Transition Metal Chemistry
studies of the nature of active species have been performed
and are discussed.
(ppm): 24.30; 39.00; 55.92; 114.56; 115.10; 118.23; 121.95;
123.00; 128.03; 128.88; 128.91; 129.11; 130.46; 137.37;
137.45; 137.92; 138.95; 141.52; 142.22; 144.70; 146.81. 31
P
NMR (CDCl3): δ (ppm): 29.42; 23.27. MS (ESI) m/z (%)
791 (M+, 78%). Anal. Calc. for C39H34N3O4PPdS.CHCl3: C,
53.53; H, 3.93; N, 4.68. Found: C, 53.75; H, 3.92; N, 4.91.
Experimental section
Materials and methods
[Pd(L2)(OTs)(PPh3)] (2)
All moisture- and air-sensitive reactions were performed
using standard Schlenk line techniques. All solvents were
purchased from Merck and distilled under nitrogen in the
presence of suitable drying agents: diethyl ether, hexane
and toluene were dried over sodium wire and benzophe-
none, methanol and absolute ethanol over calcium oxide,
while dichloromethane was dried and distilled over phos-
phorus pentoxide. The chemicals, potassium iodide, sodium
hydroxide and potassium hydroxide, were purchased from
Merck, while deuterated chloroform, styrene, 1-hexene,
trans-2-hexene, trans-2-octene, p-TsOH, hydrochloric
acid, Pd(OAc)2 (98%), PPh3, 2-methoxyaniline (≥ 99.5%)
and 2-bromoaniline (98%) were purchased from Sigma-
Aldrich and used without further purifcation. The proli-
gands N-(1H-benzoimidazol-2-ylmethyl-2-methoxy)aniline
(L1) and N-(1H-benzoimidazol-2-ylmethyl-2-bromo)aniline
(L2) were synthesized following the published literature
method [17]. The palladium complexes [Pd(L1)ClMe] (4)
published procedure [16]. Nuclear magnetic resonance spec-
tra were acquired at 400 MHz for 1H, 100 MHz for 13C and
162 MHz for 31P on a Bruker Avance spectrometer equipped
with a Bruker magnet (9.395 T). All coupling constants are
reported in Hz. Elemental analyses were carried out using
a CHNS-O Flash 2000 thermoscientifc analyzer. GC–MS
analyses were conducted on a micromass LCT premier mass
spectrometer.
Complex 2 was synthesized following the procedure
described for 1 using Pd(AcO)2 (0.1 g, 0.44 mmol),
L2 (0.13 g, 0.44 mmol), p-TsOH (0.07 g, 0.44 mmol),
1
PPh3 (0.23 g, 0.89 mmol). Yield = 0.35 (93%). H NMR
(CDCl3): δH (ppm): 2.29 (s, 3H, CH3-OTs); 5.42 (s, 2H,
CH2); 6.92–7.09 (m, 4H, Ph-Aniline); 7.34–7.41 (m, 4H,
Ph-Benz); 7.46–7.50 (m, 2H, Ph-OTs); 7.54–7.62 (m, 6H,
PPh3); 7.64–7.70 (m, 9H, PPh3); 7.72–7.84 (m, 2H, Ph-OTs).
13C NMR (CDCl3): 24.3; 52.61; 114.30; 114.55; 115.72;
118.10; 119.44; 127.38; 128.00; 128.63; 128.80; 128.91;
130.43; 132.55; 137.30; 137.46; 146.81. 31P NMR (CDCl3):
δ (ppm): 29.55; 23.23. MS (ESI) m/z (%) 841 (M+, 69%).
Anal. Calc. for C38H31BrN3O4PPdS.0.5CHCl3: C, 52.15; H,
3.58; N, 4.74. Found: C, 52.59; H, 3.30; N, 4.80.
[Pd(L1)(OTs)(PCy3)] (3)
Complex 3 was synthesized following the procedure
described for 1 using Pd(AcO)2 (0.1 g, 0.44 mmol), L1
(0.11 g, 0.44 mmol), p-TsOH (0.15 g, 0.44 mmol), PCy3
(0.24 g, 0.89 mmol). Yield=0.38 (91%). 1H NMR (CDCl3):
δH (ppm): 1.24–1.28 (m, 13H, PCy3); 1.64–1.70 (m, 17H,
PCy3); 1.76–1.86 (s, 3H, OCH3); 1.93 (s, 3H, CH3-OTs);
4.84 (s, 2H, CH2); 6.88–7.02 (m, 4H, Ph-Aniline); 7.10–7.22
(m, 4H, Ph-Benz); 7.48–7.56 (m, 4H, Ph-OTs). 13C NMR
(CDCl3): 4.00; 27.20; 28.30; 30.90; 39.10; 55.90; 114.50;
115.30; 118.30; 121.90; 123.00; 128.10; 129.10; 130.10;
132.60; 137.90; 138.90; 141.50; 144.70; 149.80. 31P NMR
(CDCl3): δ (ppm): 48.53; 53.83. MS (ESI) m/z (%) 810 (M+,
51%). Anal. Calc. for C39H52N3O4PPdS.CHCl3: C, 52.97; H,
5.96; N, 4.52. Found: C, 53.12; H, 5.57; N, 4.37.
Synthesis of palladium(II) complexes
[Pd(L1)(OTs)(PPh3)] (1)
To a solution of L1 (0.11 g, 0.44 mmol) in chloroform
(5 mL) was added dropwise a solution of Pd(AcO)2 (0.10 g,
0.44 mmol) in chloroform (10 mL) followed by a solution of
PPh3 (0.23 g, 0.89 mmol) and p-TsOH (0.07 g, 0.44 mmol)
in chloroform (10 mL). The mixture was then stirred at room
temperature for 24 h. The organic volatiles were removed
in vacuo followed by recrystallization of the crude product
from CH2Cl2-hexane solvent system to give a light yellow
General procedure for the methoxycarbonylation
reactions
The catalytic methoxycarbonylation reactions were per-
formed in a stainless steel autoclave equipped with a tem-
perature control unit and a sample valve. In a typical exper-
iment, complex 1 (22.49 mg, 0.08 mmol), PPh3 (0.04 g,
0.16 mmol), HCl (0.02 mL, 0.80 mmol) and 1-hexene
(2 mL, 15.90 mmol) were dissolved in a mixture of metha-
nol (20 mL) and toluene (40 mL). The reactor was evacu-
ated and the catalytic solution was introduced to the reactor
via a cannula. The reactor was purged three times with CO,
1
solid. Yield = 0.28 g (79%). H NMR (CDCl3): δH (ppm):
2.10 (s, 3H, OCH3); 2.32 (s, 3H, CH3-OTs); 5.33 (s, 2H,
CH2); 7.02–7.16 (m, 8H, Ph-Aniline); 7.30–7.42 (m, 2H,
Ph-OTs); 7.44–752 (m, 8H, Ph-PPh3); 7.60–7.69 (m, 7H,
Ph-PPh3); 7.74–7.82 (m, 2H, Ph-OTs). 13C NMR (CDCl3): δ
1 3