Hydrogen bonding
0
0
0
D–Hꢀ ꢀ ꢀA
<DHA
(°)
D–H (AÅ)
Hꢀ ꢀ ꢀA (AÅ)
Dꢀ ꢀ ꢀA (AÅ)
N(3)–H(3A)ꢀ ꢀ ꢀN(2)a
N(6)–H(6A)ꢀ ꢀ ꢀN(4)a
N(3)–H(3A)ꢀ ꢀ ꢀCl(2)b
N(6)–H(6A)ꢀ ꢀ ꢀCl(1)b
0.87
0.86
0.87
0.86
2.34
2.50
2.87
2.72
2.808(7)
2.797(8)
3.527(7)
3.513(7)
114
101
133
155
(2.65 lm film thickness) RESTEK Rtx-2887 fused silica capillary
column.
Y–Xꢀ ꢀ ꢀp interaction
0
Y–Xꢀ ꢀ ꢀ
p
Xꢀ ꢀ ꢀ
p
(\)c
Y–Xꢀ ꢀ ꢀ
p
Yꢀ ꢀ ꢀ
p
Xꢀ ꢀ ꢀp (AÅ)
0
0
(°)
(AÅ)
(AÅ)
C(8)–H(8)ꢀ ꢀ ꢀph ring(4)d
Au(1)–Cl(1)ꢀ ꢀ ꢀim
ring(3)d
2.98
2.923
3.777
150
81.83(5)
3.814(7)
4.171(2)
4.2. Preparation of ligand precursors and complexes
3.828(3)
3.902(3)
4.2.1. 1-(2-Nitrophenyl)imidazol
Au(2)–Cl(2)ꢀ ꢀ ꢀim
3.855
81.32(6)
4.212(2)
A mixture of imizadol (5.00 g, 73.4 mmol), 1-bromo-2-nitroben-
zene (2.00 g, 9.9 mmol), and K2CO3 (2.05 g, 14.8 mmol) was heated
at 120 °C for 36 h. After cooled to r.t., the reaction mixture was
extracted with dichloromethane three times. The solution was
treated with MgSO4, filtered, and dried in vacuo to give crude prod-
uct. The crude product was purified by chromatography (silica gel,
ethyl acetate/hexane = 2/1) to obtain yellow solid (76% yield). 1H
NMR (CDCl3): d 8.00 (d, JH–H = 8.1 Hz, 1H, analine-H), 7.73 (t, JH–H
= 4.6 Hz, 1H, aniline H), 7.63 (s, 1H, imi-H), 7.62 (m, 1H, aniline-
H), 7.48 (t, JH–H = 9.3 Hz, 1H, aniline H), 7.21 (s, 1H, imi-H), 7.07
(s, 1H, NCHN) ppm. 13C NMR (CDCl3): d 145.4, 137.3, 133.8,
130.6, 130.4, 129.7, 125.4, 120.3 ppm. Mass (MALDI): m/z 190
(M++1).
ring(1)d
a
b
c
Intramolecular hydrogen bonding.
Intermolecular hydrogen bonding.
Stacking parameter taken into account is the perpendicular distance between
the X and ring plane.
d
Here the rings (1), (3), and (4) represent the five- or six-membered ring formed
by N(1)–C(1)–N(2)–C(2)–C(3), N(4)–C(13)–N(5)–C(14)–C(15) and C(19)–C(20)–
C(21)–C(22)–C(23)–C(24) atoms, respectively.
3. Conclusions
In summary, the aniline or pyridine-functionalized metal NHC
complexes including Hg(II), Ag(I) and Au(I) are synthesized and
characterized. The crystal structures revealed that Hg atoms of
1ꢀMeOH and 3 are four-coordinate with two carbene ligands and
aniline or pyridine. Different from 1ꢀMeOH, the Au atom of 5 is
two-coordinate. 1ꢀMeOH and 5, the –NH2 group of aniline plays
an important role in stabilizing the crystal structure through intra-
molecular and intermolecular hydrogen bonding interactions. The
molecules of 5 are neatly arranged and stacked to a one-dimen-
sional hole. The PF6ꢁ anions of 3 hold two adjacent cations through
Hgꢀ ꢀ ꢀF interactions and Hꢀ ꢀ ꢀF hydrogen bonding and the crystal
packing consists of alternating anions and cation layers.
4.2.2. 3-Isopropyl-1-(2-nitrophenyl)imidazolium iodide
A mixture of 1-(2-nitrophenyl)imidazol (1.00 g, 5.30 mmol) and
2-isopropane (4.50 g, 26.4 mmol) was heated at 100 °C for 12 h.
After cooled to r.t., the reaction mixture was filtered and the resi-
due was washed with ethyl acetate. Recrystallization from CH3OH
to obtain yellow product (96% yield). 1H NMR (DMSO-d6): d 9.72 (s,
1H, NCHN), 8.41 (d, JH–H = 8.1 Hz, 1H, analine-H), 8.16 (s, 1H, imi-
H), 8.14 (s, 1H, imi-H), 8.01 (m, 3H, aniline-H), 4.76 (h, JH–H
=
6.6 Hz, 1H, iso-CH), 1.54 (d, JH–H = 6.6 Hz, 6H, CH3) ppm. 13C NMR
Fig. 8. (Left) Hydrogen bonding in 5. (Right) Top view of the rectangular tube packing of 5.

R.-T. Zhuang et al. / Polyhedron 51 (2013) 132–141
139
Fig. 9. Crystal packing drawing of 5 viewed along the c-axis.
((DMSO-d6)): 144.1, 137.0, 136.0, 133.0, 130.6, 128.6, 126.9, 124.9,
precipitation. The precipitate was collected, washed by water.
Yield: 88%. 1H NMR (Acetone-d6): d 9.21(s, 1H, NCHN), 7.89 (pesu-
do-t, JH–H = 1.8 Hz, 1H, imi-H), 7.81 (pesudo-t, JH–H = 1.8 Hz, 1H,
imi-H), 7.30 (m, 2H, aniline-H), 7.01 (d, JH–H = 9.3 Hz, 1H, aniline-
H), 6.78 (t, JH–H = 7.9 Hz, 1H, aniline-H), 5.11 (s, 2H, NH2), 4.13 (s,
3H, CH3) ppm. 13C NMR (Acetone-d6): 143.4, 137.6, 131.6, 127.0,
124.4, 123.7, 120.3, 117.4, 117.2, 36.0 ppm. Mass (MALDI): 174
(M+).
121.5, 53.5, 22.8 ppm. Mass (MALDI): m/z 232 (M+).
4.2.3. [LaH]I
Zinc (3.64 g, 55.7 mmol) and NH4Cl (0.74 g, 13.9 mmol) were
added into a MeOH solution (30 mL) containing 3-isopropyl-1-(2-
nitrophenyl)imidazolium iodide (1.00 g, 2.8 mmol) and the mix-
ture was allowed to reflux for 30 min. The reaction mixture was
then filtered and the solvent were removed in vacuo overnight to
obtain orange solid. Recrystallization from acetonitrile gave a yield
of 80%. 1H NMR (DMSO-d6): d 9.45 (s, 1H, NCHN), 8.07 (pesudo-t,
JH–H = 1.8 Hz, 1H, imi-H), 7.86 (pesudo-t, JH–H = 1.8 Hz, 1H, imi-H),
7.21 (m, Hz, 2H, aniline-H), 6.88 (d, JH–H = 8.1 Hz, 1H, aniline-H),
6.67 (t, JH–H = 9.3 Hz, 1H, aniline-H), 5.49 (s, 2H, NH2), 4.65 (h, JH–H
= 6.6 Hz, 1H, iso-CH), 1.53 (d, JH–H = 6.6 Hz, 6H, iso-CH3) ppm. 13C-
NMR (DMSO-d6): 144.3, 136.5, 131.6, 127.8, 124.4, 121.5, 120.3,
117.0, 116.5, 53.0, 22.7 ppm. Mass (MALDI): m/z 202 (M+).
4.2.7. [LcH]I
1-(2-Pyridine)imidazole (1.0 g, 6.9 mmol) was added into a THF
solution (10 mL) containing methyl iodine (3.98 g, 28 mmol) and
the mixture was allowed to stir for 24 h at r.t., and followed by fil-
tration giving a white powder. Washing the powder with diethyl
ether gave pure product. Yield: 96%. 1H NMR (DMSO-d6):
d 10.01(s, 1H, NCHN), 8.63 (d, JH–H = 4.8 Hz, 1H, py-H), 8.48 (pesu-
do-t, JH–H = 1.8 Hz, 1H, imi-H), 8.20 (t, JH–H = 7.5 Hz, 1H, py-H3),
8.00 (d, JH–H = 8.1 Hz, 1H, py-H), 7.95 (pesudo-t, JH–H = 1.8 Hz, 1H,
imi-H), 7.63 (m, 1H, py-H), 3.96 (s, 3H, CH3) ppm. 13C NMR
(DMSO-d6): 149.7, 146.8, 1441.1, 136.0, 125.7, 125.3, 119.4,
114.7, 36.92 ppm. Mass (MALDI):160 (M+).
4.2.4. [LaH]PF6
Treatment of [LaH]I (1.00 g, 3.0 mmol) with NH4PF6 (0.59 g,
3.6 mmol) in water gave pale yellow precipitation. The precipitate
was collected, washed by water. Yield: 88%. 1H NMR (Acetone-d6):
d 9.34 (s, 1H, NCHN), 8.07 (pesudo-t, JH–H = 1.8 Hz, 1H, imi-H), 7.88
(pesudo-t, JH–H = 1.8 Hz, 1H, imi-H), 7.31 (m, 2H, aniline-H), 7.01 (d,
JH–H = 9.3 Hz, 1H, aniline-H), 6.79 (t, JH–H = 7.5 Hz, 1H, aniline-H),
5.09 (s, 2H, NH2), 4.92 (h, JH–H = 6.6 Hz, 1H, iso-CH), 1.71 (d, JH–H
= 6.6 Hz, 6H, iso-CH3) ppm. 13C NMR (Acetone-d6): 143.5, 135.8,
131.6, 127.2, 124.2, 121.4, 120.5, 117.25, 117.1, 53.7, 22.0 ppm.
Mass (MALDI): 202 (M+).
4.2.8. [LcH]PF6
Treatment of [LcH]I (1.00 g, 3.5 mmol) with NH4PF6 (0.68 g,
4.2 mmol) in 15 ml water gave pale yellow precipitation. The pre-
cipitate was collected, washed by water to obtain white solid.
Yield: 86%. 1H NMR (Acetonitrile-d3): d 9.25(s, 1H, NCHN), 8.58
(d, JH–H = 0.9 Hz, 1H, py-H), 8.11 (s, 1H, imi-H), 8.07 (m, 1H, py-
H),7.73 (s, 1H, imi-H), 7.56 (m, 2H, py-H), 3.96 (s, 3H, CH3) ppm.
13C-NMR (Acetonitrile-d3): 149.5, 146.4, 140.5, 134.6, 125.4,
124.8, 119.3, 114.0, 36.50 ppm. Mass (MALDI): 160 (M+).
4.2.5. [LbH]I
Zinc (4.01 g, 61.3 mmol) and NH4Cl (0.82 g, 15.3 mmol) were
added into a MeOH solution (30 mL) containing 3-methyl-1-(2-
nitrophenyl) imidazolium iodide (1.00 g, 3.1 mmol) and the mix-
ture was allowed to reflux for 30 min. The reaction mixture was
then filtered and the solvent were removed in vacuo overnight to
obtain orange solid. Recrystallization from acetonitrile gave a yield
of 82%. 1H NMR (DMSO-d6): d 9.39 (s, 1H, NCHN), 7.90 (s, 1H,
imi-H), 7.81 (s, 1H, imi-H), 7.20 (m, 2H, aniline-H), 6.89 (d,
JH–H = 8.11 Hz, 1H, aniline-H4), 6.65 (t, JH–H = 7.7 Hz, 1H, aniline-
H5), 5.52 (s, 2H, NH2), 3.89 (s, 3H, CH3) ppm. 13C NMR (DMSO-
d6): 144.3, 138.4, 131.6, 127.6, 124.2, 124.0, 120.2, 116.9, 116.5,
36.5 ppm. Mass (MALDI): 174 (M+).
4.2.9. [Hg(La)2](PF6)2
Hg(OAc)2 (0.05 g, 0.2 mmol) was added into a MeOH solution
(5 mL) containing [LaH]PF6 (0.10 g, 0.3 mmol) and the reaction
mixture was allowed to reflux for 14 h, followed by filtration giving
a pale orange precipitation. The precipitate was collected, washed
with MeOH. Yield: 68%. 1H NMR (Acetone-d6):
d 8.08 (d,
JH–H = 1.8 Hz, 2H, imi-H), 7.86 (d, JH–H = 1.8 Hz, 2H, imi-H), 7.35
(m, 4H, aniline-H), 7.17 (d, JH–H = 8.1 Hz, 2H, aniline-H), 6.95 (t,
JH–H = 7.7 Hz, 2H, aniline-H), 5.30 (s, 4H, NH2), 4.78 (h, JH–
H = 6.6 Hz, 2H, iso-CH), 1.60 (d, JH–H = 6.6 Hz, 12H, iso-CH3) ppm.
13C NMR (Acetone-d6): 174.5, 141.72, 131.2, 127.2, 125.8, 124.0,
120.9, 119.8, 118.6, 55.44, 22.55 ppm. Mass (MALDI): 749
(M+PF6+1)+, 603 (M+1)+. Anal. Calc. for C25H34HgF12N6OP2 ([Hg(La)2
MeOH](PF6)2): C, 32.46; N, 9.08; H, 3.70. Found: C, 32.55; N, 9.08;
H, 3.37%.
4.2.6. [LbH]PF6
Treatment of [LbH]I (1.00 g, 3.3 mmol) in 5 ml of CH3OH with
10 ml aqueous solution of NH4PF6 (0.65 g, 4.0 mmol) gave orange

140
R.-T. Zhuang et al. / Polyhedron 51 (2013) 132–141
4.2.10. [Ag(La)2]I
Acknowledgments
Ag2O (0.39 g, 1.7 mmol) was added into an CH3CN solution con-
taining [LaH]I (1.00 g, 0.3 mmol) and the suspension was stirred at
room temperature for 5 h in dark and filtered through Celite. The fil-
trate was further treated with the active carbon, followed by filtra-
tion and dried in vacuo to give an air stable silver complex as a
The authors acknowledge the National Science Council (Taiwan,
ROC) and National Dong Hwa University for financial support.
Appendix A. Supplemetary material
white solid. Yield: 92%. 1H NMR (Acetone-d6):
d 7.60 (d,
JH–H = 1.8 Hz, 2H, imi-H), 7.38 (d, JH–H = 1.8 Hz, 2H, imi-H), 7.18 (m,
4H, aniline-H), 6.98 (d, JH–H = 8.1 Hz, 2H, aniline-H), 6.73 (t,
JH–H = 8.1 Hz, 2H, aniline-H), 4.77 (s, 4H, NH2), 4.60 (h,
JH–H = 6.6 Hz, 2H, iso-CH), 1.46 (d, JH–H = 6.6 Hz, 12H, iso-CH3) ppm.
13C NMR (Acetone-d6): 181.2, 143.6, 129.9, 127. 8, 125.7, 122.9
119.0, 117.0, 116.6, 54.0, 23.3 ppm. Mass (MALDI): 509 (M+).
CCDC 829830–829832 contain the supplementary crystallo-
graphic data for Au(La)Cl (5), [Hg(Lc)2](PF6)2 (3) and [Hg(La)2
MeOH](PF6)2 (1ꢀMeOH). These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk
4.2.11. AuLaCl
AuCl(SMe2) (0.05 g, 0.17 mmol) was added into a dichlorometh-
ane solution containing [AgLa2]I (0.10 g, 0.15 mmol) in dark condi-
tion and the mixture was allowed to stir for 1 h, followed by
filtration giving a pale yellow clear filtrate. The solvent was re-
moved in vacuo to yield a pale yellow powder. Yield: 79%. 1H
NMR (Acetone-d6): d 7.66 (d, JH–H = 1.8 Hz, 1H, imi-H), 7.35 (d,
JH–H = 1.8 Hz, 1H, imi-H), 7.20 (m, 2H, aniline-H), 6.91 (d,
JH–H = 8.1 Hz, 1H aniline-H), 6.72 (t, JH–H = 7.5 Hz, 1H, aniline-H),
5.08 (h, JH–H = 6.8 Hz, 1H, iso-CH), 4.66 (s, 2H, NH2), 1.58 (d, JH–
H = 6.9 Hz, 6H, iso-CH3) ppm. 13C NMR (Acetone-d6): 170.5, 143.8,
130.1, 128.2, 124.9, 123.2, 117.9, 116.9, 116.39, 53.7, 22.4 ppm.
Mass (MALDI): 398 (MꢁCl)+, 356 (MꢁClꢁisopropyl+1)+, 202(L).
Anal. Calc. for C12H16AuClN3: C, 33.23; N, 9.69; H, 3.70. Found: C,
33.32; N, 9.82; H, 3.59%.
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4.2.12. [Hg(Lb)2](PF6)2
Silimar procedure as that for [Hg(La)2](PF6)2 was applied to ob-
tain an orange product. Yield: 75%. 1H NMR (Acetone-d6): d 7.92 (d,
JH–H = 1.8 Hz, 2H, imi-H), 7.85 (d, JH–H = 1.8 Hz, 2H, imi-H), 7.33 (m,
4H, aniline-H), 7.12 (d, JH–H = 7.8 Hz, 2H, aniline-H), 6.95 (t, JH–
H = 9.3 Hz, 2H, aniline-H), 5.26 (s, 4H, NH2), 4.13 (s, 6H, CH3)
ppm. 13C-NMR (Acetone-d6): 176.5, 141.4, 131.0, 126.9, 125.60,
124.9, 124.3, 120.0, 119.0, 37.98 ppm. Mass (MALDI): 693
(M+PF6+1)+, 547 (M+1)+, 173 (L-1). Anal.Calc. for C20H22F12HgN6P2:
C, 28.70; N, 10.04; H, 2.65. Found: C, 28.76; N, 9.95; H, 2.70%.
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