Synthesis and characterization of silver and gold NHC complexes: Crystal structures and mass spectral studies

Article abstract of DOI:10.1016/j.jorganchem.2013.03.017

Mononuclear silver and gold complexes [Ag(BzlCy)(Cl)] (1) and [Au(BzlCy)(Cl)] (2) were synthesized starting from the N-heterocyclic carbene (NHC) BzlC?HCl (1,3-Dicyclohexylbenzimidazolium chloride) and characterized by NMR and ESI-MS spectral studies. Molecular structures of complexes [Ag(BzlCy)(Cl)] (1) and [Au(BzlCy)(Cl)] (2·THF) were determined by X-ray crystallography. Formation of different species of these complexes 1 and 2 in gas phase was investigated by electrospray ionization mass spectrometry in positive mode and compared with solution formulation. To better understand the nature of NHC complexes and their reactivity with phenyl acetylene in gas phase, we synthesized a negatively charge tag gold complex [Au(^SBzlCy)(Cl)] starting from ^SBzlC?HCl which prepared by the sulphonation of BzlCy. We investigated the formation of intermediate species [Au( ^SBzlCy)(PhC≡C)] by the coordination of phenyl acetylene to the charge-tag gold complex in gas phase. We compared the stability of these NHC complexes and also investigated the decomposed mixture by electrospray ionization.

Full text of DOI:10.1016/j.jorganchem.2013.03.017

Journal of Organometallic Chemistry 735 (2013) 32e37
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterization of silver and gold NHC complexes: Crystal
structures and mass spectral studies
,
b
,
c
Pramod Kumar a , Ivana Cisarova
*
a Department of Chemistry, National Institute of Technology Kurukshetra, Kurukshetra 136119, Haryana, India
b Department of Organic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 2030/8, 12843 Prague 2, Czech Republic
c Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague, Hlavova 8, 128 43 Prague 2, Czech Republic
a r t i c l e i n f o
a b s t r a c t
Article history:
Mononuclear silver and gold complexes [Ag(BzlCy)(Cl)] (1) and [Au(BzlCy)(Cl)] (2) were synthesized
starting from the N-heterocyclic carbene (NHC) BzlCy∙HCl (1,3-Dicyclohexylbenzimidazolium chloride)
and characterized by NMR and ESI-MS spectral studies. Molecular structures of complexes [Ag(Bzl-
Cy)(Cl)] (1) and [Au(BzlCy)(Cl)] (2$THF) were determined by X-ray crystallography. Formation of different
species of these complexes 1 and 2 in gas phase was investigated by electrospray ionization mass
spectrometry in positive mode and compared with solution formulation. To better understand the nature
of NHC complexes and their reactivity with phenyl acetylene in gas phase, we synthesized a negatively
charge tag gold complex [Au(SBzlCy)(Cl)] starting from SBzlCy∙HCl which prepared by the sulphonation
of BzlCy. We investigated the formation of intermediate species [Au(SBzlCy)(PhChC)] by the coordina-
tion of phenyl acetylene to the charge-tag gold complex in gas phase. We compared the stability of these
NHC complexes and also investigated the decomposed mixture by electrospray ionization.
Ó 2013 Elsevier B.V. All rights reserved.
Received 9 November 2012
Received in revised form
28 February 2013
Accepted 12 March 2013
Keywords:
Electrospray ionization
Mass spectrometry
N-Heterocyclic carbene
Silver complex
Gold complex
1. Introduction
coworkers investigated long lived charge-tagged N-heterocyclic
carbenes by electrospray ionization [9]. Lalli et al. reported
N-Heterocyclic carbenes have demonstrated remarkable reac-
tivity and this has resulted in major developments in their coordi-
nation chemistry [1,2]. NHCs strongly bind and stabilize transition
metals, leading to a wide variety of well-defined catalytic systems
[3e6]. NHC complexes of silver and gold have been employed to
catalyze carboxylation of activated arenes, aromatic heterocycles,
terminal alkynes by CeH bond activation with CO2 [5], addition of
water and methanol to alkynes [6]. It is reported that these substrate
which have activated CeH bond generated a coordinated interme-
diate species with silver and gold NHC complexes [3a,5f].
Mass spectrometry is intrinsically blind to neutral carbene
molecules hence investigated via gas phase MS experiments mainly
in ionized forms. To remove this blindness, an elegant MS strategy
has been elaborated using charge tags. With the arrival of elec-
trospray ionization (ESI), charge tags have also been used in solu-
tion to allow the favourable charge-tagged molecules directly from
solution into the isolated gas phase environment for MS mea-
surements and reactivity investigations [7,8]. Recently, Eberlin and
carboxylation of negative-charge tagged NHC by CO2 to form
negative-charge tagged imidazolium carboxylates [10].
In this report, starting from a carbene ligand BzlCy∙HCl (1,3-
Dicyclohexylbenzimidazolium chloride), we have synthesized and
characterized silver and gold complexes [Ag(BzlCy)(Cl)] (1)
[Au(BzlCy)(Cl)] (2) (Scheme 1). Molecular structures of [Ag(Bzl-
Cy)(Cl)] (1) and [Au(BzlCy)(Cl)] (2$THF) were determined by X-ray
crystallography. To investigate the coordination of terminal alkynes
(acetylide ion) to the gold complex in gas phase, we synthesized
sulphonated charge-tag gold complex [Au(SBzlCy)(Cl)] (3). The gas
phase chemistry of complexes 1e3 were investigated by electro-
spray ionization mass spectrometry and compared with solution
chemistry. Coordination of phenyl acetylene with gold complex
[Au(SBzlCy)(Cl)] generated a new species of [Au(SBzlCy)(PhChC)] at
m/z 659 which is the key intermediate in the hydration and
carboxylation of phenyl acetylene.
2. Results and discussion
2.1. Synthesis and characterization
* Corresponding author. Department of Chemistry, National Institute of Tech-
nology Kurukshetra, Kurukshetra 136119, Haryana, India. Tel.: þ91 9728182401.
E-mail address: baliyanpk@gmail.com (P. Kumar).
The silver complex [Ag(BzlCy)(Cl)] (1) prepared by the
overnight stirring of Bzlcy with Ag2O at ambient temperature in
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.03.017

P. Kumar, I. Cisarova / Journal of Organometallic Chemistry 735 (2013) 32e37
33
N
N
N
N
N
Cl
Cl
ClSO3H, 3h
Ag2O, 12h
Ag Cl
90-100 oC
CH2Cl2, rt
N
NaO3S
NaOH
SBzlCy.HCl
Ag2O, 12h
CH2Cl2, rt
BzlCy.HCl
1
[Au(DMS)(Cl)]
CH Cl
4h, rt,
2
2
N
N
N
Au Cl
Au Cl
NaO3S
N
3
2
Scheme 1. Formulation of ligands and schematic synthesis of complexes.
Fig. 1. Ortep plot of 1 showing the atom numbering scheme and the displacement
ꢀ
ellipsoids are drawn on 50% probability level. Selected bond length (A) and bond an-
dichloromethane and isolated with 72% yield [11]. [Au(BzlCy)(Cl)]
(2) was obtained by carbene transfer from complex 1 to (dime-
thylsulfide)gold(I) chloride in dichloromethane with 68% yield [12].
We synthesized sulphonated SBzlCy∙HCl carbene ligand by reaction
of BzlCy∙HCl and chlorosulphonic acid with 54% yield. [Au(SBzl-
Cy)(Cl)] (3) was synthesized by the process similar to complex 1
with 64% yield. Overall synthesis of complexes are summarized in
Scheme 1. These complexes were characterized by 1H NMR spectra
and compare well to those of analogous complexes described in the
literature [11,12].
gles (deg): Ag1ꢀCl1, 2.3691(5); Ag1ꢀC1, 2.1009(19); C1ꢀAg1ꢀCl1, 168.15(5);
N1ꢀC1ꢀAg1 125.87(13), N2ꢀC1ꢀAg1 127.96(13).
cyclohexyl ring showed the interactions with phenyl ring of
ꢀ
ꢀ
neighbour molecules at distances of 2.756 A and 3.938 A (Fig. S2).
2.3. Mass spectral studies
2.3.1. Electrospray ionization of complexes
The crystal structures for 1 and 2$THF showed the mononuclear
geometry however in gas phase, these molecules detected in
different form. At first, we investigated the complexes 1 and 2 by
electrospray ionization (ESI-MS) in positive mode and suitable
ionization conditions for the investigated solution had to be
determined. The electrospray mass spectrum of silver complex 1
showed the abundant signals correspond to [Ag(BzlCy)2]þ
2.2. Description of molecular structures
Complexes [Ag(BzlCy)(Cl)] (1) and [Au(BzlCy)(Cl)] (2$THF) were
also characterized by X-ray crystallography and have two-
coordinate silver(I) and gold(I) centre atom respectively (Fig. 1
and Fig. 2). The crystal data and data collection parameters are
shown in Table 1. The AgꢀC(NHC) and AuꢀC(NHC) bond distances
ꢀ
ꢀ
are 2.100 A and 1.996 A respectively and close to the reported
ꢀ
ꢀ
values (2.056e2.094 A for AgeC and 1.979e1.998 A for AueC)
[11,12]. As expected the silver ecarbon bond is longer than gold-
ꢀ
carbon bond. The AueC(NHC) distance (1.996 A) suggests a
single-bond character, in good accordance with their strong
s-
ꢀ
donor characteristics [11,13]. The AgeCl bond distance (2.369 A) in
ꢀ
1 and AueCl bond distance (2.2811 A) in 2$THF are consistent with
ꢀ
ꢀ
the reported values (2.332e2.362 A, for AgeCl and 2.275e2.306 A,
for AueCl) [11,12]. The coordination of chloro with gold generated a
linear geometry and the bond angles are close to 180ꢁ
(C1ꢀAu1ꢀCl1, 179.27(12)) and bisects the BzlCy ligand. However in
complex 1 the C1ꢀAg1ꢀCl1 bond angle (168.15(5)) showed more
deviation from linearity.
The non-covalent interactions are very much important for su-
pramolecular chemistry and crystal engineering [14]. In the crystal
packing of 1, the molecules were in the symmetric unit and form a
dimer linked by argentophilic interaction with a Ag(I)eAg(I) dis-
ꢀ
tance of 3.237 A. The distance between two silver centres were less
ꢀ
than the 3.44 A, the sum of twice the van der Waals radius of Ag(I)
[11,13]. In this symmetric unit, the interactions between the each
chloro and silver of neighbour molecule were at a distance of
ꢀ
3.146 A (Fig. S1). The coordinated chloro showed the H-bonding
interactions with the cyclohexyl rings AgeCleH(cyclohexyl rings)
at the distances of 2.704 Åe2.931 A. In crystal of 2$THF, the chloro
Fig. 2. Ortep plot (50% probability level) of 2$THF showing the atom numbering
ꢀ
scheme and the displacement ellipsoids are drawn on 50% probability level selected
ꢀ
atoms showed the interaction with the hydrogen of phenyl ring
bond length (A) and bond angles (deg): Au1ꢀCl1, 2.2811(10); Au1ꢀC1, 1.995(4);
ꢀ
(AueCleH(phenyl), at distance of 2.787 A. The hydrogen atom of
C1ꢀAu1ꢀCl1, 179.27(12); N1ꢀC1ꢀAu1 125.67(3), N2ꢀC1ꢀAu1 127.1(3).

34
P. Kumar, I. Cisarova / Journal of Organometallic Chemistry 735 (2013) 32e37
Table 1
m/z ¼ 279 after loss of cyclohexene molecule from cyclohexyl
group (Fig. S8).
Summary of crystal data and data collection parameters for 1 and 2∙THF.
Complex [Au(SBzlCy)(Cl)] (3) showed a sharp peak at m/z 593 in
negative mode after loss of Naþ (anion formation) (Fig. S9). At low
collision energy, [Au(SBzlCy)(Cl)]ꢀ (m/z ¼ 593) led to generate the
intense mass species at m/z ¼ 511 after loss of cyclohexene (Fig. 3).
Further enhancement in collision energy, another important spe-
cies m/z ¼ 513 and m/z ¼ 529 were generated after loss of SO3 and
SO2 molecules respectively from [Au(SBzlCy)(Cl)]ꢀ (m/z ¼ 593).
These two species again led to generate the species at m/z ¼ 431
and m/z ¼ 446 respectively after loss of cyclohexene molecules.
We got some less intense mass species at m/z ¼ 361 and m/z ¼ 279
due to loss of AuCl and AuCl with cyclohexene molecule, these
fragments are similar to the fragments in ligand [SBzlCy]ꢀ (m/
z ¼ 397).
1
2∙THF
Empirical formula
Formula weight
C19H26N2ClAg
425.74
150(2)
0.71073
Orthorhombic
A b a 2
17.3329(4)
18.7209(4)
10.9732(2)
C23H34N2OClAu
586.94
150(2)
0.71073
Monoclinic
P 21/c
13.4423(7)
10.3202(5)
17.1159(8)
108.067(2)
2257.37(19)
4
Temperature/K
ꢀ
l
(A) (MoK\
a
)
Crystal system
Space group
ꢀ
a (A)
ꢀ
b (A)
ꢀ
c (A)
b
(ꢁ)
3
ꢀ
V (A )
3560.67(13
8
1.588
Z
rcalc (gcmꢀ3
)
1.727
Crystal size (mm)
0.32 ꢂ 0.31 ꢂ 0.11
0.36 ꢂ 0.17 ꢂ 0.07
m
(MoK
F(000)
Tmin, Tmax
a
) (mmꢀ1
)
1.28
6.65
1744
1160
a
2.3.2. Reactivity with phenyl acetylene
0.682, 0.874
2.45e27.46
ꢀ22 < h < 22,
ꢀ22 < h < 24,
ꢀ11 < h < 14
3882/1/208
1.04
0.0163
0.0183
0.0397
0.0405
0.199, 0.639
1.59e27.50
ꢀ17 < h < 17,
ꢀ13 < h < 13,
ꢀ22 < h < 22
5182/0/253
1.02
0.0297
0.0476
0.0501
0.0545
To investigate the reactivity of NHC complex with terminal
alkynes, we synthesized sulphonated charge-tag NHC gold(I)
complex [Au(SBzlCy)(Cl)] (3) which showed a sharp peak at m/z 593
in negative mode (Fig. S9). We made a in situ reaction of
[Au(SBzlCy)(Cl)] and phenyl acetylene in dichloromethane solution.
In the ESI-MS process, the ionic species present in this solution are
gently transferred into the gas phase and we have recorded mass
spectra of negative ions.
Theta range for data collection
Index ranges
Data/restraints/parameters
GOFb on F2
R1c [I > 2
s
(I)]
R1 [all data]
wR2c [I > 2
s
(I)]
wR2 [all data]
At first, suitable ionization conditions for the investigated so-
lution had to be determined. At soft ionization conditions, the
most abundant signals in the mass spectrum correspond
[Au(SBzlCy)(PhChC)]ꢀ at m/z 659 and second intense peak is for
[Au(SBzlCy)]ꢀ at m/z 593. Fig. 4(a) showed the conversion of
[Au(SBzlCy)]ꢀ (m/z ¼ 593) to [Au(SBzlCy)(PhChC)]ꢀ (m/z ¼ 659).
[Au(SBzlCy)(PhChC)] is the key intermediate in the hydration
and carboxylation of phenyl acetylene. The CID of
[Au(SBzlCy)(PhChC)]ꢀ have similar pattern to the [Au(SBzlCy)(Cl)]ꢀ
(Fig. 4(b)). At low collision energy [Au(SBzlCy)(PhChC)]ꢀ (m/
z ¼ 659) led to generate the intense mass species at m/z ¼ 577 after
loss of cyclohexene molecule. Two other mass species at m/z ¼ 361
and m/z ¼ 279 due to loss of AuCl and AuCl with cyclohexene, these
fragments are common in CID of [SBzlCy]ꢀ (m/z ¼ 397) and
[Au(SBzlCy)(Cl)]ꢀ (m/z ¼ 593). Further enhancement in collision
energy, another important species at m/z ¼ 595 and m/z ¼ 579
were generated after loss of SO2 and SO3 molecules from
[Au(SBzlCy)(PhChC)]ꢀ (m/z ¼ 659). These species again led to
generate the peaks at m/z ¼ 512 and m/z ¼ 497 respectively after
loss of cyclohexene molecules. These fragmentation patterns indi-
cated that acetylide coordinated is very stable complex.
a
The range of transmission factors.
b
½
GOF ¼ [S(w(F2o ꢀ F2c)2)/(Ndiffrs ꢀ Nparams)]
.
P
P
P
P
R ¼ jjFoj ꢀ jFcjj= jFoj; wR ¼ ½ fwðFo2 ꢀ Fc2Þ2g= wðFo2Þ2ꢃ1=2
.
c
(m/z ¼ 671) species (Fig. S3). The CID of [Ag(BzlCy)2]þ (m/z ¼ 671)
led to formation of [Ag(BzlCy)]þ (m/z ¼ 389) after loss of one BzlCy
and then generated a mass species [Ag(BzlCy)(H2O)]þ (m/z ¼ 407)
after coordination to the background water (Fig. S4). In gas phase,
complex 1 showed the formulation of [Ag(BzlCy)2]þ[AgCl2]ꢀ due to
existence of AgIeAgI interactions [11]. The mass spectrum of
complex 2 showed the two abundant signals correspond to
[Au(BzlCy)2]þ (m/z ¼ 761) and [Au2(BzlCy)2(Cl)]þ (m/z ¼ 993)
(Fig. S5). The CID of [Au2(BzlCy)2(Cl)]þ (m/z ¼ 993) leads the for-
mation of [Au(BzlCy)2]þ (m/z ¼ 761) after loss of AuCl. At low
collision energy, [Au(BzlCy)2]þ (m/z ¼ 761) led to consequently loss
of two cyclohexene molecules (fragments with m/z ¼ 679 and 597
respectively) from cyclohexyl groups and further enhancement of
collision energy led to a loss of another cyclohexene molecule
(fragment with m/z ¼ 515) (Fig. S6).
The sulphonated charge tag ligand, SBzlcy∙HCl showed two
peaks at m/z 397 after loss of Naþ and m/z 361 after loss of Naþ
with HCl in negative mode. The CID of [SBzlcy]ꢀ (m/z ¼ 397)
generated a species at m/z ¼ 361 after loss of HCl (Fig. S7). The
MS/MS/MS experiment of this species (m/z ¼ 361) fragment with
We have also studied the appearance energies, Eapp, for the
fragmentations of [Au(SBzlCy)(Cl)] and the acetylene coordinated
complex [Au(SBzlCy)(PhChC)]. The energies are given in % (char-
acteristic units for the LCQ instrument). The units can be converted
to eV using a calibration [15,16], but as we are only interested in the
m/z 511
Cy = cyclohexene
-Cy
N
m/z 593
m/z 431
Au Cl
-Cy
-SO
m/z 513
O3S
N
3
-SO
-Cy
m/z 446
2
m/z 529
m/z 279
m/z 361
m/z
300
400
500
600
Fig. 3. Fragmentation of [Au(SBzlCy)(Cl)]ꢀ (m/z ¼ 593) at Ecoll ¼ 38% in dichloromethane solution.

P. Kumar, I. Cisarova / Journal of Organometallic Chemistry 735 (2013) 32e37
35
(a)
m/z 659
m/z 593
N
N
N
N
Au Cl
Au
O3S
O3S
m/z = 593
m/z = 659
450
500
550
600
650
m/z
m/z 659
Cy = Cyclohexene
(b)
-Cy
m/z 361
-SO
m/z 577
m/z 497
m/z 279
3
-Cy
m/z 579
-SO
2
m/z 512
-Cy
m/z 595
300
400
500
600
m/z
Fig. 4. (a) Negative-ion mass spectra of reaction of [Au(SBzlCy)(Cl)] and phenyl acetylene in dichloromethane solution; (b) Fragmentation of [Au(SBzlCy)(PhChC)]ꢀ (m/z ¼ 659) at
Ecoll ¼ 44% in dichloromethane.
relative differences, we use them in the original format. The
appearance energies are obtained from the dependence of relative
abundances of the parent ions and sum of all fragment ions
(Fig. S10eS13). The relative increase in the abundance of the frag-
ment ions is fitted with a sigmoid function and the appearance
energy of the fragmentations is determined from the extrapolation
of the tangent at the inflex point of the sigmoid function to zero
(Fig. S12eS13). The appearance energies, Eapp (%) for the frag-
m/z ¼ 377 generated a peak (m/z ¼ 294) after loss of cyclohexene
and further increase the CID generated a species after loss of one
more cyclohexene molecule (Fig. S14). The formation of carbonyl
group may be due to the oxidation of BzlCy ligand by gold. Recently,
Cazin and coworkers reported the formation of imidazolidin-2-one
by Cu2O during the synthesis of copper-NHC complex [17].
3. Experimental section
mentations
of
[Au(SBzlCy)(Cl)]ꢀ
(m/z
¼
659)
and
[Au(SBzlCy)(PhChC)]ꢀ (m/z ¼ 659) are 32.38 and 33.76 respec-
tively. Clearly, the Eapp energy is nearly equal for both the ions
which have similar fragmentation pattern. Both the ions showed
the elimination of SO3, SO2, AuCl and cyclohexene molecules and
required the same energy. The CID of [Au(SBzlCy)(PhChC)]ꢀ also
indicated the stability of bond between gold and acetylide ions
(AueC^C-Ph).
3.1. Materials
Unless otherwise noted all operations were performed without
taking precautions to exclude air and moisture. Bzlcy, Ag2O,
Au(DMS)Cl, Cu2O, phenyl acetylene were purchased from Sigma
Aldrich. All chemicals and solvents were used as received without
any further treatment.
2.3.3. Stability of complexes
3.2. Physical measurements
Complexes 1 and 2 are stable for one month in light and air only
in solid state. Sulphonated charge-tag [Au(SBzlCy)(Cl)] (3) is not
more stable in air and converted into a mixture of black and yellow-
white precipitate within one day. We have investigated this
decomposed mixture by electrospray ionization in negative mode
and found a peak at m/z 377 which is due to the formation of
ketonic group at carbene position (Fig. 5). The CID of mass peak at
1H NMR spectra were recorded on a Bruker ACF 300 spec-
trometer, and the chemical shifts were internally referenced by the
residual solvent signals relative to tetramethylsilane. The gas phase
experiments were performed with a Finnigan LCQ Advantage ion-
trap mass spectrometer (ThermoFinnigan, San Jose, CA, USA)
fitted with an electrospray ionization source operated in a positive
m/z 377
S
Ag( BzlCy)(Cl)]
Decomposition
Au Cl
m/z 593
N
N
N
O
O3S
N
O3S
m/z = 593
m/z = 377
350
400
450
500
550
600
m/z
Fig. 5. Typical mass spectra of decomposition of complex 3.

36
P. Kumar, I. Cisarova / Journal of Organometallic Chemistry 735 (2013) 32e37
or negative-ion mode [18,19]. In the present experiments, milli-
molar solutions of analysed complexes or mixtures were intro-
duced through a fused-silica capillary to the ESI source by a syringe
CH2-cyclohexane), 2.00 (t, J ¼ 16.2 Hz, 8H, CH2-cyclohexane), 1.82 (d,
J ¼ 12.6 Hz, 2H, CH2-cyclohexane), 1.51 (m, 4H, CH2-cyclohexane),
1.36 (m, 2H, CH2-cyclohexane). ESI-MS: m/z observed at 761 for
[Au(BzlCy)2]þ.
pump (w5 mL/min). Nitrogen was used as nebulizing and drying gas
at a source temperature of about 230 ꢁC. The operating conditions
were set as follows: spray voltage 5.0 kV, capillary voltage 12 V,
tube lens offset 47 V, heated capillary temperature 230 ꢁC. Maximal
yields of the desired ions (see the following text) were achieved by
adjusting the capillary voltage (0e100 V). Mass spectra were
recorded from m/z 50 to 2000. Collision-induced dissociation (CID)
of mass-selected precursor ions was achieved by RF-excitation of
the ions within the He buffer gas present in the ion trap as the
collision partner. The collision energy was optimized for each
experiment and is expressed in terms of the manufacturer’s
normalized collision energy (%), where the range from 0 to 100%
corresponds to a resonance excitation a.c. signal of 0e2.5 V (zero-
to-peak) at the secular frequency of the ion of interest.
3.4.3. Synthesis of [Au(SBzlCy)(Cl)] (3)
A mixture of SBzlCy∙HCl (42.0 mg, 0.1 mmol) and Ag2O (15.0 mg,
0.65 mmol) in dichloromethane (5 mL) was stirred for 12 h at room
temperature. The mixture was filtered and (dimethylsulfide)gold(I)
chloride (29.6 mg, 0.1 mmol) was added to the solution. The reac-
tion mixture was stirred for 4 h at room temperature. The mixture
was filtered through Celite and the solvent was removed by vac-
uum. The solid white product was washed with hexane. Yield: 64%.
ESI-MS: m/z observed at 593 for [Au(SBzlCy)(Cl)]ꢀ.
3.5. Xeray crystallography
Crystallographic data for 1 and 2$THF were collected on Nonius
3.3. Preparation of ligand
KappaCCD diffractometer equipped with Bruker APEX-II CCD de-
ꢀ
tector by monochromatized MoK
a
radiation (
l
¼ 0.71073 A) at a
S
3.3.1. Synthesis of Bzlcy∙HCl
temperature of 150(2) K. The data were corrected for absorption
using numerical correction from crystal shape [20]. The structures
were solved by direct methods (SHELXS) and refined by full
matrix least squares based on F2 (SHELXL97) [21]. The hydrogen
atoms were found on difference Fourier map and were recalculated
into idealized positions. All hydrogen atoms were refined as fixed
To a 2 mL of chlorosulphonic acid at 0 ꢁC in an ice bath,100 mg of
BzlCy was added and the mixture was reflux at 90e100 ꢁC for 3 h.
The reaction mixture was allowed to cool to 0 ꢁC by ice and then the
content of flask was carefully added to a 100 mL flask containing
crushed ice (10 mg) with constant stirring. The reaction mixture
again allowed to warm to room temperature and neutralized to pH
7 with NaOH. The white solid was extracted by dichloromethane
(3 ꢂ 10 mL) and dried by Na2SO4. The combined extract was
evaporated to dryness to give white solid. Yield: 54%. 1H NMR
(riding
model)
with
assigned
temperature
factors
Hiso(H) ¼ 1.2 Ueq(pivot atom).
4. Conclusions
(CDCl3, 300 MHz): d (ppm) 10.28 (s, 1H, CH-carbene), 8.35 (s, 1H, CH
aromatic) 8.15 (d, J ¼ 8.5 Hz, 1H, CH-aromatic), 7.73 (d, J ¼ 9.15 Hz,
1H, CH-aromatic), 4.6 (m, 2H, CH-cyclohexane), 2.18 (q, J ¼ 11.3 Hz,
4H, CH2-cyclohexane), 1.98e1.70 (m, 8H, CH2-cyclohexane), 1.52e
1.24 (m, 8H, CH2-cyclohexane). ESI-MS: m/z observed at 397 for
[SBzlCy]ꢀ.
In summary, synthesis and characterization of silver and gold
complexes starting from the N-heterocyclic carbene ligands
BzlCy∙HCl and SBzlCy∙HCl has been reported. Molecular structures
of 1 and 2$THF afforded two-coordinated silver(I) and gold(I) centre
atoms respectively with linear geometry. However in gas phase, the
complex 1 detected as [Ag(BzlCy)2]þ (m/z ¼ 671) and 2 as
[Au(BzlCy)2]þ (m/z ¼ 761) and [Au2(BzlCy)2(Cl)]þ (m/z ¼ 993)
species by electrospray ionization. Sulphonated charge tag gold(I)
complex [Au(SBzlCy)(Cl)] (3) showed coordination with phenyl
acetylene and the key intermediate [Au(SBzlCy)(PhChC)] which is
responsible for carboxylation and hydration of phenyl acetylene
investigated by electrospray ionization. Catalytic carboxylations of
terminal alkynes by these complexes in presence of CO2 are under
progress.
3.4. Preparation of complexes
3.4.1. Synthesis of [Ag(BzlCy)(Cl)] (1)
A mixture of BzlCy∙HCl (31.8 mg, 0.1 mmol) and Ag2O (15.0 mg,
0.65 mmol) in dichloromethane (5 mL) was stirred for 12 h at room
temperature. The mixture was filtered over Celite, and the solvent
was removed by vacuum. The white solid product was washed with
hexane. Slow evaporation of a dichloromethane/hexane layering
afforded colourless crystals suitable for X-ray crystallography.
Yield: 72%. 1H NMR (CDCl3, 300 MHz):
d
(ppm) 7.62 (q, J ¼ 3.2 Hz,
Acknowledgements
2H, CH-aromatic), 7.35 (q, J ¼ 2.9 Hz, 2H, CH-aromatic), 4.55 (t, 2H,
CH-cyclohexane), 2.32 (q, J ¼ 10.8 Hz, 4H, CH2-cyclohexane), 2.01 (t,
J ¼ 15.9 Hz, 8H, CH2-cyclohexane), 1.81 (d, J ¼ 9.6 Hz, 2H, CH2-
cyclohexane), 1.52 (m, 4H, CH2-cyclohexane), 1.37 (m, 2H, CH2-
cyclohexane). ESI-MS: m/z observed at 673 for [Ag(BzlCy)2]þ.
This work was supported by the grant No. 207/11/0338 from the
Grant Agency of the Czech Republic and the Ministry of Education
of the Czech Republic (MSM0021620857). We thank Jana Roithova
for providing the measuring time at the massspectrometric in-
strument, chemicals, and help during the measurements.
3.4.2. Synthesis of [Au(BzlCy)(Cl)] (2$THF)
A mixture of BzlCy∙HCl (31.8 mg, 0.1 mmol) and Ag2O (15.0 mg,
0.65 mmol) in dichloromethane (5 mL) was stirred for 12 h at room
temperature. The mixture was filtered and (dimethylsulfide)gold(I)
chloride (29.6 mg, 0.1 mmol) was added to the solution. The reac-
tion mixture was stirred for 4 h at room temperature. The mixture
was filtered through Celite and the solvent was removed by vac-
uum. The white solid product was washed with hexane. Slow
evaporation of a dichloromethane/tetrahydrofuran mixture affor-
ded colourless crystals. Yield: 68%. 1H NMR (CDCl3, 300 MHz):
Appendix A. Supplementary material
CCDC 893366 and 893367 contain the supplementary crystal-
lographic 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.
Appendix B. Supplementary data
d
(ppm) 7.66 (q, J ¼ 3.3 Hz, 2H, CH-aromatic), 7.33 (q, J ¼ 3.0 Hz, 2H,
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jorganchem.2013.03.017.
CH-aromatic), 5.01 (t, 2H, CH-cyclohexane), 2.43 (q, J ¼ 10.9 Hz, 4H,

P. Kumar, I. Cisarova / Journal of Organometallic Chemistry 735 (2013) 32e37
40 (2011) 2995e2999;
37
References
(c) J.H. Teles, S. Brode, M. Chabanas, Angew. Chem. Int.Ed 37 (1998) 1415e
1418.
[7] J.B. Fenn, M. Mann, C.K. Meng, S.F. Wong, C.M. Whitehouse, Science 246
(1989) 64e71.
[8] P. Chen, Angew. Chem. Int. Ed. 42 (2003) 2832e2847.
[9] Y.E. Corilo, F.M. Nachtigall, P.V. Abdelnur, G. Ebeling, J. Dupont, M.N. Eberlin,
RSC Adv. 1 (2011) 73e78.
[10] P.M. Lalli, T.S. Rodrigues, A.M. Arouca, M.N. Eberlin, B.A.D. Neto, RSC Adv. 2
(2012) 3201e3203.
[11] P. de Fremont, 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.
[12] P. de Fremont, N.M. Scott, E.D. Stevens, S.P. Nolan, Organometallics 24 (2005)
2411e2418.
[13] H.M.J. Wang, I.J.B. Lin, Organometallics 17 (1998) 972e975.
[14] G.R. Desiraju, T. Steiner, The Weak Hydrogen Bond in Structural Chemistry
and Biology, Oxford University Press, New York, 1999.
[15] A. Revesz, P. Milko, J. Zabka, D. Schroder, J. Roithova, J. Mass Spectrom. 45
(2010) 1246.
[16] E.L. Zins, C. Pepe, D. Schroder, J. Mass Spectrom. 45 (2010) 1253.
[17] C.A. Citadelle, E.L. Nouy, F. Bisaro, A.M.Z. Slawin, C.S.J. Cazin, Dalton Trans. 39
(2010) 4489e4491.
[1] F.E. Hahn, M.C. Jahnke, Angew. Chem. Int. Ed. 47 (2008) 3122e3172.
[2] (a) S. Diez-Gonzalez, S.P. Nolan, Coord. Chem. Rev. 241 (2007) 874e883;
(b) J.T. Price, N.D. Jones, P.J. Rogogna, Inorg. Chem. 51 (2012) 6776e6783;
(c) J. Gil-Rubio, V. Camara, D. Bautista, J. Vicente, 31, 2012, 5414e5426.
[3] (a) S.P. Nolan, Acc. Chem. Res. 44 (2011) 91e100;
(b) M.R. Fructos, T.R. Belderrain, P. De Fremont, N.M. Scott, S.P. Nolan,
M.M. Diaz-Requejo, P.J. Perez, Angew. Chem. Int. Ed. 44 (2005) 5284e5288;
(c) M. Jiang, L.-P. Liu, M. Shi, Y. Li, Org. Lett. 12 (2010) 116e119.
[4] (a) W.A. Herrmann, Angew. Chem. Int. Ed. 41 (2002) 1290e1309;
(b) R.S. Ramon, S. Gaillard, A. Poater, L. Cavallo, A.M.Z. Slawin, S.P. Nolan,
Chem. Eur. J. 17 (2011) 1238e1246.
[5] (a) P. Lu, T.C. Boorman, A.M.Z. Slawin, I. Larrosa, J. Am. Chem. Soc. 132 (2010)
5580e5581;
(b) S. Gaillard, A.M.Z. Slawin, S.P. Nolan, Chem. Commun. 46 (2010) 2742e2744;
(c) I.I.F. Boogaerts, S.P. Nolan, J. Am. Chem. Soc. 132 (2010) 8858e8859;
(d) I.I.F. Boogaerts, G.C. Fortman, M.R.L. Furst, C.S.J. Cazin, S.P. Nolan, Angew.
Chem. Int. Ed. 49 (2010) 8674e8877;
(e) I.I.F. Boogaerts, S.P. Nolan, Chem. Commun. 47 (2011) 3021e3024;
(f) L. Zhang, J. Cheng, T. Ohishi, Z. Hou, Angew. Chem. Int. Ed. 49 (2010) 8670e
8673;
(g) L. Ackermann, Angew. Chem. Int. Ed. 50 (2011) 3842e3844;
(h) D. Yu, Y. Zhang, Proc. Natl. Acad. Sci. U. S. A 107 (2010) 20184e20189;
(i) D. Yu, Y. Zhang, Green Chem. 13 (2011) 1275e1279.
[18] A. Tintaru, J. Roithova, D. Schroder, L. Charles, I. Jusinski, Z. Glasovac,
M. Eckert- Maksici, J. Phys. Chem. 112 (2008) 12097e12103.
[19] P. Kumar, J. Roithova, Eur. J. Mass. Spectrom. 18 (2012) 457e463.
[20] Bruker, SAINT, Bruker AXS Inc, Madison, Wisconsin, USA, 2001.
[21] G.M. Sheldrick, Acta Crystallogr. A 64 (2008) 112e122.
[6] (a) R. Casado, M. Contel, M. Laguna, P. Romero, S. Sanz, J. Am. Chem. Soc. 125
(2003) 11925e11935;
(b) M. Bouhrara, E. Jeanneau, L. Veyre, C. Coperet, C. Thieuleux, Dalton Trans.