Synthesis and structural characterization of cis isomer of 1,2,3-triazol-5-ylidene based palladium complexes

Article abstract of DOI:10.1016/j.jorganchem.2013.03.008

A palladium complex (3) of abnormal N-heterocyclic carbene (NHC) namely, 4-(hydroxymethyl)-3-methyl-1-phenyl-1H-1,2,3-triazol-5-ylidene was prepared via silver carbene transmetalation method and characterized by spectroscopic and single crystal XRD data.

Full text of DOI:10.1016/j.jorganchem.2013.03.008

Journal of Organometallic Chemistry 736 (2013) 36e41
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Note
Synthesis and structural characterization of cis isomer of 1,2,3-triazol-5-ylidene
based palladium complexes
*
Rajendran Saravanakumar, Venkatachalam Ramkumar, Sethuraman Sankararaman
Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A palladium complex (3) of abnormal N-heterocyclic carbene (NHC) namely, 4-(hydroxymethyl)-3-
methyl-1-phenyl-1H-1,2,3-triazol-5-ylidene was prepared via silver carbene transmetalation method
and characterized by spectroscopic and single crystal XRD data. Single crystal analysis revealed the
structure of the complex 3 to be a cis isomer. The synthesis of palladium complex 6 via silver carbene
transmetalation method led to a mixture of cisetrans isomers. In this case trans isomer was formed as
major product. We have reported earlier the synthesis and structural characterization of trans isomer
(trans-6). However, the presence of cis isomer was not recognized until the crude reaction mixture was
recrystallized from acetonitrile. Pure cis isomer (cis-6) was obtained by washing the cisetrans mixture
with acetonitrile followed by slow evaporation of acetonitrile solution at 35 ꢀC. Structure of cis (cis-6)
isomer was unambiguously established by single crystal XRD data.
Received 7 January 2013
Received in revised form
19 February 2013
Accepted 5 March 2013
Keywords:
N-Heterocyclic carbenes (NHCs)
Abnormal carbene
Transmetalation
Palladium
Ó 2013 Elsevier B.V. All rights reserved.
1,2,3-Triazolylidene
1. Introduction
flanked by a nitrogen atom and a non-hetero atom, typically carbon
atom, it is termed as abnormal carbene. Abnormal carbenes were
Chemistry of N-heterocyclic carbenes (NHCs) has gained mo-
mentum after the isolation of free N-heterocyclic carbene by
Arduengo and coworkers in 1991 [1] as it is evident from number of
publications that have appeared over past two decades on prop-
erties and application of NHCs [2e7]. NHCs have been used as
organocatalysts in various organic transformations [8]. More
important is their use as ligands in organometallic chemistry. NHCs
have been used as efficient ligands for transition metals and other
group metals [9e12]. Most significantly, a number of NHC-metal
complexes have been successfully used as catalyst for various re-
actions such as cross coupling reactions [13], olefin metathesis [14],
hydrogenation [15,16], CeH activation [17,18], click reaction [19,20]
etc. The remarkable stability and performance of NHC-metal
proved to be stronger sigma donors compared to normal carbenes
[23,24]. Albrecht et al., in 2008 introduced a new class of abnormal
NHC namely 1,2,3-triazolylidene as efficient ligand for transition
metals [25]. Since then it has attracted numerous researchers due
to its simple synthetic procedure and strong sigma donating ability.
In the recent past number of publications on the synthesis and
catalytic study of 1,2,3-triazolylidene-metal complexes has
increased [26e40]. The structure and stereochemistry of the vast
majority of the complexes reported so far correspond to either the
trans mononuclear or bridged binuclear complex. Herein we report
the synthesis and structural characterization of cis isomer of 1,2,3-
triazol-5-ylidene based palladium complexes. 4-(Hydroxymethyl)-
3-methyl-1-phenyl-1H-1,2,3-triazol-5-ylidene was chosen as
a
complexes have been attributed to strong
s
-donating and weak
ligand in order to explore the possibility of chelating the oxygen
atom of the pendent hydroxyl methyl group to palladium. We
report the isolation and structural characterization of cis palladium
complex formed as minor product in the synthesis of palladium
complex 6.
p-acceptor property of NHCs and strong metal-carbene bond [21].
Imidazole based NHCs have been well established compared to
other NHCs such as 1,2,4-triazolylidenes, pyrazolylidenes, tetrazo-
lylidenes, thiazolylidenes, 1,2,3-triazolylidenes etc. Based on het-
eroatom availability on the vicinity of carbene center, NHCs have
been classified as normal and abnormal carbenes [22]. If carbene
center is flanked by hetero atoms, at least one of which is typically a
nitrogen atom, it is termed as normal carbene. If carbene center is
2. Results and discussion
2.1. Synthesis of triazolium iodide 2
Triazolium salt 2 an effective precursor for preparing palladium
complex was obtained from phenyl azide and propargyl alcohol.
* Corresponding author. Tel.: þ91 44 2257 4210; fax: þ91 44 2257 0545.
E-mail address: sanka@iitm.ac.in (S. Sankararaman).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.03.008

R. Saravanakumar et al. / Journal of Organometallic Chemistry 736 (2013) 36e41
37
Scheme 1. Synthesis of triazolium salt 2 via click reaction followed by N-methylation.
Copper(I) catalyzed ‘click’ reaction between phenyl azide and
propargyl alcohol gave triazole 1 in 63% yield (Scheme 1). The crude
triazole 1 was reacted with methyl iodide at 80 ꢀC in a teflon lined
steel autoclave to give triazolium salt 2 in 83% yield (Scheme 1). In
1H NMR spectra triazole (1) and triazolium (2) protons appeared at
8.01 and 9.35 ppm, respectively.
2.2. Synthesis of palladium complex 3
Fig. 1. ORTEP diagram of compound 3 with thermal ellipsoid drawn at 30% probability.
Palladium complex 3 was obtained from triazolium iodide 2 via
silver carbene transmetalation method (Scheme 2). To a dichloro-
methane solution of triazolium iodide (2) freshly prepared Ag2O
was added and stirred at room temperature for 24 h in absence of
light (complete conversion of triazolium salt 2 to silver carbene
complex was confirmed by disappearance of triazolium proton at
9.35 ppm in 1H NMR spectrum). The silver carbene thus generated
in situ was reacted with PdCl2(CH3CN)2 and stirred additionally for
12 h at room temperature. After completion, solvent was removed
under reduced pressure to give crude product as pale yellow solid.
Analytically pure sample was obtained by washing the crude
product with acetonitrile to give off-white solid in 41% yield. The
palladium complex was characterized by spectroscopic and single
crystal XRD data.
Selected bond lengths (A) and bond angles (ꢀ): Pd1eC1
¼
1.982(3), Pd1e
ꢀ
C11 ¼ 1.965(4), Pd1eCl1 ¼ 2.371(11), N3eC1 ¼ 1.340(5), C1eC2 ¼ 1.382(5), N3eC1e
C2 103.2(3), N6eC11eC12 103.0(3), N3eC1ePd1 129.8(3), C2eC1e
Pd1 ¼ 126.9(3). Hydrogen atoms are excluded for clarity.
¼
¼
¼
Hence, NMR spectra was recorded in deuterated 1,1,2,2-
tetrachloroethane (C2D2Cl4). The 1H NMR spectrum shows two
separate AB quartet for two methylene protons (CH2OH) at 4.82 and
3.76 ppm (assigned based on 1He1H and 1He13C COSY spectra, SI
Figs. 5 and 6). This clearly indicated that in solution rotation
about CeCH2OH bond is hindered. Resonance signal due to hy-
droxyl proton merged with one of the methylene signal and
appeared at 3.77 ppm. A singlet at 3.89 ppm corresponded to
N-methyl protons.
The off-white solid is air and moisture stable for prolonged
period. It is poorly soluble in chloroform and dichloromethane.
However, it is considerably soluble in 1,1,2,2-tetrachloroethane.
Structure of the palladium complex 3 was established by single
crystal XRD (Fig. 1) (Table 1). Single crystals were obtained by slow
Scheme 2. Synthesis of palladium complex 3 via silver carbene transmetalation method.

38
R. Saravanakumar et al. / Journal of Organometallic Chemistry 736 (2013) 36e41
evaporation of chloroformeacetonitrile (1:1) solution of 3 at room
temperature (35 ꢀC). In the synthesis of palladium complex 6
(Scheme 3), trans isomer (trans-6) was formed as major product,
whereas in the synthesis of complex 3 (Scheme 2) cis isomer
was formed as major product. This might be due to interaction of
hydroxy group with palladium center during the complex
formation.
Complex 3 adopts a square planar geometry around palladium
center with cis orientation of two 1,2,3-triazol-5-ylidene ligands
and chloride ions, respectively. The N-methyl groups are oriented
anti to each other with respect to C2-axis passing between the
triazolylidene ligands, bisecting the Cl1ePdeCl2 angle. The Pd1e
2.3. Synthesis of palladium complex 6
We have reported earlier [32] the synthesis and structural
characterization of trans isomer, trans-6 (Scheme 3). However, we
did not realize the presence of cis isomer, cis-6 until the crude
product was recrystallized from acetonitrile. Herein we report the
isolation and structural characterization of cis isomer, cis-6.
Addition of freshly prepared silver oxide to a dichloromethane
solution of triazolium iodide 4 and stirring for 8 h at room tem-
perature resulted in silver carbene complex 5. The silver carbene
complex 5 was isolated and characterized by spectroscopic data
[32]. Palladium complex (6) was prepared by reacting the in situ
generated silver carbene complex with Pd(CH3CN)2Cl2. Removal of
solvent gave crude product as pale yellow solid. In the 1H NMR
spectrum of crude product the signals were broad and splitting
patterns were not clear. Recrystallization of crude product in
chloroformeacetone (1:1) mixture resulted in single crystals along
with precipitate. It was characterized by spectroscopic and single
crystal XRD data [32], and it was identified as trans isomer, trans-6.
We have established that trans-6 exists as a mixture of syneanti
conformers in solution [32].
ꢀ
ꢀ
C11 distance is 1.965 A and C12eC11eN6 bond angle is 103.0(3) ,
these bond length and angle are consistent with other 1,2,3-triazol-
5-ylidene-palladium complexes [31]. PdeC12 (palladium-chlorine)
ꢀ
distance is 2.370 A slightly longer than other cis imidazolylidenee
palladium complexes (2.341ee2.358 A) [39]. This reflects a strong
ꢀ
trans effect of 1,2,3-triazolylidene ligand. In the crystal structure
four types of weak hydrogen bonds were observed between
a
methylene hydrogen and chloride atom (C19eH19A/Cl2,
ꢀ
2.805 A), hydroxyl hydrogen and chloride atom (O1eH1/Cl1,
2.731 A), methyl hydrogen and chloride atom (C9eH9C/Cl1,
2.796 A) and N-methyl hydrogen and oxygen (C9eH9A/O2,
2.597 A).
ꢀ
Recrystallization of crude product was also attempted in
acetonitrile solvent. Crude product was partially soluble in aceto-
nitrile. The acetonitrile soluble portion was separated by filtration
ꢀ
ꢀ
Scheme 3. Synthesis of palladium complex 6 via silver carbene transmetalation method.

R. Saravanakumar et al. / Journal of Organometallic Chemistry 736 (2013) 36e41
39
Scheme 4. Interconversion of syneanti conformers of cis-6 in CDCl3.
and set for recrystallization. Slow evaporation of acetonitrile solu-
tion resulted in single crystals suitable for X-ray analysis and
spectroscopic studies. The 1H NMR spectrum is different from
trans-6 complex but, as in the case of trans-6, the 1H NMR spectrum
showed two sets of signals in the aromatic and N-methyl regions.
N-Methyl protons appeared as pair of singlet at
d 3.84 and
3.79 ppm, in approximately 1:2 ratio respectively. We presumed
that this may also exist as a pair of conformer presumably syneanti
conformer in solution (Scheme 4). Like trans-6, when 1H NMR
spectrum was recorded at 58 ꢀC two methyl signals merged and
gave a singlet at 3.80 ppm, matched with statistical average of 3.84
and 3.79 ppm. A systematic study of dynamics using VT-NMR in the
temperature range of 25e58 ꢀC revealed the coalescence temper-
ature to be 58 ꢀC and free energy of activation for interconversion
of presumed syneanti conformers of cis-6 at the coalescence
temperature is estimated [41] to be 69.88 ꢁ 0.1 kJ molꢂ1, nearly
the same as that of trans-6 [32]. It must be emphasized that once
isolated the cis-6 and trans-6 complexes were very stable and did
not interconvert in solution.
Fig. 2. ORTEP diagram of palladium complex ciseanti-6 with thermal ellipsoids at 30%
probability level. Selected bond distance (Ǻ) and angles (deg): Pd1eC1 ¼ 1.983(2), Ce
N1 ¼ 1.375(3), C1eC2 ¼ 1.384(3), Pd1eCl1 ¼ 2.366(8), N1eC1eC2 ¼ 102.7(2), N1eC1e
Pd1 ¼ 127.23(17), C2eC1ePd1 ¼ 130.00(19), C1ePd1eCl1 ¼ 90.97(7).
Table 1
Crystallographic data of complex 3 and cis-6.
Parameters
3
cis-6
Structure of the complex was unambiguously established by
single-crystal XRD data (Fig. 2) (Table 1). It was identified as cis
isomer, cis-6. A square planar geometry was observed around
palladium center with two triazolylidene ligands and two chlo-
rines placed in cis geometry, respectively. The PdeC1 bond length
Formula
Formula weight
C20H22Cl2N6O2Pd
555.74
C30H26Cl2N6Pd
647.87
Mo Ka
0.71073
Orthorhombic
Pccn
16.945(2)
11.8540(14)
14.030(2)
90
90
90
2818.1(7)
298(2)
4
11236/3513/0.0307
0.879
1312
2.10e28.30
1.016
R1 ¼ 0.0306
wR2 ¼ 0.0679
R1 ¼ 0.0597
wR2 ¼ 0.0785
Radiation
Mo K
a
ꢀ
l
(A)
0.71073
Orthorhombic
Pbca
12.9642(3)
16.3309(4)
21.1354(5)
90
Crystal system
Space group
ꢀ
ꢀ
ꢀ
a (A)
is 1.983 A, which is considerable shorter (2.035 A) than the cor-
responding trans complex (trans-6) and slightly shorter than the
other 1,2,3-triazolylidene-palladium complexes [31]. The NeCcar-
beneeC (N1eC7eC8) bond angle of 102.7ꢀ is consistent with other
1,2,3-triazolylideneepalladium complexes [31]. Pd1eCl1 distance
ꢀ
b (A)
ꢀ
c (A)
aꢀ
bꢀ
gꢀ
90
90
3
ꢀ
ꢀ
V (A )
4474.72(18)
298 (2)
8
6863/5541/0.0251
1.098
2240
2.22e28.15
1.053
R1 ¼ 0.0393
wR2 ¼ 0.0985
R1 ¼ 0.0620
wR2 ¼ 0.1108
is 2.366 A which is slightly longer than the trans-6 complex
T (K)
Z
ꢀ
(2.335 A) which indicates
triazolylidene ligand.
a strong trans effect of 1,2,3-
Reflections/unique/Rint
m
mmꢂ1
The cisetrans isomer mixture of complex 6 can also be separated
by two other methods. The cis isomer is soluble in acetonitrile
while the trans isomer is insoluble. (1) Crude product is partially
soluble in acetonitrile. Acetonitrile solution was separated by
filtration. Evaporation of acetonitrile solution gave pale yellow
solid. The pale yellow solid was dissolved in dichloromethane. Pure
cis isomer precipitated as white solid upon addition of acetone to
dichloromethane solution.
F(000)
range
q
Goodness-of-fit on F2
Final R indices
R indices (all data)
(2) The cisetrans mixture can also be separated by column
chromatography. In TLC, cis isomer appeared at w0.1 (Rf) and trans
isomer at w0.8 Rf when EtOAc/DCM (20:80) was used as eluent. The
1H NMR spectrum of column separated cis isomer shows some
impurity peaks hence, it was purified further. Addition of acetone to
dichloromethane solution of column separated cis product,
analytically pure sample was precipitated as white solid.
3. Conclusion
A hydroxy tethered 1,2,3-triazolylidene namely 4-(hydrox-
ymethyl)-3-methyl-1-phenyl-1H-1,2,3-triazolylidene has been
used as ligand for preparing a cis palladium complex (3). It was
prepared via transmetalation of the corresponding silver carbene

40
R. Saravanakumar et al. / Journal of Organometallic Chemistry 736 (2013) 36e41
with PdCl2(CH3CN)2 and characterized by spectroscopic and single
crystal XRD data. Single crystal analysis revealed complex 3 as a cis
isomer. Due to hindered rotation about CeCH2eOH axis methylene
protons appear as two separate AB quartets in C2D2Cl4. Palladium
complex 6 prepared from 1,4-diphenyl-3-methyl-1,2,3-triazolium
iodide and palladium via silver carbene transmetalation route.
Synthesis of palladium complex 6 led to a mixture of cisetrans
isomers. The trans isomer was formed as major product. We re-
ported earlier the isolation, spectroscopic and structural charac-
terization of trans isomer. However, the presence of minor isomer,
cis (cis-6) was not recognized until the crude reaction mixture was
recrystallized from acetonitrile. The cis (cis-6) isomer was isolated
and spectroscopically and structurally characterized. Like, trans
isomer (trans-6) cis (cis-6) also exists as syn-anti conformers in
solution. The free energy of activation for the interconversion of the
syn and anti isomers is estimated to be 69.8 ꢁ 0.1 kJ mol-1 from the
VT 1H NMR data.
compound (3) as off-white solid in (0.18 g) 41% yield. Single
crystals suitable for X-ray diffraction were obtained by slow
evaporation of CH3CN:CHCl3 (1:1) solution of 3 at room temper-
ature. Mp: 134e136 ꢀC; IR (KBr): 3418
(nOH), 2917, 1594,
1167 cmꢂ1
;
1H NMR (500 MHz, C2D2Cl4)
d
: 7.65 (d, 2H, J ¼ 7 Hz),
7.56 (t, 1H, J ¼ 7.5 Hz), 7.47 (t, 2H, J ¼ 8 Hz), 4.83 (dd, 1H, J ¼ 11,
9 Hz), 3.89 (s, 3H), 3.80e3.74 (m, 2H); 13C NMR (125 MHz,
C2D2Cl4)
d: 150.1, 144.4, 138.3, 129.9, 128.9, 124.4, 53.5, 36.2;
HRMS (ESI-MS): calcd for C22H26N7O2ClPd [M ꢂ Cl þ CH3CN, H]
561.0871 found 561.0873, calcd for C20H23N6O2ClPd [M ꢂ Cl þ H]
520.0606, found 520.0588; Anal. Calcd. for C20H22N6O2Cl2Pd
(555): C (43.24), H (3.96), N (15.13); found C (43.04), H (3.42),
N (14.82).
4.4. Synthesis of palladium complex 6
To a solution of 4 (250 mg, 0.69 mmol) in CH2Cl2 (20 mL) freshly
prepared Ag2O (96 mg, 0.41 mmol) was added and stirred at room
temperature for 8 h in the dark. To this Pd(CH3CN)2Cl2 (106 mg,
0.41 mmol) was added and stirred additionally for 8 h. It is then
filter through celite bed to remove the insolubles. The filtrate was
concentrated to w2 mL and the crude product was precipitated as a
yellow solid in (196 mg) 88% upon addition of excess of ether. The
1H NMR spectrum of crude reaction mixture indicates that the cis
and trans isomers were formed in approximately 1:6 ratio
respectively.
4. Experimental section
4.1. Synthesis of triazole 1
To a mixture of DMSO:H2O (9:1) (40 mL) solution phenyl azide
(4.09 g, 34.33 mmol, 1.1 equiv.) and copper iodide (1.19 g,
6.24 mmol, 0.2 equiv.) were added and stirred for 10 min. To this
propargyl alcohol (1.75 g, 31.21 mmol, 1 equiv.) was added and
stirred additionally for 24 h. Upon adding the reaction mixture to
ice cold water pale green solid was precipitated. Solvent was
filtered off and precipitate was washed with water (5 ꢃ 100 mL),
acetone (10 mL) and dried under vacuo to give 1 as a pale green
solid in (3.4 g) 63% yield. Mp: 102 ꢀC (decomposed); IR (KBr): 3381
The mixture containing cis and trans isomers can be separated in
two ways
(i) The crude product was suspended in acetonitrile (60 mL) and
warmed at 80 ꢀC for 15 min. cis isomer dissolved in acetonitrile
and the trans isomer remain undissolved. Filtration followed
by slow evaporation of acetonitrile solution leads to single
crystals. Alternatively, separation of acetonitrile solution by
filtration and evaporation under reduced pressure gave crude
cis isomer as pale yellow solid. Pure cis isomer was obtained by
dissolving the crude cis-product in dichloromethane and
precipitation by slow addition of acetone. The solution was
kept undisturbed for an hour for complete precipitation. It is
then filtered and dried under vacuo to give pure cis-6 isomer as
white solid in (25 mg) 11% yield.
(ii) The cisetrans mixture can also be separated by column chro-
matography. In TLC, cis isomer appeared at 0.1 (Rf) and trans
isomer at 0.8 Rf when EtOAc/DCM (20:80) was used as an
eluent. Column chromatography was performed with silica gel
(120e200 mesh). The trans isomer was separated using EtOAc/
DCM (5:95) as an eluent and cis isomer using DCM/MeOH
(90:10) as an eluent. The 1H NMR spectrum of column sepa-
rated cis isomer shows some impurity peaks hence, it was
purified further. Addition of acetone to dichloromethane
solution of column separated cis product, analytically pure
sample was precipitated as white solid.
(
nOH), 2924, 1594, 1011 cmꢂ1; 1H NMR (400 MHz, CDCl3)
d: 8.01 (s,
1H), 7.69e7.66 (m, 2H), 7.49e7.39 (m, 3H), 4.87 (eCH2eOH) (d, 2H,
J ¼ 4.4 Hz), 3.91 (broad, s, 1H) (eOH); 13C NMR (100 MHz, CDCl3)
148.6, 137.0, 129.7, 128.9, 120.5, 120.3, 56.3 (eCH2eOH).
d:
4.2. Synthesis of triazolium iodide 2
Methyl iodide (7.34 g, 3.24 mL, 51.72 mmol, 6 equiv.) was added
to acetonitrile (10 mL) solution of triazole 1 (1.5 g, 8.62 mmol,
1 equiv.) and heated in a teflon lined sealed steel vessel at 80 ꢀC for
36 h. After completion of reaction, solvent was removed under
vacuo and washed with ethyl acetate (5 ꢃ 10 mL) to give pale
yellow crystalline solid in (2.25 g) 83% yield. Mp: 140e142 ꢀC; IR
(KBr): 3316 (nOH), 1597, 1077 cmꢂ1 1H NMR (400 MHz, CDCl3)
; d:
9.35 (s, 1H), 7.92e7.90 (m, 2H), 7.65e7.63 (m, 3H), 5.15 (d, 2H,
J ¼ 6 Hz), 5.00 (t, 1H, J ¼ 6 Hz), 4.51 (s, 3H); 13C NMR (100 MHz,
CDCl3) d: 145.0, 134.7, 132.2, 130.7, 128.4, 121.7, 53.0 (eCH2eOH),
40.0 (eCH3eN); HRMS (ESI-MS) calcd for C10H13N3O [M þ H]þ
191.1059, found 191.1067.
4.3. Synthesis of palladium complex 3
Freshly prepared Ag2O (0.22 g, 0.94 mmol, 0.6 equiv.) was
added to CH2Cl2 (100 mL) solution of triazolium salt 2 (0.5 g,
1.57 mmol, 1 equiv.) under nitrogen atmosphere and stirred in
absence of light for 24 h (after 8 h 1H NMR for reaction mixture
shows the presence of triazolium proton peak at 9.33 ppm, hence
the reaction mixture was stirred for 24 h). To this PdCl2(CH3CN)2
(0.24 g, 0.94 mmol, 0.6 equiv.) was added and the reaction
mixture was continued stirring for 12 h. The reaction mixture was
filtered through celite bed to remove the insolubles. Solvent was
removed under reduced pressure to give crude compound 3 as
pale yellow solid. Which upon washing with acetonitrile
(2 ꢃ 15 mL) followed by ether (2 ꢃ 15 mL) resulted in pure
Mp: 238e240 ꢀC; IR (KBr): 2923, 1596, 1491 cmꢂ1
(400 MHz, CDCl3, 25 ꢀC)
;
1H NMR
: 8.39 (d, 2H, J ¼ 10.0 Hz), 8.22 (d, 2H,
d
J ¼ 9.5 Hz), 7.83 (d, 2H, J ¼ 9 Hz), 7.71 (d, 2H, J ¼ 9.5 Hz), 7.31e7.08
(m, 12H), 3.84 (s, 3H), 3.79 (s, 3H); 1H NMR (400 MHz, CDCl3, 58 ꢀC)
d
: 8.40e8.25 (broad m, 2H), 7.82e7.73 (broad m, 2H), 7.25e7.12 (m,
13
6H), 3.80 (s, 3H); C NMR (100 MHz, CDCl3, 25 ꢀC)
d: 147.4, 144.3,
144.0, 138.8, 138.3, 130.5, 130.3, 130.2, 129.9, 129.8, 129.5, 129.1,
128.9, 128.8, 128.7, 126.3, 125.9, 124.6, 124.0, 37.9, 37.7; ESI-MS m/z
611 [M ꢂ Cl]þ (showed the expected isotope pattern for mono-
nuclear complex); HRMS (ESI-MS) calcd for C30H27N6ClPd
[M ꢂ Cl þ H]þ 612.1020, found 612.1014.

R. Saravanakumar et al. / Journal of Organometallic Chemistry 736 (2013) 36e41
41
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We thank UGC for fellowship (RS), CSIR and DST, New Delhi for
financial support (SS) and the Department of Chemistry and SAIF,
IIT Madras for infrastructure facilities.
Appendix A. Supplementary material
CCDC 915854 and 915853 contain the supplementary crystal-
lographic data for complexes 3 and 6 respectively. These data can
be obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Appendix B. Supplementary material
Supplementary material related to this article can be found at
http://dx.doi.org/10.1016/j.jorganchem.2013.03.008.
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