The influence of moisture on deprotonation mode of imidazolinium chlorides with palladacycle acetate dimer

Article abstract of DOI:10.1016/j.jorganchem.2009.02.023

Deprotonation of 1,3-diorganyl imidazolinium salts, 1, with N,C-type palladacyclic acetate dimer 2 afforded novel NHC coordinated complexes 3 along with ring opening hydrolysis products 4, which may coordinate to palladium center via NH group to give 5a.

Full text of DOI:10.1016/j.jorganchem.2009.02.023

Journal of Organometallic Chemistry 694 (2009) 2179–2184
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
The influence of moisture on deprotonation mode of imidazolinium chlorides
with palladacycle acetate dimer
b
c
a
b
c
M. Emin Günay a, , Namık Özdemir , Mahmut Ulusoy , Melih Uçak , Muharrem Dinçer , Bekir Çetinkaya
*
a Department of Chemistry, Adnan Menderes University, 09010 Aydın, Turkey
b Department of Physics, Ondokuz Mayıs University, 55139 Kurupelit-Samsun, Turkey
c Department of Chemistry, Ege University, 35100 Bornova-Izmir, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Deprotonation of 1,3-diorganyl imidazolinium salts, 1, with N,C-type palladacyclic acetate dimer 2 affor-
ded novel NHC coordinated complexes 3 along with ring opening hydrolysis products 4, which may coor-
dinate to palladium center via NH group to give 5a. The hydrolysis necessitates the study of NHC complex
formation in anhydrous media. The new compounds were characterized by spectroscopic methods and
three of them (3c, 4c, 5a) by X-ray single-crystal diffraction studies.
Received 29 December 2008
Received in revised form 14 February 2009
Accepted 20 February 2009
Available online 5 March 2009
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
Palladacycles
Imidazolinium salts
N-heterocyclic carbenes
Ring opening
Hydrolysis
1. Introduction
2. Results and discussion
Although the majority of palladacycles reported to date contain
phosphines as ancillary ligands to stabilize the palladium center
[1–5], the price associated with alkyl phosphines, along with phos-
phine ligand decomposition byproduct removal difficulties, have
led to the use of N-heterocyclic carbenes (NHCs) as a versatile
ligand alternative. A number of palladacycles bearing unsaturated
NHCs have been found to be efficient catalysts for a variety of C–C
coupling reactions [6–9]. However, the studies on palladacycles
with saturated NHC ligands are limited [10].
2.1. Synthesis and characterization
Complexes with imidazolin-2-ylidenes and imidazolidin-2-yli-
denes can be prepared by various methods [16]. Among them
in situ, deprotonation reactions involving basic metal salts, such
as Pd(OAc)2, has attracted continuous interest since NHC com-
plexes can be obtained in high yields, under mild conditions, avoid-
ing the free NHC ligands which are difficult to handle, due to highly
reactive nature of the species [17–20].
In view of the above information and as part of our long-run-
ning project towards saturated NHCs [11–14], we focused our
attention on C,N-type cyclopalladated NHCs with 4-dimethylamin-
obenzyl substituted complexes. We thought it should be interest-
ing to determine the effect produced by NMe2 substituents,
which attached to p-position of N-benzyl group has shown a strong
influence, despite the isolated methylene groups between Pd
and phenyl ring [15]. In this study we sought to synthesize more
The reaction of 1a with 2 in 2:1 ratio did not proceed as we ex-
pected in THF, but rather gave 5a via the bridge cleavage by the
in situ formed formamide derivative 4. Because of the appearance
of the CHO and NH group in the product 4a, the conversions could
only have been facilitated by 2 in the presence of water. Consistent
with these when the reaction was repeated in carefully dried and
distilled toluene the formation of 3a was favored (Scheme 1).
Although the possible mechanism would be speculative, it seems
obvious that free NHC or the corresponding carbene dimer must
be generated initially followed by insertion into H–OH bond, then
cleavage of the ring and coordination of the hydrolysis product to
palladium center through NH group. Previous studies on the reac-
tivity of NHC showed that the saturated ring react instantly with
water to give formamide derivatives [21,22].
r
-donating NHC complexes of palladium(II) via direct interaction
of imidazolinium salts (1) with N,C-type palladacyclic acetate (2)
and discovered that hydrolysis of the ligand to afford N-formyl
compounds is facile.
Upon these results, we examined additional imidazolinium salts
1b and 1c to determine the scope of the reaction in the dried
* Corresponding author. Tel.: +90 256 212 8498; fax: +90 256 213 5379.
E-mail address: megunay@adu.edu.tr (M. Emin Günay).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.02.023

2180
M. Emin Günay et al. / Journal of Organometallic Chemistry 694 (2009) 2179–2184
R
N
CHO
R
N
N
(i)
NH
R
+
Pd
R
4b,c
Cl
N
R
N
OAc
3a-c
-
+
H
Pd
Cl
1/2
+
N
R
N
R
N
2
[NHC-H] +Cl-
Pd
(ii)
2
1
NCHO
R
Cl
N
c
a
b
5a
N
R =
Scheme 1. Synthesis of carbene adducts, 3a–c. Reagent and Conditions: (i) PhMe, 8 h, 110 °C; (ii) THF, 6 h, 65 °C.
toluene. We found that steric hindrance of the imidazolinium salts
do not diminish the generality of hydrolysis reaction with the basic
palladacyclic dimer 2. Thus, attempted deprotonation gave mix-
tures of desired NHC complexes 3b,c along with hydrolysis prod-
ucts 4b,c, indicating that H2O might also originate from the
crystals of imidazolinium salts. Therefore, the salts 1 were sub-
jected to TGA and observed to contain ca. 1 mol H2O. The difference
in coordination ability of hydrolysis products 4 were attributed to
the nature of alkylic R group and the steric congestion of 5b and 5c;
however the basicity of NMe2 group in 1a might play important
role here. These results suggest that the synthetic chemist must
be aware of the well-received deprotonation protocol involving
imidazolinium salts with basic transition metal precursors might
fail due to water content of the solvents or salts of any reaction
[23]. Clearly, the imidazolinium salt has a higher propensity for
the ring opening reaction than the imidazolinium counterpart. In
this connection we also noticed that for the preparation of Ag–
NHC complexes from Ag2O and saturated NHC-salts, use of molec-
ular sieve is necessary to improve the yield and purity [24,25].
All new compounds were characterized by NMR spectroscopy
and compounds 3c, 4c and 5a were further analyzed by X-ray crys-
tallography. In the 1H NMR spectra, the methylene protons show
multiplets rather than AB patterns in CDCl3. In the 13C NMR spec-
tra, the formation of 3a–c can readily be verified by the carbene
carbon atoms resonating in the range of d 201.1–207.2, which
are slightly more deshielded than those cis-PdX2(NHC) complexes
derived from saturated NHCs [26,27]. The complexes show only
one carbene signals in the 13C NMR spectra, suggesting that only
one isomer was obtained.
Fig. 1. A view of complex 3c, showing 40% probability displacement ellipsoids and
the atom-numbering scheme. H atoms have been omitted for clarity. Symmetry
codes: (i) ꢀx + 1, y ꢀ 1/2, ꢀz + 1/2; (ii) ꢀx + 1, ꢀy + 1, ꢀz; (iii) ꢀx + 1, y + 1/2, ꢀz + 1/
2.
Table 1
Selected bond lengths (Å) and angles (°) for 3c.
Bond lengths
Pd1–C12
Pd1–C11
Pd1–N1
1.9897(18)
1.990(2)
2.0807(17)
Pd1–C11
N2–C12
N3–C12
2.3868(6)
1.341(2)
1.352(2)
2.2. Structural description of 3c, 4c and 5a
Bond angles
The structure of complex 3c is shown in Fig. 1 and selected geo-
metric parameters are listed in Table 1. The complex contains a
phenylpyridine ligand, (I), with a PdII metal center, a 1,3-bis(2,
6-diisopropylphenyl)imidazolidine ligand, (II), and one chloride li-
gand. The coordination around the PdII ion is distorted cis-square-
planar, and the PdII ion is coordinated by one pyridine N atom and
one aryl C atom from the bidentate ligand (I), one carbene C atom
from the monodentate ligand (II), and one Cl atom. In the square-
planar coordination, atoms Pd1, C11, N1, Cl1 and C12 deviate by
0.026(1), ꢀ0.017(1), 0.007(1), ꢀ0.021(1) and 0.005(1) Å, respec-
tively, from the mean plane through these five atoms. The Cl-atom
occupies the trans site with respect to the metallated aryl C-atom.
A carbene C-atom satisfies the fourth coordination site in the
C12–Pd1–C11
C12–Pd1–N1
C11–Pd1–N1
97.52(8)
178.25(8)
81.13(9)
C12–Pd1–C11
C11–Pd1–C11
N1–Pd1–C11
89.36(5)
172.70(7)
91.94(7)
complex. The pyridine N- and aryl C-donor atoms form a five-
membered metallacycle (containing atoms N1/C5/C6/C11/Pd1)
with a maximum deviation from planarity being 0.056(2) Å for
atom N1. The angle sum about the divalent Pd atom is 359.9°,
the greatest deviation from orthogonality being 81.13(9)° for N1–
Pd1–C11. The bond angles at the Pd atom involving trans pairs of
substituents deviate from the expected value of 180°, being
178.25(8)° for the N1–Pd1–C12 angle and 172.70(7)° for the Cl1–

M. Emin Günay et al. / Journal of Organometallic Chemistry 694 (2009) 2179–2184
2181
bond character due to partial electron donation by nitrogen to
the carbene C-atom donor [29]. Theoretical studies also indicate
that the stability of these carbenes is due to electron donation from
the N-atom lone pairs into the formally empty p(p) orbital on the
carbene C atom [30].
The molecular structure of compound 4c is shown in Fig. 2 and
selected geometric parameters are listed in Table 2. In the com-
pound, the C13–N1 bond length of 1.333(4) Å, which is intermedi-
Table 3
Selected bond lenghts (Å) and angles (°) for 5a.
Bond lengths
Pd1–C11
Pd1–N1
Pd1–N3
Pd1–C11
O1–C23
1.983(4)
2.032(4)
2.079(4)
2.4239(13)
1.193(7)
N4–C23
1.334(7)
Fig. 2. A view of compound 4c, showing 30% probability displacement ellipsoids
and the atom-numbering scheme. H atoms have been omitted for clarity. Symmetry
codes: (i) x + 1/2, y, ꢀz + 1/2.
Bond angles
C11–Pd1–N1
C11–Pd1–N3
N1–Pd1–N3
C11–Pd1–C11
N1–Pd1–C11
C21–N3–C20–C17
C20–N3–C21–C22
C24–N4–C22–C21
N3–C21–C22–N4
80.92(18)
93.52(17)
169.71(16)
176.64(15)
96.10(12)
ꢀ179.0(4)
178.3(4)
N3–Pd1–C11
C21–N3–C20
C23–N4–C22
O1–C23–N4
89.66(11)
109.4(4)
120.7(5)
125.6(6)
Pd1–C11 angle. The plane of the phenylpyridine ligand is
quasi-coplanar with the coordination plane [interplanar dihe-
dral = 8.32(11)°], perhaps in consequence of the ‘‘protonic” H atom
at C1 forming an in-plane hydrogen bond to the adjacent Clꢀ
ligand.
As can be seen, the molecule is highly crowded with both the
carbene and phenylpyridine ligands presenting considerable steric
encumbrance around the periphery of the approximately square
planar complex. The plane of the carbene is approximately orthog-
onal to the square plane [70.39(7)°] The bonding within the N-het-
erocyclic carbene (NHC) ring indicates a pattern of delocalization
that extends from atom N2 to atom N3 through atom C12, the
N2–C12 [1.341(2) Å] and N3–C12 [1.352(2) Å] distances being sig-
nificantly shorter than the N2–C13 [1.469(2) Å] and N3–C14
[1.473(2)°] distances, in accordance with a previous study [28].
This observation is possibly indicative of a greater partial double-
C22–N4–C23–O1
C24–N4–C23–O1
C22–N4–C24–C25
4.8(10)
ꢀ83.0(6)
ꢀ179.8(6)
166.1(4)
ꢀ72.1(6)
Table 4
Summary of crystallographic data for 3c, 4c and 5a.
Parameter
3c
4c
5a
Empirical
formula
Crystal size
(mm)
C38H46ClN3Pd
C27H40N2O
C32H38ClN5OPd
0.72 ꢁ 0.63 ꢁ 0.56
0.72 ꢁ 0.37 ꢁ 0.13
0.38 ꢁ 0.32 ꢁ 0.26
Mr
686.63
408.61
650.52
Table 2
T (K)
296
296
296
Selected bond lengths (Å) and Angles (°) for 4c.
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
0.71073
Monoclinic
P21/c
12.1913(5)
15.0091(4)
21.0279(10)
90
0.71073
Orthorhombic
Pbca
11.8990(6)
22.2188(12)
19.6748(14)
90
0.71073
Monoclinic
C2/c
36.227(2)
9.8879(3)
19.3348(10)
90
Bond lengths
O1–C13
N1–C13
N1–C1
1.220(3)
1.333(4)
1.450(3)
1.466(3)
N2–C16
N2–C15
C14–C15
1.422(4)
1.461(3)
1.505(4)
N1–C14
a
(°)
b (°)
115.210(3)
90
3481.2(3)
4
1.310
0.64
90
90
5201.7(5)
8
1.044
116.270(4)
90
6210.5(5)
8
1.391
0.72
Bond angles
C13–N1–C1
C13–N1–C14
C1–N1–C13–O1
c
(°)
120.8(3)
118.9(2)
ꢀ179.4(3)
O1–C13–N1
N2–C15–C14
C14–N1–C13–O1
124.6(3)
109.2(2)
ꢀ2.6(5)
V (Å3)
Z
qcalcd (Mg/m3)
l
(mmꢀ1
)
0.06
h Range (°)
Index ranges
1.73–27.94
ꢀ15 6 h 6 15,
ꢀ19 6 k 6 19,
ꢀ27 6 l 6 27
49933
1.83–26
ꢀ14 6 h 6 14,
ꢀ27 6 k 6 27,
ꢀ24 6 l 6 24
35771
2.12–27.89
ꢀ47 6 h 6 47,
ꢀ13 6 k 6 12,
ꢀ25 6 l 6 24
31523
_
Number of
observed
reflections
Number of
independent
reflections
Number of
parameters
Goodness-of-fit
on F2
8261
5102
7390
388
271
362
1.005
0.942
1.053
Maximum/
minimum
0.43, ꢀ0.47
0.24, ꢀ0.22
0.47, ꢀ0.83
Dq )
(e Åꢀ3
R, wR (observed
0.0286, 0.0683
0.0435, 0.0715
0.0655, 0.1575
0.1524, 0.1947
0.0513, 0.1344
0.0798, 0.1451
data)a
R, wR (all data)a
Fig. 3. A view of complex 5a, showing 40% probability displacement ellipsoids and
the atom-numbering scheme. H atoms have been omitted for clarity. Symmetry
codes: (i) ꢀx + 1/2, ꢀy + 1/2, ꢀz + 1 ; (ii) ꢀx, y, ꢀz + 1/2.
a
Refinement method, full-matrix least-squares on F2.

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M. Emin Günay et al. / Journal of Organometallic Chemistry 694 (2009) 2179–2184
ate between a single and a double bond, and the bond angles
around atom N1 suggest that the lone pair of electrons on N1
undergoes delocalization, affording double-bond character to the
C13–N1 bond and forcing the O1/C13/N1/C1(C14) atoms into an al-
most planar conformation. The difference between the N2–C15 and
N2–C16 [1.461(3) and 1.422(4) Å, respectively] can be attributed to
the different hybridization of the Csp3 and Csp2 atoms.
multiplet; br., broad; signal. Coupling constants J are given in Hz.
Elemental analyses were carried out by the analytical service of
TUBITAK with a LECO CHNS 932 instrument. The thermogravime-
try (TG) curves were obtained by using TG-DTA Perkin–Elmer Dia-
mond system apparatus. The measurements were performed
under
a dynamic nitrogen atmosphere at a flow rate of
200 mL minꢀ1 up to 800 °C. Melting points was determined using
The structure of complex 5a is shown in Fig. 3 and selected geo-
metric parameters are listed in Table 3. The complex contains a
phenylpyridine (ppy) ligand, (I), with a PdII metal center, an N-
[4-(dimethylamino)benzyl]-N-{2-[4-(dimethylamino)benzyl-
amino]ethyl} formamide ligand, (II), and one chloride ligand. The
coordination around the PdII ion is distorted trans-square-planar,
and the PdII ion is coordinated by one pyridine N atom and one aryl
C atom from the bidentate ligand (I), one amine N atom from the
monodentate ligand (II), and one Cl atom. In the square-planar
coordination, atoms Pd1, Cl1, N1, N3 and C11 deviate by
0.052(2), 0.063(2), ꢀ0.105(2), ꢀ0.098(2) and 0.088(2)Å, respec-
tively, from the mean plane through these five atoms. The Cl-atom
occupies the trans site with respect to the metallated C-atom. An
amine N-atom satisfies the fourth coordination site in the complex.
The pyridine N- and aryl C-donor atoms form a five-membered
metallacycle (containing atoms N1/C5/C6/C11/Pd1) with a maxi-
mum deviation from planarity being 0.062(3) Å for atom N1. The
plane of the phenylpyridine ligand is quasi-coplanar with the coor-
dination plane [interplanar dihedral = 10.94(8)°], perhaps in conse-
quence of the ‘‘protonic” H atom at C1 forming an in-plane
hydrogen bond to the adjacent Clꢀ ligand.
an Electrothermal 9100 melting point detection apparatus.
4.2. Preparation of 1,3-bis(4-dimethylaminobenzyl)imidazolinium
chloride (1a)
A mixture of 1,2-bis(4-dimethylaminobenzylamino)ethane [34]
(3.26 g, 10.0 mmol), NH4Cl (0.53 g, 10.0 mmol) in triethyl orthofor-
mate (20 mL) was heated in a distillation apparatus until the distil-
lation of ethanol ceased. The temperature of the reaction mixture
reached 110 °C. Upon cooling to room temperature, diethyl ether
(20 mL) was added giving a colorless solid precipitate, which was
collected by filtration, and dried in vacuum. Recrystallization from
CH2Cl2/Et2O at 25 °C, gave colorless needles crystals of 1a which
was manually separated giving 82% yield (306 mg), m.p.: 222–
223 °C.
1H NMR (d, CDCl3): 2.87 [s, 12H, C6H4-p-N(CH3)2]; 3.67 [s, 4H,
NCH2CH2N]; 4.68 [s, 4H, NCH2(C6H4)-p-N(CH3)2]; 6.58 [d, 4H,
J = 8.4 Hz, Ar-CH]; 7.19 [d, 4H, J = 8.4 Hz, Ar-CH]; 10.02 [s, 1H,
NCHN]. 13C NMR (d, CDCl3): 40.5 [N(CH3)2]; 48.1 [NCH2CH2N];
51.2 [NCH2(C6H4)-p-N(CH3)2]; 113.0, 121.2, 130.3, 151.1 [Ar-C];
157.4 [NCHN].
The C23–N4 bond length of 1.334(7) Å, which is intermediate
between a single and a double bond, and the bond angles around
atom N4 suggest that the lone pair of electrons on N4 undergoes
delocalization, affording double-bond character to the C23–N4
bond and forcing the O1/C23/N4/C22(C24) atoms into an almost
planar conformation.
4.3. Preparation of chloro[1,3-bis(4-dimethylaminobenzyl)
imidazolidin-2-ylidene][2-{2-pyridyl}phenyl]palladium(II) (3a)
A
mixture of 1,3-bis(4-dimethylaminobenzyl)imidazolinium
chloride (2a), (0.233 g, 0.626 mmol) and complex 1 (0.200 g,
0.313 mmol) was heated in PhMe (5 mL) at 110 °C for 8 h. The sol-
vent was removed in vacuo, cold ether (5 mL) was added to induce
crystallization and the solid was recrystallized from CH2Cl2/hex-
ane. Yield: 0.167 g. (85%), m.p.: 165–166 °C. Anal. Calc. for
C32H36ClN5Pd: C, 60.76; H, 5.74; N, 11.07. Found: C, 60.54; H,
5.88; N, 10.48%.
The single-crystal data and X-ray collection parameters are gi-
ven in Table 4.
3. Conclusion
This study, involving deproptonation of imidazolinium salts (1)
with 2 revealed that the nature of products can be influenced by
the presence of water either in the solvent or as hydrate and N-
substituents on the ring [23,31]. Thus, N-benzyl substituted salt
1a in THF reacts only to give 5a as a result of hydrolysis of the ex-
pected NHC. The same reaction in dried toluene affords the ex-
pected Pd–NHC complex in 85% yield. Whereas N-aryl
substituted bulkier 1b and 1c with 2 yields both the Pd–NHC com-
plex (3b,c) and the formamides 4b and 4c. Such reactions might
accounts for low yields obtained in deprotonation procedures. Fur-
ther studies on the catalytic properties of NHC complexes 3a–c are
currently in progress.
1H NMR (d, CDCl3): 2.89 [s, 12H, C6H4-p-N(CH3)2]; 3.43–3.50 [m,
4H, NCH2CH2N]; 5.08 [d, 2H, J = 14.4 Hz, NCH2C6H4-p-N(CH3)2];
5.13 [d, 2H, J = 14.4 Hz, NCH2C6H4-p-N(CH3)2]; 6.63 [d, 4H,
J = 8.8 Hz, Ar-CH]; 7.08–7.20 [m, 4H, Ar-CH]; 7.28 [d, 4H,
J = 8.8 Hz, Ar-CH]; 7.58 [d, 1H, J = 8.4 Hz, Ar-CH]; 7.70 [d, 1H,
J = 8.4 Hz, Ar-CH]; 7.77 [t, 1H, J = 8.0 Hz, Ar-CH]; 9.35 [d, 1H,
J = 5.6 Hz, Ar-CH]. 13C NMR (d, CDCl3): 40.8 [N(CH3)2]; 48.2
[NCH2CH2N]; 55.2 [NCH2C6H4-p-N(CH3)2]; 112.7, 118.1, 122.2,
123.8, 123.9, 124.2, 129.9, 130.1, 137.5, 138.5, 146.8, 149.9,
150.4, 155.4, 164.3, [Ar-C], 201.1 [Pd-Ccarbene].
4.4. Preparation of chloro[4-dimethylaminobenzyl
{2-(4-dimethylaminobenzyl(formyl)amino)ethyl}ammonio]
[2-{2-pyridyl}phenyl]palladium(II) (5a)
4. Experiment
4.1. General comments
A mixture of N,N0-bis(4-dimethylaminobenzyl)imidazolinium
All reactions and manipulations of air-sensitive materials were
carried out under nitrogen and using standard Schlenk techniques.
Solvents were dried and freshly distilled prior to use. All other
chemicals were used as received. The precursors (1b,c) were pre-
pared according to the literature [32]. Palladium dimer (2) was also
prepared according to the literature [33]. NMR spectra were re-
corded at 297 K on a Varian Mercury AS 400 NMR instrument at
400 MHz (1H), 100.56 MHz (13C). NMR multiplicities are abbrevi-
ated as follows: s, singlet; d, doublet; t, triplet; sept., septet; m,
chloride (1a) (0.175 g, 0.47 mmol) and complex 2 (0.150 g,
0.234 mmol) was heated in THF (5 mL) at 65 °C for 6 h. The solvent
was removed in vacuo, cold ether (5 mL) was added to induce crys-
tallization and the white solid was recrystallized from CH2Cl2/hex-
ane. Yield: 0.100 g. (65%), m.p.: 178–180 °C. Anal. Calc. for
C32H38ClN5OPd: C, 59.08; H, 5.89; N, 10.77. Found: C, 59.34; H,
5.57; N, 10.56%.
1H NMR (d, CDCl3): 2.86–2.94 [m, 12H, C6H4-p-N(CH3)2]; 3.38–
3.85 [m, 4H, NHCH2CH2NCHO]; 4.27–4.36 [m, 2H, HNCH2C6H4-p-

M. Emin Günay et al. / Journal of Organometallic Chemistry 694 (2009) 2179–2184
2183
N(CH3)2]; 4.53–4.62 [m, 2H, NCHOCH2C6H4-p-N(CH3)2]; 6.21 [d,
4H, J = 8.0 Hz, Ar-CH]; 6.38 [d, 2H, J = 8.0 Hz, Ar-CH]; 6.62–6.69
[m, 3H, Ar-CH]; 6.99–7.15 [m, 2H, Ar-CH]; 7.21–7.27 [m, 1H, Ar-
CH]; 7.42–7.46 [m, 1H, Ar-CH]; 7.59–7.63 [t, 1H, J = 8.2 Hz, Ar-
CH]; 7.75–7.80 [q, 1H, Ar-CH]; 8.26 [s, 1H, CHO]; 9.45
[d, 1H, J = 8.0 Hz, Ar-CH]. 13C NMR (d, CDCl3): 40.6, 40.7, 40.8
[N(CH3)2]; 43.1 [CH2C6H4-p-N(CH3)2]; 45.3 [NHCH2CH2NCHO];
52.1 [NHCH2CH2NCHO]; 111.0, 112.3, 112.6, 118.3, 118.5, 119.0,
123.1, 124.1, 129.0, 129.3, 130.1, 138.6, 138.8, 146.3, 150.0,
152.5, 165.5 [Ar-C]; 163.0 [NCHO].
J = 6.0 Hz, Ar-CH]. 13C NMR (d, CDCl3): 23.7 [HC(CH3)2]; 24.6
[HC(CH3)2]; 26.5 [HC(CH3)2]; 27.3 [HC(CH3)2]; 28.7 [HC(CH3)2];
29.2 [HC(CH3)2]; 54.6 [NCH2CH2 N]; 117.6, 121.5, 123.1, 123.4,
124.5, 124.9, 129.0, 129.3, 136.8, 137.7, 137.9, 146.7, 146.8,
148.4, 150.1, 156.1, 164.4, [Ar-C], 207.2 [Pd-Ccarbene].
The remaining colorless crystals were recrystallized from
CH2Cl2/hexane to give 4c. Yield: 0.016 g. (10%), m.p.: 140–141 °C.
Anal. Calc. for C27H40N2O: C, 79.36; H, 9.87; N, 6.86. Found: C,
79.53; H, 9.34; N, 6.18%.
1H NMR (d, CDCl3): 1.14–1.15 [d, 6H, J = 7.0 Hz, CH(CH3)2];
1.17–1.18 [d, 12H, J = 7.0 Hz, CH(CH3)2]; 1.22–1.24 [d, 6H,
J = 6.7 Hz, CH(CH3)2]; 3.01–3.05 [m, 2H, CH(CH3)2]; 3.11–3.15 [m,
2H, CH(CH3)2]; 3.17–3.21 [m, 2H, NCH2CH2NH]; 3.87 [t, 2H,
NCH2CH2NH]; 7.02–7.07 [m, 3H, Ar-CH]; 7.21–7.23 [d, 1H,
J = 7.8 Hz, Ar-CH]; 7.35–7.37 [d, 2H, J = 7.8 Hz, Ar-CH]; 8.09 [s,
1H, NCHO]. 13C NMR (d, CDCl3): 23.7 [NHC6H3CH(CH3)2]; 24.4
[NHC6H3CH(CH3)2, NC6H3CH(CH3)2]; 25.6 [NC6H3CH(CH3)2]; 28.5
[NC6H3CH(CH3)2]; 48.9 [NHCH2CH2N]; 49.1 [NHCH2CH2N]; 123.7,
123.9, 124.7, 129.7, 135.7, 142.5, 143.1, 147.9 [Ar-C]; 164.1
[NCHO].
4.5. Preparation of chloro[1,3-bis(2,4,6-trimethylphenyl)imidazolidin-
2-ylidene][2-{2-pyridyl}phenyl]palladium(II), 3b and N,N’-bis(2,4,6-
trimethylphenyl)-N-formylethylenediamine (4b)
A
mixture of N,N0-bis(2,4,6-trimethylphenyl)imidazolinium
chloride (1b) (0.157 g, 0.46 mmol) and complex (0.150 g,
2
0.23 mmol) was heated in PhMe (5 mL) at 110 °C for 8 h. The sol-
vent was removed in vacuo, cold ether (5 mL) was added to induce
crystallization and the solid was recrystallized from CH2Cl2/hex-
ane. Yield: 0.103 g. (75%), m.p.: 212–213 °C. Anal. Calc. for
C32H34ClN3Pd: C, 63.79; H, 5.69; N, 6.97. Found: C, 63.28; H,
5.61; N, 6.97%.
4.6.1. Crystal structure determinations
Diffraction data for 3c, 4c and 5a were collected on a STOE IPDS
1H NMR (d, CDCl3): 2.16 [s, 6H, C6H2(CH3)3]; 2.32 [s, 6H,
C6H2(CH3)3]; 2.70 [s, 6H, C6H2(CH3)3]; 4.03–4.05 [m, 2H,
NCH2CH2N]; 4.11–4.14 [m, 2H, NCH2CH2 N]; 6.71 [s, 2H, Ar-CH];
6.87 [td, 1H, J = 8.0 Hz, Ar-CH]; 6.91 [s, 2H, Ar-CH]; 6.98 [td, 2H,
J = 8.0 Hz, Ar-CH]; 7.27 [dd, 1H, J = 8.0 Hz, Ar-CH]; 7.36 [d, 1H,
J = 8.0 Hz, Ar-CH]; 7.40 [dd, 1H, J = 8.0 Hz, Ar-CH]; 7.48 [td, 1H,
J = 8.0 Hz, Ar-CH]; 9.23 [dd, 1H, J = 8.0 Hz, Ar-CH]. 13C NMR (d,
CDCl3): 20.1 [C6H2(CH3)3]; 20.4 [C6H2(CH3)3]; 20.9 [C6H2(CH3)3];
52.0 [NCH2CH2 N]; 117.4, 121.4, 122.9, 123.6, 127.6, 129.1, 129.9,
135.2, 136.2, 137.7, 140.3, 146.3, 150.0, 154.1, 164.0 [Ar-C], 205.6
[Pd-Ccarbene]. The crude mixture was purified using flash chroma-
tography (90% Hexane–CH2Cl2, 9:1; 10% ethyl acetate). Compound
4b was obtained as a white solid. Yield: 0.010 g (7%), m.p.: 151–
152 °C. Anal. Calc. for C21H28N2O: C, 77.74; H, 8.70; N, 8.63. Found:
C, 77.62; H, 8.55; N, 8.68%.
II diffractometer using graphite-monochromated Mo Ka radiation
(k = 0.71073 Å) at 296 K. The structures were solved by direct-
methods using program SHELXS-97 [35]. All non-hydrogen atoms
were refined anisotropically by full-matrix least-squares methods
using program SHELXL-97 [36]. All hydrogen atoms were positioned
geometrically and treated using a riding model, fixing the bond
lengths at 0.96, 0.97, 0.98, 0.93 and 0.91 Å for CH3, CH2, CH, aro-
matic CH and NH, respectively. The displacement parameters of
the H atoms were constrained as Uiso(H) = 1.2Ueq (1.5Ueq for
methyl) of the carrier atom. Data collection: X-AREA [37]; cell refine-
ment: X-AREA; data reduction: X-RED32 [37]; molecular graphics:
ORTEP-3 for Windows [38]; software used to prepare material for
publication: WINGX [39] and PLATON [40].
Acknowledgments
1H NMR (d, CDCl3): 2.15–2.25 [m, 18H, C6H2(CH3)3]; 3.16 [t, 2H,
NCH2CH2NH]; 3.80 [t, 2H, NCH2CH2NH]; 4.73 [br, 1H, NH]; 6.78 [s,
2H, Ar-CH]; 6.94 [s, 2H, Ar-CH]; 8.03 [s, 1H, NCHO]. 13C NMR (d,
CDCl3): 20.3 [C6H2(CH3)3]; 21.1 [C6H2(CH3)3]; 21.6 [C6H2(CH3)3];
21.7 [C6H2(CH3)3]; 47.2 [NCH2CH2NH], 52.1 [NCH2CH2NH], 129.2,
129.5, 129.6, 129.7, 129.8, 135.9, 138.4, 143.2 [Ar-C]; 164.2
[NCHO].
Financial support from TUBITAK (Project: 104T203), Adnan
Menderes University (Project No: FEF-07006, FEF-07013 and FBE-
08001) and Ondokuz Mayıs University (Project: F-425) are grate-
fully acknowledged.
Appendix A. Supplementary material
4.6. Preparation of chloro[1,3-bis(2,6-diisopropylphenyl)imidazolidin-
2-ylidene][2-{2-pyridyl}phenyl]palladium(II) (3c) and N,N’-bis(2,6-
diisopropylphenyl)-N-formylethylenediamine (4c)
CCDC 693272, 693273 and 693274 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.jorganchem.2009.02.023.
A mixture of N,N0-bis(2,6-isopropylphenyl)imidazolinium chlo-
ride (1c) (0.197 g, 0.46 mmol) and complex 2 (0.150 g, 0.23 mmol)
was heated in PhMe (5 mL) at 110 °C for 8 h. The solvent was re-
moved in vacuo, cold ether (5 mL) was added to induce crystalliza-
tion and the solid was recrystallized from CH2Cl2/hexane. The
yellow crystals (3c) were manually separated from the reaction
mixture. Yield: 0.110 g. (70%), m.p.: 229–230 °C. Anal. Calc. for
C38H46ClN3Pd: C, 66.47; H, 6.75; N, 6.12. Found: C, 66.54; H,
7.01; N, 6.22%.
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