N-heterocyclic carbene coinage metal complexes as intense blue-green emitters

Article abstract of DOI:10.1021/om300571m

The reaction of N-methyl (Me) or N-benzyl (Bn) imidazole with 9-chloroacridine (9-ClAcr) gives the corresponding imidazolium salts, [(RimAcr)H]Cl (R = Me, Bn), which can further react with AgBF₄ or [Au(C₆F₅)(tht)], affordi

Full text of DOI:10.1021/om300571m

Article
pubs.acs.org/Organometallics
N‑Heterocyclic Carbene Coinage Metal Complexes as Intense Blue-
Green Emitters
M. Concepcion Gimeno,* Antonio Laguna, and Renso Visbal
́
́ ́ ́
Departamento de Química Inorganica, Instituto de Síntesis Química y Catalisis Homogenea (ISQCH), CSIC−Universidad de
Zaragoza, E-50009 Zaragoza, Spain
S
* Supporting Information
ABSTRACT: The reaction of N-methyl (Me) or N-benzyl (Bn) imidazole with 9-
chloroacridine (9-ClAcr) gives the corresponding imidazolium salts, [(RimAcr)H]Cl (R
= Me, Bn), which can further react with AgBF4 or [Au(C6F5)(tht)], affording the new
salts [(RimAcr)H]BF4 or [(RimAcr)H][Au(C6F5)Cl]. Silver(I) carbene complexes of
the form [AgCl(RimAcr)] or [Ag(RimAcr)2]BF4 are synthesized by reaction of the
corresponding imidazolium salts with Ag2O or Ag2O and NaOH. Transmetalation
reactions allow the synthesis of the gold and copper derivatives [MCl(RimAcr)] (M =
Au, Cu) and [Au(RimAcr)2]BF4. Treatment of [(RimAcr)H][Au(C6F5)Cl] with NaH
affords the synthesis of the carbene complexes [Au(C6F5)(RimAcr)]. The crystal
structures of these complexes show interesting π···π stacking interactions between the
acridine and/or the pentafluorophenyl groups. The imidazolium salts and the gold and
silver complexes are intense blue-green emitters.
interesting optical properties, allowing the possibility of
application as luminescent chemosensors or optoelectronic
on/off switches.10 Liquid crystalline silver(I) or gold(I) NCH
complexes have been described by the use of imidazolium salts
with long alkyl side chains.11 Some gold(I) and silver(I)
compounds show in vitro antimicrobial activity against a variety
of Gram-positive and Gram-negative bacteria and fungal
species.12 Furthermore, several gold(I) NHC complexes have
shown good antitumor properties, especially lipophilic cationic
compounds that selectively target the mitochondria of
carcinoma cells.13
In our group we are focused on the synthesis of new
imidazolium salts with different substituents that can provide
metal complexes with interesting properties. We believe that
acridine is an excellent candidate for this purpose. Bierbach et
al. have demonstrated that some gold(I) complexes with this
ligand show a selective antimicrobial activity against Mycobacte-
rium tuberculosis, although show less anticancer activity than the
analogous platinum compound in non-small-cell lung cancer
cells.14 In addition, the optical properties of a few derivatives
with this ligand have been studied.15 The investigations confirm
that these properties arise from the acridine, due to n−π* and
π−π* transfers, metal-to-ligand charge transfer (MLCT), and
face-to-face π···π stacking interactions.
INTRODUCTION
■
N-Heterocyclic carbenes (NHCs) have become a well-
established type of compound in coordination metal chemistry
since Arduengo and co-workers first isolated a free imizadole-2-
ylidene.1 NHCs have powerful σ-donating properties, better
than the ubiquitous phosphine ligands, and this can lead to
stable M-NHCs with strong metal−carbon bonds. The electron
richness of NHCs can be of significance in many reactions, and
indeed metal NHC complexes are more effective in many
catalytic reactions than the corresponding phosphine deriva-
tives.2 Several methods for the synthesis of these NHC metal
complexes have been described, the most used being the direct
reaction of the metal complex with the free carbene, usually
obtained by deprotonation of the imidazolium salt, or the
transmetalation reaction with silver(I) NHC complexes, which
is the favorite for the coinage metal NHC complexes.
Coinage metal N-heterocyclic carbene complexes are of
interest for their intriguing structural properties and numerous
applications in catalysis, medicine, and materials chemistry.3
Silver(I) NHC complexes are the most widely studied because
of their facile preparation via the Ag2O route and their
usefulness as transmetalating agents.4 The importance of the
use of NHC complexes of the three metals in catalysis is
reflected in the large number of reports and reviews dealing
with this topic. The gold derivatives are used primarily in
cycloisomerization, addition of water to alkynes and nitriles,
and C−H activation,5 silver derivatives in alkene diboration and
ring-opening polymerization,6 and copper species in reduction
and cycloaddition reactions.7 Several reports have been
published on functional materials containing gold(I) NHC
moieties. In many cases, the presence of the adapted
substituent8 or the metal−metal interactions9 result in very
Here we report on the synthesis of new imidazolium salts
containing the acridine group and the corresponding group 11
metal complexes. Coinage metal complexes with stoichiometry
[MCl(NHC)], [M(NHC)2]+, or [Au(C6F5)(NHC)], obtained
through a novel method starting from the imizadolium gold
Received: July 18, 2012
Published: October 2, 2012
© 2012 American Chemical Society
7146
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
salts, have been described. The optical properties presented by
the imidazolium salts and some of the metal complexes have
been studied.
RESULTS AND DISCUSSION
■
Synthesis and Characterization of the Imidazolium
Salts. The reaction of N-methyl (Me) or N-benzyl (Bn)
imidazole with 9-chloroacridine in toluene under reflux rapidly
gives the corresponding salt 1 or 2 in good yield (Scheme 1). In
Scheme 1. Synthesis of the Imidazolium Salts
Figure 1. ORTEP diagram of 5 with 50% probability ellipsoids. Most
hydrogen atoms are omitted for clarity. Selected bond lengths (Å) and
angles (deg): Au(1)−C(18) 1.997(10), Au(1)−Cl(1) 2.321(3),
N(1)−C(1) 1.313(11), N(1)−C(2) 1.386(11), N(1)−C(4)
1.462(10), N(2)−C(1) 1.353(11), N(2)−C(3) 1.394(11), N(2)−
C(5) 1.433(10), C(2)−C(3) 1.331(12), C(18)−Au(1)−Cl(1)
178.1(2), C(1)−N(1)−C(2) 109.6(7).
present in this complex, probably because of the presence of a
bulky countercation. In none of the crystal structures reported
with the [Au(C6F5)Cl]− fragment are these aurophilic
interactions present.16
In addition, in the packing of 5 we found the association of
molecules through π−π interactions (Figure 2). The shortest is
between the two acridines related by symmetry, with a
centroid−centroid separation between the two parallel acridine
rings of 3.585 Å with an average interplanar separation of 3.417
Å. The displacement angle of 16.61° suggests the existence of
significant intramolecular offset π···π stacking interactions.
Furthermore there are π−π interactions between the acridine
and the pentafluorophenyl ring and also between two
pentafluorophenyl moieties. Consequently a bidimensional
chain is constructed by means of these π−π interactions, with
a distribution of the molecules by charge ++−−++−−, which is
an example of π−π interactions versus Coulombic repulsions.
Synthesis and Characterization of the Complexes. The
reaction of 1 or 2 with Ag2O in dichloromethane gives the new
silver(I) complexes [AgCl(RimAcr)] (R = Me (7), Bn (8))
1
the H NMR spectrum of 1 resonances for the imidazole, the
acridine, and the methyl protons are observed. The presence of
a singlet at 9.95 ppm corresponding to the NCHN imidazolium
proton confirms the formation of 1. Analogous signals are
observed for 2 corresponding to the acridine and imidazole
rings. Additionally, a multiplet centered at 7.64 ppm and a
singlet at 5.73 ppm corresponding to the phenyl and methyl
groups, respectively, appear. The results obtained from the
elemental analysis and mass spectra are consistent with the
proposed salts. Metathesis reactions of these salts with AgBF4
in dichloromethane afford 3 or 4 in good yield. In the 1H NMR
spectra no significant changes were observed in relation to 1 or
2, but a singlet at −153.03 ppm in the 19F NMR spectrum
−
1
confirms the presence of the BF4 counteranion. Finally, we
(see Scheme 2). Upon silver complex formation, the H NMR
have prepared the first imidazolium salt that contains the
fragment [AuCl(C6F5)]− as a counteranion. Addition of
[Au(C6F5)(tht)] to a solution of 1 or 2 in a mixture of
dichloromethane/methanol gives the new derivative 5 or 6.
signals for C2−H imidazolium protons disappear, confirming
the presence of the new carbene species. In the mass spectra,
peaks at m/z 366.0 and 442.0 corresponding to [M − Cl]+
provide further evidence for the formation of these new
derivatives. The corresponding gold complexes [AuCl-
(RimAcr)] (R = Me (9), Bn (10)) are obtained, as pale
yellow solids, through carbene transfer reactions from 7 or 8
with [AuCl(tht)] in dichloromethane. In the mass spectra the
molecular peaks, [M]+, appear at m/z = 492.1 and 568,
respectively. The same transmetalation route is employed to
obtain the corresponding copper complexes, using CuCl as a
copper source. The addition of CuCl to a solution of 7 or 8 in a
dichloromethane/methanol (5:1) mixture leads to the precip-
itation of AgCl and the subsequent formation of the
corresponding copper(I) complexes [CuCl(RimAcr)] (R =
Me (11), Bn (12)) as orange-red solids, confirmed by the
presence of peaks at 357.9 and 434.0 m/z ratio, corresponding
to [M]+ in the mass spectra.
1
Again no significant changes were observed for the H and
13C{1H} NMR spectra, but the appearance of two multiplets at
−117.30 and −166.87 and a triplet of triplets at −166.19 ppm
3
4
in the 19F NMR spectrum with JF−F = 19.76 and JF−F = 2.34
and a peak in the mass spectrum with an m/z ratio of 398.7
confirm the presence of the [AuCl(C6F5)]− counteranion.
The gold-imidazolium salt 5 has been characterized by X-ray
diffraction and crystallized as a dichloromethane adduct,
5·CH2Cl2. The solid-state molecular structure is depicted in
Figure 1 together with a selection of bond lengths and angles.
The coordination around the gold center is linear, with a C1−
Au1−C18 angle of 178.1(2)° and bond distances Au−C1 of
2.321(3) Å and Au−C18 of 1.997(10) Å. Although aurophilic
interactions are likely in gold(I) complexes, there are none
7147
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
Figure 2. Offset π···π stacking interactions of 5. Acr−Acr contact: centroid−centroid distance (3.585 Å), interplanar distance (3.417 Å), torsion
angle (0.00°), and angle displacement (16.61°); Acr−C6F5 contact: centroid−centroid distance (3.728 Å), interplanar distance (3.643 Å), torsion
angle (13.62°), and angle displacement (12.26°); C6F5−C6F5 contact: centroid−centroid distance (3.649 Å), interplanar distance (3.478 Å), torsion
angle (0.00°), and angle displacement (17.61°).
Scheme 2. Synthesis of New Complexes
Silver(I) bis(carbenes) [Ag(RimAcr)2]BF4 (R = Me (13), Bn
(14)) (Scheme 2) were synthesized from imidazolium salts
with noncoordinating counteranions (3, 4). The reaction with
Ag2O does not produce the desired bis(carbene) derivatives,
and consequently an additional base, NaOH, was added in a
similar manner to that reported by Catalano et al.9a In this case,
in the mass spectra, peaks at 625.1 and 777.2 m/z ratio
corresponding to [M − BF4]+ appear. Again, the treatment of
these silver(I) complexes with [AuCl(tht)] leads to the
corresponding bis(carbene)gold(I) complexes [Au(RimAcr)2]-
BF4 (R = Me (15), Bn (16)). All of the gold(I) and silver(I)
derivatives mentioned until now are yellow and show a high
polar solubility in solvents such as methanol and DMSO. We
did not obtain the expected results on attempting to prepare
the copper(I) bis(carbene) due to decomposition to unknown
copper(II) derivatives, which are easily detectable by the
appearance of a blue color in the reaction mixture.
Finally, we have designed an easy method for the preparation
of gold(I) complexes with two different organometallic ligands
of the scarcely represented type NHC−Au−C6F5. The
treatment of gold-imidazolium salt 5 or 6 with NaH in dried
THF rapidly gives the corresponding free carbene, which is able
to displace the chlorine atom and coordinate to the gold center,
giving the complexes [Au(C6F5)(RimAcr)] (R = Me (17), Bn
7148
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
(18)). The formation of the carbene species is confirmed by
the disappearance of the resonance for the C2−H imidazolium
proton and by the presence of the molecular peaks in the mass
spectra at m/z = 624.1 and 700.1, respectively.
accordance with previous work reported by Hashmi in which
the deshielding of the carbene carbons is due to the poor π-
donor ability of the pentafluorophenyl ring.18 Some studies of
the relation of the carbene chemical shift and the basicity of the
ligands coordinated trans to it have been carried out. For the
gold complexes we have chemical shifts of 171.4, 184.2, and
191.7 for the chlorine, carbene, and pentafluorophenyl ligands,
which is in agreement with the increasing basicity of the
ligands.19
X-ray Structure Analysis. The molecular structures of
complexes [MCl(MeimAcr)] (M = Ag (7), Au (9), Cu (11))
have been established by X-ray diffraction. In the structures of
the silver and copper species, 7 and 11, two molecules are
associated around an inversion center, giving dimeric structures
with lateral metal−chlorido interactions (Figure 3). While the
length of direct silver−chlorido bond is 2.3818(11) Å, the
length of the additional interaction is substantially longer at
2.9113(10) Å. For the copper derivative the direct Cu−Cl bond
is 2.2060(9) Å, with an interaction of 2.58322(7) Å. This is
reflected in the Ccarbene−M−Cl angles, where a proportional
decrease from linearity around 15° for Ag(I) and 25° for Cu(I)
is observed (Table 2). The interplanar angle between the
acridine and the carbene rings for 7 is almost perpendicular,
82.66°, while for 11 the angle is 77.59°.
13C{1H} NMR spectroscopy is a useful tool for the study of
NHCs. All the chemical shifts of the C2−H corresponding to
the imidazolium salts were found around 135 ppm. The
formation of the Ag(I) complexes [AgCl(NHC)] and [Ag-
(NHC)2Ag]BF4 causes a downfield shift in the carbene carbon
signals between 38 and 48 ppm (Table 1). The chemical shifts
Table 1. Chemical Shifts (ppm) of the Carbenic Carbon of
the Imidazolium Salts (δSalt) and Complexes (δC)
δC(Salt) (ppm) of 1− δC(Salt) (ppm) of 2−
5, δC (ppm) of 7− 6, δC (ppm) of 8−
compound
17, R = Me
18, R = Bn
a
[(RimAcr)H]Cl
(1) 135.5
(2) 135.7
b
a
[(RimAcr)H]BF4
(3) 135.1
(4) 134.0
b
[(RimAcr)H][AuCl(C6F5)]
(5) 135.1
(7) 174.0
(9) 171.4
(11) 182.0
(13) 182.2
(15) 184.2
(6) 135.1
(8) 179.1
(10) 171.7
(12) 180.8
(14) 181.7
(16) 184.1
(18) 191.7
a
[AgCl(RimAcr)]
a
[AuCl(RimAcr)]
c
[CuCl(RimAcr)]
a
[Ag(RimAcr)2]BF4
a
[Au(RimAcr)2]BF4
b
[Au(C6F5)(RimAcr)]
(17) 191.7
The structure of the gold compound is mononuclear with a
linear geometry, C−Au−Cl angle of 177.7(2)°, and shows a
very weak aurophilic interaction of 3.622 Å, which, despite
being at the limit of the sum of the van der Waals radii for gold,
3.6 Å, could influence the packing of the molecule in the solid
state. The M−C bond lengths are 2.091(3) for silver, 1.969(8)
for gold, and 1.901(2) Å for copper, which are similar to those
found in the same type of carbene complexes.7d,20 The largest
corresponds to the silver complex, in accordance with the fact
that the covalent radius for gold is smaller than that of silver.
The interplanar angle between the acridine and the carbene
rings for 9 is 72.14°.
All of the complexes NHC−M−Cl (7, 9, and 11) in the solid
state show π···π stacking interactions between the acridine rings
of different molecules. For the complexes of NHC−M--X type
(7, 9, and 11) the interplanar and centroid−centroid distances
found were from 3.319 to 3.616 and 3.607−3.887 Å,
respectively, causing a parallel displacement from 14.22° to
a
b
c
NMR in DMSO-d6. NMR in Acetone-d6. NMR in CD2Cl2.
observed for the [MCl(NHC)] complexes range from 171 to
182 ppm, and an upfield displacement is observed in the order
[CuCl(NHC)] > [AgCl(NHC)] > [AuCl(NHC)]. For the
bis(carbene) complexes no comparison with the copper
derivative can be made, but the chemical shifts of the silver
and gold species are similar at 182.2 and 184.2 ppm,
respectively, and downfield related to the [MCl(NHC)]
complexes. These chemical shifts are comparable to other
group 11 NHC complexes reported.7d,9,17,18 It is noteworthy
commenting that in the bis(carbene) silver species [Ag-
(PhCH2imAcr)2]BF4 the resonance for the carbene carbon
appears as two doublets as a consequence of the coupling with
the two silver nuclei, with coupling constants of JC‑107Ag
184.4 and JC‑109Ag = 212.6 Hz. The chemical shift of
[Au(C6F5)(NHC)] is the highest, 191.7 ppm. This is in
1
=
1
Figure 3. ORTEP diagram of 7 (a) and 11 (b) with 50% probability ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond lengths and
angles are depicted in Tables 2 and 3, respectively.
7149
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
Table 2. Selected Bond Lengths (Å), Angles (deg), and Torsion Angles (deg) for Complexes 7, 9, 11, 13, 15, and 17
d
compound
M−Ccarbene
M−X
Ccarbene−M−X
torsion angle
torsion angle
a
a
7
2.091(3)
1.969(8)
1.901(2)
2.096(4)
2.019(4)
2.3818(11)
162.63(9)
82.66
72.14
77.59
67.80
69.96
a
a
9
2.286(2)
177.7(2)
a
a
11
13
15
2.2060(9)
153.77(7)
c
c
e
e
f
2.095(5)
173.62(16)
83.53
0.00
c
c
2.019(4)
180.000(1)
b
b
17
2.014(8)
2.041(9)
177.1(3)
67.36
15.96
a
b
c
d
e
X = Cl. X = Cpentafluorophenyl. X = Ccarbene. Torsion angle between the acridine and the carbene rings. Torsion angle between the carbene rings.
f
Torsion angle between the pentafluorophenyl and the carbene rings.
31.36°. Curiously, only for the silver(I) complex is there a
pyridine−pyridine ring contact, while for the gold(I) and
copper(I) complexes there are pyridine−arene ring contacts
(Table 3).
Ccarbene−M bond distance compared with the [MCl(NHC)]
complexes, as has been observed previously in other
bis(carbene) derivatives.9 In the solid state, complex 13
shows a Ccarbene−Ag(I)−Ccarbene bond angle of 173.62(16)°,
corresponding to an almost linear environment around the
silver(I) center, but with the carbene rings almost in a
perpendicular disposition, with a torsion angle of 83.53°. For
complex 15 the Ccarbene−Au(I)−Ccarbene bond angle is the ideal
180° because the gold atom lies in a symmetry center. In both
cases, there is a decrease of the interplanar angle between the
acridine and the carbene rings, but more accentuated in the
silver(I) complex than in the gold(I) derivative, with values of
14.86° and 2.18° for 13 and 15, respectively, compared to the
values found in the NHC−M−Cl complexes (Table 2). Both
complexes show π···π stacking interactions in the solid state.
The interplanar distance and the centroid−centroid distance
are 3.342 and 3.607 Å for 13 and 3.323 and 3.632 Å for 15,
causing displacement angles of 22.10° and 23.80°, respectively.
Once again, the aromatic contact is pyridine−pyridine for the
Ag(I) complex, while for the Au(I) complex the aromatic
contact is pyridine−phenyl (Table 3).
Table 3. Interplanar Distance (Å), Centroid−Centroid
Distance (Å), Displacement Angle (deg), and Aromatic
Contact for Complexes 7, 9, 11, 13, 15, and 17
interplanar
distance
centroid−centroid displacement
aromatic
contact
compound
distance
angle
5
3.417
3.616
3.319
3.542
3.342
3.323
3.509
3.585
3.796
3.887
3.739
3.607
3.632
3.620
16.61
17.71
31.36
21.11
22.10
23.80
14.22
py−py
py−py
py−ph
py−ph
py−py
py−ph
py−ph
7
9
11
13
15
17
Figure 4b shows the crystal packing for compound 9 with the
aurophillic and the π···π stacking interactions.
The solid-state structures of the complexes 13 and 15 (as
perchlorate salts) have been established by X-ray diffraction
analysis and are depicted in Figure 5. Several attempts to
crystallize complex 15, [Au(RimAcr)2]BF4, led to crystals with
a pronounced pseudosymmetry; for this reason the complex
with a different counteranion, perchlorate, was prepared and
the X-ray structure determined. There is an increase of the
The solid-state molecular structure of 17 (Figure 6a) reveals
a displacement of 15.96° in the torsion angle between the
acridine and carbene rings. The Ccarbene−M and M−
Cpentafluorophenyl distances of 2.014(8) and 2.041(9) Å,
respectively, are consistent with the other example with a
pentafluorophenyl ligand.18 The Au−Ccarbene distance is higher
Figure 4. (a) ORTEP diagram of 9 with 50% probability ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond lengths and angles are
depicted in Tables 2 and 3, respectively. (b) Crystal packing of 9. View along the crystallographic b axis.
7150
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
Figure 5. ORTEP diagram of 13 (a) and 15 (b) with 50% probability ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond lengths and
angles are depicted in Tables 2 and 3, respectively.
Figure 6. (a) ORTEP diagram of 17 with 50% probability ellipsoids. Hydrogen atoms are omitted for clarity. Selected bond lengths and angles are
depicted in Tables 2 and 3, respectively. (b) Offset π···π stacking interactions of 17.
than in the corresponding chlorido derivatives, showing the
higher trans influence of the pentafluorophenyl ring. Figure 6b
shows a bidimensional chain of complex 17 where the
molecules are disposed in such a way that the acridine and
the pentafluorophenyl rings are found almost in a parallel
disposition between themselves. The interplanar distance
between the acridine rings is 3.509 Å, and the centroid−
centroid distance between the aromatic rings is 3.620 Å with a
parallel displacement of 14.22° (Table 3); for the C6F5−C6F5
contact the centroid−centroid distance is 3.567 Å, the
interplanar distance 3.334 Å, and the angle of displacement
20.82°. All these data confirm the presence of π···π stacking
interactions.
Optical Properties. The diffuse reflectance spectrum of the
9-chloroacridine in the solid state has been measured for
comparison purposes and shows absorptions at 240, 270, and
360 nm. The imidazolium salts show strong absorption bands
between 250 and 400 nm. The metal carbene complexes display
a similar broad band that goes from 250 to 400 nm. These
bands can be attributed to the acridine chromophore π→π* or
n→π* transitions, which are in agreement with the reported
data for acridine-based derivatives.21
The emission spectrum of the 9-chloroacridine shows two
moderate bands at 280 and 390 nm, which is different from the
emission spectra of the imidazolium salts 1−6, which are
emissive at room temperature and at low temperature, showing
a strong green fluorescence around 530−540 nm (see Table 4),
with a not very intense shoulder around 390 nm. The
substitution of the chloro by an imidazol moiety changes the
emission properties of the compound, and this is similar to
other 9-substituted acridine systems such as 9-aminoacridine.22
These moderately intense emissions can be assigned to
intraligand π→π* and n→π* transitions. The presence of a
gold atom as a counteranion in the gold-imidazolium salts 5
and 6 does not change the emission behavior of the initial salt.
There is no difference between the energy of the emissions for
the Me and the Bn derivatives at room temperature for chloride
as counteranion, although a small blue shift is observed for the
−
Bn derivatives with BF4 or [Au(C6F5)Cl]− as counteranions.
At low temperature this difference is present for all the
imidazolium salts.
7151
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
show only the band at 390 nm. These emissions are clearly
intraligand transitions, and the increase in the energy of the
emissions can be attributed to the destabilization of the π*
orbital of the acridine moiety. As the carbenes are good σ-
electron donors, a withdrawing of electron density from the
acridine would take place when the free carbene coordinates to
a metal center, producing a larger energy gap between the
orbitals involved in the transitions. The emission spectra of the
imidazolium salts 1 and 2 and their metal complexes are shown
in Figure 7. The presence of the methyl or benzyl subtituent in
the imidazolium moiety produces a more pronounced blue shift
in the emissions, exemplified by the gold compounds 9 and 10,
[AuCl(RimAcr)], which changes from 530 to 470 nm on going
from Me to Bn (see Figure 8). Again this change can be
Table 4. Emission Maxima (nm) for the Compounds in the
Solid State upon Excitation (values given in parentheses)
compound
9-chloroacridine
λmax (298 K)
390(250)
λmax (77 K)
380(250)
[(CH3imAcr)H]Cl (1)
390(245),
530(370)
390(245),
545(370)
[(PhCH2imAcr)H]Cl (2)
390(245),
530(370)
390(245),
560(370)
[(CH3imAcr)H]BF4 (3)
540(370)
530(370)
540(370)
555(370)
550(370)
[(PhCH2imAcr)H] BF4 (4)
[(CH3imAcr)H][AuCl(C6F5)] (5) 360(245),
530(370)
[(PhCH2imAcr)H][AuCl(C6F5)]
(6)
360(245),
540(360)
560(360)
[AgCl(CH3imAcr)] (7)
[AgCl(PhCH2imAcr)] (8)
[AuCl(CH3imAcr)] (9)
[AuCl(PhCH2imAcr)] (10)
390(245),
507(370)
390(245),
515(370)
390(245),
480(370)
390(245),
475(370)
390(245),
530(370)
390(245),
520(370)
390(245),
470(370)
390(245),
480(370)
[CuCl(CH3imAcr)] (11)
[CuCl(PhCH2imAcr)] (12)
[Ag(CH3imAcr)2]BF4 (13)
[Ag(PhCH2imAcr)2]BF4 (14)
[Au(CH3imAcr)2]BF4 (15)
390(245)
390(245)
470(370)
520(370)
390(245)
390(245)
475(370)
525(370)
390(245),
530(370)
390(245),
525(370)
[Au(PhCH2imAcr)2]BF4 (16)
390(245),
470(370)
390(245),
475(370)
[Au(C6F5)(CH3imAcr)] (17)
[Au(C6F5)(PhCH2imAcr)] (18)
500(370)
515(360)
510(370)
535(360)
Figure 8. Emission spectra for complexes 9 and 10 in the solid state at
room temperature.
The behavior of these imidazolium salts with the acridine
moiety resembles those of other imidazolium salts derived from
the 4,5-bis-bromomethylacridine, which acts as a fluorescent
chemosensor for pyrophosphate and dihydrogen phosphate,23
or the anthracene-substituted imidazolium salts, in which the
assignments of the emitting states are based on the π→π*
excited states of the anthracene ligand.8a
The metal complexes are luminescent in the solid state at
room temperature, showing similar emissions around 500 nm
with a small blue shift. A much less intense shoulder at 390 nm
is observed for some of the complexes. The copper derivatives
attributed to a stabilization of the π* orbital of the acridine
because the presence of a substituent with better electronic
properties, the methyl group, could require less electron density
from the acridine moiety. At 77 K all the complexes show the
same emissions, with the exception of 5 and 6, where only the
lower energy emission is observed with a slightly red shift. For
the rest of the complexes the first emission remains at the same
energy and the second emission is red-shifted.
Figure 7. (a) Normalized room-temperature emission spectra for compound 1 and complexes 7, 9, 13, 15, and 17 in the solid state upon excitation
at 370 nm. (b) Normalized room-temperature emission spectra for compound 2 and complexes 8, 10, 14, 16, and 18 in the solid state upon
excitation at 370 nm.
7152
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
Although the emission energies point to a fluorescent nature
of the emissions, the lifetimes of two representative compounds
have been measured. The imidazolium salt 1 and the gold
complex 17 show values of 34.8 and 35 ns, respectively, which
indicates, as expected, a fluorescent nature of the emissions.
Comparison with other N-heterocyclic gold complexes such
as [AuCl(NHC)], where NHC is the anthracene-substituted
carbene, shows this complex is not luminescent in the solid
state, but the corresponding complexes with acetylide ligands
are. The origin of the emissions has been proposed to be
localized at the 1π−π* excited states of the NHC ligand and not
the 3π−π* of the acetylide.8a Other NHC gold complexes such
as [AuCl(MeimMe)] present two different emissions in the
solid state, one attributed to an intraligand transition and the
other to a Au-centered transition, because aurophilic
interactions are present. The corresponding carbazole deriva-
tive [Au(cbz)(MeimMe)] presents low-energy emission bands
at 584−592 nm, which are likely to arise from the transitions
involving mainly carbazole tuned by Au.24
interactions present in these molecules in the solid state that
are not present in solution.
In Figure 10 it is possible to appreciate the different
luminescence in the solid state and in solution for the
Figure 10. (a) Samples of 1 (solid state and solution) and 17 (solid
state and solution) under normal light. (b) The same samples under
UV light.
imidazolium salt [(CH3imAcr)H]Cl (1) and for the gold
complex [Au(C6F5)(CH3imAcr)] (17).
The electronic absorption spectra in methanol solutions have
been measured for the imidazolium salt [(CH3imAcr)H]Cl (1),
the silver complex [AgCl(CH3imAcr)] (7), and the gold
derivative [AuCl(CH3imAcr)] (9). All the compounds present
similar absorption spectra to that of 9-chloroacridine or acridine
itself; the latter shows one absorption at 250 nm and another at
355 nm. The imidazolium salt 1 shows also the same two
absorptions at 250 (ε 78 000) and 365 (ε 9900) nm, for the
silver complex 7 at 245 (ε 83 000) and 360 (ε 9700) nm, and
for the gold derivative 9 at 260 (ε 100 000) and 365 (ε 9700),
which are also assigned at an intraligand absorption involving
the acridine group. The methanol solutions of 1, 7, and 9 are
luminous when irradiated with a UV lamp. The emission
spectra show an intense structured band with maxima around
410, 435, and 455 nm, independently when excited at 270 or
375 nm (see Figure 9). The imidazolium salt and the metal
CONCLUSIONS
■
New imidazolium salts containing the acridine chromophore
with different counteranions have been synthesized. The salt
[(CH3imAcr)H][AuCl(C6F5)] shows an interesting structural
framework with formation of a bidimensional chain through
π···π stacking interactions between cations and anions of the
form ++−−++, an example of such interactions versus
Coulombic respulsions. Silver(I) N-heterocyclic carbene
complexes have been obtained by reaction of the imidazolium
salts with Ag2O. [AgCl(NHC)] complexes have been prepared
from the imidazolium salts with a chloride counteranion, and
the bis(carbene) species, [M(NHC)2]+, from the imidazolium
salts with a noncoordinating counteranion. The corresponding
group 11 metal complexes have been synthesized by the
transfer of the carbene from the corresponding silver(I)
carbene complexes. The gold-imidazolium salts can lead
directly to the gold-carbene derivatives by reaction with a
base. The crystal structures of these complexes show π···π
stacking interactions between the acridine and pentafluor-
ophenyl rings of different molecules. The [AuCl(NHC)]
species show a supramolecular structure based on the
aurophilic and π···π stacking interactions.
The imidazolium salts and most of the complexes are intense
blue-green emitters in the solid state and blue emitters in
solution. The coordination of the metals produces a blue shift
of the emissions. The origin of the emissions can be assigned to
intraligand π−π* transitions. Further studies of the potential of
these complexes as catalysts, anticancer agents, or optical
materials are being undertaken.
EXPERIMENTAL SECTION
■
Figure 9. Excitation and emission spectra for complex 7 in methanol at
room temperature (c = 1.22 × 10−3 M).
Instrumentation. C, H, and N analysis were carried out with a
Perkin-Elmer 2400 microanalyzer. Mass spectra were recorded on a
Bruker Esquire 3000 PLUS, with the electrospray (ESI) technique, and
on a Bruker Microflex (MALDI-TOF). H, 13C{H}, and 19F NMR,
1
including 2D experiments, were recorded at room temperature on a
Bruker Avance 400 spectrometer (1H, 400 MHz; 13C, 100.6 MHz; 19F,
376.5 MHz) or on a Bruker Avance II 300 spectrometer (1H, 300
MHz; 13C, 75.5 MHz; 19F, 282.3 MHz), with chemical shifts (δ, ppm)
reported relative to the solvent peaks of the deuterated solvent.25 The
solution absorption spectra were recorded with a Unicam UV-4 in
methanol. The diffuse-reflectance UV spectra of solid samples were
recorded with a Unicam UV-4 spectrophotometer and using a
Spectralon RSA-UC-40 Labsphere integrating sphere. The solid
complexes display a similar behavior, and both correspond to
the emissions observed for acridine in solution; consequently
an intraligand origin for the emissions is proposed. There is a
big difference in the emissions of the compounds in solution
compared with the solid state; a great blue shift is observed and
the emissions are very similar among acridine, imidazolium
salts, and the metal complexes. This different behavior in the
luminescent properties can be due to the extended π−π
7153
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
samples were mixed with silica to form a homogeneous powder. The
mixtures were placed in a homemade cell equipped with a quartz
window. Steady-state photoluminescence spectra were recorded with a
Jobin-Yvon-Horiba fluorolog FL-3-11 spectrometer using band
pathways of 3 nm for both excitation and emission.
General Procedure for the Synthesis of 5 and 6. A mixture of
1 or 2 (0.2 mmol) and [Au(C6F5)(tht)] (0.0904 g, 0.2 mmol) in
dichloromethane (ca. 15 mL) was stirred at room temperature for 3 h,
at which point the formation of an off-white precipitate was observed.
Then the solution was filtered through Celite, the yellow filtrate was
reduced to minimum volume under vacuum, and the product was
precipitated with hexane to give 5 or 6 as a yellow solid.
Starting Materials. The starting materials [AuCl(tht)]26 and
[Au(C6F5)(tht)]27 were prepared according to published procedures.
All other reagents were commercially available. Solvents were used as
received without purification or drying, except for tetrahydrofuran
(THF), which was dried with a SPS solvent purification system.
General Procedure for the Synthesis of 1 and 2. 1-
Methylimidazole or 1-benzylimidazole (1.80 mmol) was added to a
suspension of 9-chloroacridine (0.3367 g, 1.58 mmol) in toluene (ca.
10 mL), and the solution was heated at 140 °C for 12 h with stirring. A
yellow precipitate started to form during the course of reaction. After
cooling, the solid was collected by filtration, washed with hexane (ca.
20 mL), and dried under vacuum to give the product 1 or 2 as a yellow
solid.
1
[(CH3imAcr)H][AuCl(C6F5)] (5). Yield: 0.1 g (66.85%). H NMR
(acetone-d6, 400 MHz, 294 K): δ 9.77 (s, 1H, im), 8.38−8.37 (m, 1H,
3
acr), 8.36−8.35 (m, 2H, acr, im), 8.31 (m, 1H, im), 8.02 (ddd, J =
8.76 Hz, 3J = 5.44 Hz, 4J = 2.50 Hz 2H, acr), 7.82−7.76 (m, 4H, acr),
4.43 (s, 3H, CH3). 13C{1H} NMR (acetone-d6, 100.6 MHz, 294 K): δ
151.0 (acr), 141.1 (acr), 135.1 (im),133.0 (acr), 131.8 (acr), 130.9
(acr), 127.3 (im), 127.3 (im), 123.8 (acr), 123.6 (acr), 38.8 (CH3). 19
F
NMR (acetone-d6, 376.5.3 MHz, 294 K): δ −117.30 (m, o-F),
3
4
−166.19 (tt, J = 19.76 Hz, J = 2.34 Hz, p-F), −166.87 (m, m-F).
ESI+-MS, m/z: 260.1 [M]+. ESI−-MS: 398.7 [M]−. Anal. Calcd (%) for
C23H14N3ClF5Au: C, 41.87; H, 2.14; N, 6.37. Found: C, 41.68; H,
2.43; N, 6.07.
1
[(CH3imAcr)H]Cl (1). Yield: 0.4540 g (97.6%). H NMR (DMSO-
3
1
d6, 400 MHz, 294 K): δ 9.95 (s, 1H, im), 8.37 (d, J = 8.74 Hz, 2H,
[(PhCH2imAcr)H][AuCl(C6F5)] (6). Yield: 0.1080 g (73.4%). H
acr), 8.32 (m, 2H, im), 8.03 (ddd, 3J = 8.71 Hz, 3J = 6.43 Hz, 4J = 1.47
Hz, 2H, acr), 7.82−7.74 (m, 4H, acr), 4.13 (s, 3H, CH3). 13C{1H}
NMR (DMSO-d6, 100.6 MHz, 294 K): δ 148.5 (acr), 139.3 (acr),
135.5 (im), 131.4 (acr), 129.3 (acr), 128.8 (acr), 124.9 (im), 124.9
(im), 122.2 (acr), 121.6 (acr), 36.6 (CH3). MALDI+-MS, m/z: 260.1
[M]+. Anal. Calcd (%) for C17H14N3Cl: C, 69.03; H, 4.77; N, 14.21.
Found: C, 69.42; H, 4.38; N, 13.93.
NMR (acetone-d6, 400 MHz, 294 K): δ 9.88 (s, 1H, im), 8.40−8.39
3
(m, 1H, im) 8.39−8.38 (m, 1H, im), 8.35 (d, J = 8.83 Hz, 2H, acr),
3
3
4
8.01 (ddd, J = 8.80 Hz, J = 6.18 Hz, J = 1.76 Hz, 2H, acr), 7.80−
7.73 (m, 4H, acr, 2H, Ph), 7.56−7.50 (m, 3H, Ph), 5.97 (s, 2H, CH2).
13C{1H} NMR (acetone-d6, 100.6 MHz, 294 K): δ 151.0 (acr), 140.6
(acr), 135.4 (Ph), 135.1 (im) 133.0 (acr), 131.9 (acr), 131.3 (Ph),
131.3 (Ph), 131.0 (Ph), 131.0 (Acr), 127.9 (im), 126.2 (im), 123.7
(acr), 123.5 (acr), 55.9 (CH2). 19F NMR (acetone-d6, 376.5.3 MHz,
294 K): δ −117.27 (m, o-F), −166.13 (tt, 3J = 19.80 Hz, 4J = 2.35 Hz,
p-F), −166.82 (m, m-F). ESI+-MS, m/z: 336.1 [M]+. ESI−-MS: 398.7
[M]−. Anal. Calcd (%) for C29H18N3ClF5Au: C, 47.33; H, 2.47; N,
5.71. Found: C, 46.98; H, 2.65; N, 5.35.
[(PhCH2imAcr)H]Cl (2). Yield: 0.4906 g (83.5%). 1H NMR
3
(DMSO-d6, 400 MHz, 294 K): δ 10.15 (s, 1H, im), 8.40 (d, J =
1.54 Hz, 2H, acr), 8.39 (s, 1H, im), 8.37 (s, 1H, im), 8.03 (dddd, 3J =
8.70 Hz, 3J = 6.62 Hz, 4J = 1.29 Hz, 2H, acr), 7.81 (ddd, 3J = 8.74 Hz,
3J = 6.62 Hz, 4J = 1.08 Hz, 2H, acr), 7.68−7.64 (m, 2H, acr, 2H, Ph),
7.54−7.44 (m, 3H, Ph), 5.73 (s, 2H, CH2). 13C{1H} NMR (DMSO-
d6, 100.6 MHz, 294 K): δ 148.4 (acr), 139.0 (acr), 135.7 (im), 134.2
(Ph), 131.4 (acr), 129.4 (acr), 129.1 (Ph), 129.0 (acr), 128.9 (Ph),
128.7 (Ph), 125.6 (im), 123.9 (im), 121.9 (acr), 121.4 (acr), 52.8
(CH2). MALDI+-MS, m/z: 336.2 [M]+. Anal. Calcd (%) for
C23H18N3Cl: C, 74.29; H, 4.88; N, 11.30. Found: C, 74.03; H, 4.63;
N, 11.12.
General Procedure for the Synthesis of 7 and 8. Ag2O (0.038
g, 0.165 mmol) was added to a solution of 1 or 2 (0.33 mmol) in a
mixture (ca. 18 mL) of CH2Cl2/MeOH (5:1). The mixture was
protected from light and stirred for 4 h at room temperature. Then the
solution was filtered through Celite, the bright yellow filtrate was
reduced to minimum volume under vacuum, and the product was
precipitated with Et2O to give 3 or 8 as a yellow solid.
General Procedure for the Synthesis of 3 and 4. AgBF4 (0.127
g, 0.65 mmol) was added to a solution of 1 or 2 (0.65 mmol) in a
mixture (ca. 18 mL) of CH2Cl2/MeOH (5:1), and the solution was
heated at room temperature for 2 h with stirring. A white precipitate
started to form during the course of reaction. Then, the mixture was
filtered through Celite, the bright yellow filtrate was reduced to
minimum volume under vacuum, and the product was precipitated
with Et2O to give the product 3 or 4 as a yellow solid.
[AgCl(CH3imAcr)] (7). Yield: 0.1002 g (75.4%). 1H NMR
3
(DMSO-d6, 400 MHz, 294 K): δ 8.26 (d, J = 8.70 Hz, 2H, acr),
7.90−7.82 (m, 4H, acr, im), 7.53 (br, 2H, acr), 7.33 (br, 2H, acr), 3.60
(br, 3H, CH3). 13C{1H} NMR (DMSO-d6, 100.6 MHz, 294 K): δ
174.0 (imcarb), 148.4 (acr), 139.7 (acr), 130.8 (acr), 129.3 (acr), 127.8
(acr), 125.0 (im), 123.8 (im), 122.1 (acr), 121.8 (acr), 37.9 (CH3).
ESI+-MS, m/z: 366.0 [M − Cl]+, 260.1 [M − Ag − Cl]+. Anal. Calcd
(%) for C17H13N3ClAg: C, 50.71; H, 3.25; N, 10.44. Found: C, 50.94;
H, 2.91; N, 10.13.
1
[(CH3imAcr)H]BF4 (3). Yield: 0.185 g (82%). H NMR (acetone-
d6, 400 MHz, 294 K): δ 9.66 (s, 1H, im), 8.37 (dm, 3J = 8.83 Hz, 2H,
acr), 8.31 (“t”, 3J = 1.73 Hz, 1H, im), 8.27 (“t”, 3J = 1.81 Hz, 1H, im),
[AgCl(PhCH2imAcr)] (8). Yield: 0.1106 g (70.0%). 1H NMR
(DMSO-d6, 400 MHz, 294 K): δ 8.22 (br, 2H, acr), 7.86 (br, 2H, acr,
2H, im), 7.45 (br, 2H, acr), 7.31−7.21 (m, 2H, acr, 3H, Ph), 6.93 (br,
2H, Ph), 4.93 (br, 2H, CH2). 13C{1H} NMR (DMSO-d6, 100.6 MHz,
294 K): δ 179.1 (imcarb), 148.4 (acr), 139.5 (acr), 136.2 (Ph), 130.8
(acr), 129.3 (Ph), 128.7 (acr), 128.0 (Ph), 127.9 (Ph), 127.3 (acr),
125.6 (im), 122.9 (im), 121.8 (acr), 121.7 (acr), 54.1 (CH2). ESI+-MS,
m/z: 442.0 [M − Cl]+. Anal. Calcd (%) for C23H17N3ClAg: C, 57.70;
H, 3.58; N, 8.78. Found: C, 57.58; H, 3.35; N, 8.56.
3
3
4
8.01 (ddd, J = 8.81 Hz, J = 6.02 Hz, J = 1.92 Hz, 2H, acr), 7.83−
7.76 (m, 4H, acr), 4.38 (s, 3H, CH3). 13C{1H} NMR (acetone-d6, 75.5
MHz, 294 K): δ 151.0 (acr), 137.2 (acr), 135.1 (im), 133.1 (acr),
131.8 (acr), 130.9 (acr), 128.2 (im), 127.3 (im), 123.9 (acr), 123.7
(acr), 38.7 (CH3). 19F NMR (acetone-d6, 376.5 MHz, 294 K): δ
−153.03. MALDI+-MS, m/z: 260.1 [M]+. Anal. Calcd (%) for
C17H14N3BF4: C, 58.82; H, 4.07; N, 12.11. Found: C, 59.12; H,
3.84; N, 11.78.
General Procedure for the Synthesis of 9 and 10. A mixture of
7 or 8 (0.15 mmol) and [AuCl(tht)] (0.048 g, 0.15 mmol) in
dichloromethane (ca. 20 mL) was protected from light and stirred at
room temperature for 1.5 h, at which point the formation of an off-
white AgCl precipitate was observed. Then the solution was filtered
through Celite, the bright yellow filtrate was reduced to minimum
volume under vacuum, and the product was precipitated with hexane
to give 9 or 10 as a yellow solid.
[(PhCH2imAcr)H]BF4 (4). Yield: 0.2063 g (75.0%). 1H NMR
3
(DMSO-d6, 400 MHz, 294 K): δ 9.94 (s, 1H, im), 8.38 (d, J = 8.93
3
Hz, 2H, acr), 8.39 (s, 1H, im), 8.32 (s, 1H, im), 8.04 (ddd, J = 8.60
Hz, 3J = 6.62 Hz, 4J = 1.04 Hz, 2H, acr), 7.82 (ddd, 3J = 8.56 Hz, 3J =
6.65 Hz, 4J = 0.75 Hz, 2H, acr), 7.67 (d, 3J = 8.64 Hz, 2H, acr), 7.62−
7.61 (m, 2H, Ph), 7.54−7.47 (m, 2H, Ph), 5.68 (s, 2H, CH2). 13C{1H}
NMR (DMSO-d6, 100.6 MHz, 294 K): δ 148.5 (acr), 139.0 (acr),
135.4 (Ph), 134.0 (im), 131.4 (acr), 129.4 (acr), 129.1 (Ph), 129.0
(acr, Ph), 128.7 (Ph), 125.7 (im), 123.9 (im), 121.9 (acr), 121.5 (acr),
52.9 (CH2). 19F NMR (DMSO-d6, 376.5 MHz, 294 K): δ −148.24.
ESI+-MS, m/z: 336.1 [M]+. Anal. Calcd (%) for C23H18N3BF4: C,
65.27; H, 4.29; N, 9.93. Found: C, 65.52; H, 4.38; N, 10.13.
[AuCl(CH3imAcr)] (9). Yield: 0.065 g (88.3%). 1H NMR (DMSO-
d6, 400 MHz, 294 K): δ 8.35 (d, 3J = 8.72 Hz, 2H, acr), 8.00−7.97 (m,
3
2H, acr, 2H, im), 7.75 (m, 2H, acr), 7.56 (d, J = 8.63 Hz, 2H, acr),
4.02 (s, 3H, CH3). 13C{1H} NMR (DMSO-d6, 100.6 MHz, 294 K): δ
171.4 (imcarb), 148.7 (acr), 139.6 (acr), 131.2 (acr), 129.3 (acr), 128.2
7154
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
(acr), 124.5 (im), 123.9 (im), 122.6 (acr), 122.4 (acr), 38.0 (CH3).
ESI+-MS, m/z: 492.1 [M]+. Anal. Calcd (%) for C17H13N3ClAu: C,
41.52; H, 2.66; N, 8.55. Found: C, 41.75; H, 2.49; N, 8.29.
128.1 (Ph), 127.9 (Ph), 127.2 (acr), 125.7 (im), 122.9 (im), 121.7
(acr), 121.6 (acr), 54.0 (CH2). 19F NMR (DMSO-d6, 376.5 MHz, 294
K): δ −148.24. ESI+-MS, m/z: 777.2 [M]+. Anal. Calcd (%) for
C46H34N6BF4Ag: C, 63.84; H, 3.96; N, 9.71. Found: C, 63.56; H, 4.12;
N, 9.92.
[AuCl(PhCH2imAcr)] (10). Yield: 0.0728 g (85.5%). 1H NMR
(DMSO-d6, 400 MHz, 294 K): δ 8.36 (d, 3J = 8.75 Hz, 2H, acr), 8.11
(d, 3J = 1.90 Hz, 1H, im), 8.06 (d, 3J = 1.88 Hz, 1H, im), 7.99 (ddd, 3J
General Procedure for the Synthesis of 15 and 16. A mixture
of 13 or 14 (0.075 mmol) and [AuCl(tht)] (0.0241 g, 0.075 mmol) in
dichloromethane (ca. 15 mL) was stirred at room temperature for 30
min, at which point the formation of an off-white AgCl precipitate was
observed. Then the solution was filtered through Celite, the bright
yellow filtrate was reduced to minimum volume under vacuum, and
the product was precipitated with Et2O to give 15 or 16 as a yellow
solid.
3
4
= 8.51 Hz, J = 6.67 Hz, J = 0.97 Hz, 2H, acr), 7.79−7.76 (m, 2H,
acr), 7.55−7.49 (m, 2H, acr, 4H, Ph), 7.12−7.17 (m, 1H, Ph), 5.63 (s,
2H, CH2). 13C{1H} NMR (DMSO-d6, 100.6 MHz, 294 K): δ 171.7
(imcarb), 148.7 (acr), 139.5 (acr), 136.3 (Ph), 131.3 (acr), 129.4 (Ph),
128.9 (acr), 128.4 (Ph), 128.2 (Ph), 127.5 (acr), 125.3 (im), 123.0
(im), 122.3 (acr), 122.7 (acr), 54.0 (CH2). ESI+-MS, m/z: 568.0 [M]+.
Anal. Calcd (%) for C23H17N3ClAu: C, 48.65; H, 3.02; N, 7.40. Found:
C, 48.43; H, 3.17; N, 7.63.
[Au(CH3imAcr)2]BF4 (15). Yield: 0.0338 g (55.4%). 1H NMR
(DMSO-d6, 400 MHz, 294 K): δ 8.25 (d, 3J = 8.70 Hz, 2H, acr), 7.85
(d”t”, J = 7.60 Hz, 2H, acr), 7.81−7.79 (m, 2H, im), 7.48 (d”t”, J =
General Procedure for the Synthesis of 11 and 12. A mixture
of 7 or 8 (0.082 mmol) and CuCl (8.2 mg, 0.082 mmol) in
dichloromethane (ca. 15 mL) was protected from light and stirred at
room temperature for 3 h, at which point the formation of an off-white
AgCl precipitate was observed. Then the solution was filtered through
Celite, the orange filtrate was reduced to minimum volume under
vacuum, and the product was precipitated with Et2O to give 11 or 12
as an orange solid.
3
7.52 Hz, 2H, acr), 7.23 (d, J = 8.62 Hz, 2H, acr), 3.39 (s, 3H, CH3).
13C{1H} NMR (DMSO-d6, 100.6 MHz, 294 K): δ 184.2 (imcarb),
148.2 (acr), 138.5 (acr), 130.7 (acr), 129.3 (acr), 127.8 (acr), 124.9
(im), 124.2 (im), 122.0 (acr), 121.7 (acr), 36.8 (CH3). 19F NMR
(DMSO-d6, 282.3 MHz, 294 K): δ −148.23. ESI+-MS, m/z: 715.1
[M]+. Anal. Calcd (%) for C34H26N6BF4Au: C, 57.25; H, 3.67; N,
11.78. Found: C, 57.03; H, 3.42; N, 11.92.
[CuCl(CH3imAcr)] (11). Yield: 0.0245 g (83.2%). 1H NMR
3
1
(CD2Cl2-d23, 400 MHz, 294 K): δ 8.31 (d, J = 8.83 Hz, 2H, acr),
[Au(PhCH2imAcr)2]BF4 (16). Yield: 0.0619 g (86.5%). H NMR
3
4
(DMSO-d6, 400 MHz, 294 K): δ 8.35 (d, 3J = 8.79 Hz, 2H, acr), 8.10
(d, 3J = 1.52 Hz, 1H, im), 8.05 (d, 3J = 1.73 Hz, 1H, im), 8.00 (ddd, 3J
7.84 (ddd, J = 8.72 Hz, J = 6.22 Hz, J = 1.65 Hz, 2H, acr), 7.62−
3
3
7.56 (m, 4H, acr), 7.37 (d, J = 1.693 Hz, 1H, im), 7.28 (d, J = 1.68
Hz, 1H, im), 4.13 (s, 3H, CH3). 13C{1H} NMR (CD2Cl2-d6, 100.6
MHz, 294 K): δ 182.0 (imcarb), 149.7 (acr), 140.0 (acr), 131.1 (acr),
130.3 (acr), 128.3 (acr), 127.3 (im), 123.9 (im), 123.1 (acr), 122.7
(acr), 39.1 (CH3). ESI+-MS, m/z: 357.9 [M]+. Anal. Calcd (%) for
C17H13N3ClCu: C, 56.99; H, 3.66; N, 11.73. Found: C, 56.78; H, 3.83;
N, 11.51.
3
4
= 8.45 Hz, J = 6.57 Hz, J = 0.90 Hz, 2H, acr), 7.79−7.76 (m, 2H,
Acr), 7.55−7.48 (m, 2H, Acr, 4H, Ph), 7.31 (t, 3J = 7.43 Hz, 1H, Ph),
5.63 (s, 2H, CH2). 13C{1H} NMR (DMSO-d6, 100.6 MHz, 294 K): δ
184.1 (imcarb), 148.7 (acr), 140.8 (acr), 136.0 (Ph), 130.9 (acr), 129.4
(Ph), 129.0 (acr), 128.7 (Ph), 127.5 (Ph), 127.1 (acr), 122.3 (im),
121.7 (im), 117.8 (acr), 117.3 (acr), 62.9 (CH2). 19F NMR (DMSO-
d6, 376.5 MHz, 294 K): δ −148.24. ESI+-MS, m/z: 867.25 [M]+. Anal.
Calcd (%) for C46H34N6BF4Au: C, 57.88; H, 3.59; N, 8.80. Found: C,
57.65; H, 3.87; N, 8.51.
[CuCl(PhCH2imAcr)] (12). Yield: 0.0314 g (88.1%). 1H NMR
(CD2Cl2-d2, 300 MHz, 294 K): δ 8.35 (d, 3J = 8.80 Hz, 2H, acr), 7.88
(ddd, 3J = 8.66 Hz, 3J = 6.38 Hz, 4J = 1.458 Hz, 2H, acr), 7.81 (ddd, 3J
3
4
= 8.74 Hz, J = 6.62 Hz, J = 1.084 Hz, 2H, acr), 7.67−7.56 (m, 4H,
acr), 7.52−7.45 (m, 5H, Ph), 7.33 (d, 3J = 1.80 Hz, 1H, im), 7.29 (d, 3J
= 1.80 Hz, 1H, im), 5.62 (s, 2H, CH2). 13C{1H} NMR (CD2Cl2-d2,
75.5 MHz, 294 K): δ 180.8 (imcarb), 149.9 (acr), 141.8 (acr), 136.0
(Ph), 131.2 (acr), 130.6 (Acr), 129.7 (Ph), 129.3 (Ph), 128.5 (acr),
125.1 (im), 123.2 (Acr), 122.6 (acr), 121.8 (acr), 56.3 (CH2). ESI+-
MS, m/z: 434.04 [M]+. Anal. Calcd (%) for C23H18N3ClCu: C, 63.59;
H, 3.94; N, 9.67. Found: C, 63.42; H, 4.23; N, 9.43.
General Procedure for the Synthesis of 17 and 18. A mixture
of 5 or 6 (0.2 mmol) and an excess of HNa in dried THF (ca. 15 mL)
was stirred at room temperature for 1.5 h, at which point the color of
the solution changed from yellow to yellow-green. Then, the solution
was filtered through Celite, and the filtrate was evaporated under
vacuum. The product was redissolved with dichloromethane (ca. 3
mL) and finally precipitated with hexane to give 17 or 18 as a yellow
solid.
1
General Procedure for the Synthesis of 13 and 14. A mixture
of 3 or 4 (0.26 mmol), Ag2O (0.0151 g, 0.065 mmol), and Bu4NBF4
(10 mg) in dichloromethane (ca. 20 mL) was stirred at room
temperature for 1.5 h. The entire time the mixture was protected from
light, then NaOH (1 N, 3 mL) was added, and stirring was continued
for a further 15 min. Then the solution was filtered through Celite, the
yellow-orange filtrate was reduced to minimum volume under vacuum,
and the product was precipitated with Et2O to give 13 or 14 as a
yellow solid.
[Au(C6F5)(CH3imAcr)] (17). Yield: 0.1054 g (84.5%). H NMR
3
(acetone-d6, 400 MHz, 294 K): δ 8.31 (dm, J = 8.82 Hz, 2H, Acr),
7.96 (d, 3J = 1.81 Hz, 1H, im), 7.93 (ddd, 3J = 8.93 Hz, 3J = 4.79 Hz, 4J
= 1.54 Hz 2H, acr), 7.87 (d, 3J = 1.91 Hz, 1H, im), 7.71−7.70 (m, 4H,
acr), 4.23 (s, 3H, CH3). 13C{1H} NMR (acetone-d6, 100.6 MHz, 294
K): δ 191.7 (imcarb), 151.3 (acr), 141.8 (acr), 132.6 (acr), 131.7 (acr),
129.7 (acr), 126.4 (im), 125.5 (im), 124.9 (acr), 124.7 (acr), 39.5
(CH3). 19F NMR (acetone-d6, 376.5.3 MHz, 294 K): δ −118.11 (m, o-
3
4
F), −163.88 (tt, J = 19.55 Hz, J = 1.295 Hz, p-F), −166.34 (m, m-
C6F5). ESI+-MS, m/z: 624.1 [M]+. Anal. Calcd (%) for C23H13N3F5Au:
C, 44.32; H, 2.10; N, 6.74. Found: C, 44.11; H, 2.28; N, 6.51.
[Ag(CH3imAcr)2]BF4 (13). Yield: 0.07 g (75.7%). 1H NMR
3
(DMSO-d6, 400 MHz, 294 K): δ 8.25 (d, J = 8.63 Hz, 2H, acr),
1
7.87−7.83 (m, 1H, im, 2H, acr), 7.76 (s, 1H, im), 7.47 (br, 2H, acr),
7.26 (br, 2H, acr), 3.49 (br, 3H, CH3). 13C{1H} NMR (DMSO-d6,
100.6 MHz, 294 K): δ 182.2 (imcarb), 148.4 (acr), 139.6 (acr), 130.7
(acr), 129.4 (acr), 127.7 (acr), 125.0 (im), 123.8 (im), 122.0 (acr),
121.7 (acr), 37.9 (CH3). 19F NMR (DMSO-d6, 376.5 MHz, 294 K): δ
−148.23. ESI+-MS, m/z: 625.1 [M]+. Anal. Calcd (%) for
C34H26N6BF4Ag: C, 57.25; H, 3.67; N, 11.78. Found: C, 57.53; H,
3.41; N, 11.46.
[Au(C6F5)(PhCH2imAcr)] (18). Yield: 0.1108 g (79.2%). H NMR
(acetone-d6, 400 MHz, 294 K): δ 8.32 (d, 3J = 8.80 Hz, 2H, acr), 8.04
3
3
3
4
(d, J = 1.95 Hz, 1H, im), 7.94 (ddd, J = 8.77 Hz, J = 6.32 Hz, J =
3
1.63 Hz, 2H, acr), 7.92 (d, J = 1.85 Hz, 1H, im), 7.75−7.65 (m, 4H,
acr, 2H, Ph), 7.52−7.44 (m, 3H, Ph), 5.82 (s, 2H, CH2). 13C{1H}
NMR (DMSO-d6, 100.6 MHz, 294 K): δ 191.7 (imcarb), 151.3 (acr),
144.0 (Ph), 138.4 (acr), 132.6 (acr), 131.7 (acr), 130.9 (Ph), 130.4
(Ph), 130.1 (Ph), 129.8 (acr), 127.0 (im), 125.8 (im), 124.8 (acr),
124.5 (acr), 56.5 (CH2). 19F NMR (acetone-d6, 376.5.3 MHz, 294 K):
1
[Ag(PhCH2imAcr)2]BF4 (14). Yield: 0.0828 g (73.6%). H NMR
(DMSO-d6, 400 MHz, 294 K): δ 8.20 (d, 3J = 8.73 Hz, 2H, acr), 7.85−
δ −118.07 (m, o-F), −163.78 (tt, J = 19.55 Hz, J = 1.21 Hz, p-F),
−166.30 (m, m-F). ESI+-MS, m/z: 700.1 [M]+. Anal. Calcd (%) for
C29H17N3F5Au: C, 49.80; H, 2.45; N, 6.01. Found: C, 49.69; H, 2.35;
N, 6.18.
3
4
3
7.81 (m, 2H, acr, 2H, im), 7.43 (ddd, J = 8.64 Hz, 3J = 6.62 Hz, 4J =
3
0.99 Hz, 2H, acr), 7.31−7.27 (m, 1H, Ph), 7.20 (d, J = 7.67 Hz, 2H,
3
3
Ph), 7.16 (d, J = 8.50 Hz, 2H, acr), 6.99 (d, J = 7.19 Hz, 2H, Ph),
4.88 (s, 2H, CH2). 13C{1H} NMR (DMSO-d6, 100.6 MHz, 294 K): δ
181.7 (2d, JC‑107Ag = 184.4 Hz, JC‑109Ag = 212.6 Hz, imcarb), 148.3
Crystallography. Crystals were mounted in inert oil on glass fibers
and transferred to the cold gas stream of an Xcalibur Oxford
Diffraction diffractometer equipped with a low-temperature attach-
1
1
(acr), 139.3 (acr), 136.0 (Ph), 130.8 (acr), 129.4 (Ph), 128.7 (acr),
7155
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
ment. Data were collected using monochromated Mo Kα radiation (λ
= 0.71073 Å). Scan type: ω. Absorption corrections based on multiple
scans were applied with the program SADABS28 or using spherical
harmonics implemented in SCALE3 ABSPACK29 scaling algorithm
(15). The structures were solved by direct methods and refined on F2
using the program SHELXL-97.30 All non-hydrogen atoms were
refined anisotropically. In all cases, hydrogen atoms were included in
calculated positions and refined using a riding model. Refinements
were carried out by full-matrix least-squares on F2 for all data. Further
details of the data collection and refinement are given in the
Supporting Information.
Carcedo, C.; Knight, J. C.; Pope, S. J. A.; Fallis, I. A. Organometallics
2011, 30, 2553.
(9) (a) Catalano, V. J.; Moore, A. L.; Shearer, J.; Kim, J. Inorg. Chem.
2009, 48, 11362. (b) Chen, W.; Liu, B.; Jin, S. Organometallics 2007,
26, 3660. (c) Catalano, V. J.; Etogo, A. O. Inorg. Chem. 2007, 46, 5608.
(d) Lin, I. J. B.; Wang, H. M. J.; Chen, C. Y. L. Organometallics 1999,
18, 1216. (e) Catalano, V. J.; Strasser, C. E. J. Am. Chem. Soc. 2010,
132, 10009. (f) Catalano, V. J.; Etogo, A. O. J. Organomet. Chem. 2005,
690, 6041.
(10) (a) Yam, V. W. W.; Lee, J. K. W.; Ko, C. C.; Zhu, N. J. Am.
Chem. Soc. 2009, 131, 912. (b) Au, V. K. M.; Wong, K. M. C.; Zhu, N;
Yam, V. W. W. J. Am. Chem. Soc. 2009, 131, 9076.
ASSOCIATED CONTENT
* Supporting Information
(11) (a) Lee, C. K.; Vasam, C. S.; Huang, T. W.; Wang, H. M. J.;
Yang, R. W.; Lee, C. S.; Lin, I. J. B. Organometallics 2006, 25, 3768.
(b) Lee, K. M.; Lee, C. K.; Lin, I. J. B. Angew. Chem., Int. Ed. Engl.
1997, 36, 1850.
■
S
Seven X-ray crystallographic files, in CIF format, for
compounds 5, 7, 9, 11, 13, 15, and 17. This material is
available free of charge via the Internet at http://pubs.acs.org.
(12) (a) Melaiye, A.; Sun, Z.; Hindi, K.; Mildsted, A.; Ely, D.;
Reneker, D. H.; Tessier, C. A.; Youngs, W. J. J. Am. Chem. Soc. 2005,
127, 2285. (b) Patil, S.; Deally, A.; Gleeson, B.; Muller-Bunz, H.;
AUTHOR INFORMATION
Corresponding Author
*E-mail: gimeno@unizar.es.
̈
̇
■
Paradisi, F.; Tacke, M. Metallomics 2011, 3, 74. (c) Ozdemir, I.;
Temelli, N.; Gunal, S.; Demir, S. Molecules 2010, 15, 2203.
̈
(13) (a) Barnard, P. J.; Berners-Price, S. J. Coord. Chem. Rev. 2007,
251, 1889. (b) Hickey, J. L.; Ruhayel, R. A.; Barnard, P. J.; Baker, M.
V.; Berners-Price, S. J.; Filipovska, A. J. Am. Chem. Soc. 2008, 130,
12570. (c) Teyssot, M. L.; Jarrousse, A. S.; Manin, M.; Chevry, A.;
Roche, S.; Norre, F.; Beaudoin, C.; Morel, L.; Boyer, D.; Mahiou, R.;
Gautier, A. Dalton Trans. 2009, 6894. (d) Lemke, J.; Pinto, A.; Neihoff,
F.; Vasylyeva, V.; Merzler-Nolte, N. Dalton Trans. 2009, 7063.
(14) Bierbach, U.; Eiter, L. C.; Hall, N. W.; Day, C. S.; Saluta, G.;
Kucera, G. L. J. Med. Chem. 2009, 52, 6519.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
́
Authors thank the Ministerio de Economia y Competitividad
(MEC/FEDER CTQ2010-20500-C02-01) for financial sup-
port.
(15) (a) Cao, Q.-Y.; Lu, X.; Li, Z.-H.; Zhou, L.; Yang, Z.-Y.; Liu, J.-H.
J. Organomet. Chem. 2010, 695, 1323. (b) Hu, T.-L.; Yu, Q.; Wei, Z.-
Z.; Li, J.-R. J. Mol. Struct. 2009, 931, 68. (c) Li, Z.-M.; Liu, C.-S.; Chen,
P.-Q.; Yang, E.-C.; Tian, J.-L.; Bu, X.-H.; Sun, H.-W.; Lin, Z. Inorg.
Chem. 2006, 45, 5812.
(16) (a) Strasser, C. E.; Coetzee, K.; Cronje, S.; Raubenheimer, H. G.
Acta Crystallogr. Sect. E 2009, 65, m1499. (b) Briggs, D. A.; Raptis, R.
G.; Fackler, J. P., Jr. Acta Crystallogr. Sect. C 1988, 44, 1313.
REFERENCES
■
(1) Arduengo, A. J., III; Harlow, R. L.; Kline, M. A. J. Am. Chem. Soc.
1991, 113, 361.
(2) (a) Bourissou, D.; Guerret, O.; Gabbai, F. P.; Bertrand, G. Chem.
Rev. 2000, 100, 39. (b) Hermann, W. A. Angew. Chem., Int. Ed. 2002,
41, 1290. (c) Crabtree, R. H.; Peris, E. Chem. Rev. 2004, 248, 2239.
(d) N-Heterocyclic Carbenes in Synthesis; Nolan, S. P., Ed.; Wiley-VCH:
(17) (a) De Frem
Lightbody, O. C.; Macdonald, C. L. B.; Clyburne, J. A. C.; Abernethy,
C. D.; Nolan, S. P. Organometallics 2005, 24, 6301. (b) de Fremont, P.;
́
ont, P.; Scott, N. M.; Stevens, E. D.; Ramnial, T.;
Weinheim, 2006. (e) Marion, N.; Díez-Gonzal
Angew. Chem., Int. Ed. 2007, 46, 2988. (f) Poyatos, M.; Mat
Peris, E. Chem. Rev. 2009, 109, 3677.
(3) (a) Nolan, S. P. Acc. Chem. Res. 2011, 44, 91. (b) Youngs, W. J.;
Garrison, J. C. Chem. Rev. 2005, 105, 3978. (c) Requejo, M. M.; Perez,
́
ez, S.; Nolan, S. P.
́
a., J. A.;
́
Scott, N. M.; Stevens, E. D.; Nolan, S. P. Organometallics 2005, 24,
2411.
́
(18) Limbach, M.; Pazicky, M.; Loos, A.; Ferreira, M. J.; Serra, D.;
̌
́
P. J. Chem. Rev. 2008, 108, 3379. (d) Lin, J. C. Y.; Huang, R. T. W.;
Lee, C. S.; Bhattacharyya, A.; Hwang, W. S.; Lin, J. B. Chem. Rev. 2009,
3561. (e) Hindi, K. M.; Panzner, M. J.; Tessier, C. A.; Cannon, C. L.;
Youngs, W. J. Chem. Rev. 2009, 109, 3859.
Vinokurov, N.; Rominger, F.; Jakel, C.; Hashmi, A. S. K. Organo-
̈
metallics 2010, 29, 4448.
(19) Huynh, H. V.; Han, Y.; Jothibasu, R.; Yang, J. A. Organometallics
2009, 28, 5395.
(20) (a) Newman, C. P.; Clarkson, G. J.; Rourke, J. P. J. Organomet.
Chem. 2007, 692, 4962. (b) De Fremont, P.; Scott, N. M.; Stevens, E.
́
D.; Nolan, S. P. Organometallics 2005, 24, 2411.
(21) Elangovan, A.; Chiu, H.; Yang, S.; Ho, T. Org. Biomol. Chem.
2004, 3113.
(22) Sandeep, P.; Bisht, P. B. Chem. Phys. 2006, 326, 521.
(23) Kim, S. K.; Seo, D.; Han, S. J.; Son, G.; Lee, I. J.; Lee, C.; Lee, K.
D.; Yoon, J. Tetrahedron 2008, 64, 6402.
(24) Wang, H. M. J.; Vasam, C. S.; Tsai, T. Y. R.; Chen, S. H.; Chang,
A. H. H.; Kin, I. J. B. Organometallics 2005, 24, 486.
(25) Fulmer, G. R.; Miller, A. J. M.; Sherden, N. H.; Gottlieb, H. E.;
Nudelman, A.; Stoltz, B. M.; Bercaw, J. E.; Goldberg, K. I.
Organometallics 2010, 29, 2176.
(4) (a) Garrison, J. C.; Youngs, W. J. Chem. Rev. 2005, 105, 3978.
(b) Lin, I. J. B.; Vasam, C. S. Coord. Chem. Rev. 2007, 251, 642.
(5) (a) Jimen
́
ez-Nunez, E.; Echavarren, A. M. Chem. Rev. 2008, 108,
ez-Carrillo, V.; Echavarren, A. M. J. Am. Chem. Soc.
̃
3326. (b) Lop
́
2010, 132, 9292. (c) Rivilla, I.; Gom
́
ez-Emeterio, B. P.; Fructos, M. R.;
Díaz-Requejo, M. M.; Perez., P. J. Organometallics 2011, 30, 2855.
(d) Marion, M.; Nolan, S. P. Chem. Soc. Rev. 2008, 1776. (e) Zeldin, R.
M.; Toste, F. D. Chem. Sci. 2011, 2, 1706.
́
́
́ ́
(6) (a) Ramírez, J.; Corberan, R.; Sanau, M.; Peris, E.; Fernandez., E.
Chem. Commun. 2005, 3056. (b) Sentman, A. C.; Csihony, S.; Nyce,
G. W.; Waymouth, R. M.; Hedrick, J. L. J. Org. Chem. 2005, 70, 2391.
(7) (a) Fraser, P. K.; Woodward, S. Tetrahedron Lett. 2001, 42, 2747.
(b) Díaz-Gon
(c) Díaz-Gon
Gon
́
zalez, S.; Nolan, S. P. Aldrichim. Acta 2008, 41, 43.
zalez, S.; Nolan, S. P. Synlett 2007, 70, 4784. (d) Díaz-
zalez, S.; Escudero-Adam, E. C.; Benet-Buschholtz, J.; Stevens, E.
́
́
(26) Uson
(27) Uson
́
, R.; Laguna, A. Inorg. Synth. 1982, 21, 71.
, R.; Laguna, A.; Laguna, M. Inorg. Synth. 1989, 26, 85.
́
́
D.; Slawin, A. M. Z.; Nolan, S. P. Dalton Trans. 2010, 39, 7595.
(e) Larsen, A. O.; leu, W.; Oberhuber, C. N.; Capbell, J. E.; Hoveyda,
A. H. J. Am. Chem. Soc. 2004, 126, 11130.
(28) Sheldrick, G. M. SADABS, Program for Absorption Correction;
University of Gottingen: Gottingen, Germany, 1996.
̈
̈
(29) CrysAlisPro, Version 1.171.35.11; Agilent Technologies.
Multiscan absorption correction with SCALE3 ABSPACK scaling
algorithm.
(8) (a) Che, C.-M.; Chow, A. L.-F.; So, M.-H.; Lu, W.; Zhu, N. Chem.
Asian J. 2011, 6, 544. (b) Thompson, M. E.; Krylova, V. A.; Djurovich,
P. I.; Whited, M. T. Chem. Commun. 2010, 46, 6696. (c) Dervisi, A.;
7156
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157

Organometallics
Article
(30) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement; University of Gottingen: Gottingen, Germany, 1997.
̈
̈
7157
dx.doi.org/10.1021/om300571m | Organometallics 2012, 31, 7146−7157