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H. Yasuda et al. / Journal of Organometallic Chemistry 682 (2003) 66ꢃ72
/
were recorded on a JEOL-LA400WB superconducting
high-resolution spectrometer (400 MHz for 1H).
31P{1H}-NMR spectra were referenced to external 85%
phosphoric acid. IR spectra were recorded on a Shi-
madzu FTIR-8500 spectrometer. The elemental analyses
were carried out using a CE-EA 1110 automatic
elemental analyzer. The reaction products were analyzed
by GC using a capillary column: J&W Scientific DB-1
(60 m) on a Shimadzu GC-14A gas chromatograph
equipped with a flame ionization detector (FID) using
o-terphenyl as the internal standard. The GCMS
analysis was performed using a Shimadzu GC-17A gas
chromatograph connected to a QP-5000 mass spectro-
meter (EI 70 eV). The GC and GCMS analyses of the
product solutions containing 1 were conducted after the
solutions were mixed with excess 30% H2O2 and stirred
3.2. Thermolysis
A solution of 1 (50 mg, 0.063 mmol) in toluene (5 ml)
was heated to 100 8C and stirred at the same tempera-
ture for 2 h. The solution color quickly changed from
yellow to dark brown. After cooling, o-terphenyl (50
mg) was added to the reaction mixture as the internal
standard for GC analysis. Then excess 30% H2O2 was
added to the product solution as mentioned above. The
yield of DPC was 30% on 0.5 Pd by GC. The products
were further identified using GCMS by the comparison
of the retention time and fragmentation pattern with
authentic samples. The thermolysis was also followed by
31P{1H}-NMR. To an NMR tube (5 mm in diameter)
containing 1 (20 mg, 0.025 mmol) was added toluene-d8
(0.5 ml). The NMR tube was sealed under vacuum, and
then heated at 100 8C for 24 h. After cooling, the
31P{1H}-NMR spectrum was recorded at r.t. The
31P{1H}-NMR showed that 1 was completely converted
whereas PdCl2(PPh3)2 was a major palladium species
among several phosphine-containing species. The yield
of PdCl2(PPh3)2 was determined as follows. Because the
solubility of (PPh3)2PdCl2 in toluene is poor, the toluene
was removed under vacuum after the thermolysis and
the products were dissolved in CDCl3. Then, the yield
was measured by 31P-NMR using PMe(CH2CH2CF3)2
sealed in a glass tube as the external standard. The yield
of PdCl2(PPh3)2 thus estimated was 32% based on Pd.
The thermolysis of 1 in the presence of four equivalents
of PPh3 was carried out analogously. The yield of DPC
was 44% on 0.5 Pd. The thermolysis of 1 in the presence
of CO (1 atm) was also carried out analogously. The
yield of DPC was 31% on 0.5 Pd.
for 2ꢃ3 h at room temperature (r.t.): The injection of a
/
solution containing 1 alone in a GC or GCMS instru-
ment brought about the production of DPC resulting
from the decomposition of 1 in the injector port
(200 8C). When excess 30% H2O2 was added to the
solution of 1 followed by stirring for 2 h at room
temperature, 1 was decomposed and no DPC formation
was observed upon injection in the instrument.
3.1. Synthesis of PdCl(CO2Ph)(PPh3)2 (1)
To a solution of Pd(PPh3)4 (1.07 g, 0.93 mmol) in
toluene (60 ml) was added phenyl chloroformate (0.12
ml, 0.93 mmol). After stirring the reaction mixture for 1
h at room temperature, the solvent was evaporated. The
resulting product was repeatedly washed with ether and
dried under vacuum to give a pale yellow solid (0.72 g,
3.3. Reaction with methyl iodide
98% yield). Recrystallization from a THFꢃhexane
/
To a toluene (5 ml) solution of 1 (50 mg, 0.063 mmol)
was added one equivalent of methyl iodide (4.3 ml, 0.069
mmol) at room temperature. The reaction mixture was
then heated to 100 8C and stirred for 2 h. The yields of
phenyl acetate, anisole, and DPC determined by GC
were 58% (on Pd), 4% (on Pd), and 9% (on 0.5 Pd),
respectively.
1
solution at 4 8C gave yellow single crystals of 1. H-
NMR (400 MHz, THF-d8, 25 8C, ppm): d 5.47 (m, 2H,
ortho-H, CO2Ph), 6.76 (m, 3H, meta- and para-H,
CO2Ph), 7.32ꢃ
7.80 (m, 30H, PPh3). 13C{1H}-NMR
/
(100.4 MHz, THF-d8, 25 8C, ppm): d 121.96, 124.27,
128.17, 154.04 (CO2Ph), 128.96, 131.05, 132.74, 135.87
(PPh3), 182.18 (CO). 31P{1H}-NMR (161.7 MHz, THF-
d8, 25 8C, ppm): d 18.33 (s). IR (KBr, cmꢀ1): 1686
(nCO). Anal. Calc.: C, 65.58; H, 4.48; Cl, 4.50. Found: C,
64.94; H, 4.67; Cl, 4.92%.
PdCl(CO2Ph)(P(p-tolyl)3)2 (3) was synthesized in 82%
yield as yellow crystalline solids as described for the
synthesis of 1, but using Pd(P(p-tolyl)3)4 as a starting
material. Complex 3 had a better solubility in ether than
1. 1H-NMR (400 MHz, THF-d8, 25 8C, ppm): d 2.33 (s,
18H, Me), 5.41 (m, 2H, ortho-H, CO2Ph), 6.75 (m, 3H,
meta- and para-H, CO2Ph), 7.14 (d, 12H, meta-H, p-
tolyl), 7.63 (m, 12H, ortho-H, p-tolyl). 31P{1H}-NMR
(161.7 MHz, THF-d8, 25 8C, ppm): d 14.68 (s).
3.4. Reaction with phenyl chloroformate
To a toluene (5 ml) solution of 1 (50 mg, 0.063 mmol)
was added one equivalent of phenyl chloroformate (7.9
ml, 0.063 mmol). The reaction mixture was heated at
100 8C for 2 h. The yield of DPC on Pd was 73% based
on GC. The reaction with phenyl chloroformate was
also followed by 31P{1H}-NMR. To an NMR tube (5
mm in diameter) containing 1 (20 mg, 0.025 mmol) were
added toluene-d8 (0.5 ml) and phenyl chloroformate (3.1
ml, 0.025 mmol). The mixture was heated at 100 8C for 2
h. The 31P{1H}-NMR at room temperature revealed
Yasuda, Hiroyuki
