N-heterocyclic carbene complexes of Rh(I) and electronic effects on catalysts for 1,2-addition of phenylboronic acid to aldehydes

Article abstract of DOI:10.1002/aoc.1746

1,3-Diarylsubstituted imidazolinium salts, (NHC-H)Cl, 3, containing hydrogen or alkyl groups at the 4,5-positions of the imidazolidine ring, served as precursors to rhodium(I) complexes [RhCl(NHC)COD], 4, which were converted into cis-[RhCl(NHC)(CO)₂] complexes, 5. All compounds prepared were characterized by elemental analyses, ¹H NMR and ¹³C NMR. The relative σ-donor/π-acceptor strength of the NHC ligands was determined by means of IR spectroscopy of 5. The ability of NHCs in 4 to enchance activity was explored in the 1,2-addition of phenylboronic acid to aldehydes. A good correlation was observed between catalytic activity and the electron-donating power of the NHC ligands.

Full text of DOI:10.1002/aoc.1746

Full Paper
Received: 28 May 2010
Revised: 22 September 2010
Accepted: 22 September 2010
Published online in Wiley Online Library: 12 December 2010
(wileyonlinelibrary.com) DOI 10.1002/aoc.1746
N-heterocyclic carbene complexes of Rh(I)
and electronic effects on catalysts
for 1,2-addition of phenylboronic acid
to aldehydes
Hayati Tu¨rkmen∗ and Bekir C¸etinkaya
1,3-Diarylsubstituted imidazolinium salts, (NHC-H)Cl, 3, containing hydrogen or alkyl groups at the 4,5-positions of the
imidazolidine ring, served as precursors to rhodium(I) complexes [RhCl(NHC)COD], 4, which were converted into cis-
[RhCl(NHC)(CO)2] complexes, 5. All compounds prepared were characterized by elemental analyses, 1H NMR and 13C NMR. The
relative σ-donor/π-acceptor strength of the NHC ligands was determined by means of IR spectroscopy of 5. The ability of NHCs
in 4 to enchance activity was explored in the 1,2-addition of phenylboronic acid to aldehydes. A good correlation was observed
c
between catalytic activity and the electron-donating power of the NHC ligands. Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Supporting information may be found in the online version of this article.
Keywords: arylation; diarylmethanol; rhodium; electronic effects; imidazol-2-ylidene; NHC
Introduction
Results and Discussion
Synthesis and Characterization of Ligand Precursors
and Complexes
During the last 15 years, the synthesis and applications of
N-heterocyclic carbene (NHC) complexes have witnessed an
explosive growth.[1–9] Among the NHC ligands studied, imidazol-
2-ylidene and its saturated analog imidazolin-2-ylidene are the
most common and they are now known as normal NHCs which
are good σ-donors, but weak π-acceptors.[10] As a result, NHCs
are often compared with phosphines for catalytic reactions.
It has been established that the complexes such as I offer
the distinctive advantage of greater stability over the classical
M/phosphine systems as the latter suffer from sensitivity to air,
moisture and heating.[1] Furthermore, the structure of the NHC
ligands can be altered by a modular approach. The preparation
procedures developed allow multiple variations in the nature
of the substituents on the nitrogen and carbon atoms on the
ring.[11]
In a recent study on the complexes (I), we observed that
the variation of the p-substituents (X) has a significant influence
on the catalytic behavior of the Suzuki coupling of NHC–Pd
complexes.[12] Only a few references referring to 4,5-substituted
imidazol(in)-2-ylidene ligands can be found in the literature.[13]
On the other hand, the rhodium-catalyzed 1,2-addition of aryl
boronic acids has also enjoyed significant development: in situ
formed and preformed NHC complexes of rhodium have been
successfully applied to 1,2-arylations of aldehydes.[14,15] However,
some questions concerning the influence of steric and electronic
properties of the NHC ligands remain unanswered and deserve a
detailed examination. Therefore, the main aim of this paper was
to modify the p-substituent of the aryl moiety (ring A) and 4,5-
position of of the imidazolidine (ring B) to quantify the electronic
influence of X, R and R’ substituents on the catalytic activities of II
(Scheme 1).
The structures of NHC complexes can be modified in several
ways to tune their electronic properties, which are important
for homogeneous catalysis.[1] The desired NHC precursors (3) and
Rh(I)complexes(4)derivedfromthemweresynthesizedaccording
to Scheme 2. Apart from these complexes, unsymmetrical aryl
containing NHC complex (4i) was also included for comparison.
Acombinationofcommerciallyavailableanilinesand1,2-diones
with varying steric and electronic substituents was used to obtain
diimines (1), which were reduced to diamines (2) by means of
NaBH3CN and than the diamines were cyclized into imidazolinium
chlorides (3) via CH(OEt)3 in the presence of chloride. These salts
were deprotonated by [Rh(µ-OMe)COD]2 to afford the (NHC)-
Rh(I) complexes, 4 (Scheme 2). The resulting compounds, which
contain hydrogen, alkyl or a combination of these groups on the
C4 –C5 positions of the imidazolidine ring and aryl groups on the
nitrogen atoms, were characterized by 1H NMR and 13C NMR.
The 1H NMR spectra of these salts exhibit characteristic NHC-H
resonance around δ = 9.72–9.82 ppm. The formation of the salts
is also supported by a resonance around δ = 158.0–159.9 ppm in
the 13C NMR spectrum for the NHCN carbon atom.
The structurally and sterically similar 1,3-bis(2,6-dimethyl-
phenyl)imidazolinium salts containing H, CH3, Br and Cl groups
are known in the literature.[12] Rh–NHC complex (4) was obtained
∗
Correspondence to: Hayati Tu¨rkmen, Department of Chemistry, Ege University,
35100 Bornova-Izmir, Turkey. E-mail: hayati.turkmen@ege.edu.tr
Department of Chemistry, Ege University, 35100 Bornova-Izmir, Turkey
c
Appl. Organometal. Chem. 2011, 25, 226–232
Copyright ꢀ 2010 John Wiley & Sons, Ltd.

N-heterocyclic carbene complexes of Rh(I)
R
R'
B
N
N
N
N
A
PdLm
RhLn
X
X
X
X
II
I
Scheme 1. Structural ring represantation of NHCs and N-substitents.
Ar
Ar
Ar
R
R
R
R
NH
N
N
+
O
O
-
(iii)
(i)
(ii)
Cl
NH
Ar
2
N
Ar
1
R'
N
R'
R'
R'
Ar
(NHC-H)Cl,
3
Ar
N
Ar
N
CO
R
R
(iv)
(v)
Rh
(NHC-H)Cl,
3
Rh
CO
N
R'
R'
N
Cl
Cl
Ar
Ar
5
4
c
f
i
a
b
d
g
h
e
CH3
H
CH3
CH3
CH3
Br
Cl
CH3
CH3
Ar
:
R
:
:
Me
Me
Me
Et
2035
Me
H
H
H
H
H
H
H
H
H
Pr
R'
H
Me
H
CO(cm-1)*: 2037
2036
2035
2040
2038
2043
2051
2039
Scheme 2. Synthesis of imidazolinium salts, 3, rhodium complexes, 4 and 5, and average carbonyl stretching wavenumbers (cm−1) of 5 in CH2Cl2. The
asterisk refers to the average carbonyl stretching frequencies of 5. Reagent and conditions: (i) Ar–NH2, EtOH, RT; (ii) NaCNBH3, MeOH, RT, 24 h, after 65 ◦C,
8 h; (iii) NH4Cl, HC(OEt)3, 130 ◦C, 4 h; (iv) [(Rh(OMe)(COD)]2, PhCH3, 110 ◦C, 2 h; (v) CO, CH2Cl2, 0.5 h.
throughreactionofimidazoliniumsalt(3)usingthebasiccharacter
of [Rh(µ-OMe)(COD)]2. Rhodium complexes are stable crystalline
substances, the structures of which have been elucidated by
NMR spectroscopy. 13C chemical shifts, which provide a useful
steric effects. The C–O stretching frequencies in [RhCl(NHC)(CO)2]
complexes which derived from 4 are sensitive to the substituent
at the p-position of the phenyl ring of the 1,3-disubstituted
imidazolidine ring if we ignore the contribution of the C4 –C5
substitution. The ν(CO)av data, given in Scheme 2, indicate that the
basicity decreases in the following order: d = c > b > a > i >
f > e > g > h. However, the backbone alkyl substituents on
the imidazolin-2-ylidene ring also significantly increase the donor
ability. This observation is consistent with the literaturedata.[20g]
The 13C NMR spectra of cis-[RhCl(CO)2NHC] complexes (5) gave
a carbenic signal at 205.7–206.8 ppm as a doublet. Coupling
constants J(13C–103Rh) for 5 are in the range 41–42 Hz.
diagnostic tool for Rh–carbene complexes, show that Ccarb is
13
substantially deshielded. Values of δ(
δ = 209.6–215.2 ppm.
C
) are in the range
carb
Direct comparison of the electronic properties of NHCs could
be done measuring the carbonyl stretching frequencies of
NHC-containing carbonyl complexes such as [(NHC)-Ni(CO)3],
[RhX(NHC)(CO)2] or [IrX(NHC)(CO)2]: more basic ligands induce
lower stretching frequencies.[16–21] Thus, the carbonyl complexes
of type 5 have been synthesized by replacing the COD ligand with
excess CO.
Catalytic Experiments
The IR spectra of the complexes allowed us to evaluate
simultaneously subtle electronic influence of H, Me, Br and Cl
as well as R and Rꢁ groups without possible complications due to
Catalyst testing was conducted in order to access the effects of
X, R, Rꢁ substituents on the NHC ligands to catalyze arylation of
c
Appl. Organometal. Chem. 2011, 25, 226–232
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
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H. Tu¨rkmen and B. C¸etinkaya
Table 1. Rhodium–carbene catalyzed addition of phenylboronic acid to aldehydes
OH
O
H
4(1%), DMF/ water,
80 °C, 4 h
C
H
B(OH)2
+
Rn
R
n
Entry
4
Aldehyde
Yield (%)a
1
2
3
4
5
6
7
8
9
a
b
c
89
90
91
90
78
90
66
65
43
O
H
H3CO
d
e
f
g
h
i
10
11
12
13
14
15
16
17
18
a
b
c
84
90
91
87
82
89
63
60
45
O
H
Cl
d
e
f
g
h
i
19
20
21
22
23
24
25
26
27
a
b
c
83
94
94
93
80
93
67
58
37
CH3
CH3
O
H
H3C
d
e
f
g
h
i
28
29
30
31
32
33
34
35
36
a
b
c
93
92
90
89
79
88
64
61
33
H3CO
H3CO
O
d
e
f
H
H3CO
g
h
i
a Yields were determined by gas chromatography for an average of three runs.
aldehydes using PhB(OH)2 as source of aryl and the products
were analyzed by GC. For the sake of comparison, the previously
used conditons were chosen: the addition of phenylboronic acid
to aromatic aldehydes with 1 mol% of catalyst 4 in the presence
of KOBut –PhB(OH)2 (1 : 2) in DMF–H2O (3 : 1) was screened at
80 ◦C. The data in Table 1 reveal that complexes 4a–4d and
4f are efficient and the relative activity sequence after 4 h is
b ≈ c ≈ d ≈ a ≈ f > e > g > h > i. The activities of the different
catalysts (Table 1) range from 33% for catalyst 4i up to 94% for
catalysts 4a–4d. The addition of phenylboronic acid to aldehydes
proceeded in high yields and quite rapidly, even with a low cat-
alyst loading. Under those conditions, 4-methoxybenzaldehyde,
2,4,6-trimethylbenzaldehyde, 3,4,5-trimethoxybenzaldehyde and
4-chlorobenzaldehyde reacted cleanly to good yields (Table 1,
entries 3, 12, 20, 21 and 29). We could show that electron-rich and
bulky NHC ligands lead to a higher activity with yields up to 94%.
Compound 4b appears to be the most active catalyst; but 4a,
bearing one Me at the 4-position, is similar to SIMes (4f). This
sequence can be explained on the basis of electron-donating
groups present both at the p-position of the aryl and the 4,5-
positions of the imidazolidine rings. It is clear that the alkyls as
electron releasing groups increase the rate of arylation. The length
of the alkyl chain at the 4,5-positions seems not to be influential.
The 2,4-dimethyl derivative 4i, an isomer of 4e, exhibited the
lowest activity of the nine complexes tested. A similar trend was
observed in the NHC-Pd catalyzed Suzuki–Miyaura coupling.[12]
c
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Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2011, 25, 226–232

N-heterocyclic carbene complexes of Rh(I)
This observation again stresses the importance of steric factors as
well as electronic parameters.
Withtheexceptionof 4iand4f, comparisonof boththecatalytic
activity of [RhCl(NHC)COD] and IR data on [RhCl(NHC)(CO)2] clearly
demostrated that there is a good correlation between electron
donation power and catalytic effciency.
The compound 1d was prepared in the same way as 1a from
2,4,6-trimethylaniline (2.0 g, 14.8 mmol) and 2,3-hexanedione
(0.84g, 7.4 mmol) to give yellow crystals of 1d. Yield: 2.34 g,
1
91%. H NMR (400 MHz, CDCl3): δ 6.90 (s, 2 H, Ar–H), 6.88 (s, 2
H, Ar–H), 2.51 (t, 2 H, J = 4.0 Hz, N CCH2CH2CH3), 2.30 (s, 3 H,
N
CCH3), 2.02 (s, 18 H, Ar–CH3), 1.53 (m, 2 H, N CCH2CH2CH3),
0.84 (t, 3 H J = 3.9 Hz, N CCH2CH2CH3). 13C NMR (100 MHz,
CDCl3): δ 171.8, 167.8 (N C) 145.9, 145.3, 132.3, 132.2, 128.9,
128.5,124.6,124.5(Ar–C),31.1(N CCH2CH2CH3),20.7(N CCH3),
20.6 (N CCH2CH2CH3), 17.9, 17.8, 17.4, 16.3 (Ar–CH3), 14.5
(N CCH2CH2CH3). Anal. calcd for C24H32N2 (M = 334.5): C, 82.71;
H, 9.25; N, 8.04. Found: C, 82.72; H, 9.31; N, 8.08%.
Conclusion
The electronic effect of substituents on the 1,2-addition reaction
rateofphenylboronicacidtoaldehydeswasstudiedbyvaryingthe
substituents in both rings (i.e. A and B of NHC, in structure II). The
general trend observed in most cases was that electron releasing
groups increased the efficiency while electron–withdrawing
groups retarded the reaction rate. The X group on the phenyl
ring had a significant influence wheras the R and Rꢁ groups at
the 4,5-positions of the imidazolidine ring appeared to play a less
important role in the complex’s catalytic activity. In particular,
4b and 4c bearing methyl, ethyl at the C4 –C5 positions of the
imidazolidine ring showed better catalytic activity. These studies
allowed us to compare the p-position of the phenyl ring of the
1,3-disubstituted imidazolidin ring and the C4 –C5 positions of the
imidazolidine ring.
General Procedure for 2
A suspension of 1 (12.5 mmol) in MeOH (50 ml) was treated at
room temparature under argon with NaCNBH3 (3.92 g, 62.5 mmol)
in portions of 1 g over a period of 20 min. To the mixture was
added bromo cresole green until a color change from green to
yellow occurred, then 0.1 M HCl was added to the solution which
was stirred for 24 h and heated subsequently for 8 h under reflux.
It was cooled to room temparature and 0.1 M (15 ml) KOH solution,
100 ml H2O and CH2Cl2 were added. The water phase was washed
with CH2Cl2 for a few more times. After the washing steps all
of the CH2Cl2 phases were combined and dried with MgSO4.
The solvent was concentrated and then ethanol was added. The
precipitate was filtered and washed with ethanol. Drying under
vacuum provided NMR spectroscopically pure off-white crystals of
2.
Based on CO IR streching frequencies, the following complexes
can be ranked from most electron-rich to least: d = c > b > a >
i > f > e > g > h.
2a. Yield: 3.93 g, 88%. 1H NMR (400 MHz, CDCl3): δ 6.82 (br, 2 H,
Ar–H), 6.74 (br, 2 H, Ar–H), 3.29 [m, 1 H, N(CH3)CHCH2N], 3.20 [m,
2 H, N(CH3)CHCH2N], 2.23, 2.17, 2.14, 1.94 (s, 18 H, Ar–CH3), 1.17
[d, 3 H J = 3.0 Hz, N(CH3)CHCH2N]. 13C NMR (100 MHz, CDCl3): δ
172.4, 167.3 (N C) 146.1, 140.6, 131.9, 131.3, 128.4, 128.0, 125.1,
124.7 (Ar–C), 53.0, 51.9 [N(CH3)CHCH2N], 17.9, 17.8, 17.7, 16.7, 15.9
[Ar–CH3, N(CH3)CHCH2N]. Anal. calcd for C21H30N2 (M = 310.5): C,
81.24; H, 9.74; N, 9.02. Found: C, 81.22; H, 9.80; N, 9.16%.
Experimental
All reactions for the preparation of salts were carried out under
Ar in flame-dried glassware using standard Schlenk-type flasks.
Anhydrous solvents were either distilled from appropriate drying
agents or purchased from Merck and degassed prior to use by
purging with dry argon and standing over molecular sieves. NMR
spectra were recorded at 297 K on a Varian Mercury AS 400 at
400 MHz (1H), 100.56 MHz (13C). Elemental analyses were carried
out using the analytical service of Tubıtak with a Carlo Erba Stru-
mentazione Model 1106 apparatus. Rhodium comlexes derived
from 3b were recently published.[16] The other compounds were
prepared according to the literature procedures.[12,16]
1
2c. Yield: 3.94 g, 87%. H NMR (400 MHz, CDCl3): δ 6.84 (br, 2
H, Ar–H), 3.29–3.14 [m, 2 H, N(CH3)CHCH(CH2CH3)N], 2.23, 2.17,
2.14, 1.94 (s, 18 H, Ar–CH3), 1.83 [m, 2 H, N(CH3)CHCH(CH2CH3)N],
1.18 [d, 3 H, J = 3.3 Hz, N(CH3)CHCH(CH2CH3)N], 1.05 [t, 3 H,
J = 3.4 Hz, N(CH3)CHCH(CH2CH3)N]. 13C NMR (100 MHz, CDCl3): δ
172.7, 167.6 (N C) 146.0, 145.6, 132.4, 132.3, 128.7, 128.6, 124.6,
124.5 (Ar–C), 52.9, 51.7 [N(CH3)CHCH(CH2CH3)N], 22.2, 20.7, 17.9,
17.8, 17.7, 16.7, 11.4 [Ar–CH3, N(CH3)CHCH(CH2CH3)N]. Anal. calcd
forC23H34N2 (M= 338.5):C, 81.60;H, 10.12;N, 8.28. Found:C, 81.62;
H, 10.15; N, 8.36%.
2d. Yield: 3.74 g, 85%. 1H NMR (400 MHz, CDCl3): δ 6.77 (br,
4 H, Ar–H), 3.28–3.24 [m, 2 H, HN(CH3)CHCH(CH2CH2CH3)NH],
2.96 (br, 2 H, NH), 2.23, 2.18, 2.12 (s, 18 H, Ar–CH3), 1.40–1.38 [m,
4 H, HN(CH3)CHCH(CH2CH2CH3)NH], 1.14 [d, 3 H, J = 3.3 Hz, HNCH
(CH3)CH(CH2CH2CH3)NH], 1.05 [t, 3 H J = 3.4 Hz, HN(CH3)CHCH
(CH2CH2CH3)NH]. 13C NMR (100 MHz, CDCl3): δ 140.1, 129.6, 129.5,
129.4, 128.5 (Ar–C), 59.9, 54.1 [HN(CH3)CHCH(CH2CH2CH3)NH),
33.7, 20.5, 20.4, 20.2, 19.1, 18.6, 18.6 [HN(CH3)CHCH(CH2CH2CH3)
NH, Ar–CH3], 16.9 [HN(CH3)CHCH(CH2CH2CH3)NH], 14.4 [HN(CH3)
CHCH(CH2CH2CH3)NH]. Anal. calcd for C24H36N2 (M = 352.6): C,
81.76; H, 10.29; N, 7.95. Found: C, 81.72; H, 10.31; N, 8.03%.
1a. To a solution of 2,4,6-trimethylaniline (2.0 g, 14.8 mmol) in
100 ml ethanol was added at 25 ◦C a mixture of a 35% aqueous
solution of methylglyoxal (0.54 g, 7.4 mmol). The resulting yellow
precipiate was collected by filtration and dried in vacuum. Yield:
2.08 g, 92%. 1H NMR (400 MHz, CDCl3): δ 8.05 (s, 1 H, N CH) 6.92
(s, 2 H, Ar–H), 6.90 (s, 2 H, Ar–H), 2.30, 2.22, 2.17, 2.03, 2.01 (s, 21
H, N CCH3, Ar–CH3). 13C NMR (100 MHz, CDCl3): δ 164.5 (N C)
145.0, 128.8, 128.7, 128.5, 128.4, 126.6, 124.5 (Ar–C), 20.7, 20.6,
18.1, 17.6 (Ar–CH3), 14.9 (N CCH3). Anal. calcd for C21H26N2 (M =
306.4): C, 82.31; H, 8.55; N, 9.14. Found: C, 82.32; H, 8.52; N, 9.18%.
The compound 1c was prepared in the same way as 1a
from2,4,6-trimethylaniline(2.0 g,14.8 mmol)and2,3-pentandione
(0.82 g, 7.4 mmol) to give yellow crystals of 1c. Yield: 2.18 g, 88%.
1H NMR (400 MHz, CDCl3): δ 6.90 (s, 2 H, Ar–H), 6.89 (s, 2 H, Ar–H),
2.55 (q, 2 H, J = 3.3 Hz, N CCH2CH3), 2.29 (s, 3 H, N CCH3),
2.03, 2.02, 2.00, 1.94 (s, 18 H, Ar–CH3), 1.06 (t, 3 H, J = 3.3 Hz,
N
CCH2CH3). 13C NMR (100 MHz, CDCl3): δ 172.7, 167.6 (N C)
146.0, 145.6, 132.4, 132.3, 128.7, 128.6, 124.6, 124.5 (Ar–C), 22.2
(NCH3), 20.7 (N CCH2CH3), 17.9, 17.8, 17.7, 16.7 (Ar–CH3), 11.4
(N CCH2CH3). Anal. calcd for C23H30N2 (M = 334.5): C, 82.59; H,
9.04; N, 8.37. Found: C, 82.62; H, 9.01; N, 8.38%.
General Procedure for 3
A mixture of 2 (10 mmol), triethyl orthoformate 10 ml and
ammonium chloride (0.54 g, 10.2 mmol) was heated at 130 ◦C
c
Appl. Organometal. Chem. 2011, 25, 226–232
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
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H. Tu¨rkmen and B. C¸etinkaya
in a distillation apparatus until ethanol distillation ceased. After
cooling to RT, to the reaction mixture was added 50 ml diethyl
ether. A colorless solid precipitated which was collected by
filtration. Purification was achieved by repeated recrystallizations
from ethanol–ether.
3a. Yield: 3.35 g, 92%. 1H NMR (400 MHz, CDCl3): δ 9.72 (s,
1 H, NCHN) 6.88 (s, 2 H, Ar–H), 6.86 (s, 2 H, Ar–H), 5.07–4.79
(m, 1 H, NCHCH3CH2N), 4.74 (m, 1 H, NCHCH3CH2N), 3.84 (m,
1 H, NCHCH3CH2N), 2.33, 2.29, 2.23, 2.22 (s, 18 H, Ar–CH3),
1.41 (s, 3 H, NCHCH3CH2N). 13C NMR (100 MHz, CDCl3): δ 159.6
(NCHN) 140.8, 139.9, 135.6, 134.8, 130.0, 129.9, 129.7, 128.5 (Ar–C),
60.1 (NCHCH3CH2N), 58.0 (NCHCH3CH2N), 20.9, 20.8, 18.8, 18.2
(Ar–CH3), 17.8 (NCHCH3). Anal. calcd for C22H29N2Cl (M = 356.9):
C, 74.03; H, 8.19; N, 7.85. Found: C, 74.02; H, 8.22; N, 7.92%.
3c. Yield: 3.35 g, 88%. 1H NMR (400 MHz, CDCl3): δ 9.80 (s, 1 H,
NCHN), 6.90 (s, 2 H, Ar–H), 6.87 (s, 2 H, Ar–H), 5.12–5.07 [m, 2 H,
N(CH3)CHCH(CH2CH3)N], 3.84 [m, 2 H, N(CH3)CHCH(CH2CH3)N],
138.7, 138.5, 129.8, 129.5, 127.7, 126.9, 126.7, 124.0 (Ar–C), 96.0,
66.9 (COD–CH), 53.4, 52.0 [N(CH3)CHCH(CH2CH3)N], 31.9, 28.3
(COD–CH2), 19.8, 19.0, 18.7, 17.7, 17.0, 16.3, 15.3, 14.9, 14.0
[Ar–CH3, N(CH3)CHCH(CH2CH3)N]. Anal. calcd for C33H48ClN2Rh
(M = 595.1): C, 64.59; H, 7.45; Cl,5.96; N, 4.71. Found: C, 64.62;
H7.50; Cl,7.35; N, 4.66%.
4d. Yield: 0.26 g, 85%. 1H NMR (400 MHz, CDCl3):
7.40 (d, 2.0 Hz, H, Ar–H), 7.33 (d, 1.9 Hz,
δ
J
=
2
J
=
2 H, Ar–H), 4.45 (s, 2 H, COD–CH), 3.33–3.30 [m, 2 H,
N(CH3)CHCH(CH2CH2CH3)N], 3.24 (d, J = 0.6 Hz, 2 H, COD–CH),
2.30 [m, 2 H, N(CH3)CHCH(CH2CH2CH3)N], 2.19, 2.17, 2.16,
2.15, 2.10, 1.90 (s, 18 H, Ar–CH3), 1.73 (t, J = 1.0 Hz, 4 H,
COD–CH2), 1.60 (t, J = 1.0 Hz, 4 H, COD–CH2), 1.23–1.19 [m,
8 H N(CH3)CHCH(CH2CH2CH3)N]. 13C NMR (100 MHz, CDCl3): δ
209.6 (d, J = 48.5 Hz, Rh–C), 144.0, 143.8, 141.3, 140.9, 139.0, 138.0,
129.5, 129.3, 128.0, 127.4, 126.5, 124.9(Ar–C), 96.4, 67.0(COD–CH),
52.9, 51.0 [N(CH3)CHCH(CH2CH2CH3)N], 31.7, 29.0 (COD–CH2),
19.6, 19.2, 18.9, 18.7, 17.3, 16.3, 15.4, 14.9, 13.1, 12.9 [Ar–CH3,
N(CH3)CHCH(CH2CH2CH3)N]. Anal. calcd for C33H46ClN2Rh (M =
609.1): C, 65.07; H, 7.61; Cl,5.82; N, 4.60. Found: C, 65.13; H, 7.59;
Cl,5.82; N, 4.63%.
2.30, 2.27, 2.24, 2.20 (s, 18 H, Ar–CH3), 1.41 [s,
3 H,
N(CH3)CHCH(CH2CH3)N], 1.33 [s, 3 H, N(CH3)CHCH(CH2CH3)N].
13C NMR (100 MHz, CDCl3): δ 159.9 (NCHN) 141.0, 139.7,
136.5, 135.5, 131.1, 129.8, 128.6, 125.5 (Ar–C), 60.3, 58.0
[N(CH3)CHCH(CH2CH3)N], 21.0, 20.7, 18.9, 18.7 (Ar–CH3), 17.8,
17.5, 17.3 [N(CH3)CHCH(CH2CH3)N]. Anal. calcd for C24H33N2Cl (M
= 384.9): C, 74.87; H, 8.64; N, 7.28. Found: C, 74.92; H, 8.72; N, 7.20%.
3d. Yield: 3.35 g, 88%. 1H NMR (400 MHz, CDCl3): δ 9.82
(s, 1 H, NCHN), 6.87 (s, 2 H, Ar–H), 6.83 (s, 2 H, Ar–H),
5.07–4.79 [m, 2 H, N(CH3)CHCH(CH2CH2CH3)N], 3.00–2.55 [m,
4 H, N(CH3)CHCH(CH2CH2CH3)N], 2.30, 2.27, 2.24, 2.20 (s, 18 H,
Ar–CH3), 1.43 [s, 3 H, N(CH3)CHCH(CH2CH2CH3)N], 1.30 [s, 3 H,
N(CH3)CHCH(CH2CH2CH3)N]. 13C NMR (100 MHz, CDCl3): δ 158.0
(NCHN) 141.0, 138.4, 134.9, 133.9, 131.0, 129.0, 128.7, 128.5 (Ar–C),
58.7, 58.0 [N(CH3)CHCH(CH2CH2CH3)N], 22.7, 21.5, 20.9, 20.8, 18.8,
18.2, 17.4, 17.0 [Ar–CH3, N(CH3)CHCH(CH2CH2CH3)N]. Anal. calcd
for C25H35N2Cl (M = 399.0): C, 75.25; H, 8.84; N, 7.02. Found: C,
75.22; H, 8.88; N, 7.23%.
4e. Yield: 0.26 g, 70%. 1H NMR (400 MHz, CDCl3): δ 7.15 (d, J
= 1.9 Hz, 4 H, Ar–H), 7.19 (t, J = 1.9 Hz, 2 H, Ar–H), 4.39 (s, 2
H, COD–CH), 3.84 (m, 4 H, NCH2CH2N), 3.27 (d, J = 0.6 Hz, 2 H,
COD–CH), 2.58, 2.30 (s, 12 H, Ar–CH3), 1.78 (t, J = 1.0 Hz, 4 H,
COD–CH2), 1.56 (t, J = 1.0 Hz, 4 H, COD–CH2). 13C NMR 100 MHz
(CDCl3): δ 211.8 (d, J = 48.0 Hz, Rh–C) 137.9, 137.7, 134.5, 128.2,
127.2, 126.7 (Ar–C), 96.5, 66.5 (COD–CH), 50.2 (NCH2CH2N), 31.6,
27.1 (COD–CH2), 19.0, 17.4 (Ar–CH3). Anal. calcd for C27H34ClN2Rh
(M = 524.9): C, 61.78; H, 6.53; Cl,6.75; N, 5.34%. Found: C, 61.83; H,
6.48; Cl,6.66; N, 6.69.
4f. Yield: 0.22 g 79%. 1H NMR (400 MHz, CDCl3): δ 7.32 (s, 2 H,
Ar–H), 7.02 (s, 2 H, Ar–H), 4.47 (s, 2 H, COD–CH), 3.86 (m, 4 H,
NCH2CH2N), 3.36 (d, J = 0.6 Hz, 2 H, COD–CH), 2.59, 2.34, 2.31 (s,
18 H, Ar–CH3), 1.78 (t, J = 1.3 Hz, 4 H, COD–CH2), 1.56 (t, J = 1.9 Hz,
4 H, COD–CH2). 13C NMR (100 MHz, CDCl3): δ 211.7 (d, J = 48.0 Hz,
Rh–C) 137.9, 136.8, 135.3, 134.1, 128.9, 127.3 (Ar–C), 96.2, 66.5
(COD–CH), 50.3 (NCH2CH2N), 31.6, 27.1 (COD–CH2), 20.0, 18.9,
17.3 (Ar–CH3). Anal. calcd for C29H38ClN2Rh (M = 552.9): C, 62.99;
H, 6.93; Cl,6.41; N: 5.07%. Found: C, 62.93; H, 6.88; Cl,6.45; N, 5.09.
4g. Yield: 0.18 g, 85%. 1H NMR (400 MHz, CDCl3): δ 7.36 (s, 2 H,
Ar–H), 7.32 (s, 2 H, Ar–H), 4.54 (s, 2 H, COD–CH), 3.81 (m, 4 H,
NCH2CH2N), 3.29 (s, 2 H, COD–CH), 2.61, 2.32 (s, 12 H, Ar–CH3),
1.81(t, J= 1.3 Hz, 4H, COD–CH2), 1.56(t, J= 1.3 Hz4H, COD–CH2).
13C NMR 100 MHz, CDCl3): δ 213.8 (d, J = 48.1 Hz, Rh–C) 141.3,
137.8, 132.4, 132.0, 130.8, 122.1 (Ar–C), 97.7, 68.1 (COD–CH), 51.4
(NCH2CH2N), 32.8, 28.3 (COD–CH2), 20.2, 18.7 (Ar–CH3). Anal.
calcd for C27H32Br2ClN2Rh M = 682.7): C: 47.50, H: 4.72, Cl,5.19; N:
4.10%. Found: C, 47.53; H, 4.78; Cl,5.25; N, 4.19%.
Synthesis of [RhCl(COD)(NHC)] Derivatives, 4
A mixture of imidazolinium salt (0.50 mmol) and [Rh(µ-OMe)(1,5-
COD)]2 (0.25 mmol) was heated under reflux in toluene (5 ml) for
2 h. Hexane (15 ml) was then added and the precipitate formed
was filtered off and crystallized from CH2Cl2/Et2O (1/5 ml).
4a. Yield: 0.23 g, 81%. 1H NMR (400 MHz, CDCl3): δ 6.85 (d,
J = 2.1 Hz, 2 H, Ar–H), 6.77 (d, J = 2.0 Hz, 2 H, Ar–H), 4.43 (s, 2 H,
COD–CH), 3.33 [m, 1 H, N(CH3)CHCH2N], 3.28 (d, J = 0.6 Hz, 2 H,
COD–CH), 3.24 [m, 2 H, N(CH3)CHCH2N], 2.20, 2.19, 2.17, 2.15, 2.12
1.94 (s, 18 H, Ar–CH3), 1.68 (t, J = 1.0 Hz, 4 H, COD–CH2), 1.53 (t,
J = 1.0 Hz 4 H, COD–CH2), 1.12 [d, 3 H J = 3.0 Hz, N(CH3)CHCH2N].
13C NMR (100 MHz, CDCl3): δ 212.8 (d, J = 48.3 Hz, Rh–C), 146.2,
143.7, 139.4, 139.3, 138.4, 138.0, 128.1, 127.9, 127.6, 126.8, 126.5,
124.7 (Ar–C), 96.9, 66.7 (COD–CH), 53.1, 51.8 [N(CH3)CHCH2N],
31.6, 27.1(COD–CH2), 17.9, 17.8, 17.7, 16.7, 15.6, 15.314.0(Ar–CH3,
N(CH3)CHCH2N).Anal.calcdforC30H40ClN2Rh(M=567.0):C,63.55;
H, 7.11; Cl,6.25; N, 4.94. Found: C, 63.52; H7.12; Cl,6.22; N, 4.89%.
4c. Yield: 0.22 g, 77%. 1H NMR (400 MHz, CDCl3): δ 7.35 (d,
J = 1.9 Hz, 2 H, Ar–H), 7.17 (d, J = 1.9 Hz, 2 H, Ar–H), 4.40 (s, 2
H, COD–CH), 3.38–3.36 [m, 2 H, N(CH3)CHCH(CH2CH3)N], 3.25 (d,
J = 0.6 Hz, 2 H, COD–CH), 2.33 [m, 2 H, N(CH3)CHCH(CH2CH3)N],
2.27, 2.21, 2.19, 2.15, 1.99, 1.97 (s, 18 H, Ar–CH3), 1.67 (t,
J = 1.0 Hz 4 H, COD–CH2), 1.56 (t, J = 1.1 Hz, 4 H, COD–CH2),
1.14–1.10 [m, 6 H N(CH3)CHCH(CH2CH3)N]. 13C NMR (100 MHz,
CDCl3): δ 210.7 (d, J = 48.0 Hz, Rh–C), 143.2, 143.0, 140.4, 139.9,
1
4h. Yield: 0.17 g, 64%. H NMR (400 MHz, CDCl3): δ 8.12 (d, J
= 7.9 Hz, 2 H, Ar–H), 7.32 (d, J = 7.9 Hz, 2 H, Ar–H), 7.26 (s, 2 H,
Ar–H), 4.46 (s, 2 H, COD–CH), 3.86 (m, 4 H, NCH2CH2N), 3.22 (s, 2
H, COD–CH), 2.40, 2.23 (s, 12 H, Ar–CH3), 1.81 (t, J = 1.3 Hz, 4 H,
COD–CH2), 1.75 (t, J = 1.4 Hz 4 H, COD–CH2). 13C NMR (100 MHz,
CDCl3): δ 215.2 (d, J = 49.0 Hz, Rh–C) 138.1, 138.0, 134.4, 131.6,
131.0, 127.6 (Ar–C), 97.3, 66.9 (COD–CH), 52.6 (NCH2CH2N), 31.6,
27.1 (COD–CH2), 19.5, 18.7 (Ar–CH3). Anal. calcd for C27H34ClN2Rh
(M = 524.9): C, 61.78; H, 6.53; Cl,6.75; N, 5.34%. Found: C, 61.73; H,
6.70; Cl,6.70; N, 5.29%.
4i. Yield: 0.24 g, 80%. 1H NMR (400 MHz, CDCl3): δ 8.12 (d, J =
7.9 Hz, 2 H, Ar–H), 7.32 (d, J = 7.9 Hz, 2 H, Ar–H), 7.26 (s, 2 H,
Ar–H), 4.46 (s, 2 H, COD–CH), 3.79 (m, 4 H, NCH2CH2N), 3.22 (s, 2
c
wileyonlinelibrary.com/journal/aoc
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2011, 25, 226–232

N-heterocyclic carbene complexes of Rh(I)
H, COD–CH), 2.53, 2.07 (s, 12 H, Ar–CH3), 1.81 (t, J = 1.3 Hz, 4 H,
COD–CH2), 1.75 (t, J = 1.4 Hz, 4 H, COD–CH2). 13C NMR (100 MHz,
CDCl3): δ 212.5 (d, J = 48.0 Hz, Rh–C) 140.1, 136.8, 136.6, 131.1,
129.6, 120.9 (Ar–C), 97.3, 66.9 (COD–CH), 50.2 (NCH2CH2N), 31.6,
27.1(COD–CH2),19.0,17.3(Ar–CH3).Anal.calcdforC27H33Cl3N2Rh
(M = 593.8): C, 54.61, H, 5.43, Cl,17.91; N, 4.72%. Found: C, 54.63;
H, 5.55; Cl,17.95; N, 4.83%.
5f. Yield: 0.12 g, 92%. 1H NMR (400 MHz, CDCl3): δ 6.91 (s, 4 H,
Ar–H), 3.79 (s, 4 H, NCH2CH2N), 2.41 (s, 12 H, Ar–CH3), 2.37 (s, 6 H,
Ar–CH3). 13C NMR (100 MHz, CDCl3): δ 206.8 (d, J = 41.3 Hz, Rh–C),
1
185.0 (d, 1J103Rh = 52,5 Hz, Rh–CO), 182.8 (d, J103Rh = 73.3 Hz,
Rh–CO), 142.5, 137.9, 137.0, 129.4 (Ar–C), 51.3 (NCH2CH2N), 19.0
(Ar–CH3). Anal. calcd for C23H26ClN2O2Rh (M = 500.8): C, 55.16; H,
5.23; Cl,7.08; N, 5.59. Found: C, 55.19; H, 5.18; Cl,7.12; N, 5.58%. IR
(CH2Cl2): υ = 2081, 1996 (CO) cm−1
.
5g. Yield: 0.15 g, 93%, 1H NMR (400 MHz, CDCl3): δ 7.24 (s, 4 H,
Ar–H), 3.93 (s, 4 H, NCH2CH2N), 2.48 (s, 12 H, Ar–CH3). 13C NMR
(100 MHz, CDCl3): δ 206.7 (d, J = 42.0 Hz, Rh–C), 184.7 (d, 1J103Rh
Synthesis of [RhCl(CO)2(NHC)] Derivatives, 5
1
= 53,1 Hz, Rh–CO), 182.9 (d, J103Rh = 74.0 Hz, Rh–CO), 142.0,
RhCl(NHC)(COD), 4 (0.25 mmol) was disolved in 5 ml dichloro-
methane. Carbon monoxide was bubbled through the solution
for 30 min. A color change from orange to pale was observed. The
reaction mixture was stirred at room temparature for 2 h. Pentane
was added to the mixture which was filtered.
137.8, 137.0, 128.0 (Ar–C), 52.4 (NCH2CH2N), 19.4 (Ar–CH3). Anal.
calcd for C21H20Br2ClN2O2Rh (M = 630.6): C, 40.00; H, 3.20; Cl,5.62;
N, 4.44. Found: C, 40.09; H, 3.14; Cl,5.58; N, 4.46%. IR (CH2Cl2):
υ = 2092, 1994 (CO) cm−1
.
5h. Yield: 0.10 g, 84%. 1H NMR (400 MHz, CDCl3): δ 7.28 (d, J =
1.9 Hz, 2 H, Ar–H), 7.17 (d, J = 1.9 Hz, 2 H, Ar–H), 6.95 (s, 2 H, Ar–H),
3.81 (s, 4 H, NCH2CH2N), 2.27 (s, 6 H, Ar–CH3), 2.21 (s, 6 H, Ar–CH3).
13C NMR (100 MHz, CDCl3): δ 206.8 (d, J = 41.0 Hz, Rh–C), 184.6 (d,
5a. Yield: 0.12 g, 96%. 1H NMR (400 MHz, CDCl3): δ 6.78 (d, J
= 2.1 Hz, 2 H, Ar–H), 6.72 (d, J = 2.1 Hz, 2 H, Ar–H), 3.43 [m,
1 H, N(CH3)CHCH2N], 3.30 [m, 2 H, N(CH3)CHCH2N], 2.27, 2.23,
2.21, 2.19, 2.17, 2.13 (s, 18 H, Ar–CH3), 1.16 [d, 3 H, J = 2.8 Hz,
N(CH3)CHCH2N]. 13C NMR (100 MHz, CDCl3): δ 205.8 (d, J = 41.3 Hz,
1J103Rh = 52,9 Hz, Rh–CO), 182.5 (d, J103Rh = 73.7 Hz, Rh–CO),
1
139.4, 137.6, 137.0, 131.9, 127.5, 123.1 (Ar–C), 51.7 (NCH2CH2N),
19.9, 19.0 (Ar–CH3). Anal. calcd for C21H22ClN2O2Rh (M = 472.8):
C, 53.35; H, 4.69; Cl,7.50; N, 5.93. Found: C, 53.24; H, 4.73; Cl,7.45; N,
1
1
Rh–C), 185.5 (d, J103Rh = 53,2 Hz, Rh–CO), 182.7 (d, J103Rh =
74.6 Hz, Rh–CO), 146.3, 144.7, 140.0, 139.8, 138.7, 128.1 (Ar–C),
53.8, 51.3 (N(CH3)CHCH2N), 18.5, 18.3, 17.7, 17.3, 16.5, 16.0, 14.4
(Ar–CH3, N(CH3)CHCH2N). Anal. calcd for C21H23ClN2O2Rh (M =
514.9): C, 55.99; H, 5.48; Cl,6.89; N, 5.44. Found: C, 55.90; H, 5.50;
5.91%. IR (CH2Cl2): υ = 2103, 1999 (CO) cm−1
.
5i. Yield: 0.11 g, 96%. 1H NMR (400 MHz, CDCl3): δ 7.99 (s, 4 H,
Ar–H), 3.88 (s, 4 H, NCH2CH2N), 2.51 (s, 12 H, Ar–CH3). 13C NMR
(100 MHz, CDCl3): δ 206.8 (d, J = 42.0 Hz, Rh–C), 185.1 (d, 1J103Rh
Cl,6.85; N, 5.46%. IR (CH2Cl2): υ = 2079, 1995 (CO) cm−1
.
5c. Yield: 0.13 g, 96%. 1H NMR (400 MHz, CDCl3): δ 7.00 (d,
J = 2.0 Hz, 2 H, Ar–H), 6.90 (d, J = 1.9 Hz, 2 H, Ar–H),
3.86–3.84 [m, 2 H, N(CH3)CHCH(CH2CH3)N], 2.33 [m, 2 H,
N(CH3)CHCH(CH2CH3)N], 2.20, 2.19, 2.18, 2.13, 2.07, 2.03, (s, 18
H, Ar–CH3), 1.23–1.20 [m, 6 H N(CH3)CHCH(CH2CH3)N]. 13C NMR
(100 MHz, CDCl3): δ 206.0 (d, J = 41.3 Hz, Rh–C), 185.0 (d,
1
= 53,3 Hz, Rh–CO), 182.7 (d, J103Rh = 74.4 Hz, Rh–CO), 143.8,
138.0, 137.6, 128.9 (Ar–C), 51.7 (NCH2CH2N), 18.2 (Ar–CH3). Anal.
calcd for C21H20Cl3N2O2Rh (M = 541.6): C, 46.57; H, 3.72; Cl,19.64;
N, 5.17. Found: C, 46.50; H, 3.69; Cl,19.65; N, 5.13%. IR (CH2Cl2):
υ = 2080, 1997 (CO) cm−1
.
1
1J103Rh = 53,1 Hz, Rh–CO), 182.3 (d, J103Rh =74.5 Hz, Rh–CO),
General Procedure for Rhodium–Carbene Catalyzed Addition
of Phenylboronic Acid to Aldehydes
142.1, 141.9, 141.0, 139.7, 138.9, 138.7, 135.8, 134.4 (Ar–C), 53.2,
52.7 [N(CH3)CHCH(CH2CH3)N], 20.1, 19.8, 19.6, 18.9, 17.9, 17.8,
16.5, 14.9, 14.1 [Ar–CH3, N(CH3)CHCH(CH2CH3)N]. Anal. calcd for
C26H32ClN2O2Rh (M = 542.9): C, 57.52; H, 5.94; Cl,6.53; N, 5.16.
Found: C, 57.60; H, 5.91; Cl,6.55; N, 5.16%. IR (CH2Cl2): υ = 2077,
Phenylboronic acid (1.20 g, 9.8 mmol), KOBut (4.9 mmol), the
aromatic aldehyde (4.9 mmol), diethyleneglycol di-n-butyl ether
(0.6 mmol, internal standard), rhodium–carbene catalyst (1 mol%)
and N,N-dimethylformamide (15 ml) were introduced into a
Schlenk tube and then water (5 ml) was added. The resulting
mixture was heated for 4 h at 80 ◦C under an argon atmosphere,
cooled to ambient temperature and extracted with ethyl acetate
(30 ml). After drying over MgSO4 the organic phase was evapo-
rated. The conversion was monitored by gas chromatography.
1993 (CO) cm−1
.
5d. Yield: 0.13 g, 88%. 1H NMR (400 MHz, CDCl3): δ 7.23
(d, J = 1.9 Hz, 2 H, Ar–H), 7.19 (d, J = 1.9 Hz, 2 H, Ar–H),
3.33–3.30 [m, 2 H, N(CH3)CHCH(CH2CH2CH3)N], 2.33 [m, 2 H,
N(CH3)CHCH(CH2CH2CH3)N], 2.23, 2.21, 2.18, 2.16, 2.15, 2.13 (s, 18
H, Ar–CH3), 1.27–1.25 [m, 8 H N(CH3)CHCH(CH2CH2CH3)N]. 13C
NMR (100 MHz, CDCl3): δ 206.7 (d, J = 41.7 Hz, Rh–C), 185.5 (d,
1
1J103Rh = 52,8 Hz, Rh–CO), 183.2 (d, J103Rh = 74.7 Hz, Rh–CO),
Supporting information
144.5, 144.0, 142.0, 141.0, 138.7, 130.9, 130.2, 128.0 (Ar–C), 52.3,
51.9 [N(CH3)CHCH(CH2CH2CH3)N], 20.0, 19.8, 18.7, 18.3, 17.9, 16.1,
15.7, 15.0, 14.1, 13.7 [Ar–CH3, N(CH3)CHCH(CH2CH2CH3)N]. Anal.
calcd for C27H34ClN2O2Rh (M = 556.9): C, 58.23; H, 6.15; Cl,6.37;
N, 5.03. Found: C, 58.17; H, 6.09; Cl,6.38; N, 5.06%. IR (CH2Cl2):
Supporting information may be found in the online version of this
article.
Acknowledgment
υ = 2076, 1993 (CO) cm−1
.
5e. Yield: 0.11 g, 90%. 1H NMR (400 MHz, CDCl3): δ 7.25 (t,
J = 0.6 Hz, 4 H, Ar–H), 7.17 (d, J = 2.0 Hz, 2 H, Ar–H), 4.04
(s, 4 H, NCH2CH2N), 2.48 (s, 12 H, Ar–CH3). 13C NMR (100 MHz,
CDCl3): δ 205.7 (d, J = 41.0 Hz, Rh–C), 185.1 (d, 1J103Rh = 53,4 Hz,
Rh–CO), 182.9 (d, 1J103Rh =74.7 Hz, Rh–CO), 139.1, 137.6, 131.1,
128.2 (Ar–C), 51.7 (NCH2CH2N), 19.1 (Ar–CH3). Anal. calcd for
C21H22ClN2O2Rh (M = 472.8): C, 53.35; H, 4.69; Cl,7.50; N, 5.93.
Found: C, 53.39; H, 4.63; Cl,7.55; N, 5.83%. IR (CH2Cl2): υ = 2084,
Financial support fromTurkish Academy of Science (TUBA) is
gratefully acklowledged.
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c
Appl. Organometal. Chem. 2011, 25, 226–232
Copyright ꢀ 2010 John Wiley & Sons, Ltd.
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