B. Ak et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
5
ware, and solvents were dried using established procedures and
distilled under argon just prior to use. Analytical grade and deuter-
ated solvents were purchased from Merck. The starting materials
4.3.2. (S)-Bis[[N-(2-diphenylphosphinite-1-phenyl)ethyl]-1,10-
ferrocenylmethyldiamine(dichloro
dienyl iridium(III))] 2
g
5-pentamethylcyclopenta-
ferrocene,
L
-phenyl alaninol,
L
-phenyl glycinol,
L
-leucinol,
L
-isoleu-
A solution of the (S)-bis[N-(2-diphenylphosphinite-1-phenyl)
cinol, (S)-(+)-1-amino-2-propanol, (R)-(ꢀ)-2-amino-1-phenylethanol,
ethyl]-1,10-ferrocenylmethyl diamine (123 mg, 0.14 mmol) and [Ir
(R)-(ꢀ)-2-amino-1-butanol, (1S,2R)-(+)-2-amino-1,2-diphenylethanol,
(g l-Cl)Cl]2 (112 mg, 0.14 mmol) in 25 mL of CH2Cl2 was
5-C5Me5)(
PPh2Cl and Et3N were purchased from Fluka and used as received.
stirred at room temperature for 2 h. The resulting yellow solution
was concentrated to 2 mL under reduced pressure, and the addi-
tion of hexane (30 mL) caused the precipitation of a dark yellow
solid. The supernatant solution was decanted, and the solid was
washed with hexane/diethylether (1:1) and dried by vacuum,
1,10-Ferrocenedicarboxyaldehyde,49 and Ir( 5-C5Me5)(
g l-Cl)Cl]2
50
were prepared according to the literature. 1H NMR (at 400.1 MHz),
13C NMR (at 100.6 MHz) and 31P–{1H} NMR (at 162.0 MHz) spectra
were recorded on a Bruker AV400 spectrometer, with TMS (tetram-
ethylsilane) as an internal reference for 1H NMR and 13C NMR or
85% H3PO4 as an external reference for 31P–{1H} NMR. The IR spectra
were recorded on a Mattson 1000 ATI UNICAM FT-IR spectrometer as
KBr pellets. Specific rotations were taken on a Perkin–Elmer 341
model polarimeter. Elemental analysis was carried out on a Fisons
EA 1108 CHNS-O instrument. Melting points were recorded by a Gal-
lenkamp Model apparatus with open capillaries. GC analyses were
performed on a Shimadzu GC 2010 Plus Gas Chromatograph equipped
with a cyclodex-B (Agilent) capillary column (30 m ꢁ 0.32 mm I.
yielding iridium complex 2. Yield: 195 mg, 82%; [a]
20 = +89.2 (c
D
1.2, MeOH); mp: 138–140 °C. 31P–{1H} NMR (CDCl3, 162.0 MHz,
ppm): 74.13 (s, OAPPh2). IR (KBr pellet in cmꢀ1): (NAH): 3335,
(CAH): 3072, 3030, 2925, 2870, (CACACp): 1440, (OAP): 1025;
Anal. calcd for [C72H80N2O2P2FeIr2Cl4] (1649.4 g/mol): C, 52.42;
N, 1.70; H, 4.90; found: C, 52.25; N, 1.56; H, 4.68.
4.3.3. (S)-Bis[[N-(2-diphenylphosphinite-1-iso-butyl)ethyl]-1,10-
ferrocenylmethyldiamine(dichloro
dienyl iridium(III))] 3
g
5-pentamethylcyclopenta-
D. ꢁ 0.25
lm film thickness). Racemic samples of alcohols were
obtained by reduction of the corresponding ketones with NaBH4
and used as the authentic samples for ee determination. The GC
parameters for asymmetric transfer hydrogenation of ketones were
as follows; initial temperature, 50 °C; initial time 1.1 min; solvent
delay, 4.48 min; temperature ramp 1.3 °C/min; final temperature,
150 °C; initial time 2.2 min; temperature ramp 2.15 °C/min; final
temperature, 250 °C; initial time 3.3 min; final time, 44.33 min; injec-
tor port temperature, 200 °C; detector temperature, 200 °C, injection
A solution of the (S)-bis[N-(2-diphenylphosphinite-1-iso-butyl)
ethyl]-1,10-ferrocenyl methyl diamine (128 mg, 0.16 mmol) and
[Ir(g l-Cl)Cl]2 (127 mg, 0.16 mmol) in 25 mL of CH2Cl2
5-C5Me5)(
was stirred at room temperature for 45 min. The resulting yellow
solution was concentrated to 2 mL under reduced pressure, and
the addition of hexane (30 mL) caused the precipitation of a dark
yellow solid. The supernatant solution was decanted, the solid
was washed with hexane/diethylether (1:1) and dried by vacuum,
volume, 2.0
lL.
yielding iridium complex 3. Yield: 230 mg, 90%; [a]
20 = +72.5 (c 1.2,
D
MeOH); mp: 128–130 °C. 31P–{1H} NMR (CDCl3, 162.0 MHz, ppm):
72.90 (s, OAPPh2). IR (KBr pellet in cmꢀ1): (NAH): 3323,
(CAH):3060, 2980, 2965, 2860, (CACACp): 1435, (OAP): 1027;
Anal. calcd for [C68H88N2O2P2FeIr2Cl4] (1609.4 g/mol): C, 50.74;
N, 1.74; H, 5.52; found: C, 50.60; N, 1.66; H, 5.33.
4.2. General procedure for the transfer hydrogenation of
ketones
Typical procedure for the catalytic hydrogen-transfer reaction:
a
solution of the Ir(III)-complexes 1–8, (0.01 mmol), NaOH
4.3.4. (S)-Bis[[N-(2-diphenylphosphinite-1-sec-butyl)ethyl]-1,10-
ferrocenylmethyldiamine(dichloro
dienyl iridium(III))] 4
(0.05 mmol) and the corresponding ketone (1 mmol) in degassed
2-propanol (10 mL) was refluxed until the reaction was
completed. A sample of the reaction mixture was then taken
off, diluted with acetone and analyzed immediately by GC.
The conversions obtained are related to the residual unreacted
ketone.
g
5-pentamethylcyclopenta-
A solution of the (S)-bis[N-(2-diphenylphosphinite-1-sec-butyl)
ethyl]-1,10-ferrocenyl methyldiamine (128 mg, 0.16 mmol) and [Ir
(g l-Cl)Cl]2 (127 mg, 0.16 mmol) in 25 mL of CH2Cl2 was
5-C5Me5)(
stirred at room temperature for 90 min. The resulting yellow solu-
tion was concentrated to 2 mL under reduced pressure, and addi-
tion of hexane (30 mL) caused the precipitation of a dark yellow
solid. The supernatant solution was decanted, the solid was
washed with hexane/diethylether (1:1) and dried by vacuum,
4.3. Synthesis of iridium complexes of the ferrocene based
C2-symmetric phosphinites 1–8
yielding iridium complex 4. Yield: 225 mg, 88%; [a]
20 = +83.8 (c
D
4.3.1. (S)-Bis[[N-(2-diphenylphosphinite-1-benzyl)ethyl]-1,10-
ferrocenylmethyldiamine(dichloro
iridium(III))] 1
1.2, MeOH); mp: 129–131 °C. 31P–{1H}NMR (CDCl3, 162.0 MHz,
ppm): 73.21 (s, OAPPh2). IR (KBr pellet in cmꢀ1): (NAH): 3325,
(CAH):3070, 2952, 2925, 2870, (CACACp): 1450, (OAP): 1008;
Anal. calcd for [C68H88N2O2P2FeIr2Cl4] (1609.4 g/mol): C, 50.74;
N, 1.74; H, 5.52; found: C, 50.58; N, 1.60; H, 5.23.
g
5-pentamethylcyclopentadienyl
A
solution of (S)-bis[N-(2-diphenylphosphinite-1-benzyl)-
ethyl]-1,10-ferrocenylmethyl diamine(120 mg, 0.14 mmol) and [Ir
5-C5Me5)(
-Cl)Cl]2 (112 mg, 0.14 mmol) in 25 mL of CH2Cl2
(g
l
was stirred at room temperature for 1 h. The resulting yellow
solution was concentrated to 2 mL under reduced pressure,
and the addition of hexane (30 mL) caused the precipitation of a
dark yellow solid. The supernatant solution was decanted, and
the solid was washed with hexane/diethyl ether (1:1) and dried
by vacuum, yielding iridium complex 1. Yield: 200 mg, 87%;
4.3.5. (S)-Bis[[N-2-diphenylphosphinitepropyl]-1,10-ferrocenyl-
methyldiamine(dichloro
iridium(III))] 5
g
5-pentamethylcyclopentadienyl
A solution of the (S)-bis[N-2-diphenylphosphinite propyl]-1,10-
ferrocenylmethyldiamine (124 mg, 0.17 mmol) and [Ir(
-Cl)Cl]2 (135 mg, 0.17 mmol) in 25 mL of CH2Cl2 was stirred at
g
5-C5Me5)
(l
[a]
20 = +53.9 (c 1.2, MeOH); mp: 149–152 °C. 31P–{1H} NMR (CDCl3,
D
room temperature for 3 h. The resulting yellow solution was con-
centrated to 2 mL under reduced pressure, and the addition of hex-
ane (30 mL) caused the precipitation of a dark yellow solid. The
supernatant solution was decanted, and the solid was washed with
hexane/diethylether (1:1) and dried by vacuum, yielding iridium
162.0 MHz, ppm): 73.07 (s, O-PPh2). IR (KBr pellet in cmꢀ1):
(NAH): 3320, (CH): 3050, 3025, 2930, 2859, (CACACp): 1440
(OAP):
1010;
Anal.
Calcd
for
[C74H84N2O2P2FeIr2Cl4]
(1677.5 g/mol): C, 52.98; N, 1.67; H, 5.06; found: C, 52.80; N,
1.37; H, 4.80.
complex 5. Yield: 112 mg, 81%; [a]
20 = +77.6 (c 1.2, MeOH); mp:
D