E. Tas et al. / Journal of Organometallic Chemistry 694 (2009) 446–454
447
bond-forming processes. Therefore, the initial step was the selec-
tion of a potential catalytic system amenable to systematic struc-
tural and electronic variation. The fact that the steric hindered
Pd(II) metal complexes are thermally stable and not sensitive to
oxygen or moisture, as well as their ready economical synthetic ac-
cess, prompted us to study their activity as catalysts in C–C bond-
forming reactions. The other aim of this study is to establish a com-
parative electro-spectrochemical study on the new mono-and
dinuclear Pd(II) complexes based on the different molecular struc-
tures with NONO donor sites.
with (L4), followed by cooling to room temperature. The crystals
were filtered in vacuum. The products were the recrystallized in
ethanol. The products were soluble in common solvents such as
CHCl3, CH3CH2OH and DMF and DMSO.
2.1.1. For (L1) ligand
Color: Yellow; m.p: 283 °C; Yield (%): 72; Anal. Calc. for
C40H50N2O2 (F.W: 590.4 g/mol): C, 81.31; H, 8.53; N, 4.74. Found:
C, 8.52; H, 8.42; N, 5.16%. 1H NMR (75 MHz, CDCl3, Me4Si, ppm):
d = 13.68 (s, 2H, –OH, D-exchangeable), d = 8.73 (s, 2H, HC@N),
d = 8.22–8.19 (d, 2H, J = 9, Ar–CH), d = 7.58–7.49 (m, 4H, Ar–CH),
d = 7.29–7.21 (m, 4H, Ar–CH), d = 1.51 (s, 18H, C–CH3); d = 1.34 (s,
18H, C–CH3), 13C NMR (300 MHz, CDCl3, Me4Si, ppm): 164.97
(C@N); 158.37, 146.50, 140.79, 137.10, 128.91, 127.01, 122.08,
118.63, 114.89 (Ar–C); 35.20, 34.25, 31.50, 29.47 (C–CH3), IR (KBr
2. Experimental
All reagents and solvents used in this study were of reagent-
grade quality and obtained from commercial suppliers (Fluka,
Merck and Aldrich). The elemental analyses were carried out in
the facilities of Inonu University (Malatya, Turkey). The IR spectra
were recorded on a Perkin Elmer Spectrum RXI FT-IR Spectrometer
as KBr pellets. The 1H and 13C NMR spectra were recorded on a Bru-
ker-Avence 300 MHz spectrometers. The Magnetic Susceptibilities
were determined on a Sherwood Scientific Magnetic Susceptibility
Balance (Model MK1) at room temperature (20 °C) using
Hg[Co(SCN)4] as a calibrant; the diamagnetic corrections were cal-
culated from Pascal’s constants [25]. The electronic spectral studies
were conducted on a Perkin Elmer model Lambda 25 UV–visible
spectrophotometer in the wavelength 200–1100 nm. The cyclic
voltammograms (CV) were carried out using CV measurements
with Princeton Applied Research Model 2263 potentiostat con-
trolled by an external PC. A three electrode system (BAS model so-
lid cell stand) was used for CV measurements in DMSO and
consisted of a 1.6 mm diameter of platinum disc electrode as work-
ing electrode, a platinum wire counter electrode, and an Ag/AgCl
reference electrode. Tetra-n-butylammonium perchlorate (TBAP)
was used as a supporting electrolyte. The reference electrode was
separated from the bulk solution by a fritted-glass bridge filled
with the solvent/supporting electrolyte mixture. The ferrocene/fer-
rocenium couple (Fc/Fc+) was used as an internal standard but all
the potentials in the paper were referenced to the Ag/AgCl refer-
ence electrode. The solutions containing ligands and mono- and
dinuclear Pd(II) metal complexes were deoxygenated by a stream
of high purity nitrogen for at least 5 min. before running the exper-
iment and the solution was protected from air by a blanket of
nitrogen during the experiment. The UV–Vis spectroelectrochemi-
cal experiments were performed with a home-built thin-layer cell
which utilized a light transparent platinum gauze working elec-
trode. A platinum wire counter electrode and a Ag/AgCl reference
electrode were used for spectroelectrochemical cell. Potentials
were applied and monitored with a Princeton Applied Research
Model 2263 potentiostat. Time-resolved UV–Vis spectra were re-
corded on Agillent Model 8453 diode array spectrophotometer.
pellets,
2480–3615
375 and in DMSO: 275, 370.
m v(C@N), 2865–2957 v(Aliph C–H),
max/cmꢀ1): 1613
m
(OHꢁ ꢁ ꢁN). UV–Vis (kmax, nm) in CH2Cl2: 241, 275,
2.1.2. For (L2) ligand
Color: Yellow; m.p: 268 °C; Yield (%): 70; Anal. Calc. for
C43H52N2O2 (F.W: 628.9 g/mol): C, 82.12; H, 8.33; N, 4.45. Found:
C, 81.75; H, 8.25; N, 4.60%. 1H NMR (75 MHz, CDCl3, Me4Si,
ppm): d = 13.84 (s, 2H, –OH, D-exchangeable), d = 8.74 (s, 2H,
HC@N), d = 7.81–7.78 (d, 2H, J = 9, Ar–CH), d = 7.51 (s, 2H, Ar–CH),
d = 7.47–7.46 (d, 4H, J = 3, Ar–CH), d = 7.26–7.25 (d, 2H, J = 3, Ar–
CH), d = 3.98 (s, 2H, Cyc-CH2), d = 1.49 (s, 18H, C–CH3); d = 1.34 (s,
18H, C–CH3), 13C NMR (75 MHz, CDCl3, Me4Si, ppm): 162.90,
158,31 (C@N), 147,44, 144,77, 140,58, 139,93, 136,98, 127,96,
126,77, 120,59, 120,49, 118,43, 117,82 (Ar–C), 35.14, 34.03,
31.51, 29.45 (C–CH3), 36,98 (C–CH3) IR (KBr pellets,
1619 (C@N), 2868–2906 (Aliph C-H), 2480–3680 v(OHꢁ ꢁ ꢁN).
m
max/cmꢀ1):
v
v
UV–Vis (kmax, nm) in CH2Cl2: 241, 283, 382, 392 and in DMSO:
254, 377, 382, 401.
2.1.3. For (L3) ligand
Color: Dark White; m.p: 238 °C; Yield (%): 65; Anal. Calc. for
C40H50N2O2 (F.W: 590.4 g/mol): C, 81.31; H, 8.53; N, 4.74. Found:
C, 79.72; H, 8.06; N, 4.46%. 1H NMR (300 MHz, CDCl3, Me4Si, ppm):
d = 13.58 (s, 2H, –OH, D-exchangeable), d = 8.69 (s, 2H, HC@N),
d = 7.39–6.58 (m, 10H, Ar–CH), d = 1.45 (s, 18H, C–CH3); d = 1.31 (s,
18H, C–CH3), 13C NMR (75 MHz, CDCl3, Me4Si, ppm): 153.94
(C@N), 141.36, 141.15, 137.34, 134.75, 126.80, 125.54, 124.23,
121.69, 118.89, 114.05, 107.11 (Ar–C), 31.63, 29.68, (C–CH3),
35.28, 34.06 (C–CH3) IR (KBr pellets,
m
max/cmꢀ1): 1602
(OH). UV–Vis (kmax, nm)
v(C@N),
2866–2954 (Aliph C–H), 3314 and 3410
v
v
in CH2Cl2: 232, 287, 329, 343 and in DMSO: 285, 332, 347.
2.1.4. For (L4) ligand
Color: Yellow; m.p: 146 °C; Yield (%): 75; Anal. Calc. for
C43H52N2O3 (F.W: 644.4 g/mol): C, 80.09; H, 8.13; N, 4.34. Found:
C, 79.78; H, 8.04; N, 4.46%. 1H NMR (300 MHz, CDCl3, Me4Si,
ppm): d = 13.36 (s, 1H, –OH, D-exchangeable), 13.32 (s, 1H, –OH,
D-exchangeable), d = 8.71 (s, 1H, HC@N), d = 8.70 (s, 1H, HC@N),
d = 7.88–7.20 (m, 12H, Ar–CH), d = 1.44–1.43 (d, 18H, J = 3, C–
CH3); d = 1.33–1.31 (d, 18H, J = 6, C–CH3), 13C NMR (300 MHz,
CDCl3, Me4Si, ppm): 189.91 (C@O); 160.3, 159.9, 153.2, 153.0
(C@N); 140.9–112.6 (Ar–C); 25.9, 23.8 ve 29.5, 28.5 (C–CH3). IR
2.1. Synthesis of ligands
N,N0-[1,5-naphthalene]-3,5-Bu2t -salicylaldimine (L1), N,N0-[2,7-
fluarene]-3,5-But2-salicylaldimine (L2), N,N0-[1,8-naphthaline]-3,
5-But -salicylaldimine (L3) and N,N0-[3,4-benzophenon]-3,5-But2-
2
salicylaldimine) (L4) ligands were synthesized by the reaction of
1.58 g (10 mmol) 1,5-diaminonaphthalene in 40 mL absolute
methanol for (L1), 1.96 g (10 mmol) 2,7-diaminofluarene in 40 mL
absolute methanol for (L2), 1.58 g (10 mmol) 1,8-diaminonaphtha-
line in 40 mL absolute methanol for (L3) and 2.12 g (10 mmol) 3,4-
diaminobenzofenonin in 40 mL absolute methanol for (L4) and
4.70 g (20 mmol) 3,5-But2-salicylaldehyde in 40 mL absolute meth-
anol. Also, 3–4 drops of formic acid were added as catalyst. The
mixtures were refluxed 48 h for (L1) with (L2) and 6–8 h for (L3)
(KBr pellets,
(Aliph C-H), 2219–3505
284, 301, 408 and in DMSO: 263, 339.
m v(C@O), 1615 v(C@N), 2869–2965
max/cmꢀ1): 1657
v
v(OHꢁ ꢁ ꢁN). UV–Vis (kmax, nm) in CH2Cl2:
2.2. Synthesis of mono- and dinuclear Pd(II) metal complexes
0.59 g, 1.0 mmol ligand (L1), 0.63 g, 1.0 mmol ligand (L2), 0.59 g,
1.0 mmol ligand (L3) or 0.64 g, 1.0 mmol ligand (L4) were dissolved