D. Pandiarajan, R. Ramesh / Journal of Organometallic Chemistry 708-709 (2012) 18e24
23
center. The catalytic efficiency of the one of the palladium(II)
hydrazone complexes (3) was determined in SuzukieMiyaura
cross-coupling reaction and was found to be excellent. This facile,
mild and general protocol represents, to a certain extent, a new
advance in SuzukieMiyaura cross-coupling reactions.
in CDCl3: d
21.76 (s). 1H NMR (400 MHz, CDCl3, Me4Si): 8.9 (1H, br s,
OH py), 8.5 (1H, s, HC]N), 7.9 (2H, d, AreH), 7.4 (2H, d, AreH) and
7.4e7.8 (15H, m, PPh3), 4.9 (2H, s, py CH2O), 1.9 (3H, s, CH3 py).
[Pd(PPh3)(L4)]: Yield: 90 mg, 94%. M.p. 224 ꢁC. C34H30N3O4PPd
(682.0): calcd. C 59.88, H 4.43, N 6.16; found C 59.95, H 4.48, N 6.23.
MS (ESI): m/z ¼ 681.7 [Mþ]. IR (KBr, nmax/cmꢀ1): 3256 (OH), 1675
4. Experimental section
(C]Nazomethine), 1371 (CeO). 31P-{1H} NMR in CDCl3: 21.78 (s). 1H
d
NMR (400 MHz, CDCl3, Me4Si): 8.9 (1H, br s, OH py), 8.5 (1H, s, HC]
N), 7.9 (2H, d, AreH), 7.3 (2H, d, AreH) and 7.4e7.8 (15H, m, PPh3),
4.9 (2H, s, py CH2O), 3.8 (3H, s, OeCH3), 1.9 (3H, s, CH3 py).
[Pd(PPh3)(L5)]: Yield: 65 mg, 66%. M.p. 242 ꢁC. C33H27N4O5PPd
(696.9): calcd. C 56.87, H 3.90, N 8.04; found C 56.93, H 3.86, N 8.09.
MS (ESI): m/z ¼ 696.7 [Mþ]. IR (KBr, nmax/cmꢀ1): 3208 (OH), 1685
4.1. Reagents and materials
The ligands (1e5) were prepared as per the procedure previ-
ously reported [42,43]. Commercially available Pd(PPh3)2Cl2 was
purchased from Aldrich. pyridoxal hydrochloride, substituted
benzoic acid hydrazide and aryl bromides, arylboronic acids were
purchased from Aldrich. All the reagents used were chemically pure
and analar grade. All solvents were distilled using the standard
procedures [56].
(C]Nazomethine), 1346 (CeO). 31P-{1H} NMR in CDCl3: 21.77 (s). 1H
d
NMR (400 MHz, CDCl3, Me4Si): 8.9 (1H, br s, OH py), 8.5 (1H, s, HC]
N), 8.2 (2H, d, AreH), 7.4 (2H, d, AreH) and 7.4e7.8 (15H, m, PPh3),
4.9 (2H, s, py CH2O), 1.9 (3H, s, CH3 py).
4.2. Methods and instrumentation
4.4. General procedure for SuzukieMiyaura coupling reactions
Microanalytical (C, H, N) data were obtained with a Per-
kineElmer model 240C elemental analyzer. Melting Points were
recorded in the Boetius micro heating table and are uncorrected.
Infrared spectra of complexes were recorded in KBr pellets with
In a typical run, an oven dried 25 mL flask equipped with a stir
bar was charged with a known catalyst (0.001 mmol), base
(1.5 mmol) and phenylboronic acid (0.75 mmol). To the above
mixture methanol (5 mL) and aryl halide (0.5 mmol) were added.
The reactions were allowed to reflux at 70 ꢁC. After the specified
time the flask was removed from the oil bath. The solvent was
removed and water (10 mL) was added followed by extraction with
diethyl ether (3 ꢂ 10 mL) and the catalyst was regenerated. The
combined organic layers were washed with water (3 ꢂ 10 mL),
dried over anhydrous Na2SO4, and filtered. The organic layers were
evaporated under reduced pressure and the residue was analyzed
by 1H NMR. All the conversions were taken from 1H NMR spec-
troscopy based on arylbromide methyl group [57,58] and the 1H
NMR data of all the products were given in supporting information.
a
PerkineElmer 597 spectrophotometer in the range
4000e400 cmꢀ1. Electronic spectra were recorded on a Varian Cary
300 Bio UVevis spectrophotometer using cuvettes of 1 cm path
length. 1H NMR spectra were recorded with a Bruker 400 MHz
spectrometer. All 1H, 31P NMR spectra were taken in pure deu-
teriated DMSO solvents. Chemical shifts (d) are given in ppm and
refer to TMS as internal standard. The proton signals of the
deuterated solvents were used as internal standards for the 1H NMR
spectra and 85% H3PO4 for the 31P NMR spectra. Mass spectra were
recorded using a Thermo Finnigan LCQ Advantage MAX 6000 ESI
mass spectrometer.
4.5. X-ray crystallography
4.3. General procedure for synthesis of palladium complexes
Single crystals of [Pd(PPh3)(L3)] (3) were grown by slow evap-
oration of chloroformemethanol solution at room temperature. A
crystal of dimensions 0.30 ꢂ 0.26 ꢂ 0.22 mm was selected and the
data were collected. Significant crystal data collection and refine-
ment parameters are listed in Table S1 (supporting information). A
single crystal of suitable size was mounted on the top of a glass
fiber, and transferred to a Stoe IPDS diffractometer using mono-
All Pd(II) complexes were prepared by a general method. An
equimolar ratio of the ligand (1 mmol), Pd(PPh3)2Cl2 (1 mmol) and
triethylamine (0.2 mL) were mixed in dry methanol with constant
stirring. The resulting yellow solution was stirred and heated under
reflux for 3 h. The reactions were monitored by thin-layer chro-
matography. The solid was obtained from the above reaction are
washed with cold methanol, ether and dried in vacuo. Single
crystals of suitable for X-ray diffraction analysis were grown from
mixture of chloroformemethanol solution at room temperature.
[Pd(PPh3)L1] (1) Yield: 49 mg, 52%. M.p. 238 ꢁC. C33H28N3O3PPd
(651.9): calcd. C 60.79, H 4.33, N 6.44; found C 60.72, H 4.38, N 6.49.
MS (ESI): m/z ¼ 651.8 [Mþ]. IR (KBr, nmax/cmꢀ1): 3178 (OH), 1607
chromated MoKa radiation. Corrections were made for Lorentz and
polarization effects as well as for absorption (numerical). The
structures were solved and refined by full-matrix least-squares
techniques on F2 using the SHELX-97 program [59,60]. The
absorption corrections were done by the multi scan technique. All
data were corrected for Lorentz and polarization effects, and the
non-hydrogen atoms were refined anisotropically. Hydrogen atoms
were included in the refinement process as per the riding model.
CCDC 837648 contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The
(C]Nazomethine), 1372 (CeO). 31P-{1H} NMR in CDCl3: 21.77 (s). 1H
d
NMR (400 MHz, CDCl3, Me4Si): 8.9 (1H, br s, OH py), 8.5 (1H, s, HC]
N), 8 (2H, d, AreH) and 7.3 (2H, d, AreH), 7.4e7.8 (15H, m, PPh3), 4.9
(2H, s, py CH2O), 1.9 (3H, s, CH3 py).
[Pd(PPh3)(L2)]: Yield: 72 mg, 73%. M.p. 249 ꢁC. C33H27ClN3O3PPd
(686.4): calcd. C 57.74, H 3.96, N 6.12; found C 57.76, H 3.93, N 6.20.
MS (ESI): m/z ¼ 687.7 [Mþ]. IR (KBr, nmax/cmꢀ1): 3179 (OH), 1610
(C]Nazomethine), 1368 (CeO). 31P-{1H} NMR in CDCl3:
d
21.78 (s). 1H
Acknowledgment
NMR (400 MHz, CDCl3, Me4Si): 8.9 (1H, br s, OH py), 8.5 (1H, s, HC]
N), 7.9 (2H, d, AreH), 7.3 (2H, d, AreH) and 7.4e7.8 (15H, m, PPh3),
4.9 (2H, s, py CH2O), 1.9 (3H, s, CH3 py).
Financial support by the Council of Scientific and Industrial
Research (CSIR) New Delhi [Grant 01(2156)/07/EMR-II] is gratefully
acknowledged. One of the authors S.D.P thanks CSIR for the award
of Senior Research Fellowship (SRF). We thank DST-FIST, UGC-SAP
India for X-ray, NMR facility, School of chemistry, Bharathidasan
University, Tiruchirappalli.
[Pd(PPh3)(L3)]: Yield: 78 mg, 75%. M.p. 236 ꢁC.
C33H27BrN3O3PPd (730.8): calcd. C 54.23, H 3.72, N 5.75; found C
54.29, H 3.66, N 5.71. MS (ESI): m/z ¼ 731.6 [Mþ]. IR (KBr, nmax
/
cmꢀ1): 3310 (OH), 1623 (C]Nazomethine), 1398 (CeO). 31P-{1H} NMR