Dichloro-Bis(aminophosphine) Complexes of Palladium
FULL PAPER
75.4 MHz): d=50.6 (overlapping signals), 33.5 (brs), 30.5 (d, J=28.5 Hz),
29.0 (brs), 27.9 (d, J=22.2 Hz), 27.3 (brs), 25.7 ppm (s); 31P{1H} NMR
(C6D6, 121.5 MHz): d=99.3 ppm (s); elemental analysis calcd (%) for
C16H31N2P: C 68.05, H 11.06, N 9.92; found: C 68.22, H 11.14, N 9.81.
sented herein is extremely simple, highly convenient, and,
most important, universally applicable. The reactions are ex-
tremely clean (side-products have only rarely been detect-
ed).[38] As a consequence, the isolated yields of the coupling
products are typically only between 5 and 10% (sometimes
up to 15%) lower than the conversions reported. The cata-
lytic activities of the aminophosphine-based systems were
found to be dramatically improved compared with their
phosphine analogue due to significantly faster palladium
nanoparticle formation. Decomposition products are dicy-
clophosphinate, cyclohexylphosphonate, and phosphate,
which can easily be separated from the coupling products, a
great advantage when compared to non-water-soluble phos-
phine-based systems.
Preparation of
PACHTUGNERTN(UNG NC5H10)ACHTUGNTRNE(NUNG C6H11)2: Phosphorus trichloride (5 mL,
57.31 mmol) was dissolved in diethyl ether (400 mL) and cooled to
À788C. Cyclohexyl Grignard reagent C6H11MgBr (2 equiv, 1m, 114.6 mL)
was slowly added. After complete addition (monitored by 31P{1H} NMR
spectroscopy), the reaction mixture was warmed up to room temperature
and stirred for an hour and then an excess of piperidine (17 mL,
~3 equiv) was added. After stirring for an additional hour at room tem-
perature, the reaction mixture was filtered. The solid was washed with di-
ethyl ether (100 mL). The combined pale-yellow filtrates were dried in
vacuo and extracted with pentane to give 81% of the pure phosphine as
a colorless oil that solidified upon standing. 1H NMR (C6D6, 300 MHz):
d=2.94 (brs, 4H), 1.89–1.65 (m, 6H), 1.39–1.13 ppm (m, 22H); 13C{1H}
NMR (C6D6, 75.4 MHz): d=52.4 (brs), 36.6 (d, J=65.1 Hz), 30.5 (d, J=
33.6 Hz), 29.9 (brs), 27.5 (overlapping signals), 25.4 ppm (s); 31P{1H}
NMR (C6D6, 121.5 MHz): d=76.5 (s); elemental analysis calcd (%) for
C17H32NP: C 72.56, H 11.46, N 4.98; found: C 72.71, H 11.69, N 4.80.
General procedure for the synthesis of [(P
CAHUTTNGRNENG(U (NC5H10)3ÀnHCAUTNTGREN(NUGN C6H11)n)2Pd(Cl)2]
Experimental Section
(1–4): [Pd(cod)(Cl)2] (100 mg, 0.35 mmol) was suspended in toluene
AHCTUNGTRENNUNG
(10 mL). After the addition of solutions of toluene (10 mL) containing
2 equiv of the appropriate ligand, the reaction mixture was stirred for
10 min. Removal of the volatiles under reduced pressure and the addition
of pentane, followed by filtration afforded the yellow, analytically pure
palladium complexes 1–4 in almost quantitative yields.
Data for catalyst 1: 1H NMR (C6D6): d=3.35 (s, 24H; NCH2), 1.50 (s,
24H; NCH2CH2), 1.46 ppm (s, 12H; CH2); 13C{1H} NMR (C6D6): d=48.5
(s, NCH2), 27.0 (s, NCH2CH2), 25.7 ppm (s, NCH2CH2CH2); 31P{1H}
NMR (C6D6): d=92.5 ppm (s, PACTHUNRTGNE(GNU NC5H10)3); elemental analysis calcd (%)
for C30H60Cl2N6P2Pd: C 48.43, H 8.13, N 11.29; found: C 48.71, H 8.29, N
11.36.
Data for catalyst 2: 1H NMR (C6D6): d=3.31 (brs, 8H), 3.21 (brs, 8H),
2.24 (m, 4H), 1.82–1.21 ppm (m, 42H); 13C{1H} NMR (C6D6): d=49.0
(brs), 38.6 (t, J=71.5 Hz), 28.6 (brs), 27.5 (overlapping signals), 27.0
(overlapping signals), 25.5 ppm (s); 31P{1H} NMR (C6D6): d=102.7 ppm
General procedures: All synthetic operations for the catalyst preparation
were carried out in oven-dried glassware using a combination of glove-
box (M. Braun 150B-G-II) and Schlenk techniques under a dinitrogen at-
mosphere. Solvents were reagent grade or better and freshly distilled
under a N2 atmosphere by standard procedures. Deuteriated solvents
were purchased from Armar, dried by standard procedures, and degassed
by freeze–thaw cycles before use. All chemicals were purchased from Al-
drich Chemical Co., Acros Organics, or Fluka and used without further
purification.
Analysis: 1H, 13C{1H}, and 31P{1H} NMR data were recorded at 500.13,
125.76, and 202.46 MHz, respectively, on a Bruker DRX-500 spectrome-
ter or at 300.1, 121.5, and 75.4 MHz, respectively, on a Varian Gemini
spectrometer. Chemical shifts (d) are expressed in parts per million
(ppm) and coupling constants (J) are given in Hz. The 1H and 13C NMR
chemical shifts are reported relative to tetramethylsilane; the resonance
of the residual protons of the solvent was used as the internal standard
for 1H (d=7.15 ppm benzene) and all deuterium solvent peaks for 13C
(d=128.0 ppm benzene). All measurements were carried out at 298 K.
Abbreviations used in the description of NMR data are as follows: s, sin-
glet; d, doublet; t, triplet; m, multiplet. Elemental analyses were per-
formed on a Leco CHNS-932 analyzer at the University of Zurich, Swit-
zerland.
(s,
P
(NC5H10)
E
elemental
analysis
calcd
(%)
for
C32H62Cl2N4P2Pd: C 51.79, H 8.42, N 7.55; found: C 51.78, H 8.31, N 7.46.
Data for catalyst 3: 1H NMR (C6D6): d=3.21 (brs, 8H), 3.62 (brs, 4H),
3.32–2.28 (m, 4H), 1.95–1.16 ppm (m, 48H); 13C{1H} NMR (C6D6): d=
51.8 (t, J=49.5 Hz), 35.9 (t, J=50.3 Hz), 30.4 (s), 28.6 (s), 27.5–27.2
(overlapping signals), 25.0 ppm (s); 31P{1H} NMR (C6D6): d=80.0 ppm (s,
PACTHUNRTGNNEG(U NC5H10)CAHTUNGTRENN(UNG C6H11)2); elemental analysis calcd (%) for C34H64Cl2N2P2Pd:
C 55.17, H 8.72, N 3.78; found: C 55.24, H 8.80, N 3.77.
Preparation of PACHTUNGTRENNUNG(NC5H10)3: Phosphorus trichloride (5 mL, 57.31 mmol)
was dissolved in diethyl ether (200 mL) and cooled in an ice bath to 08C.
Piperidine (42.5 mL, 429.8 mmol, 7.5 equiv) was slowly added dropwise,
during which the formation of a white precipitate (C5H10N·HCl) was ob-
served. After complete addition, the suspension was allowed to warm up
to room temperature and was then stirred for an additional hour. The re-
action mixture was filtered and the solid was washed with additional di-
ethyl ether (100 mL). The pale-yellow filtrate was dried in vacuo to give
12.36 g (43.61 mmol, 76%) of an off-white solid. 1H NMR (C6D6): d=
2.95 (t, 3JHH =5.0 Hz, 12H), 1.45 ppm (brs, 18H); 13C{1H} NMR (C6D6):
d=47.3 (d, 2JPC =64.4 Hz), 27.5 (d, 3JPC =19.6 Hz), 26.1 ppm (s); 31P{1H}
General procedure for Suzuki cross-coupling reactions of aryl and benzyl
bromides with arylboronic acids: All catalytic reactions were carried out
in reaction vessels open to the air. A round-bottomed flask was charged
with the newly purchased or freshly recrystallized arylboronic acid
(2.0 mmol), the aryl halide, powdered K3PO4 (2.2 mmol), and toluene
(2.5 mL) of technical quality. The mixture was vigorously stirred and
heated to 808C. Then the correct amount of catalyst was added by sy-
ringe as a toluene solution. Samples were periodically taken from the re-
action mixture, quenched with water, extracted with ethyl acetate, and
analyzed by GC–MS. At the end of catalytic reaction, the reaction mix-
tures were allowed to cool to room temperature, quenched with water
(adjusted to an appropriate pH when biaryls with acidic or basic groups
had to be extracted), and extracted with ethyl acetate (3ꢃ40 mL). The
combined extracts were dried (MgSO4) and evaporated to dryness. The
crude material was purified by flash chromatography on silica gel, as nec-
essary. Isolated yields of the coupling products were typically between 5
and 10% (sometimes up to 15%) lower than the conversions reported in
the tables.
NMR (C6D6): d=117.3 ppm (s, P
ACHTUGNTERN(NGNU NC5H10)3).
Preparation of (NC5H10)2A(C6H11): Phosphorus trichloride (5 mL,
P
N
CHTUNGTRENNUNG
57.31 mmol) was dissolved in diethyl ether (400 mL) and cooled to
À788C. Cyclohexyl Grignard reagent C6H11MgBr (1 equiv, 1m, 57.3 mL)
was slowly added. After complete addition (monitored by 31P{1H} NMR
spectroscopy), an excess of piperidine (34 mL, ~6 equiv) was added and
then the reaction mixture was warmed up to room temperature and
stirred for an additional hour before filtering it. The solid was washed
with diethyl ether (100 mL). The combined pale-yellow filtrates were
dried in vacuo and extracted with pentane to give 84% of the pure phos-
phine as a colorless solid. Colorless crystals were obtained by recrystalli-
zation in pentane. 1H NMR (C6D6, 300 MHz): d=2.92 (t, 3JHH =4.8 Hz,
8H), 1.80–1.62 (m, 5H) 1.40–1.14 ppm (m, 18H); 13C{1H} NMR (C6D6,
Chem. Eur. J. 2010, 16, 4075 – 4081
ꢁ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4079