NHC-amide donor ligands in rhodium complexes: Syntheses and characterisation

Article abstract of DOI:10.1016/j.jorganchem.2014.10.020

Rhodium(I) complexes bearing amide-functionalised NHC ligands were synthesized in high yields through various synthetic routes and from different metal precursors, showing the versatility of such systems. By changing the ancillary ligands on the rhodium f

Full text of DOI:10.1016/j.jorganchem.2014.10.020

Journal of Organometallic Chemistry 775 (2015) 195e201
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
NHC-amide donor ligands in rhodium complexes: Syntheses and
characterisation
Stefan Warsink*, Johan A. Venter, Andreas Roodt
Department of Chemistry, University of the Free State, PO Box 339, Bloemfontein 9300, South Africa
a r t i c l e i n f o
a b s t r a c t
Article history:
Rhodium(I) complexes bearing amide-functionalised NHC ligands were synthesized in high yields
through various synthetic routes and from different metal precursors, showing the versatility of such
systems. By changing the ancillary ligands on the rhodium from cyclooctadiene to carbonyls the coor-
dination behaviour of the NHC-amide ligand could be influenced. When a more basic precursor was
employed for complexation, bidentate behaviour with the amide in an anionic mode was observed. All
reported complexes are synthesized in high yields and under ambient conditions, which shows their
robustness. The monodentate rhodium(I) biscarbonyl NHC complexes were shown to be able to activate
iodomethane.
Received 17 June 2014
Received in revised form
9 October 2014
Accepted 10 October 2014
Available online 27 October 2014
Keywords:
Rhodium
Silver
© 2014 Elsevier B.V. All rights reserved.
NHC complexes
Bidentate ligands
Introduction
this work, we propose to use N-heterocyclic carbene (NHC) ligands;
they are strong s-donor ligands that form strong bonds to various
In the 1960s, the Monsanto Company developed the rhodium-
catalysed process for acetic acid synthesis from methanol and
carbon monoxide. The process is also catalysed by iodide, gener-
ating iodomethane in situ [1]. This is currently one of the largest
industrially applied homogeneously catalysed reactions, with a
multi-million tonne production per year. The oxidative addition of
iodomethane is the rate-determining step [2], and research has
focused on improving the propensity of the catalyst for this reac-
tion by rational ligand design. Research has either focused on the
use of monodentate ligands, or on the introduction of a bidentate
ligand, either symmetrical or heteroditopic [3]. Other studies have
dealt with the introduction of differently substituted tertiary
phosphine ligands, evaluating their steric and electronic impact on
the oxidative addition [4]. Often observed for rhodium complexes
bearing suitably functionalized ligands is the secondary reaction of
the rhodium(III) methyl complex with its carbonyl ligand to form
the rhodium(III) acyl species [5].
(transition) metals [6]. An advantage of these ligands over phos-
phines is their relative stability. Also, because they are less prone to
dissociation from the metal, no excess ligand needs to be used in
the synthesis or in the catalytic process. They have been used
successfully as ligands for various processes [7].
Rhodium NHC complexes have only sparsely been used in
iodomethane oxidative addition [8], one example showing con-
version to the rhodium(III) alkyl species [9], while another shows
exclusive acyl formation [10]. No reports are available employing
bidentate NHC ligands, either homo- or heteroditopic. In our lab-
oratories, research focuses on the development of (hetero)biden-
tate scaffolds for numerous applications [11]; the development of a
donor-functionalized NHC-system was therefore a logical pro-
gression of our research interests. We have chosen to focus our
designs on the incorporation of a secondary amide donor [12], as it
could potentially be deprotonated to yield a mono-anionic biden-
tate ligand set [13]. In this contribution we describe the synthesis
and structural properties of these systems as well as an exploratory
study of their reactivity towards iodomethane.
Increase of the electron density on the rhodium metal center by
using strong donor ligands has been shown to be an effective
method of activating the system towards oxidative addition.
Traditionally, phosphine ligands have been used to affect this. In
Results and discussion
* Corresponding author. Current address: Organic Chemistry and Catalysis,
Debye Institute of Nanomaterials Science, Faculty of Science, Utrecht University,
Universiteitsweg 99, 3584 CH Utrecht, The Netherlands. Tel.: þ31 30 2533120;
fax: þ31 30 2523615.
Ligand synthesis
The imidazolium salts 1 and 2 are readily synthesized [14] from
1-mesityl imidazole [15] and a chloroethyl amide, which in turn is
E-mail address: stefanwarsink@gmail.com (S. Warsink).
http://dx.doi.org/10.1016/j.jorganchem.2014.10.020
0022-328X/© 2014 Elsevier B.V. All rights reserved.

196
S. Warsink et al. / Journal of Organometallic Chemistry 775 (2015) 195e201
Scheme 1. Synthesis of imidazolium salts (Mes ¼ 2,4,6-trimethylphenyl).
obtained by coupling 2-chloroethylamine hydrochloride with the
appropriate aroyl chloride (Scheme 1) [16].
An interesting possibility offered by this high-yielding and
simple procedure is that the robust amide-moiety could be used to
link the NHC-fragment to a solid support if a heterogenized catalyst
is required [17].
obtained from the 13C NMR spectra, where the characteristic signal
for the NCN carbon is observed at 181.7 ppm. This signal appeared
broadened through ligand exchange in solution. Although the
neutral mono-NHC complex is also a possible product, literature
precedent validates the structure shown in Scheme 2 [7,20].
The mesityl imidazolium salts are characterized by a signal in
the 1H NMR spectra at 9.5 ppm in DMSO-d6 and at 9.9 ppm in
CDCl3. The signal for the amide-hydrogen appears as a triplet
around 9 ppm with a coupling of 5 Hz caused by the neighbouring
methylene group. Even in the case of DMSO the splitting is clearly
present, indicating that there is very slow to no exchange of the
hydrogen with the water present in the deuterated solvent. Crystals
of 1 suitable for X-ray crystallography were obtained by slow
evaporation of a chloroform solution (Fig. 1).
Rhodium(I) complex synthesis
Transmetallation of the NHC to the well-known chlorido-
rhodium(I) 1,5-cyclooctadiene (cod) dimer was performed without
taking any special precautions to exclude air or moisture from the
reaction mixture, obtaining the product in high yields (Scheme 3).
Instead of deprotonation of the secondary donor, as is often seen
with bidentate ligands in conjunction with this mildly basic
rhodium precursor [21], the amide remains protonated. Initially,
this was inferred from 1H NMR experiments, where the signal for
the amide hydrogen could still be observed. However, an upfield
shift to just above 8 ppm was also noted for this signal, indicating
that the proton is more strongly shielded. In addition to this effect, a
clear bidentate interaction of the ligand was visible, evidenced by
the splitting of the signals for the ethylene bridge hydrogens into an
AA’BB0 pattern. From 13C NMR analysis, the signal for the carbene is
observed at 182.4 ppm, with a JRh-C of 52 Hz. These values are in the
same range as for similar reported complexes [8].
Several coordination modes that fit these observations are
possible, but definitive proof of the molecular structure was given
by X-ray crystallography. Both 5 and 6 showed the same arrange-
ment, in which the amide hydrogen shows an interaction with the
rhodium-bound chlorido ligand. The two complexes crystallize
differently (Figs. 2 and 3); whereas complex 5 crystallized with one
molecule in the asymmetric unit, that of 6 contained two complex
molecules (a and b in Table 1) and a molecule of chloroform.
The structure clearly shows the geometry of the molecule.
Hydrogen bonds from the amide to the chloride and to the imi-
dazolium proton, as well as
pep interactions constitute an inter-
molecular network in the solid state; no significant intramolecular
interactions are present.
Silver(I) complex synthesis
From the preligands, the silver(I) complexes were synthesized
first [18]. These species are routinely used to obtain the NHC
without the need for stringent air- and moisture-free reaction
conditions [19], and are excellent transfer agents for the carbene
ligand. After reaction of the imidazolium salts with half an equiv-
alent of silver(I) oxide in dichloromethane, the products 3 and 4
were obtained in near quantitative yields (Scheme 2).
The observed uptake of the silver(I) oxide confirms that the
reaction proceeds to completion, and the 1H NMR spectra clearly
show the disappearance of the imidazolium C-2 hydrogen, indi-
cating carbene-formation. Definitive proof for carbene formation is
Scheme 2. Synthesis of silver(I) NHC complexes.
Fig. 1. Displacement ellipsoid plot of
1 (50% probability). Non-relevant hydrogen
atoms are omitted for clarity.
Scheme 3. Transmetallation to chloridorhodium(I) cyclooctadiene.

S. Warsink et al. / Journal of Organometallic Chemistry 775 (2015) 195e201
197
Table 1
Selected bond lengths (Å) and angles (ꢁ) for complex 5 and 6.
Complex
5
6a
2.036 (8)
6b
Rh1eC01
2.038 (2)
2.035 (8)
2.400 (2)
2.087 (7)
2.113 (7)
2.187 (8)
2.227 (7)
3.346 (2)
89.66 (19)
87.0 (2)
Rh1eCl1
Rh1eCcod (cisNHC
2.3958 (9)
2.0912 (17)
2.1116 (18)
2.2018 (19)
2.212 (2)
3.3806 (17)
92.01 (5)
86.50 (6)
2.3998 (19)
2.109 (7)
2.113 (6)
2.190 (7)
2.232 (8)
3.395 (8)
89.0 (2)
)
Rh1eCcod (transNHC
)
Cl1eN3
C01eRh1eCl1
Cod-bite angle ca
Cod-jaw angle ja
87.31 (17)
77.4 (3)
78.59 (9)
77.6 (4)
a
For discussion on the
c bite- and j jaw-angles of cyclooctadiene ligands in
transition metal complexes, see Ref. [22].
2081 and 2005 cmꢀ1 in methanol, irrespective of the remote aryl
substituent. With the use of a modified protocol for Tolman's
Electronic Parameter (TEP) [23], the donor strength of the NHC-
ligand can be determined. According to this scale, the carbene
has a donor strength comparable to tricyclohexyl phosphine,
without suffering from disadvantages associated with this ligand,
such as ligand dissociation and decomposition by oxidation. The
complexes 7 and 8 are very stable in the solid state and in solution,
showing no signs of decomposition after standing in non-dried
dichloromethane, methanol or methanol containing an excess of
acetic acid. Also, these complexes appear to be stable in water for
prolonged periods. All attempts to obtain complexes with a
rhodium-amido coordination by deprotonation with mild base or
chloride-abstraction with for example silver-salts were
unsuccessful.
From these experiments, it was clear that use of the afore-
mentioned precursors did not lead to carbonyl-bearing bidentate
NHCeN complexes. Therefore, recourse was taken to a more basic
rhodium-precursor; [Rh(OMe) (cod)]2. This precursor should be
able to deprotonate the amide donor in situ and the exchange of the
chloride ligand for the methoxide moiety should therefore facilitate
the bidentate coordination. After the NHC silver complexes 3 and 4
were subjected to this precursor under the same mild reaction
conditions, it became clear that the desired reactivity exists
(Scheme 5).
Fig. 2. Displacement ellipsoid plot of 5, showing the intramolecular hydrogen bond
(50% probability). Non-relevant hydrogen atoms and atom labels are omitted for
clarity.
Both complexes have the same general distorted square planar
conformation, with the most obvious feature the distorted boat-
like 8-membered ring of the ‘bidentate’ ligand. All three
hydrogen bond lengths are of similar magnitude, as are the car-
beneerhodium bond lengths. The bond lengths of the rhodium
center to the cyclooctadiene carbons trans to the NHC are signifi-
cantly longer than those trans to the chlorido ligand; this is caused
by the greater trans-influence of the
s-donor carbene ligand as
compared to the chloride.
For application in methanol carbonylation, the rhodium com-
plexes should bear a carbonyl ligand. When 5 and 6 were treated
with CO under various conditions, no exchange of the cyclo-
octadiene was observed, even though this procedure is reported to
be facile [8]. Alternatively, when the silver(I) NHC complexes were
reacted with [RhCl(CO)2]2, a different reactivity compared to the
cod-analogue was observed. Instead of the hydrogen bond inter-
action with the chloride, monodentate coordination of the NHC
took place (Scheme 4).
This monodentate behaviour could be easily observed in the 1H
NMR spectra, which showed no diastereotopicity in contrast to 5
and 6. The amide-proton is observed at 7.5 ppm, which is signifi-
cantly upfield from the cod-analogues. In the 13C NMR spectra, the
NHC carbon is observed at 185 ppm with a JRh-C of 54 Hz, which
corresponds to monodentate RhCl(CO)2(NHC) complexes reported
in literature [8]. The carbonyl ligands of 7 and 8 show signals in IR
spectroscopy at 2083 and 2004 cmꢀ1 in dichloromethane and at
For both complexes 9 and 10, the absence of a signal for the
amide proton was noted in 1H NMR spectroscopy, as well as a
Scheme 4. Synthesis of chloridorhodium biscarbonyl NHC complexes.
Fig. 3. Displacement ellipsoid plot of the asymmetric unit of 6, showing the intra-
molecular hydrogen bond (50% probability). Non-relevant hydrogen atoms and atom
labels are omitted for clarity.
Scheme 5. Synthesis of bidentate Rh(NHC-N) (cod) complexes.

198
S. Warsink et al. / Journal of Organometallic Chemistry 775 (2015) 195e201
significant downfield shift for the signals of the ortho-aryl and
ethylene linker hydrogens, indicating the anionic character of the
amide. The bidentate character of the ligand is clearly visible, as in 5
and 6, which indicates that the deprotonated amido-nitrogen co-
ordinates to the rhodium center. Alternatively, when the basic
rhodium precursor was reacted with imidazolium salts 1 and 2
directly, hydrogen bond-containing complexes 5 and 6 were ob-
tained in good yields, obviating the need for the intermediate silver
complex [24]. This pathway highlights the rich reactivity of these
compounds with respect to different transition metal precursors.
As with 5 and 6, treatment of the bidentate complexes did not show
exchange of the cyclooctadiene ligand; only starting material (9 or
10) was recovered.
From the results discussed above, it appeared that it was
necessary to combine the basic functionality of the alkoxide ligand
with the presence of carbonyl ligands in the rhodium precursor.
However, for rhodium carbonyl complexes, literature involving
bridging alkoxy-species is sparse, and deals with in situ character-
isation only [25]. When the available protocol was employed with
our ligand system, only the monodentate complexes 7 and 8 were
isolated in yields of 74e77% (Scheme 6).
dicarbonyl complexes, but the amide donor engages in a hydrogen
bond interaction with the rhodium-bound chloride instead when
cyclooctadiene is present. When a rhodium precursor with more
basic ligands is used, the coordination can be switched to bidentate
behaviour depending on the NHC source. Unequivocal evidence of
the structure of the different complex classes was obtained by
combining the results of various analytical techniques. It has to be
noted that all the complexes were shown to be extremely robust
and resilient against air and moisture, making their applicability
highly feasible. Additionally, the diverse and tunable coordination
behaviour could significantly enhance the functionality of the
complexes. When the rhodium NHC dicarbonyl complexes were
employed in a model reaction to probe their potential usefulness in
methanol carbonylation, formation of rhodium(III) acyl species was
observed, proving the developed complexes as viable targets.
Experimental section
NMR spectroscopic data were acquired on a Bruker Advance II
600 MHz spectrometer. 1H NMR data are listed in the order:
chemical shift (
solvent peak of DMSO-d6 [
CDCl3
d
, reported in ppm and referenced to the residual
Clearly, the remaining presence of the chloride in the reaction
mixture hampers the isolation of the desired products. Despite our
efforts with various rhodium precursors and reaction conditions
[26], we were not successful in isolating complexes in which the
bidentate coordination mode of the NHC-amide ligand was present
together with carbonyl ligands.
d
¼ 2.50 ppm], CD2Cl2 [ ¼ 5.32 ppm] or
d
[d
¼ 7.26 ppm]), multiplicity, coupling constant (J, in Hz),
number of protons, assignment. Proton decoupling experiments
were used to assist in the assignment of proton signals. Proton
decoupled 13C NMR data are listed in the order: chemical shift (
d,
reported in ppm and referenced to the residual solvent peak of
DMSO-d6 ¼ 77.0 ppm] or CDCl3
¼ 39.5 ppm], CD2Cl2
¼ 77.0 ppm]), multiplicity, coupling constant (J, in Hz) where
[
d
[d
[d
Exploratory iodomethane oxidative addition studies
appropriate, number of carbons, assignment. HMQC experiments
were performed to assist in the allocation of signals. FT-IR spectra
were recorded on a Bruker Tensor 27 spectrophotometer equipped
with a temperature sensor accurate within 0.3 ꢁC in the range of
3000e600 cmꢀ1 via the ATR or in a NaCl cell. Elemental analyses
were performed in duplicate on a Leco Truspec Micro. 1-mesityl
imidazole [15] and N-(2-chloroethyl)-benzamide [16] are known
compounds and were synthesized according to literature pro-
cedures. All other chemicals were used as received from the
supplier.
As the carbonyl-ligand containing complexes are designed with
use in methanol carbonylation in mind, they were tested in a model
reaction often performed in our laboratory: the oxidative addition
of iodomethane to yield the rhodium(III) alkyl complex B (Scheme
7).
This is the first step in the catalytic cycle, and is usually also the
rate-determining one [1]. Often, the subsequent migratory inser-
tion of a carbonyl ligand, leading to the rhodium(III) acyl species C,
can also be observed [5]. Both steps are equilibria, although the
ligands used determine to what side they lie. The behaviour of
newly developed catalysts in this transformation gives valuable
insights in their viability for the whole process. When a solution of
complex 7 or 8 was reacted with iodomethane, ‘direct’ conversion
to complex C was observed as evidenced by a broad and complex
signal around 1650 cmꢀ1 in IR, which corresponds to an acyl ligand
[9]. Further research into the activity and selectivity of these
complexes is in process.
N-(2-chloroethyl)-4-methoxybenzamide
The product was obtained as a white microcrystalline solid in a
yield of >95%. 1H NMR (300 MHz, CDCl3):
d
7.76 (d, 3J(HH) ¼ 8.8 Hz,
2H, aryl-H), 6.93 (d, 3J(HH) ¼ 8.8 Hz, 2H, aryl-H), 6.52 (broad s, 1H,
NH), 3.85 (s, 3H, OCH3), 3.80-3.70 (m, 4H, 2 CH2). 13C NMR
(151 MHz, CDCl3): d 167.2 (CO), 162.4 (p-aryl-C), 128.8 (m-aryl-CH),
126.3 (i-aryl-C), 113.8 (o-aryl-CH), 55.4 (OCH3), 44.2 (ClCH2), 41.6
(NHCH2).
Conclusion
Synthesis of imidazolium salts
The ligands described in this work show versatile coordination
chemistry; they bind as monodentate ligands in rhodium
1 mmol 1-mesityl imidazole and 1 mmol of 2-chloroethyl amide
were suspended in 10 mL acetonitrile, which was refluxed for a
period of 48 h. The pure product precipitated from the reaction
mixture and was collected by filtration.
(1-(2-benzamido)-ethylene-3-mesityl)-imidazolium chloride 1
The product was obtained as an off-white solid in a yield of
>95%. 1H NMR (300 MHz, DMSO-d6):
d 9.51 (s, 1H, NCHN), 8.95 (t,
3J(HH) ¼ 5.0 Hz, 1H, NH), 8.11 (s, 1H, CH), 7.87 (s, 1H, CH), 7.82 (d,
3J(HH) ¼ 7.2 Hz, 2H, o-Ph-H), 7.51 (t, 3J(HH) ¼ 7.1 Hz, 1H, p-Ph-H),
7.45 (m, 2H, m-Ph-H), 7.07 (s, 2H, m-Mes-H), 4.48 (t,
3J(HH)
¼
5.0 Hz, 2H, NCH2), 3.79 (dt, 3J(HH)
¼
5.0 Hz,
Scheme 6. Attempted synthesis of biscarbonyl bidentate rhodium complex.
3J(HH) ¼ 5.0 Hz, 2H, NHCH2), 2.27 (s, 3H, p-Mes-CH3), 1.90 (s, 6H, o-

S. Warsink et al. / Journal of Organometallic Chemistry 775 (2015) 195e201
199
Scheme 7. Observed reactivity between iodomethane and rhodium.
Mes-CH3). 13C NMR (151 MHz, DMSO-d6):
d
167.1 (CO), 140.6 (p-
CD2Cl2): d 181.6 (broad, NCN), 166.9 (CO), 162.2 (p-aryl-C), 139.0 (p-
Mes-C), 138.1 (NCN), 134.8 (o-Mes-C), 134.1 (p-Ph-CH), 131.9 (i-
Mes-C), 131.6 (i-Ph-C), 129.6 (m-Mes-CH), 128.7 (o-Ph-CH), 127.7
(m-Ph-CH), 124.2 (CH), 124.1 (CH), 49.9 (NCH2), 39.5 (NHCH2), 21.0
(p-Mes-CH3), 17.2 (o-Mes-CH3).
Mes-C), 135.5 (i-Mes-C), 134.9 (o-Mes-C), 129.3 (m-Mes-CH), 129.0
(o-aryl-CH), 126.2 (i-aryl-C), 122.6 (CH), 121.8 (CH), 112.4 (m-aryl-
CH), 55.3 (OCH3), 51.1 (NCH2), 40.0 (NHCH2), 20.8 (p-Mes-CH3), 17.2
(o-Mes-CH3).
(1-(2-(4-methoxybenzamido))-ethylene-3-mesityl)-imidazolium
chloride 2
Synthesis of rhodium(I) NHC complexes from silver(I) NHC
complexes
The product was obtained as an off-white solid in a yield of
>95%. 1H NMR (300 MHz, CDCl3):
d 9.87 (s, 1H, NCHN), 9.12 (t,
To 10 mL of a 10 mM silver(I) NHC solution was added 0.5
equivalent of the rhodium dimer precursor. Immediately, a yellow
suspension is formed. After 1 h of stirring, the reaction mixture is
filtered over a pad of celite, after which the pure product is obtained
by concentration of the solution.
3J(HH) ¼ 5.0 Hz, 1H, NH), 8.02 (d, 3J(HH) ¼ 8.7 Hz, 2H, aryl-H), 7.95
(s, 1H, CH), 7.02 (s, 1H, CH), 6.85 (s, 2H, Mes-H), 6.82 (d,
3J(HH) ¼ 8.7 Hz, 2H, aryl-H), 5.00 (t, 3J(HH) ¼ 5.2 Hz, 2H, NCH2),
4.05 (dt, 3J(HH) ¼ 5.2 Hz, 3J(HH) ¼ 5.0 Hz, 2H, NHCH2), 3.77 (s, 3H,
OCH3), 2.25 (s, 3H, p-Mes-CH3), 1.78 (s, 6H, o-Mes-CH3). 13C NMR
(151 MHz, CDCl3):
d 167.4 (CO), 162.2 (p-aryl-C), 141.2 (p-Mes-C),
Chlorido[(h
4-1,5-cyclooctadiene) ((1-(2-benzamido)-ethylene-3-
(2,4,6-trimethylphenyl))-imidazol-2-ylidene)rhodium(I)] 5
138.1 (NCHN), 134.2 (o-Mes-C), 130.5 (i-Mes-C), 129.7 (m-Mes-CH),
129.6 (o-aryl-CH), 125.3 (i-aryl-C), 123.7 (CH), 123.0 (CH), 113.5 (m-
aryl-CH), 55.3 (OCH3), 49.2 (NCH2), 38.9 (NHCH2), 21.0 (p-Mes-
CH3), 17.1 (o-Mes-CH3).
The product was obtained as a yellow microcrystalline solid in a
yield of 97%. 1H NMR (600 MHz, CDCl3):
d
8.20 (d, 3J(HH) ¼ 6.8 Hz,
1H, NH), 7.94 (d, 3J(HH)
¼
7.1 Hz, 2H, o-Ph-H), 7.42 (t,
3J(HH)
¼
7.4 Hz, 1H, p-Ph-H), 7.35 (dt, 3J(HH)
¼
7.4 Hz,
3J(HH) ¼ 7.1 Hz, 2H, m-Ph-H), 7.15 (d, 3J(HH) ¼ 1.9 Hz, 1H, CH), 7.05
Synthesis of silver(I) NHC complexes
(broad s, 1H, Mes-H), 6.93 (broad s, 1H, Mes-H), 6.73 (d,
3J(HH)
¼
1.9 Hz, 1H, CH), 5.99 (ddd, 3J(HH)
¼
13.6 Hz,
To a suspension of 0.1 mmol imidazolium salt in 10 mL
dichloromethane was added 0.05 mmol silver(I) oxide. The reaction
mixture was stirred at room temperature for 16 h, after which it
was filtered over a pad of celite. The resulting colourless solution
was then concentrated in vacuo to yield the pure product.
3J(HH) ¼ 11.7 Hz, 2J(HH) ¼ 5.2 Hz, 1H, NCH2), 4.83 (m, 2H, cod-CH),
4.56 (m, 1H, NHCH2), 4.42 (ddd, 3J(HH) ¼ 13.6 Hz, 3J(HH) ¼ 5.2 Hz,
2J(HH) ¼ 2.8 Hz, 1H, NCH2), 3.81 (dddd, 3J(HH) ¼ 14.3 Hz,
3J(HH) ¼ 5.0 Hz, 2J(HH) ¼ 2.8 Hz, 3J(HH) ¼ 6.8 Hz, 1H, NHCH2), 3.53
(m, 1H, cod-CH), 3.02 (m, 1H, cod-CH), 2.45 (m, 1H, cod-CH2), 2.37
(s, 3H, p-Mes-CH3), 2.17 (s, 3H, o-Mes-CH3), 2.15 (m, 1H, cod-CH2),
2.03 (m, 1H, cod-CH2), 1.97 (m, 1H, cod-CH2), 1.85 (s, 3H, o-Mes-
CH3), 1.82 (m, 1H, cod-CH2), 1.67 (m, 1H, cod-CH2), 1.6e1.4 (m, 2H,
Chlorido[(1-(2-benzamido)-ethylene-3-mesityl)-imidazol-2-
ylidene]silver(I) 3
The product was obtained as a colourless oil in a yield of >95%.
cod-CH2). 13C NMR (151 MHz, CDCl3):
d
182.4 (d, 2J(RhC) ¼ 52 Hz,
1H NMR (300 MHz, CD2Cl2):
d 9.0-8.0 (broad s, 1H, NH), 7.92 (d,
3J(HH) ¼ 6.9 Hz, 2H, o-Ph-H), 7.44 (t, 3J(HH) ¼ 7.1 Hz, 1H, p-Ph-H),
NCN), 168.2 (CO), 138.7 (p-Mes-C),136.9 (i-Mes-C), 135.9 (o-Mes-C),
134.0 (o-Mes-C), 133.7 (i-Ph-C), 131.3 (m-Mes-CH), 129.6 (m-Mes-
CH), 128.3 (p-Ph-CH), 128.1 (o-Ph-CH), 127.6 (m-Ph-CH), 124.0 (CH),
7.4-7.3 (m, 3H, m-Ph, CH), 6.86 (broad s, 3H, Mes-H, CH), 4.44 (t,
3J(HH)
¼
5.9 Hz, 2H, NCH2), 3.96 (dt, 3J(HH)
¼
5.7 Hz,
119.8 (CH), 97.8 (d, 2J(RhC)
¼
6.9 Hz, cod-CH), 97.2 (d,
3J(HH) ¼ 5.5 Hz, 2H, NHCH2), 2.34 (s, 3H, p-Mes-CH3), 1.69 (s, 6H, o-
2J(RhC) ¼ 7.3 Hz, cod-CH), 69.4 (d, 2J(RhC) ¼ 15 Hz, cod-CH), 67.3 (d,
2J(RhC) ¼ 14 Hz, cod-CH), 48.6 (NCH2), 38.1 (NHCH2), 34.7, 30.9,
29.6, 27.6 (cod-CH2), 21.1 (p-Mes-CH3), 19.3 (o-Mes-CH3), 17.9 (o-
Mes-CH3). Anal. Calcd. for C29H35N3ORhCl (579.97): C, 60.06; H,
6.08; N, 7.25. Found: C, 60.37; H, 6.36; N, 6.94.
Mes-CH3). 13C NMR (151 MHz, CD2Cl2):
d 181.7 (NCN), 167.3 (CO),
138.9 (p-Mes-C), 135.5 (i-Mes-C), 134.9 (o-Mes-C), 133.9 (p-Ph-H),
131.3 (i-Ph-H), 128.9 (m-Mes-CH), 128.2 (o-Ph-CH), 127.5 (m-Ph-
CH), 122.5 (CH), 121.8 (CH), 50.9 (NCH2), 40.0 (NHCH2), 20.8 (p-
Mes-CH3), 17.1 (o-Mes-CH3). 13C NMR (151 MHz, CD2Cl2):
d 181.8
(NCN), 167.3 (CO), 138.9 (p-Mes-C), 135.5 (i-Mes-C), 134.9 (o-Mes-
C), 133.9 (i-Ph-C), 131.3 (p-Ph-CH), 128.9 (m-Mes-CH), 128.2 (o-Ph-
CH), 127.5 (m-Ph-CH), 122.5 (CH), 121.8 (CH), 50.9 (NCH2), 40.0
(NHCH2), 20.8 (p-Mes-CH3), 17.1 (o-Mes-CH3).
Chlorido[(h
4-1,5-cyclooctadiene) ((1-(2-(4-methoxybenzamido))-
ethylene-3-(2,4,6-trimethylphenyl))-imidazol-2-ylidene)
rhodium(I)] 6
The product was obtained as a yellow microcrystalline solid in a
Chlorido[(1-(2-(4-methoxybenzamido))-ethylene-3-mesityl)-
imidazol-2-ylidene]silver(I) 4
yield of 96%. 1H NMR (600 MHz, CDCl3):
d
8.06 (d, 3J(HH) ¼ 6.7 Hz,
1H, NH), 7.94 (d, 3J(HH)
¼
8.9 Hz, 2H, aryl-H), 7.14 (d,
The product was obtained as a pale oil in a yield of >95%. 1H
3J(HH) ¼ 1.9 Hz, 1H, CH), 7.06 (broad s, 1H, Mes-H), 6.94 (broad s,
1H, Mes-H), 6.86 (d, 3J(HH) ¼ 8.9 Hz, 2H, aryl-H), 6.73 (d,
NMR (300 MHz, CD2Cl2):
d 9.0-8.0 (broad s, 1H, NH), 7.92 (d,
3J(HH) ¼ 8.5 Hz, 2H, aryl-H), 7.37 (d, 3J(HH) ¼ 1.7 Hz, 1H, CH), 6.88
(d, 3J(HH) ¼ 1.7 Hz, 1H, CH), 6.87 (d, 3J(HH) ¼ 8.5 Hz, 2H, aryl-H),
6.86 (s, 2H, Mes-H), 4.47 (t, 3J(HH) ¼ 6.3 Hz, 2H, NCH2), 3.96 (dt,
3J(HH) ¼ 6.3 Hz, 3J(HH) ¼ 6.3 Hz, 2H, NHCH2), 3.84 (s, 3H, OCH3),
2.34 (s, 3H, p-Mes-CH3),1.70 (s, 6H, o-Mes-CH3). 13C NMR (151 MHz,
3J(HH)
¼
1.9 Hz, 1H, CH), 5.99 (ddd, 3J(HH)
¼
13.7 Hz,
3J(HH) ¼ 11.9 Hz, 2J(HH) ¼ 5.1 Hz, 1H, NCH2), 4.81 (broad s, 2H, cod-
CH), 4.55 (m, 1H, NHCH2), 4.40 (ddd, 3J(HH)
¼
13.7 Hz,
3J(HH) ¼ 12.9 Hz, 2J(HH) ¼ 5.1 Hz, 1H, NCH2), 3.80 (s, 3H, OCH3),
3.78 (m, 1H, NHCH2), 3.53 (m, 1H, cod-CH), 3.03 (m, 1H, cod-CH),

200
S. Warsink et al. / Journal of Organometallic Chemistry 775 (2015) 195e201
2.45 (m, 1H, cod-CH2), 2.37 (s, 3H, p-Mes-CH3), 2.19 (s, 3H, o-Mes-
CH3), 2.16 (m, 1H, cod-CH2), 2.04 (m, 1H, cod-CH2), 1.97 (m, 1H, cod-
CH2), 1.85 (s, 3H, o-Mes-CH3), 1.84 (m, 1H, cod-CH2), 1.66 (m, 2H,
cod-CH2), 1.53 (m, 1H, cod-CH2), 1.49 (m, 1H, cod-CH2). 13C NMR
3J(RhC) ¼ 53 Hz, NCN), 172.6 (CO), 136.3 (o-Mes-C), 135.7 (i-Mes-C),
135.2 (o-Mes-C), 129.0 (m-Mes-CH), 128.8 (p-Ph-CH), 128.5 (m-
Mes-CH), 128.3 (o-Ph-CH), 126.7 (m-Ph-CH), 121.7 (CH), 120.8 (CH),
96.7 (d, 3J(RhC) ¼ 8.9 Hz, cod-CH), 89.1 (d, 3J(RhC) ¼ 8.1 Hz, cod-
CH), 71.6 (d, 3J(RhC) ¼ 11 Hz, cod-CH), 71.0 (d, 3J(RhC) ¼ 13 Hz,
cod-CH), 51.9 (NCH2), 45.6 (NeCH2), 34.1 (cod-CH2), 31.7 (cod-CH2),
29.9 (cod-CH2), 28.0 (cod-CH2), 20.9 (p-Mes-CH3), 17.9 (o-Mes-
CH3), 17.3 (o-Mes-CH3). Anal. Calcd. for C29H34N3ORh (543.51): C,
64.09; H, 6.31; N, 7.73. Found: C, 63.73; H, 6.36; N, 7.94.
(151 MHz, CDCl3):
d
182.4 (d, 1J(RhC) ¼ 53 Hz, NCN), 167.7 (CO),
162.0 (p-aryl-C), 138.0 (p-Mes-C), 136.9 (i-Mes-C), 135.9 (o-Mes-C),
134.0 (o-Mes-C), 129.6 (m-Mes-CH), 129.4 (o-aryl-CH), 128.3 (m-
Mes-CH), 126.2 (i-aryl-C), 123.9 (CH), 119.8 (CH), 113.3 (m-aryl-CH),
97.8 (d, 1J(RhC) ¼ 6.9 Hz, cod-CH), 97.2 (d, 1J(RhC) ¼ 7.3 Hz, cod-CH),
69.4 (d, 1J(RhC) ¼ 14 Hz, cod-CH), 67.2 (d, 1J(RhC) ¼ 14 Hz, cod-CH),
55.3 (OCH3), 48.7 (NCH2), 38.1 (NHCH2), 34.7, 30.9, 29.6, 27.6 (cod-
CH2), 21.1 (p-Mes-CH3), 19.4 (o-Mes-CH3), 17.9 (o-Mes-CH3). Anal.
Calcd. for C30H37N3O2RhCl (609.99): C, 59.07; H, 6.11; N, 6.89.
Found: C, 59.32; H, 6.28; N, 6.79.
(h
4-1,5-cyclooctadiene)[(1-(2-(4-methoxybenzamidato))-ethylene-
3-(2,4,6-trimethylphenyl))-imidazol-2-ylidene-
2C,N]rhodium(I) 10
k
The product was obtained as an orange solid in a yield of 93%.
d
1H NMR (600 MHz, CD2Cl2):
d
8.51 (d, 3J(HH) ¼ 8.7 Hz, 2H, o-Ar-
H), 7.20 (d, 3J(HH) ¼ 1.7 Hz, 1H, CH), 7.11 (broad s, 1H, Mes-H), 7.02
Chlorido[cis-dicarbonyl((1-(2-benzamido)-ethylene-3-(2,4,6-
trimethylphenyl))-imidazol-2-ylidene)rhodium(I)] 7
(broad s, 1H, Mes-H), 6.82 (d, 3J(HH) ¼ 8.7 Hz, 2H, m-Ar-H), 6.74 (d,
3J(HH)
¼
1.7 Hz, 1H, CH), 5.45 (ddd, 3J(HH)
¼
22.0 Hz,
The product was obtained as a yellow solid in a yield of 94%. 1H
3J(HH) ¼ 12.8 Hz, 2J(HH) ¼ 3.8 Hz, 1H, NCH2), 4.77 (m, 1H, NeCH2),
4.41 (m, 1H, NCH2), 3.84 (s, 3H, OCH3), 3.65 (m, 1H, cod-CH), 3.57
(m, 1H, NeCH2), 3.46 (m, 2H, cod-CH), 2.87 (m, 1H, cod-CH), 2.44 (s,
3H, p-Mes-CH3), 2.31 (m, 1H, cod-CH2), 2.03 (m, 1H, cod-CH2), 2.00
(s, 3H, o-Mes-CH3), 1.96 (m, 1H, cod-CH2), 1.87 (s, 3H, o-Mes-CH3),
1.82 (m, 1H, cod-CH2), 1.53 (m, 2H, cod-CH2), 1.40 (m, 1H, cod-CH2),
NMR (600 MHz, CDCl3):
d
7.85 (d, 3J(HH) ¼ 8.1 Hz, 2H, o-Ph-H), 7.56
(t, 3J(HH) ¼ 5.2 Hz, 1H, NH), 7.47 (t, 3J(HH) ¼ 7.4 Hz, 1H, p-Ph-H),
7.39 (dd, 3J(HH) ¼ 8.1 Hz, 3J(HH) ¼ 7.4 Hz, 2H, m-Ph-H), 7.28 (d,
3J(HH)
¼
1.7 Hz, 1H, CH), 6.97 (s, 2H, Mes-H), 6.90 (d,
3J(HH) ¼ 1.7 Hz,1H, CH), 4.79 (t, 3J(HH) ¼ 5.8 Hz, 2H, NCH2), 4.18 (dt,
3J(HH) ¼ 5.8 Hz, 3J(HH) ¼ 5.2 Hz, 2H, NHCH2), 2.36 (s, 3H, p-Mes-
1.24 (m, 1H, cod-CH2). 13C NMR (151 MHz, CD2Cl2):
d 180.0 (d,
CH3), 1.98 (s, 6H, o-Mes-CH3). 13C NMR (151 MHz, CDCl3):
d
184.8 (d,
2J(RhC) ¼ 54 Hz, NCN), 172.2 (CO), 160.4 (p-Ar-C), 139.2 (p-Mes-C),
136.5 (i-Mes-C), 135.7 (o-Mes-C), 134.3 (o-Mes-C), 130.0 (o-Ar-CH),
129.3 (m-Mes-CH), 128.5 (m-Mes-CH), 126.3 (i-Ar-C), 121.6 (CH),
120.8 (CH), 111.7 (m-Ar-CH), 96.8 (d, 2J(RhC) ¼ 8.6 Hz, cod-CH), 89.3
(d, 2J(RhC) ¼ 7.4 Hz, cod-CH), 71.5 (d, 2J(RhC) ¼ 12 Hz, cod-CH), 71.0
(d, 2J(RhC) ¼ 12 Hz, cod-CH), 55.2 (OCH3), 51.9 (NCH2), 45.6
(NeCH2), 34.2, 31.6, 30.0, 28.0 (cod-CH2), 20.9 (p-Mes-CH3), 17.8 (o-
Mes-CH3), 17.3 (o-Mes-CH3). Anal. Calcd. for C30H36N3O2Rh
(573.53): C, 62.82; H, 6.33; N, 7.33. Found: C, 62.49; H, 6.25; N, 6.99.
2J(RhC) ¼ 54 Hz, NCN), 182.0 (d, 2J(RhC) ¼ 75 Hz, CO), 175.3 (d,
2J(RhC) ¼ 53 Hz, CO), 168.0 (CO), 139.5 (p-Mes-C), 135.1 (i-Mes-C),
133.5 (o-Mes-C), 131.6 (p-Ph-CH), 131.1 (i-Ph-C), 129.3 (m-Mes-CH),
128.3 (o-Ph-CH), 127.3 (m-Ph-CH), 123.7 (CH), 121.9 (CH), 49.1
(NCH2), 38.6 (NHCH2), 21.2 (p-Mes-CH3), 18.1 (o-Mes-CH3). Anal.
Calcd. for C23H23N3O3RhCl (527.81): C, 52.34; H, 4.39; N, 7.96.
Found: C, 52.71; H, 4.76; N, 7.81.
Chlorido[cis-dicarbonyl((1-(2-(4-methoxybenzamido))-ethylene-3-
(2,4,6-trimethylphenyl))-imidazol-2-ylidene)rhodium(I)] 8
The product was obtained as a beige solid in a yield of 96%. 1H
Synthesis of chloridorhodium cyclooctadiene NHC complexes 5 and
6 from imidazolium salts
NMR (300 MHz, CDCl3):
d
7.82 (d, 3J(HH) ¼ 4.4 Hz, 2H, aryl-H), 7.45
(t, 3J(HH) ¼ 2.6 Hz,1H, NH), 7.27 (d, 3J(HH) ¼ 0.9 Hz,1H, CH), 6.97 (s,
To a suspension of 0.1 mmol imidazolium salt in dichloro-
methane was added 0.5 equivalent of [Rh(OMe) (cod)]2. The
resulting suspension was stirred overnight. The obtained yellow
solution was filtered over a pad of celite, and concentrated in vacuo
to yield the pure products 5 and 6 in a yield of 89 and 92%,
respectively.
2H, Mes-H), 6.89 (d, 3J(HH)
¼
0.9 Hz, 1H, CH), 6.87 (d,
3J(HH) ¼ 4.4 Hz, 2H, aryl-H), 4.77 (t, 3J(HH) ¼ 2.9 Hz, 2H, NCH2), 4.15
(dt, 3J(HH) ¼ 2.9 Hz, 3J(HH) ¼ 2.6 Hz, 2H, NHCH2), 3.83 (s, 3H,
OCH3), 2.36 (s, 3H, p-Mes-CH3), 1.99 (s, 6H, o-Mes-CH3). 13C NMR
(151 MHz, CDCl3):
d
184.8 (d, 2J(RhC) ¼ 54 Hz, NCN), 182.0 (d,
2J(RhC) ¼ 76 Hz, CO),175.2 (d, 2J(RhC) ¼ 44 Hz, CO),167.5 (CO),162.2
(p-aryl-C), 139.5 (p-Mes-C), 135.1 (i-Mes-C), 135.0 (o-Mes-C), 129.3
(m-Mes-CH), 129.1 (o-aryl-CH), 125.9 (i-aryl-C), 123.7 (CH), 121.9
(CH), 113.5 (m-aryl-CH), 55.4 (OCH3), 49.1 (NCH2), 38.5 (NHCH2),
21.1 (p-Mes-CH3), 18.1 (o-Mes-CH3). Anal. Calcd. for
X-ray structure determination for compounds 1, 5 and 6
The X-ray intensity data were collected at 100(2) K on a Bruker
X8 ApexII 4K Kappa CCD diffractometer equipped with an Oxford
C
24H25N3O4RhCl (557.83): C, 51.67; H, 4.52; N, 7.53. Found: C, 52.02;
Crystream cooling unit, using graphite monochromated MoKa ra-
H, 4.91; N, 7.15.
diation. Images were collected at 20 s (1), 10 s (5) and 60 s (6)
exposure time per image respectively. Data collection strategies
were calculated with the program APEX2 [27]. Data reduction and
cell refinement were performed with the SAINT-Plus package [27].
The data were corrected for absorption using the SADABS program
[28]. Using the program suite WinGX [29], the structures were
solved by Patterson interpretation and phase expansion using
SHELXL97, and refined with full-matrix least squares on F2 using
SHELXL97 [30]. All non-hydrogen atoms were refined anisotropi-
cally and all hydrogen atoms were fixed at calculated positions
except for the NH hydrogen-atoms, which were located in the
Fourier maps and refined; all of them were given an overall
isotropic thermal parameter. Additional details regarding data
collection are provided in the CIF files. Full crystallographic data
have been deposited at the Cambridge Crystallographic Data
Centre.
(h
4-1,5-cyclooctadiene)[(1-(2-benzamidato)-ethylene-3-(2,4,6-
trimethylphenyl))-imidazol-2-ylidene-
2C,N]rhodium(I) 9
k
The product was obtained as an orange solid in a yield of 94%. 1H
NMR (600 MHz, CD2Cl2): 8.49 (d, 3J(HH) ¼ 6.9 Hz, 2H, o-Ph-H), 7.38
(t, 3J(HH) ¼ 7.3 Hz, 1H, p-Ph-H), 7.31 (dt, 3J(HH) ¼ 7.3 Hz,
3J(HH) ¼ 6.9 Hz, 2H, m-Ph-H), 7.21 (d, 3J(HH) ¼ 1.7 Hz, 1H, CH), 7.12
(broad s, 1H, Mes-H), 7.02 (broad s, 1H, Mes-H), 6.75 (d,
3J(HH) ¼ 1.7 Hz, 1H, CH), 5.45 (m, 1H, NCH2), 4.76 (m, 1H, NeCH2),
4.42 (m, 1H, NCH2), 3.65 (m, 1H, cod-CH), 3.59 (m, 1H, NeCH2), 3.47
(m, 2H, cod-CH), 2.73 (m, 1H, cod-CH), 2.46 (m, 1H, cod-CH2), 2.44
(s, 3H, p-Mes-CH3), 2.10 (m, 1H, cod-CH2), 2.00 (s, 3H, o-Mes-CH3),
1.98 (m, 1H, cod-CH2), 1.91 (s, 3H, o-Mes-CH3), 1.80 (m, 1H, cod-
CH2), 1.59 (m, 1H, cod-CH2), 1.52 (m, 1H, cod-CH2), 1.29 (m, 1H, cod-
CH2), 1.20 (m, 1H, cod-CH2). 13C NMR (151 MHz, CD2Cl2):
d 179.1 (d,

S. Warsink et al. / Journal of Organometallic Chemistry 775 (2015) 195e201
201
c) R.J. Adcock, D.H. Nguyen, S. Ladeira, C. Le Berre, P. Serp, P. Kalck, Inorg.
Chem. 51 (2012) 8670;
d) G.L. Williams, C.M. Parks, C.R. Smith, H. Adams, A. Haynes, A.J.H.M. Meijer,
G.J. Sunley, S. Gaemers, Organometallics 30 (2011) 6166;
e) J. Rankin, A.C. Benyei, A.D. Poole, D.J. Cole-Hamilton, J. Chem. Soc. Dalton
Trans. (1999) 3771;
f) L. Gonsalvi, H. Adams, G.J. Sunley, E. Ditzel, A. Haynes, J. Am. Chem. Soc. 124
(2002) 13597;
g) L. Gonsalvi, J.A. Gaunt, H. Adams, A. Castro, G.J. Sunley, A. Haynes, Organ-
ometallics 22 (2003) 1047.
Crystal data for (1-(2-benzamido)-ethylene-3-mesityl)-imidazolium
chloride 1
ꢀ
369.88, triclinic, space group Pı,
[C21H24N3O]Cl,
M
¼
a ¼ 7.0950(5) Å, b ¼ 7.8294(6) Å, c ¼ 17.3969(14) Å,
a
¼ 98.292(4)ꢁ,
b
m
¼ 90.401(4)ꢁ,
g
¼ 98.021(4) ꢁ, V ¼ 946.53(13) Å3, Z ¼ 2,
¼ 0.22 mmꢀ1, F(000) ¼ 392.0, T ¼ 100(2) K, 10878 measured
reflections, 4032 independent (Rint
¼
0.040), R1
¼
0.0442,
wR2 ¼ 0.1139 for I > 2
s
(I).
[4] A. Brink, A. Roodt, G. Steyl, H.G. Visser, Dalton Trans. 39 (2010) 5572.
[5] a) J.A. Venter, J.G. Leipoldt, R. van Eldik, Inorg. Chem. 30 (1991) 2207;
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Crystal data for chlorido[(
h
4-1,5-cyclooctadiene) ((1-(2-benzamido)-
ethylene-3-(2,4,6-trimethylphenyl))-imidazol-2-ylidene)rhodium(I)]5
ꢀ
RhC29H35ClN3O, M ¼ 579.96, triclinic, space group Pı, a ¼ 8.5310
(5) Å, b ¼ 12.3359 (7) Å, c ¼ 12.9324 (8) Å,
a
¼ 94.8118 (17)ꢁ,
b
m
¼ 98.5242 (18)ꢁ,
g
¼ 103.4192 (18)ꢁ, V ¼ 1299.26 (13) Å3, Z ¼ 2,
b) S. Warsink, R.M. Drost, M. Lutz, A.L. Spek, C.J. Elsevier, Organometallics 29
(2010) 3109.
¼ 0.79 mmꢀ1, F(000) ¼ 600.0, T ¼ 100(2) K, 15237 measured
reflections, 6166 independent (Rint
¼
0.021), R1
¼
0.0234,
[8] a) W. Gil, A.M. Trzeciak, Coord. Chem. Rev. 255 (2011) 473;
b) J.M. Praetorius, C.M. Crudden, Dalton Trans. 37 (2008) 4079;
c) M.S. Datt, J.J. Nair, S. Otto, J. Organomet. Chem. 690 (2005) 3422;
d) A.R. Chianese, X. Li, M.C. Janzen, J.W. Faller, R.H. Crabtree, Organometallics
22 (2003) 1663.
wR2 ¼ 0.0601 for I > 2
s
(I).
Crystal data for chlorido[(
h
4-1,5-cyclooctadiene) ((1-(2-(4-methoxy-
[9] H.C. Martin, N.H. James, J. Aitken, J.A. Gaunt, H. Adams, A. Haynes, Organo-
metallics 22 (2003) 4451.
[10] J.M. Wilson, G.J. Sunley, H. Adams, A. Haynes, J. Organomet. Chem. 690 (2005)
6089.
[11] a) A. Roodt, H.G. Visser, A. Brink, Cryst. Rev. 17 (2011) 241;
b) M. Schutte, G. Kemp, H.G. Visser, A. Roodt, Inorg. Chem. 50 (2011) 12486;
c) M. Schutte, A. Roodt, H.G. Visser, Inorg. Chem. 51 (2012) 11996.
[12] a) H. Jong, B.O. Patrick, M.D. Fryzuk, Can. J. Chem. 86 (2008) 803;
b) W.B. Cross, C.G. Daly, Y. Boutadla, K. Singh, Dalton Trans. 40 (2011) 9722.
[13] a) L. Busetto, M.C. Cassani, C. Femoni, M. Mancinelli, A. Mazzanti, R. Mazzoni,
G. Solinas, Organometallics 30 (2011) 5258;
benzamido))-ethylene-3-(2,4,6-trimethylphenyl))-imidazol-2-ylidene
rhodium(I)] 6
2(C30H37ClN3O2Rh) $ CHCl3, M ¼ 1339.34, triclinic, space group
ꢀ
Pı, a ¼ 13.2793 (15) Å, b ¼ 13.7014 (15) Å, c ¼ 17.1427 (17) Å,
a
¼ 90.783 (6)ꢁ,
b
¼ 106.881 (6)ꢁ,
g
¼ 98.826 (6)ꢁ, V ¼ 2943.7 (6) Å3,
Z ¼ 2,
m
¼ 0.84 mmꢀ1, F(000) ¼ 1380.0, T ¼ 100(2) K, 36281
measured reflections,13825 independent (Rint ¼ 0.117), R1 ¼0.0714,
wR2 ¼ 0.2305 for I > 2
s(I).
b) C.-Y. Liao, K.-T. Chan, J.-Y. Zeng, C.-H. Hu, C.-Y. Tu, H.M. Lee, Organome-
tallics 26 (2007) 1692;
General procedure for oxidative addition IR experiments
c) Y. Unger, T. Strassner, J. Organomet. Chem. 713 (2012) 203.
[14] P.L. Arnold, S.H. Mungur, A.J. Blake, C. Wilson, Angew. Chem. Int. Ed. 42 (2003)
5981.
[15] J. Liu, J. Chen, J. Zhao, Y. Zhao, L. Li, H. Zhang, Synthesis (2003) 2661.
[16] W.-J. Yoo, C.-J. Li, J. Am. Chem. Soc. 128 (2006) 13064.
[17] a) D.B. Bagal, R.A. Watile, M.V. Khedkar, K.P. Dhake, B.M. Bhanage, Catal. Sci.
Technol. 2 (2012) 354;
In two separate volumetric flasks, dichloromethane solutions of
the rhodium NHC complex (10 mmol/L) and iodomethane (1 mol/L)
were prepared. After mixing 250 mL of each solution in a NaCl-cell,
the reaction was followed by FT-IR.
ꢁ
ꢁ
ꢁ
b) G. Lazaro, M. Iglesias, F.J. Fernandez-Alvarez, P.J. Sanz Miguel, J.J. Perez-
Torrente, L.A. Oro, ChemCatChem 5 (2013) 1133.
Acknowledgements
[18] a) H.M.J. Wang, I.J.B. Lin, Organometallics 17 (1998) 972;
ꢁ
b) H.-L. Su, L.M. Perez, S.-H. Lee, J.H. Reibenspies, H.S. Bazzi, D. Bergbreiter,
The authors thank the South African NRF and THRIP, the Uni-
versity of the Free State Research Fund and the Materials and
Nanosciences Research Cluster for financial support. The views
expressed do not necessarily represent that of the NRF.
Organometallics 31 (2012) 4063;
c) A. Biffis, M. Cipani, C. Tubaro, M. Basato, M. Costante, E. Bressan, A. Venzo,
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