1,3-Diarylimidazolidin-2-ylidene (NHC) complexes of Pd(II): Electronic effects on cross-coupling reactions and thermal decompositions

Article abstract of DOI:10.1016/j.jorganchem.2006.05.020

The synthesis of 1,3-diarylimidazolidin-2-ylidene (NHC) precursor, 1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride, (3b) has been extended to the electronically and sterically modified NHC precursors 3a (X = H), 3c (X = Br) and 3e (X = Cl) in order t

Full text of DOI:10.1016/j.jorganchem.2006.05.020

Journal of Organometallic Chemistry 691 (2006) 3749–3759
www.elsevier.com/locate/jorganchem
1,3-Diarylimidazolidin-2-ylidene (NHC) complexes of Pd(II):
Electronic effects on cross-coupling reactions
and thermal decompositions
*
Hayati Turkmen, Bekir C¸ etinkaya
¨
Department of Chemistry, Ege University, EU Kampusu, 35100 Bornova-Izmir, Turkey
Received 13 December 2005; received in revised form 7 May 2006; accepted 12 May 2006
Available online 20 May 2006
Abstract
The synthesis of 1,3-diarylimidazolidin-2-ylidene (NHC) precursor, 1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride, (3b) has
been extended to the electronically and sterically modified NHC precursors 3a (X = H), 3c (X = Br) and 3e (X = Cl) in order to inves-
tigate the electronic effect of a p-substituent (X) on cross-coupling catalysts. Complexes of the type PdCl2(NHC)2 (5), PdCl2(NHC)(PPh3)
(6) and [RhCl(NHC)(cod)] (7) were prepared from 3 or 4d (1,3-bis(2,4-dimethylphenyl)-2-trichloromethylimidazolidin). Initial decompo-
sition temperatures of the complexes 5 and 6 were determined by TGA. In situ formed complexes from Pd(OAc)2 and 3 as well as the
preformed complexes 5 and 6 have been tested as catalysts in coupling of phenylboronic acid with 4-haloacetophenones. The electron
donating ability of NHCs derived from 3 was assessed by measuring C–O frequencies in the respective [RhCl(NHC)(CO)2] complex 8
which was prepared by replacement of cod ligand of 7 with CO. An interesting correlation between the electron-donating nature of
the aryl substituent and catalytic activity and also initial decomposition temperature of the complexes 5 and 6 was observed.
Ó 2006 Elsevier B.V. All rights reserved.
Keywords: Palladium; N-heterocyclic carbenes; Electronic effects; Cross-coupling; Thermal gravimetric analysis
1. Introduction
X
X
N
N
Recently, N-heterocyclic carbene (NHC) ligands are
receiving intensive attention in the fields of coordination
chemistry and homogeneous catalysis because organome-
tallic compounds containing NHC ligands exhibit high
reactivities. NHCs have appeared as sterically and electron-
ically tunable ligands which make stable coordinative
bonds with transition metals [1–3]. Dramatic improve-
ments in C–C coupling activity have been observed with
complexes (A, M = palladium; L = ligands other than
NHC; X = Me) using five-membered NHCs as ligands.
Since then, a number of five-membered NHC ligands with
different substituents have been studied [4,5].
MLn
A
It was found that ligands bearing two bulky Aryl groups
(Ar = Mes or 2,6-di-i-propylphenyl) promote the reaction
of unactivated aryl chlorides [6,7]. The ligands may afford
coordinatively unsaturated mono- or dicarbene ligated
complexes and accelerate the catalytic steps, that is, oxida-
tive addition, transmetalation and reductive elimination
[8]. The steric bulk of the ligand is believed to aid the reduc-
tive elimination of product, while electron richness of the
ligand imparts a high catalytic performance via an oxida-
tive addition step [7]. Since Hermann’s discovery in 1995
[9] many structural modifications, including steric tuning
*
Corresponding author. Tel.: +90 232 3881092; fax: +90 232 38881036.
E-mail address: bekir.cetinkaya@ege.edu.tr (B. C¸ etinkaya).
0022-328X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.05.020

3750
H. Tu¨rkmen, B. C¸ etinkaya / Journal of Organometallic Chemistry 691 (2006) 3749–3759
O
O
R
R
R
R
R
R
Ar NH2
Ar N
N Ar
i
ii
iv
Ar NH
NHAr
2a, b, c, d, e
1a, b, c, d, e
iii
Ar
R
H
Ar
N
Ar
N
+
R
R
R
R
H
H
a
Cl-
CCl3
N
N
Ar
CH3
CH3
b
b'
c
H
Ar
4d
3a, b, c, d, e
Me
vii
v
vi
Br
H
Ar
Ar
Ar
N
Cl
CH3
R
R
R
R
d
e
Cl
R
R
H
H
N
N
Pd PPh3
Cl
Pd
Cl
N
Ar
Cl
N
Ar
N
Ar
5a, b, c, d, e
6a, b, c, d, e
Scheme 1. (i) EtOH, 16 h, RT. (ii) THF, NaBH4, 24 h, RT. (iii) HC(OEt)3, NH4Cl, 130 °C. (iv) AcOH, Cl3CCHO, 3 h, RT. (v) DCM, Ag2O, 24 h, RT,
then PdCl2(MeCN)2, 2 days, RT. (vi) THF, NaH, 4 h, 65 °C then PhCH3, [PdCl2(PPh3)]2, 4 h, 110 °C. (vii) PhCH3, [PdCl2(PPh3)]2, 4 h, 110 °C.
Table 1
Thermal analysis data for complexes 5 and 6
Entry
Complex
TG
DTG
Theoretical wt. loss (%)
Observed wt. loss (%)
Peak temperature (°C)
1
2
3
4
5
6
6
7
8
5a
5b
80.73
80.39
87.45
83.17
75.92
79.64
80.15
76.25
81.73
79.77
75.31
77.46
70.30
82.86
82.04
86.59
83.70
70.83
75.12
82.87
75.37
79.97
65.64
73.47
70.11
69.82
393
370
378
315
320
5b0
5c
5d
5e
6a
376
334, 362
232, 329, 371
339, 354
323, 371
322, 354
330, 350
330, 360, 367, 373
6b
6b0
6c
9
10
11
12
6d
6e
PdCl2(PPh3)2
R
R
N
Ar
N
Ar
Cl Pd Cl
L
L : NHC (5), PPh3 (6)
a
c
b'
b
d
e
H
R
Me
H
H
H
H
Ar
CH
Br
Cl
H
CH
CH
3
3
3

H. Tu¨rkmen, B. C¸ etinkaya / Journal of Organometallic Chemistry 691 (2006) 3749–3759
3751
and changing the ligand backbone structure, had been pur-
sued on NHC ligands [5]. However, an important parame-
ter on the ligand design, the ligand electronic structure, has
not been systematically investigated. Such effects have been
observed in several catalytic systems [10]. While this work
has been in progress, ligand electronic effects have been
reported in a benzimidazol-2-ylidene palladium(II) cata-
lytic system [11]. Despite these studies, a systematic
account of electronic effects on a palladium–NHC catalyst
system has yet to be reported. Here we describe the prepa-
ration, characterization, catalytic activities and thermal
stabilities of two series of palladium–NHC complexes (5
and 6) that incorporate H, Me, Br, Cl groups at the p-posi-
tion of N-aryl substituent of NHC ligand.
In order to enlarge our set of NHC ligands and to better
understand the role of the electron donating Me substitu-
ents at the 4- and 5-positions and the ortho-methyl substit-
uents in the aryl of NHC complexes 5 and 6, we have also
prepared the related new salts 3b0 and 3d (which is an iso-
mer of 3a).
The characterization of the new compounds (1–6),
except 1a, 2a, 3a, has been carried out by elemental analy-
sis, FTIR, NMR spectroscopy and, in addition, thermal
gravimetric analysis (TGA) was applied to the complexes
5 and 6.
The NMR spectra of the compounds are very diagnostic
with all signals well resolved. The singlets in the spectral
region between 7.86 and 10.29 ppm confirmed the presence
of C2–H in 3. Of course, these signals are not present in the
spectra of the complexes (5 and 6) [16].
2. Results and discussion
1
The H NMR spectra of 5 and 6 showed one singlet
Originally, we thought that changing the electronic nat-
ure of the p-substituent X on compound A might effect the
catalytic activity of NHC complexes. This would be a
purely electronic affect as changing the p-substituent from
H, to CH3, Br or Cl is not expected to cause a significant
change in steric bulk at the metal center.
resonance due to the methyl groups at the 2,6-position
of the aromatic ring at d 1.83–2.57 along with a singlet
resonance due to ring CH2 (d 3.65–4.04) and aromatic sig-
nals. Additionally, the signals due to the carbene carbon
of the NHC ligand were observed at d 194.9–199.4 in
the 13C{1H} NMR spectra. Furthermore, 13C{1H}
NMR spectra of 6 revealed doublets due to coupling of
2.1. Preparation of ligand precursors and NHC complexes
the phosphorus atom in the trans position, J(P–C) =
183.8–185.3 Hz. It is worth noting that the coupling in
the analogous imidazol-2-ylidene complex has not been
observed [16]. The 13C{1H} NMR signals of the carbene
carbon atoms of 6 (d 194.9–198.8) are slightly shifted to
higher field as compared to their signals in the bisNHC
complexes 5 (d 196.7–199.4). These observations indicate,
once more, the close similarity between saturated NHCs
and tertiary phosphines [17].
In the case of 6d trans-configuration has been confirmed
by X-ray diffraction studies [18], and attempts to convert
complex 6 into the cis-isomer in the presence of PPh3 were
unsuccessful.
Compound 3b has been previously reported [12]; how-
ever, for a complete comparison of electronic properties,
3a, 3c, 3d, 3e and 4d were also deemed necessary. The gen-
eral route to the p-substituent containing ligand precursors
(3 and 4d) to prepare Pd–NHC complexes is shown in
Scheme 1. This route typically used commercially available
anilines. The imidazolinium salts (3) prepared in Scheme 1
were subsequently palladated in a deprotonation reaction
using Ag2O or NaH; in the case of 6d, we had to prepare
the 2-trichloromethylimidazolidine (4d) as intermediate
reagent [13–15].
Table 2
O
O
Pd(OAc)2 (1,5 % mol), 3 ( 3 % mol)
(HO)2BPh
+
Y
Ph
Cs2CO3, 80 0C, 2 h
Entry
3
Y
Conversion (%)
Yield (%)
1
2
3
4
5
6
7
8
9
a
a
b
b
b0
b0
c
Cl
Br
Cl
Br
Cl
Br
Cl
Br
Cl
Br
Cl
Br
75
93
79
100
81
100
70
89
86
93
82
70
92
71
100
77
98
42
87
78
78
28
48
c
d
d
e
10
11
12
e
85
Reaction conditions: 1.0 mmol of phenylboronic acid, 1.5 mmol Cs2CO3, dioxane (3 mL). GC-yield using diethyleneglycol-di-n-butylether as the internal
standard.

3752
H. Tu¨rkmen, B. C¸ etinkaya / Journal of Organometallic Chemistry 691 (2006) 3749–3759
2.2. Thermogravimetric analyses (TGA)
The thermal decompositions of 5 occur in one step
whereas 6 occur in multiple steps. The residues correspond
to PdCl or PdCl2. The initial decomposition temperatures
within the series 5 increase in the following order:
d ꢀ c < b < e < a.
TGA has been extensively employed in the study of
coordination compounds [19]. However, to the best of
our knowledge no report has been published dealing with
its use for the investigation of NHC complexes. In this
study we employed this technique to obtain evidence for
the influence of closely related ligands coordinated to the
Pd atom on the initial decomposition temperatures and
on the thermal decomposition steps. The steps, initial and
final temperatures, partial and total weight losses for the
decomposition of compounds 5 and 6 are given Table 1.
The thermal behavior of Pd complexes of PdCl2(NHC)2
and their mixed-ligand complexes PdCl2(NHC)(PPh3)
was studied by TG and DTG in a dynamic N2 atmosphere.
The lower thermal stability of d may be attributed to the
unsymmetrical substitution on the aryl ring of NHC
ligand. Thus, if the restriction would play an important
role 5a should be less stable than 5d.
The complexes 5 and 6 exhibit very high thermal stability
and degradation of PPh3 complexes follow a complicated
process. In the case of biscarbene complexes (5) both
NHC ligands are simultaneously lost. Whereas in the case
of mixed complexes (6), first PPh3, and then the NHC is
lost. Thus, once more it was observed that the Pd–NHC
Table 3
O
O
5 or 6 (1,5 % mol)
(HO)2BPh
+
Y
Ph
Cs2CO3, 80 0C, 2 h
Entry
Catalyst
Y
Conversion (%)
Yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
5a
5a
5b
5b
5b0
5b0
5c
5c
5d
5d
5e
5e
6a
6a
6b
6b
6b0
6b0
6c
6c
6d
6d
6e
6e
Cl
Br
Cl
Br
Cl
Br
Cl
Br
Cl
Br
Cl
Br
Cl
Br
Cl
Br
Cl
Br
Cl
Br
Cl
Br
Cl
Br
43
95
48
97
50
80
99
89
97
67
19
28
83
99
100
100
97
95
94
95
97
93
90
87
28
69
35
89
43
60
3
39
40
41
0
20
78
90
88
92
93
92
23
89
8
33
7
43
R
R
Ar
N
N Ar
Cl Pd Cl
L
L : NHC (5), PPh3 (6)
a
c
b'
b
d
e
H
R
Me
H
H
H
H
Ar
CH
Br
Cl
H
CH
CH
3
3
3
Reaction conditions: 1.0 mmol of phenylboronic acid, 1.5 mmol Cs2CO3, 1.5 mol % 5 or 6, dioxane (3 mL). GC-yield using diethyleneglycol-di-n-
butylether as the internal standard.

H. Tu¨rkmen, B. C¸ etinkaya / Journal of Organometallic Chemistry 691 (2006) 3749–3759
3753
bond is stronger than the Pd–PR3 bond. In the case of
[PdCl2(PPh3)]2, the loss of one PPh3 was followed by partial
loss of PPh3. These data indicate that NHC complexes are
thermally stable above 300 °C and the initial decomposition
temperature is sufficiently sensitive to reflect a p-substituent
effect within a series of NHC complexes. These observations
further confirm that the electron-donating nature of the
peripheral substituent has a marked influence on the
metal–ligand interactions which subsequently determines
the catalyst life.
The catalytic activity is also influenced by the nature of
the p-ligands (NHC vs. PPh3) on the palladium center, as
indicated by the significant increase in the reaction rate on
going from 5 to 6 (Table 3, compare entries 1–12 to 13–
24) and a similar trend is found. These observations are in
agreement with earlier findings [8,20]. The complexes 5e
and 6e derived from the substituted p-chloroaniline showed
almost no catalytic activity against the aryl chloride (entries
11 and 23, respectively). In contrast to benzimidazol-2-yli-
dene system [11], 1,3-dimesityl-4,5-dimethylimidazolidin-
2-ylidene complexes (5b0 and 6b0) are not significantly better
than their bare analogous (5b and 6b; of Table 3, entries 3–6
and 15–18, respectively).
2.3. Catalytic cross-coupling reactions
The aim of this research was to gain a preliminary
insight into the effects of p-substituents on the aryl group
of the NHC ligand on the cross-coupling reaction. It is well
known that the activities of NHC complexes are influenced
by the steric bulk and electronegativities of ortho-substitu-
ents and the way the catalyst is prepared [7,8,20].
The coupling of 4-bromoacetophenone with phenylbo-
ronic acid (in dioxane at 80 °C, Cs2CO3 as base) was
used as the model reaction in order to highlight the influ-
ence of para substituents (H, Me, Br and Cl) on the
catalytic activity and the protocol was also applied to
4-chloroacetophenone. The reactivity of in situ generated
catalysts and preformed complexes 5 and 6 were com-
pared and the relevant results are reported in Tables 2
and 3.
The results indicate that the highest yield can be
achieved with the in situ formed complexes prepared from
3 and Pd(OAc)2 (in a 2:1 ratio) with 4-bromoacetophenone
(entries 2, 4, 8). As expected [20], under the same condi-
tions, the yield is significantly lower with 4-chloroacetophe-
none (entries 1, 3, 7). These results also indicate that among
the salts used, 3b and 3b0 could be the most effective cata-
lyst precursors. As the electron-donating property of the p-
substituent increased (Cl < Br < H < Me), the catalytic
activity increased. In order to rule out the possibility of
intervention of p-bromo substituents in the Suzuki cou-
pling, the reaction between PhB(OH)2 and 5c/6c was car-
ried out under the same catalytic reaction conditions and
the starting palladium complexes 5c/6c were recovered
and remain unchanged. It is worth noting that the catalyst
derived from 3d, the isomer of 3a, is very effective for 4-
chloroacetophenone. Whether this efficiency is due to the
different topology imparted by 2,4-dimethylphenyl groups
(compared to the 2,6-dimethylphenyl) remains unclear at
this point.
Table 4
Carbonyl stretching wavenumbers (cmꢁ1) of 8a
R
H
Ar
(CO)/sym.
2078
(CO)/asym.
1996
8a
8b
8b0
8c
H
CH3
CH3
Br
H
2074
2072
2092
2080
2103
1958
1953
1994
1997
1999
Me
H
8d
H
CH3
8e
H
Cl
a
Recorded in CH2Cl2.
Ar
CO
Rh
Cl
R
R
N
RhCl(OMe)(COD) 2
+2CO
-COD
NHC-H +Cl-
CO
RhCl(NHC)COD
N
PhMe, 110 ˚C
3
7
Ar
8
Scheme 2.

3754
H. Tu¨rkmen, B. C¸ etinkaya / Journal of Organometallic Chemistry 691 (2006) 3749–3759
In order to rationalize the observed differences in cata-
thermogravimetric (DTG) curves were obtained using a
lytic activity, we measured IR stretching frequencies in
[RhCl(NHC)(CO)2] complexes which were prepared
according to Scheme 2. The full characterization of 7 and
8 will be reported in due course. The C–O stretching fre-
quencies of carbonyl complexes 8, recorded in CH2Cl2 solu-
tion (Table 4), indicate that the basicity increases in the
order: e < d < c < a < b ꢂ b0. The data also show that the
symmetrical m(CO) in the respective [RhCl(NHC)(CO)2]
complexes does correlate with the catalytic activity of
in situ formed Pd–NHC complexes as well as preformed 5
and 6 (Tables 2 and 3, respectively) [21,22].
Perkin–Elmer Pyris 6 analyzer in the range 50–950 °C in
alumina crucibles under nitrogen (flux rate: 20 cm3 minꢁ1
)
at a heating rate of 20 °C minꢁ1 using alumina as refer-
ence. FTIR spectra were recorded on a Perkin–Elmer
Spectrum 100 Series.
4.1. Preparation of N,N0-bis(2,6-dimethylphenyl)imine (1a)
To a solution of 2,6-dimethylphenylamine (1.21 g,
10 mmol) in 100 mL ethanol was added at 25 °C a mixture
of a 40% aqueous solution of glyoxal (0.72 g, 5 mmol). The
mixture was stirred for 16 h at 25 °C. The resulting yellow
precipitate was collected by filtration and dried in vacuum.
Yield: 2.13 g, 85%; m.p = 154–155 °C. Anal. Calc. for
C18H20N2; C, 81.78; H, 7.63; N, 10.60. Found: C, 81.70;
3. Conclusion
The structurally and sterically similar 1,3-bis(2,6-dimeth-
ylphenyl)imidazolinium salts with H, CH3, Br and Cl sub-
stituents at the p-position of the aryl ring were used to
prepare two series of palladium–NHC complexes 5 and 6.
In this way o-substituents of NHC’s were held constant
and only the nature of the p-substituent was varied. In both
cases the efficiency increased with the electron donating nat-
ure of the p-substituent (Cl < Br < H < Me). To better
understand from a chemical view point the reasons behind
the difference in activity we studied their TG analyses which
indicated that the initial decomposition temperatures are
relatively sensitive to the p-substituents of the aryl ring.
The in situ prepared catalysts and the preformed com-
plexes allowed us to evaluate simultaneously subtle elec-
tronic influence of H, Me, Br and Cl without possible
complications due to steric effects. The C–O stretching fre-
quencies in [RhCl(NHC)(CO)2] complexes which derived
from 3 are sensitive to p-substituents. The data indicate
clearly the superiority of the complex with the most elec-
tron donating NHC 5b and 6b. Hence, the electron donat-
ing capability of the complexes, as well as the steric bulk,
appears to play a role in the complex’s catalytic activity
[7,8]. In contrast to the substituents at the 4-position of
the aryl ring, the oxidative addition step is less sensitive
to the methyl substituents in the 4,5-positions of the imi-
dazolidine ring. These results indicate that NHC ligand
design should focus on creating electron-rich carbene with
a carefully selected steric environment.
1
H, 7.72; N, 9.89%. H NMR (CDCl3): d = 2.19 (s, 12H,
ortho-CH3), 6.93 (t, 2H J = 7.7 Hz, para-CH), 7.07 (d,
4H, J = 7.6 Hz, meta-CH), 8.13 (s, 2H, HC@N); 13C{H}
NMR (CDCl3): d = 18.20 (ortho-CH3), 125.5, 126.5,
128.9, 148.4 (Ar), 163.2 (HC@N). The synthesis of 1b, 2b
and 3b were carried out using literature methods [12].
4.2. Preparation of N,N0-bis(2,4,6-trimethylphenyl)-1,2-
bis(methyl)ethanediimine (1b0)
Compound 1b0 was prepared in the same way as 1a from
2,4,6-trimethylphenylamine (1.88 g, 13.9 mmol) and 2,3-
butadione (0.60 g, 6.95 mmol) to give yellow crystals of
1b0. Yield: 1.85 g, 83%; m.p = 53–55 °C. Anal. Calc. for
C22H28N2; C, 82,45; H, 8.81; N, 8.74. Found: C, 82.17;
H, 8.99; N, 8.98%.
1H NMR (CDCl3): d = 2.26 (s, 6H, para-CH3), 2.30 (s,
6H, ortho-CH3), 2.38 (s, 6H, ortho-CH3), 3.18 (s, 6H,
N@CCH3), 7.19 (s, 2H, meta-CH), 7.22 (s, 2H, meta-CH);
13C{H} NMR (CDCl3): d = 18.5 (s, para-CH3), 19.2
(ortho-CH3), 20.1 (ortho-CH3), 25.5 (N@C–CH3), 128.9,
130.4, 130.5, 134.8, 136.3, 140.3 (Ar), 162.65 (s, N@C).
4.3. Preparation of N,N0-bis(4-bromo-2,6-
dimethylphenyl)imine (1c)
Compound 1c was prepared in the same way as 1a from
4-bromo-2,6-dimethyl phenylamine (2.00 g, 10 mmol)
and glyoxal (0.72 g, 5 mmol) to give yellow crystals of 1c.
Yield: 1.47 g, 70%; m.p = 198–200 °C. Anal. Calc. for
C18H18N2Br2; C, 51.21; H, 4.30; N, 6.64. Found: C,
51.32; H, 4.41; N, 6.58%.
4. Experimental
All manipulations were performed by using Schlenk-
type flasks under dry argon and standard high vacuum-
line techniques. The solvents were analytical grade and
distilled under argon from sodium benzophenone (tolu-
ene, diethyl ether), sodium–potassium (pentane), P2O5
(dichloromethane), Mg/I2 (methanol). NMR spectra were
recorded at 297 K on a Varian Mercury AS 400 NMR
spectrometer at 400 MHz (1H), 100,56 MHz (13C). Ele-
mental analyses were carried out by the analytical service
of TUBITAK with a Carlo Erba Strumentazione Model
1106 apparatus. Thermogravimetric (TG) and differential
1H NMR (CDCl3): d = 2.15 (s, 12H, ortho-CH3), 7.22 (s,
4H, meta-CH), 8.05 (s, 2H, HC@N); 13C{H} NMR
(CDCl3): d = 18.3 (ortho-CH3); 118.7, 128.7, 131.2, 148.8
(Ar), 163.6 (s, HC@N).
4.4. Preparation of N,N0-bis(2,4-dimethylphenyl)imine (1d)
Compound 1d was prepared in the same way as 1a
from 2,4-dimethylphenylamine (1, 21, 10 mmol) in 100 mL

H. Tu¨rkmen, B. C¸ etinkaya / Journal of Organometallic Chemistry 691 (2006) 3749–3759
3755
ethanol and glyoxal (0.72 g, 5 mmol) to give yellow crystals
4.8. Preparation of N,N0-bis(2,4-
dimethylphenyl)ethylenediamine (2d)
of 1d. Yield: 2.27 g, 86%; m.p = 147–149 °C. Anal. Calc. for
C18H20N2: C, 81.78; H, 7.63; N, 10.60. Found: C, 81.78; H,
7.10; N, 10.36%.
Compound 2d was prepared in the same way as 2a from
N,N0-bis(2,4-dimethylphenyl)imine 1d (2.64 g, 10 mmol)
and sodium borohydride (1.60 g, 41 mmol) to give a color-
less solid of 2d. Yield: 3.62 g, 85%; m.p = 67 °C. Anal.
Calc. for C18H24N2: C, 80.55; H, 9.01; N, 10.44. Found:
C, 80.50; H, 7.87; N, 10.19%.
1H NMR (CDCl3): d = 2.24 (s, 6H, para-CH3), 2.28 (s,
6H, ortho-CH3), 6.85 (d, 2H, J = 7.9 Hz, ortho-CH), 6.93
(d, 2H, J = 7.9 Hz, meta-CH), 6.97 (s, 2H, meta-CH),
8.22 (s, 2H, HC@N); 13C{H} NMR (CDCl3): d = 18.2
(para-CH3), 21.4 (ortho-CH3), 117.5, 127.8, 131.8,133.5,
137.7, 147.4 (Ar), 159.3 (HC@N).
1H NMR (CDCl3): d = 2.01 (s, 6H, ortho-CH3), 2.15 (s,
6H, ortho-CH3), 3.35 (s, 4H, NCH2), 6.50 (d, 2H,
J = 8.0 Hz, ortho-CH), 6.81 (s, 2H, meta-CH), 6.85 (d,
2H, J = 8.03 Hz, meta-CH); 13C{H} NMR (CDCl3):
d = 17.9 ( ortho-CH3), 20.7 (para-CH3); 43.9 (NCH2),
110.7, 123.0, 127.1, 127.8, 145.7 (Ar).
4.5. Preparation of N,N0-bis(4-chloro-2,6-
dimethylphenyl)imine (1e)
Compound 1e was prepared in the same way as 1a from
4-chloro-2,6-dimethyl phenylamine (1.55 g, 10 mmol) and
glyoxal (0.72 g, 5 mmol) to give yellow crystals of 1e. Yield:
4.9. Preparation of N,N0-bis(4-chloro-2,6-
dimethylphenyl)ethylenediamine (2e)
2.76
g
83%; m.p = 201–202 °C. Anal. Calc. for
C18H18N2Cl2: C, 64.87; H, 5.44; N, 8.41. Found: C,
64.91; H, 5.67; N, 8.33%.
Compound 2e was prepared in the same way as 2a from
N,N0-bis(4-bromo-2,6-dimethylphenyl)imine 1b (3.33 g,
10 mmol) and sodium borohydride (1.60 g, 41 mmol) to
give colorless solid of 2c. Yield: 2.76 g, 82%; m.p = 96–
98 °C. Anal. Calc. for C18H22N2Cl2: C, 64.10; H, 6.57; N,
8.31. Found: C, 64.32; H, 6.83; N, 8.12%.
1H NMR (CDCl3): d = 2.16 (s, 12H, ortho-CH3), 7.08 (s,
4H, meta-CH), 8.07 (s, 2H, HC@N); 13C{H} NMR
(CDCl3): d = 18.4 (ortho-CH3); 128.3, 128.5, 130.1, 148.4
(Ar), 163.8 (HC@N).
4.6. Preparation of N,N0-bis(2,6-
dimethylphenyl)ethylenediamine (2a)
1H NMR (CDCl3): d = 2.27 (s, 12H, ortho-CH3), 3.15 (s,
4H, NCH2), 6.99 (s, 4H, meta-CH); 13C{H} NMR
(CDCl3): d = 18.7 (ortho-CH3), 49.0 (NCH2), 127.0,
128.7, 131.6, 144.6 (Ar).
A
suspension of N,N0-bis(2,6-dimethylphenyl)imine
(2.64 g, 10 mmol) 1a in 40 mL THF was treated at 0 °C
with sodium borohydride (1.60 g, 41 mmol) in portions
of 1 g over a period of 1 h. The mixture was stirred for
24 h at RT and heated subsequently for 2 h under reflux.
To the mixture was added 50 mL of 20% NaCl and 50 mL
of ice-water. A colorless solid precipitated and was col-
lected by filtration and dried under vacuum. Yield:
2.38 g, 89%; m.p = 39–40 °C. Anal. Calc. for C20H24N2:
C, 80.55; H, 9.01; N, 10.44. Found: C, 81.01; H, 9.11;
N, 10.03%.
4.10. Preparation of 1,3-bis(2,6-
dimethylphenyl)imidazolinium chloride (3a)
A mixture of N,N0-bis(2,6-dimethylphenyl)ethylenedia-
mine (2a) (2.68 g, 10 mmol), triethyl orthoformate 10 mL
and ammonium chloride (0.54 g, 10.2 mmol) was heated
in a distillation apparatus until the ethanol distillation
ceased. The temperature of the reaction mixture reached
130 °C. After cooling to RT, to the reaction mixture was
added 30 mL of ether. A colorless solid precipitated which
was collected by filtration. Purification was achieved by
repeated recrystallizations from ethanol/ether. Yield:
2.51 g, 80%; m.p = 364–365 °C. Anal. Calc. for C18H23-
N2Cl: C, 72.48; H, 7.36; N, 8.90. Found: C, 72.45; H,
7.35; N, 9.15%.
1H NMR (CDCl3): d = 2.18 (s, 12H, ortho-CH3), 3.35 (s,
4H, NCH2), 7.12 (d, 4H, J = 7.6 Hz, meta-CH), 7.51 (t, 2H,
J = 7.7 Hz, para-CH); 13C{H} NMR (CDCl3): d = 18.6
(ortho-CH3), 46.9 (NCH2), 115.8, 130.6, 130.9, 143.8 (Ar).
4.7. Preparation of N,N0-bis(4-bromo-2,6-
dimethylphenyl)ethylenediamine (2c)
1H NMR (CDCl3): d = 2.51 (s, 12H, ortho-CH3), 4.70 (s,
4H, Im-H4,5), 7.21 (d, 4H, J = 7.60 Hz, meta-CH), 7.31 (t,
2H, J = 7.60 Hz, para-CH), 9.38 (s, 1H, Im-H2); 13C{H}
NMR (CDCl3): d = 18.4 (ortho-CH3), 52.1 (Im-C4,5),
130.4, 131.3, 134.0, 136.6 (Ar), 161.3 (Im-C2).
Compound 2c was prepared in the same way as 2a from
N,N0-bis(4-bromo-2,6-dimethylphenyl)imine 1b (4.22 g,
10 mmol) and sodium borohydride (1.60 g, 41 mmol) to
give colorless solid of 2c. Yield: 3.62 g, 85%; m.p = 97–
99 °C. Anal. Calc. for C18H22N2Br2: C, 50.73; H, 5.20;
N, 6.57. Found: C, 51.01; H, 5.19; N, 6.64%.
4.11. Preparation of 1,3-bis(2,4,6-trimethylphenyl)-4,5-
bis(methyl)imidazolinium chloride (3b0)
1H NMR (CDCl3): d = 2.17 (s, 12H, ortho-CH3), 3.05 (s,
4H, NCH2), 7.04 (s, 4H, meta-CH); 13C{H} NMR
(CDCl3): d = 18.6 (ortho-CH3), 48.9 (NCH2), 114.7,
131.2, 132.0, 145.7 (Ar).
A suspension of 1b0 (4 g, 12.5 mmol) in MeOH (50 mL)
was treated at room temperature under argon with NaC-
NBH3 (3.92 g, 62.5 mmol) in portions of 1 g over a period

3756
H. Tu¨rkmen, B. C¸ etinkaya / Journal of Organometallic Chemistry 691 (2006) 3749–3759
of 20 min. To the mixture was added bromo cresole green
and until a color change from green to yellow occurred,
0.1 N HCl was added. The solution was stirred for 20 h
and heated subsequently for 4 h under reflux. It was
cooled to room temperature and 0.1 N (10 mL) KOH
solution, (100 mL) H2O and (50 mL) 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. Et2O Æ HCl was
added to the CH2Cl2 solution. The obtained colorless
solid was filtered off and recrystallized from methanol
(10 mL)/diethyl ether (20 mL). Triethyl orthoformate
(10 mL) was added without isolation of the latter
compound. The mixture was stirred for 6 h in an oil bath
at 140 °C under an argon atmosphere. Meanwhile EtOH,
formed as a by product, is removed from the medium via
distillation. It was then cooled to room temperature and
Et2O (15 mL) was added. The resulting colorless solid
was filtered off and was crystallized from methanol
(5 mL)/diethyl ether (15 mL). Yield: 3.98 g, 86%;
m.p = 278–280 °C. Anal. Calc. for C23H31N2Cl: C,
74.47; H, 8.42; N, 7.55. Found: C, 74.91; H, 8.02; N,
7.83%.
1H NMR (CDCl3): d = 2.34 (s, 6H, para-CH3), 2.43 (s,
6H, ortho-CH3), 4.68 (s, 4H, Im-H4,5), 7.07 (d, 2H
J = 7.60 Hz, ortho-CH), 7.28 (s, 2H, meta-CH), 7.75 (d,
2H, J = 7.85 Hz meta-CH), 8.54 (s, 1H, Im-H2); 13C{H}
NMR (CDCl3): d = 18.4 (ortho-CH3), 21.4 (para-CH3),
53.3 (Im-C4,5), 126.6, 128.4, 132.3, 132.5, 132.5, 140.2
(Ar), 157.9 (Im-C2).
4.14. Preparation of 1,3-bis(4-chloro-2,6-
dimethylphenyl)imidazolinium chloride (3e)
Compound 3e was prepared in the same way as 3a from
N,N0-bis(4-chloro-2,6-dimethyl
phenyl)ethylenediamine
(2e) (3.37 g, 10 mmol), 10 mL of triethyl orthoformate
and ammonium chloride (0.54 g, 10.2 mmol) to give white
crystals of 3e. Yield: 3.26 g, 85%; mp = 345–346 °C. Anal.
Calc. for C19H21N2Cl3: C, 59.47; H, 5.52; N, 7.30. Found:
C, 59.45; H, 5.73; N, 7.49%.
1H NMR (CDCl3): d = 2.14 (s, 12H, ortho-CH3), 3.70 (s,
4H, Im-H4,5), 7.07 (s, 4H, meta-CH), 7.86 (s, 1H, Im-H2);
13C{H} NMR (CDCl3): d = 18.7 (ortho-CH3), 43.9 (Im-
C4,5), 129.2, 134.4, 137.0, 138.7 (Ar), 163.6 (Im-C2).
1H NMR (CDCl3): d = 1.40 (d, 6H, J = 1,4 Hz
Im ꢁ CH34;5), 2.23 (s, 6H, ortho-CH3), 2.29 (s, 6H, ortho-
CH3), 2.33 (s, 6H, para-CH3), 4.34 (m, 2H, Im-H4,5), 6.88
(s, 2H, meta-CH), 6.90 (s, 2H, meta-CH), 10.29 (s, 1H,
4.15. Preparation of 1,3-bis(2,4-dimethylphenyl)-2-
(trichloromethyl)imidazolidine (4d)
A 50 mL Schlenk tube was charged with 2d (1.21 g,
4.51 mmol) and 5 mL CH3COOH. The solution was trea-
ted with Cl3CCHO (1.00 mL, 10.17 mmol) and was left
to stand for 3 h at room temperature. The solid formed
was filtered and was recrystallized in CH2Cl2/hexane.
Yield: 1.33 g, 74%; m.p. = 144–145 °C. Anal. Calc. for
C20H23Cl3N2: C, 60.39; H, 5.83; N, 7.04. Found: C,
60.54; H, 5.48; N, 6.83%.
Im-H2); 13C{H} NMR (CDCl3): d = 17.9 (Im ꢁ CH 4;5);
3
18.5 ( ortho-CH3), 19.2 (ortho-CH3), 21.2 (para-CH3),
66.9 (Im-C4,5), 128.9, 130.4, 130.5, 134.8, 136.3, 140.3
(Ar), 160.6 ( Im-C2).
4.12. Preparation of 1,3-bis(4-bromo-2,6-
dimethylphenyl)imidazolinium chloride (3c)
1H NMR (CDCl3): d = 2.23 (s, 6H, para-CH3), 2.30 (s,
6H, ortho-CH3), 3.08 (s, 2H, NCH2), 3.82 (s, 2H, NCH2),
5.68 (s, H, NCHCCl3N), 6.72 (s, 2H, meta-CH), 6.96 (dd,
2H, J = 3.6 Hz, ortho-CH), 7.20 (d, 2H, J = 3.61, Ar-
CH); 13C NMR (CDCl3): d = 18.9 (para-CH3), 21.2
(ortho-CH3), 55.3 (NCH2), 92.4 (NCHCCl3N), 108.1
(NCHCCl3N), 122.8, 127.8, 132.4, 134.5, 135.5, 147.2
(Ar).
Compound 3c was prepared in the same way as 3a
from N,N0-bis(4-bromo-2,6-dimethylphenyl)ethylenedia-
mine (2c) (4.26 g, 10 mmol), 10 mL of triethyl orthofor-
mate and ammonium chloride (0.54 g, 10.2 mmol) to
give white crystals of 3c. Yield: 4.11 g, 87%; mp = 358–
360 °C. Anal. Calc. for C18H22N2Br2Cl: C, 48.28; H,
4.48; N, 5.93. Found: C, 49.40; H, 4.35; N, 6.01%.
1H NMR (CDCl3): d = 2.46 (s, 12H, ortho-CH3), 4.55 (s,
4H, Im-H4,5), 7.60 (s, 4H, meta-CH), 9.31 (s, 1H, Im-H2);
13C{H} NMR (CDCl3): d = 17.8 (ortho-CH3), 51.4
(Im-C4,5), 123.6, 132.1, 133.5, 139.3 (Ar), 161.1 (Im-C2).
4.16. trans-Bis[1,3-bis(2,6-dimethylphenylimidazolidin-2-
ylidene)]dichloropalladium(II) (5a)
Imidazolinium salt 3a (0.31 g, 10 mmol) was dissolved
in 50 mL CH2Cl2 and Ag2O (0.12 g, 5 mmol) added.
The resulting black suspension was protected from light
and stirred for 24 h at RT until only a voluminous light
grey precipitate remained, followed by addition of
PdCl2(NCCH3)2 (0.13 g, 5 mmol). The yellow color faded
after several minutes, and after a further two days the
reaction was filtered. The CH2Cl2 removed in vacuo,
and the residue was washed with Et2O. The crude prod-
uct was recrystallized from CH2Cl2/Et2O. Yield: 0.44 g,
60%; m.p = 304–306 °C; t(NCN) (cmꢁ1) = 1457. Anal.
4.13. Preparation of 1,3-bis(2,4-
dimethylphenyl)imidazolinium chloride (3d)
Compound 3d was prepared in the same way as 3a from
N,N0-bis(2,4-dimethyl phenyl)ethylenediamine (2d) (2.68 g,
10 mmol), 10 mL of triethyl orthoformate and ammonium
chloride (0.54 g, 10.2 mmol) to give white crystals of 3d.
Yield: 2.91 g, 93%; m.p = 290–292 °C. Anal. Calc. for
C18H23N2Cl: C, 72.48; H, 7.36; N, 8.90. Found: C, 70.53;
H, 6.25; N, 8.52%.

H. Tu¨rkmen, B. C¸ etinkaya / Journal of Organometallic Chemistry 691 (2006) 3749–3759
3757
Calc. for C38H44N2Cl2Pd: C, 62.17; H, 6.04; N, 7.63.
Found: C, 62.14; H, 6.35; N, 7.89%.
1H NMR (CDCl3): d = 2.10 (s, 12H, ortho-CH3), 2.44 (s,
12H, para-CH3), 3.67 (s, 8H, Im-H4,5), 6.80 (d, 4H,
J = 1.9 Hz, ortho-CH), 6.93 (s, 4H, meta-CH), 7.16 (d,
4H, J = 1.9 Hz, meta-CH); 13C{H} NMR (CDCl3):
d = 18.3 (ortho-CH3), 21.6 (para-CH3), 52.9 (Im-C4,5),
127.3, 129.9, 131.6, 135.8, 136.7, 137.5 (Ar), 199.2
(C–Pd).
1H NMR (CDCl3): d = 2.13 (s, 24H, ortho-CH3), 3.67 (s,
8H, Im-H4,5), 7.06 (d, 8H, J = 2.0 Hz, meta-CH), 7.23 (t,
4H, J = 2.0 Hz, para-CH); 13C{H} NMR (CDCl3):
d = 19.3 (ortho-CH3), 51.1 (Im-C4,5), 127.6, 128.8, 137.4,
138.6 (Ar), 198.7 (C–Pd).
4.17. trans-Bis[1,3-bis(2,4,6-trimethylphenylimidazolidin-2-
ylidene)]dichloropalladium(II) (5b)
4.21. trans-Bis[1,3-bis(4-chloro-2,6-
dimethylphenylimidazolidin-2-
ylidene)]dichloropalladium(II) (5e)
The product was obtained in a similar fashion to 5a as
yellow crystals. Yield: 0.49 g, 62%; m.p = 348–350 °C;
t(NCN) (cmꢁ1) = 1456. Anal. Calc. for C42H52N4Cl2Pd: C,
63.84; H, 6.63; N, 7.09. Found: C, 63.51; H, 6.94; N, 7.55%.
1H NMR (CDCl3): d = 2.10 (s, 24H, ortho-CH3), 2.43 (s,
12H, para-CH3), 3.65 (s, 8H, Im-H4,5), 6.86 (s, 8H, meta-
CH); 13C{H} NMR (CDCl3): d = 19.2 (ortho-CH3), 21.4
(para-CH3), 51.2 (Im-C4,5), 129.4, 136.1, 136.8, 137.1
(Ar), 199.0 (C–Pd).
The product was obtained in a similar fashion to 5a as
yellow crystals. Yield: 0.61 g 70%; m.p = >323 °C; t(NCN)
(cmꢁ1) = 1457. Anal. Calc. for C38H42N4Cl6Pd Æ 4H2O: C,
48.35; H, 5.13; N, 5.94. Found: C, 48.38; H, 5.28; N, 5.82%.
1H NMR (CDCl3): d = 2.14 (s, 24H, ortho-CH3), 3.68 (s,
8H, Im-H4,5), 7.07 (s, 8H, meta-CH); 13C{H} NMR
(CDCl3): d = 19.2 (ortho-CH3), 50.9 (Im-C4,5), 128.6,
133.1, 136.7, 139.4 (Ar), 199.4 (C–Pd).
4.18. trans-Bis[1,3-bis(2,4,6-trimethylphenyl)-4,5-
bis(methyl)imidazolidin-2-ylidene]dichloro palladium(II)
(5b0)
4.22. trans-[1,3-Bis(2,6-dimethylphenyl)imidazolidin-2-
ylidene]dichlorotriphenylphosphine palladium(II) (6a)
A suspension of the salt 3a (0.16 g, 0.5 mmol) and
sodium hydride (0.17 g, 0.75 mmol) in THF (10 mL) was
heated under reflux for 4 h. The mixture was cooled to
25 °C, and volatiles were removed. The residue was
charged with [PdCl2(PPh3)]2 (0.22 g, 0.25 mmol) and tolu-
ene (5 mL). The mixture was heated under reflux for 4 h,
after which it was cooled to room temperature and hexane
(10 mL) was added. The resulting cream precipitate was fil-
tered off and recrystallized from CH2Cl2/Et2O. Yield:
0.11 g, 63%; m.p. = 275–277 °C; t(NCN) (cmꢁ1) = 1456.
Anal. Calc. for C37H38Cl2N2PPd: C, 61.90; H, 5.19; N,
3,90. Found: C, 61.77; H, 4,55; N, 4.77%.
The product was obtained in a similar fashion to 5a as
cream crystals. Yield: 0.62 g, 73%; m.p = >318 °C; t(NCN)
(cmꢁ1) = 1449. Anal. Calc. for C46H60N4Cl2Pd: C, 65.28;
H, 7.15; N, 6.62. Found: C, 65.22; H, 7.30; N, 6.91%.
1H NMR (CDCl3): d = 1.01 (d, 24H J = 1.5 Hz,
Im ꢁ CH34;5), 1.83 (s, 12H, ortho-CH3) 1.86 (s, 12H, ortho-
CH3), 2.43 (s, 12H, para-CH3), 3.62 (m, 4H, Im-H4,5), 6.85
(s, 4H, meta-CH); 6.87 (s, 4H, meta-CH); 13C{H} NMR
(CDCl3): d = 19.5 (Im ꢁ CH34;5), 20.0 (ortho-CH3), 20.1
(ortho-CH3), 21.4 (para-CH3), 65.8 (Im-C4,5), 129.2, 130.0,
134.8, 136.5, 137.2, 138.2 (Ar), 196.7 (C–Pd).
1H NMR (CDCl3): d = 2.57 (s, 12H, ortho-CH3), 4.04 (s,
4H, Im-H4,5), 7.31–7.17 (m, 21H, Ar, PPh3); 13C{H} NMR
(CDCl3): d = 19.6 (ortho-CH3), 51.2 (Im-C4,5), 127.8 (d,
JC–P = 9.9 Hz, m-C PC6H5), 129.9 (d, JC–P = 2.3 Hz, p-C
PC6H5), 130.6 (d, JC–P = 44.2 Hz, ipso-C PC6H5), 128.6,
128.7, 132.3, 138.0 (Ar), 135.1 (d, JC–P = 10.7 Hz, o-C
4.19. trans-Bis[1,3-bis(4-bromo-2,6-
dimethylphenylimidazolidin-2- ylidene)]dichloropalladium(II)
(5c)
The product was obtained in a similar fashion to 5a as
yellow crystals. Yield: 0.77 g 74%; m.p = >320 °C; t(NCN)
(cmꢁ1) = 1457. Anal. Calc. for C38H40N4Br4Cl2Pd: C,
43.48; H, 3.84; N, 5.34. Found: C, 43.51; H, 4.35; N, 5.64%.
1H NMR (CDCl3): d = 2.12 (s, 24H, ortho-CH3), 3.69 (s,
8H, Im-H4,5), 7.24 (s, 8H, meta-CH), 13C{H} NMR
(CDCl3): d = 19.1 (ortho-CH3), 50.8 (Im-C4,5), 121.6,
131.6, 137.1, 139.6 (Ar), 199.4 (C–Pd).
2
PC6H5), 197.5 (d, JC–P = 184.5 Hz, C–Pd); 31P{H}
NMR (CDCl3): d = 21.27.
4.23. trans-[1,3-Bis(2,4,6-trimethylphenyl)imidazolidin-2-
ylidene]dichlorotriphenylphosphine palladium(II) (6b)
The product was obtained in a similar fashion to 6a as
yellow crystals. Yield: 0.30 g, 75%; m.p = 272–274 °C;
t(NCN) (cmꢁ1) = 1457. Anal. Calc. for C39H41Cl2N2PPd:
C, 62.79; H, 5.54; N, 3,75. Found: C, 61.63; H, 5,55; N,
4.20. trans-Bis[1,3-bis(2,4-dimethylphenylimidazolidin-2-
ylidene)]dichloropalladium(II) (5d)
1
3.75%. H NMR (CDCl3): d = 2.41 (s, 12H, ortho-CH3),
The product was obtained in a similar fashion to 5a as yel-
low crystals. Yield: 0.44 g, 60%; m.p = 185–186 °C; t(NCN)
(cmꢁ1) = 1456. Anal. Calc. for C38H46N4Cl2Pd Æ 2H2O: C,
59.26; H, 6.28; N, 7.27. Found: C, 60.01; H, 6.32; N, 7.40%.
2.53 (s, 6H, para-CH3), 4.00 (s, 4H, Im-H4,5), 7.30–7.16
(m, 19H, Ar, PPH3); 13C{H} NMR (CDCl3): d = 19.5
(ortho-CH3), 21.4 (para-CH3), 51.45 (Im-C4,5), 127.7 (d,
JC–P = 9.9 Hz, m-C PC6H5), 129.4 (Ar), 129.9 (d, JC–P
=

3758
H. Tu¨rkmen, B. C¸ etinkaya / Journal of Organometallic Chemistry 691 (2006) 3749–3759
2.3 Hz, p-C PC6H5), 130.7 (d, JC–P = 43.5 Hz, ipso-C
PC6H5), 135.2 (d, JC–P = 10.7 Hz, o-C PC6H5), 135.6,
Ar, PPh3), 7.88 (d, J = 1.9 Hz, 2H, Ar); 13C{H} NMR
(CDCl3): d = 18.0 (ortho-CH3), 20.8 (para-CH3), 51.9
(Im-C4,5), 127.2 (d, JC–P = 10.0 Hz, m-C PC6H5), 129.8
(d, JC–P = 42.4 Hz, ipso-C PC6H5), 126.6, 129.4, 129.9,
2
137.6, 138.0 (Ar), 197.2 (d, JC–P = 185.3 Hz, C–Pd);
31P{H} NMR (CDCl3): d = 20.88.
131.3 (Ar, p-C PC6H5), 134.4 (d, JC–P = 11.3 Hz, o-C
2
4.24. trans-[1,3-Bis(2,4,6-trimethylphenyl)-4,5-
bis(methyl)imidazolidin-2-ylidene]dichloro
triphenylphosphine palladium(II) (6b0)
PC6H5), 135.3, 136.4, 137.5 (Ar), 196.8 (d, JC–P
180.8 Hz, C–Pd), 31P{H} NMR (CDCl3): d = 19.46.
=
4.27. trans-[1,3-Bis(4-chloro-2,6-
dimethylphenyl)imidazolidin-2-ylidene]dichlorotriphenyl
phosphinepalladium(II) (6e)
The product was obtained in a similar fashion to 6a as
yellow crystals. Yield: 0.60 g, 78%; m.p = 230–232 °C;
t(NCN) (cmꢁ1) = 1449. Anal. Calc. for C41H45Cl2N2PPd:
C, 63.61; H, 3.62; N, 5.86. Found: C, 63.97; H, 3,70; N,
5.75%. 1H NMR (CDCl3): d = 1,29 (d, J = 1.2 Hz,
Im ꢁ CH34;5), 2.41 (s, 6H, ortho-CH3), 2.44 (s, 6H, ortho-
CH3), 2.63 (s, 6H, para-CH3), 4.01 (m, 2H, Im-H4,5), 6.94
(s, 2H, meta-CH), 7.07 (s, 2H, meta-CH), 7.26–7.31 (m,
15H, PPh3); 13C{H} NMR (CDCl3): d = 19.6 (s,
Im ꢁ CH34;5), 19.9 (ortho-CH3), 20.1 (ortho-CH3), 21.4
(para-CH3), 63.2 (Im-C4,5), 127.9 (d, JC–P = 9.9 Hz, m-C
PC6H5), 129.4 (d, JC–P = 2.3 Hz, p-C PC6H5), 129.6 (Ar),
The product was obtained in a similar fashion to 6a as
yellow crystals. Yield: 0.26 g, 68%; m.p = 270 °C; t(NCN)
(cmꢁ1) = 1457. Anal. Calc. for C37H35Cl4N2PPd: C,
56.47; H, 4.48; N, 3,56. Found: C, 56.53; H, 4,50; N,
1
3.80%. H NMR (CDCl3): d = 2.53 (s, 12H, ortho-CH3),
3.99 (s, 4H, Im-H4,5), 7.19–7.33 (m, 19H, Ar, PPH3);
13C{H} NMR (CDCl3): d = 19.6 (ortho-CH3), 51.3 (Im-
C4,5), 127.8 (d, JC–P = 10.6 Hz, m-C PC6H5), 129.4 (Ar),
129.9 (d, JC–P = 2.3 Hz, p-C PC6H5), 130.3 (d, JC–P
=
130.6 (d, JC–P = 43.5 Hz, ipso-C PC6H5), 134.6 (d, JC–P
=
44.3 Hz, ipso-C PC6H5), 135.0 (d, JC–P = 11.4 Hz, o-C
2
10.7 Hz, o-C PC6H5), 137.6, 137.7, 137.8, 138.1,138.7
PC6H5), 133.9, 136.6, 139.4 (Ar), 198.3 (d, JC–P
184.5 Hz, CPd); 31P{H} NMR (CDCl3): d = 21.50.
=
2
(Ar), 194.9 (d, JC–P = 185.3 Hz, C–Pd); 31P{H} NMR
(d, CDCl3): d = 21.01.
Acknowledgment
4.25. trans-[1,3-Bis(4-bromo-2,6-
dimethylphenyl)imidazolidin-2-ylidene]dichlorotriphenyl
phosphinepalladium(II) (6c)
Financial support from Ege university (Projects 03-BIL-
015) and (05-FEN- 020) is gratefully acknowledged.
The product was obtained in a similar fashion to 6a as
yellow crystals. Yield: 0.34 g, 77%; m.p = 267 °C; t(NCN)
(cmꢁ1) = 1457. Anal. Calc. for C37H35Cl2Br2N2PPd: C,
50.74; H, 4.03; N, 3,20. Found: C, 51.33; H, 4,25; N,
Appendix A. Supplementary data
Supplementary data associated with this article can
be found, in the online version, at doi:10.1016/
j.jorganchem.2006.05.020.
1
3.25%. H NMR (CDCl3): d = 2.52 (s,12H, ortho-CH3),
3.99 (s, 4H, Im-H4,5), 7.24–7.36 (m, 19H, Ar, PPH3);
13C{H} NMR (CDCl3): d = 19.5 (ortho-CH3), 51.2 (Im-
C4,5), 127.7 (d, JC–P = 9.9 Hz, m-C PC6H5), 129.4 (Ar),
129.9 (d, JC–P = 2.3 Hz, p-C PC6H5), 130.7 (d, JC–P
=
References
43.5 Hz, ipso-C PC6H5), 135.1 (d, JC–P = 10.7 Hz, o-C
2
PC6H5), 135.6, 137.6, 138.0 (Ar), 198.7 (d, JC–P
183.8 Hz, CPd); 31P{H} NMR (CDCl3): d = 21.50.
=
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