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D.E. Bergbreiter et al. / Inorganica Chimica Acta 359 (2006) 1912–1922
2.5. Synthesis of 3,5-di(dicyclopentylphosphinomethyl)-
aniline-borane
2.7. Synthesis of 4-phthalimido-2,6-
bis(dicyclopentylphosphinomethyl)aniline-borane (30)
A solution of N-acetyl-3,5-di(dicyclopentylphosphinom-
ethyl)aniline-borane complex (2.45 g) in 10 mL of 95%
EtOH was allowed to react with NaOH (3.75 g) at reflux
for 20 h. After neutralization with concentrated HCl, the
majority of the solvent was removed under pressure. The
remaining residue was taken up in 50 mL of CH2Cl2,
washed with saturated Na2CO3 (3 · 10 mL), and dried over
MgSO4. The organic solvents were removed under pressure
to yield after chromatography (hexane/EtOAc 1/1) 1.3 g
(58% yield) of product: 1H NMR (300 MHz, CDCl3)
0.23–0.60 (br d, J = 114 Hz, 6H), 1.55–2.13 (m, 36H),
2.92 (d, J = 10.8 Hz, 4H), 3.48 (br, s, 2H), 6.46 (s, 2H),
6.50 (s, 1H); 31P NMR (CDCl3) 30.41; 13C NMR (CDCl3)
26.25 (d, J = 8.3 Hz), 26.75 (d, J = 9.18 Hz), 28.22 (d, J =
12.95 Hz), 30.80 (d, J = 29.05 Hz), 32.60 (d, J = 33.58 Hz),
115.14 (t, J = 3.02 Hz), 121.35, 135.16 (d, J = 1.51 Hz),
135.20 (d, J = 2.26 Hz), 146.70.
A
0.6-g sample 2,6-bis(dicyclopentylphosphinom-
ethyl)aniline-borane (29) (1.25 mmol) and 0.22 g
(1.5 mmol) of phthalic anhydride were added to 30 mL of
toluene and then refluxed for 24 h. The solvent was re-
moved under pressure, the resulting mixture was taken
up with 50 mL of dichloromethane, washed with 1 N HCl
(20 mL · 1), brine (20 mL · 2), and dried over MgSO4.
The solvent was removed under reduced pressure. Silica
gel chromatography (hexane/EtOAc 2/1) yielded 0.73 g of
product (96%): 31P NMR (CDCl3) 31.79; 1H NMR
(300 MHz, CDCl3) 0.40 (d, br, J = 103 Hz, 6H), 1.68 (m,
32H), 2.10 (m, 4H), 3.07 (d, J = 10.8 Hz, 4H), 7.20 (s,
3H), 7.79 (m, 2H), 7.94 (m, 2H).
2.8. Synthesis of 4-amino-2,6-
bis(dicyclopentylphosphinomethyl)phenylpalladium
trifluoroacetate (33)
2.6. Synthesis of 4-N-acetamido-2,6-
di(dicyclopentylphosphinomethyl)phenylpalladium
trifluoroacetate
A solution of 80 mg of 4-phthalimido-2,6-bis(dicycl-
opentyl-phosphinomethyl)phenylpalladium trifluoroace-
tate and 2 mL (34.90 mmol) of hydrazine hydrate in
20 mL of ethanol was stirred at room temperature for
48 h. Afterwards the solvent was removed under reduced
pressure. Silica gel chromatography (EtOAc/hexane 1/1)
yielded 42 mg of product (60%): 31P NMR (CDCl3)
A solution of N-acetyl-3,5-bis(dicyclopentylphosphi-
nomethyl)aniline-borane (0.3 g, 0.57 mmol) in 10 mL of
freshly distilled THF and 10 mL of diethylamine was deox-
ygenated (freeze–pump–thaw, 5 cycles) and then heated to
60 ꢁC for 12 h. The solvents were carefully removed under
reduced pressure at room temperature. Then the free bis-
phosphine was dissolved in 10 mL of degassed THF and a
solution of Pd(O2CCF3)2 (189.5 mg, 0.57 mmol) in 10 mL
of degassed THF was added slowly. The reaction mixture
was stirred at room temperature for 12 h and then at
65 ꢁC for 48 h. The solvents were removed under reduced
pressure. Column chromatography using silica gel (hexane/
EtOAc 1/1) afforded 34 mg of product (10% yield): 1H
NMR (300 MHz, CDCl3): 1.52–2.02 (m, 32H), 2.11 (s,
3H), 2.42 (m, 4H), 3.13 (t, J = 4.5 Hz, 4H), 7.20 (s, 2H),
7.39 (s, 1H); 31P NMR (CDCl3, d): 52.56; 13C NMR
(CDCl3, d): 24.59, 26.36 (t, J = 4.53 Hz), 26.53(t, J =
3.55 Hz), 28.96, 29.31 (t, J = 3.01 Hz), 35.48 (t, J =
12.06 Hz), 114.40 (t, J = 11.09 Hz), 135.40, 150.60 (t,
J = 11.62 Hz), 153.89, 168.24.
1
52.12; H NMR (300 MHz, CDCl3) 1.49–2.06 (m, 32H),
2.40 (m, 4H), 3.07 (t, J = 4.5 Hz, 4 H), 3.38 (s, br, 2H),
6.41 (s, 2H); 13C NMR (CDCl3) 26.29 (t, J = 4.5 Hz),
26.53 (t, J = 3.54 Hz), 28.97, 29.32 (t, J = 3.02 Hz), 29.67,
35.26 (t, J = 12.60 Hz), 35.38 (t, J = 12.07 Hz), 110.58 (t,
J = 11.54 Hz), 143.26, 147.48, 150.97 (t, J = 11.09 Hz).
2.9. X-ray characterization of palladacycles
Crystals of the complexes 28, 32, and 34 were obtained
from a mixture of dichloromethane and hexane. In each
of these cases, the trifluoroacetate anion was replaced by
a chloride anion in the crystalline solids that were isolated
and in turn analyzed by X-ray crystallography. The details
of the crystal data for structures 10a, 10b, 10c, 25, 28, 32,
and 34 are provided in the supplementary material.
The same procedure using 4-phthalimido-2,6-bis(dicyclo-
pentylphosphinomethyl)aniline-borane 33 mg (8.5% yield)
4-phthalimido-2,6-bis(dicyclopentylphosphinomethyl)phe-
nylpalladium trifluoroacetate (31): 1H NMR (300 MHz,
CDCl3) 1.52–2.02 (m, 32H), 2.44 (m, 4H), 3.23 (t, J =
4.2 Hz, 4H), 7.07 (s, 2H), 7.80 (dd, J = 3.0 and 5.4 Hz,
2H), 7.95 (dd, J = 3.3 and 5.4 Hz, 2H); 31P NMR (CDCl3,
d) 52.88; 13C NMR (CDCl3) 26.28 (t, J = 4.5 Hz), 26.54 (t,
J = 3.5 Hz), 29.06, 29.30 (t, J = 2.5 Hz), 35.32 (t, J =
12 Hz), 35.41 (t, J = 12 Hz), 120.43 (t, J = 11 Hz),
123.60, 128.47, 131.78, 134.29, 150.88 (t, J = 11.5 Hz),
159.41, 167.52.
3. Results and discussion
The general route to the thioarene-containing ligands
used to prepare SCS-Pd(II) complexes is shown in Scheme
1. This route typically used commercially available thioa-
renes. In the case of 2,4-dimethoxythiophenol and 4-dime-
thylaminothiophenol, we had to prepare the thioarene
using established chemistry (Eqs. (1) and (2)). In all the
syntheses of bisthioarene ligands, the same general route
was used [13]. The starting 5-amino isophthalic acid was
esterified and the resulting ester reduced using LiAlH4,
forming the amino diol. The NH2 group was protected