A. Pfaltz et al.
FULL PAPER
45.2 Hz; 1’’), 132.3 (4’), 132.4 (4’’), 132.7 (3’), 132.7 (3’’), 133.2 (8), 133.6
Experimental Section
(6’’), 133.7 (6’), 134.0 (11), 134.1 (9), 134.7 (10), 141.1 (d, 2J(P,C)
=
8.4 Hz; 2’), 142.9 (d, 2J(P,C) = 13.4 Hz; 2’’), 163.8 ppm (2), 1 quart. C
missing (Al-O-C(CF3)3); IR (KBr): n˜ = 3067w, 2972m, 2895w, 2848w,
1596m, 1566w, 1489m, 1457m, 1378m, 1353s, 1302vs, 1278vs, 1242vs,
1219vs, 1168s, 1124m, 1070w, 1062w, 974vs, 833m, 756m, 728vs, 684w,
561m, 536m, 511w, 449mcmÀ1; MS (ESI, CH2Cl2): m/z (%): positive
mode: 716.3 ([M{193Ir}Àanion)]+, 100); negative mode: 967.1
([MÀcation]À, 100); = À93.7 (c = 0.5, CHCl3); elemental analysis calcd
(%) for C51H42AlF36IrNO5P: C 36.40, H 2.52, N 0.83; found: C 36.57, H
2.75, N 0.75.
General: Dichloromethane was freshly distilled from calcium hydride or
purchased in sure-seal bottles from Fluka and kept under an inert atmos-
phere. (E)-1,2-Diphenyl-1-propene (1) was purchased from Lancaster
and used without further purification, or it was prepared from acetophe-
none and benzylmagnesium chloride.[18] Hydrogen gas used in the experi-
ments was purchased at Carbagas Switzerland (quality 45, 99.995%). Iri-
dium complexes (À)-[(h4-1,5-cyclooctadiene)-{(4S)-2-[(2-(di-o-tolylphos-
phino)phenyl]-4,5-dihydro-4-tert-butyl-oxazole}iridium(i)]hexafluorophos-
phate (3a) and (À)-[(h4–1,5-cyclooctadiene)-{(4S)-2-[(2-(di-o-tolylphos-
phino)phenyl]-4,5-dihydro-4-tert-butyl-oxazole}iridium(i)]tetrakis[3,5-bis-
(trifluoromethyl)phenyl]borate (3d) were prepared according to litera-
ture procedures.[5a,b] Complexes 3b and 3c were prepared from the
chloro complex through ion exchange with silver salts. Complex 3e was
CCDC-201707 contains the supplementary crystallographic data for this
ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB21EZ, UK; fax: (+
44)1223-336033; or deposit@ccdc.cam.uk).
À
prepared from NaB(C6F5)4, as for the BArF complex. HBArF·Et2O and
[NBu4]BArF were prepared according to literature procedures.[16]
Kinetic studies: The kinetic studies were carried out and interpreted with
the isolation as well as the initial rate method.[19] Reactions were carried
out in a 50 mL high-pressure autoclave with a magnetic stirrer (typically
at 1200 minÀ1). The vessel was kept at a constant temperature (Haake
thermostat) and pressure, and hydrogen was metered through a dosing
valve as needed to maintain constant pressure during the reaction. The
progress of the reaction was monitored by following the pressure drop in
a hydrogen reservoir (33 mL) on the high-pressure side of the dosing
valve which was initially set at ꢀ175 bar. Data pairs of (pressure, time)
were collected every 6 s throughout the reaction. The pressure drop was
related to the molar uptake of hydrogen using a computer program
which was calibrated for this autoclave by SolviasAG. The reaction rate
was determined from the maximum slope of the hydrogen pressure drop
in the reservoir by means of the computer program ANFGES.EXE.
Export of the molar amount of hydrogen in the reservoir was made possi-
ble by a small addition to this software.[20] The values obtained were then
adjusted by addition of a constant for a starting point of 0.25 mol H2 in
the reservoir to be able to overlay the curves. The conversion was deter-
mined by GC analysis, the enantioselectivities were checked by chiral
HPLC analysis.
Gas chromatography was carried out on a Carlo Erba HRGC Mega2
Series MFC800 (column: Restek Rtx-1701, 0.25 mm, 30 m, 60 kPa He).
HPLC analysis was performed with a Shimadzu SCL-10A with a Daicel
ChiralcelOJ column. GC: 21.0 min (1), 18.2 min (2), (1008C, 2 min iso-
therm, 78C minÀ1, 2508C, 5 min). HPLC: 13.9 min ((R)-2), 22.7 min ((S)-
2), 27.5 min (1), (ChiralcelOJ; 254 nm; heptane/2-propanol 99:1).
(À)-[(h4-1,5-cyclooctadiene)-{(4S)-2-[(2(di-o-tolylphosphino)phenyl]-4,5-
dihydro-4-tert-butyl-oxazole}iridium(i)]
tetrakis(perfluoro-tert-butoxy)-
aluminate (3 f): To a stirred solution of (4S)-2-[(2(di-o-tolylphosphino)-
phenyl]-4,5-dihydro-4-tert-butyl-oxazole (100 mg, 0.24 mmol) in dry
CH2Cl2 (5 mL) was added [{IrCl(cod)}2] (81 mg, 0.12 mmol). The red sol-
ution was heated for 2 h at 488C in a closed vial. After the mixture had
been cooled to room temperature, Li[Al{OC(CF3)3}4][10] (305 mg,
0.31 mmol) was added, resulting in a lighter color. After 5 min, water
(5 mL) was added, resulting in a gel-like mixture. Phase separation was
followed by extraction of the organic layer with water and filtration over
MgSO4. The light red complex was recrystallized from diethyl ether and
pentane to give single crystals suitable for X-ray crystallography (381 mg,
0.23 mmol; 94%).
General hydrogenation procedure: The autoclave was purged 4 times
with 3–5 bar Ar and cooled to the desired temperature under Ar pres-
sure. (E)-1,2-Diphenyl-1-propene and the iridium catalyst were dissolved
in dry dichloromethane (35 mL) under argon and transferred versus a
counterstream of argon into the autoclave. The autoclave was sealed,
purged with argon (3), and the solution was stirred for 5 min to equili-
brate to the temperature. Stirring was stopped, the autoclave was purged
with argon (3) and then with hydrogen (3, 7–13 bar). After the auto-
clave had been pressurized to the desired hydrogen pressure, the tight-
ness of apparatus was checked for 5 min by monitoring changes in the re-
servoir pressure. The reaction was started when stirring was commenced.
Stirring was stopped after the reservoir pressure had remained constant
for several minutes at the end of the reaction, and the autoclave was de-
pressurized and flushed with Ar (3). A sample (normally 0.3 mL, de-
pending on the substrate concentration) of the resulting yellow solution
was taken and concentrated in vacuo. Heptane (1 mL) was added, and
the suspension was filtered through a syringe filter to remove catalyst
residues. The resulting solution was used directly for GC and HPLC anal-
ysis.
1H NMR (400 MHz, CD2Cl2, 300 K, TMS): d = 0.56 (s, 9H; R), 1.50
(mc, 1H; cod), 1.63 (mc, 1H; cod), 2.08 (mc, 2H; cod), 2.36 (s, 3H; 7’, o-
Toleq), 2.44 (mc, 2H; cod), 3.05 (br, 1H; cod trans to N), 3.10 (s, 3H; 7’’,
o-Tolax), 3.48 (br, 1H; cod trans to N), 4.00 (br, 1H; cod trans to P), 4.41
(dd, 3J(H,H) = 9.6 Hz, 1H; 4), 4.64 (brd, 1H; 5), 4.79 (dd, 2J(H,H) =
3
7.6 Hz, J(H,H) = 9.6 Hz, 1H; 5), 4.93 (mc, 1H; cod trans to P), 6.52 (br,
À
1H; 6’’), 6.89 (brd, J(H,H) = 7.1 Hz, 1H; Ar H), 7.07 (br, 1H; 5’’), 7.25
À
À
À
(mc, 3H; Ar H), 7.44 (mc, 5H; Ar H), 7.65 (mc, 1H; Ar H), 7.76 (mc,
Acknowledgements
À
1H; Ar H), 8.30 ppm (d, J(H,H)
=
7.9 Hz, 1H; 11); 31P{1H} NMR
(163 MHz, CD2Cl2, 300 K, (PhO)3P=O d = 18): two conformers due to
hindered rotation around the P–o-Tol bond: d = 9.5 (s, 89%), 17.3 ppm
We would like to thank Dr. Hans-Ulrich Blaser and Dr. Benoît Pugin
(both SolviasAG), Prof. Donna G. Blackmond (Imperial College
London), Dr. Lasse Greiner (RWTH Aachen), and Thomas Schultz
(University of Basel) for advice and helpful discussions. We also thank
Mr. Stephan Burckhardt (formerly SolviasAG) for technical assistance.
We are grateful to Dr. Ingo Krossing (University of Karlsruhe) for a
sample of Li[Al{OC(CF3)3}4] and to Prof. JØrôme Lacour (University of
Geneva) for a sample of D-TRISPHAT. We thank Mr. Markus Neubur-
ger (University of Basel) for measuring X-ray diffraction data and for his
help with the refinement, and Mrs. Esther Hörmann (University of
Basel) for valuable experimental contributions. Financial support by the
(s, 11%); 19F{1H} NMR (CD2Cl2, 376 MHz, 300 K, FCCl3):
d =
À76.8 ppm (s); 13C{1H} NMR (CDCl3, 101 MHz; 300 K, TMS): d = 24.3
(d, 3J(P,C) = 5.8 Hz; 7’’), 24.8 (3 C; tBu-CH3), 25.2 (cod-CH2), 25.5 (d,
3J(P,C) = 4.6 Hz; 7’), 28.2 (cod-CH2), 32.7 (cod-CH2), 34.2 (tBu quart.
C), 35.5 (cod-CH2), 67.4 (br; cod-CH trans to N), 67.5 (br; cod-CH trans
to N), 69.9 (5), 74.5 (4), 90.0 (d, 2J(P,C) = 13.4 Hz; cod-CH trans to P),
95.0 (d, 2J(P,C)
= =
10.7 Hz; cod-CH trans to P), 119.3 (d, 1J(P,C)
52.9 Hz, 1’), 121.2 (q, 1J(F,C) = 292.1 Hz, 12 C; CF3), 127.1 (5’), 127.2
(5’’), 127.9 (6), 128.1 (d, 1J(P,C)
=
61.7 Hz; 7), 130.0 (d, 1J(P,C)
=
4692
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2004, 10, 4685 – 4693