Chiral and nonchiral [OsX2(diphosphane)(diamine)] (X: Cl, OCH2CF3) complexes for fast hydrogenation of carbonyl compounds

Article abstract of DOI:10.1002/chem.200902809

The osmium complexes trans-[OsCl₂(dppf)(diamine)] (dppf: 1,1′-bis(diphenylphosphino)ferrocene; diamine: ethylenediamine in 3, propylenediamine in 4) were prepared by the reaction of [OsCl ₂(PPh₃)₃] (1) with the ferrocenyl diphosphane, dppf and the corresponding diamine in dichloromethane. The reaction of derivative 3 with NaOCH₂CF₃ in toluene afforded the alkoxide cis-[Os(OCH₂CF₃)₂(dppf) (ethylenediamine)] (5). The novel precursor [Os₂Cl ₄(P(m-tolyl)₃)₅] (2) allows the synthesis of the chiral complexes trans-[OsCl₂(diphosphane)(1,2-diamine)] (6-9; diphosphane: (R)-[6,6′dimethoxy(1,1′-biphenyl)-2,2′-diyl] bis[1,1-bis(3,5-dimethylphenyl)phosphane] (xylMeObiphep) or (R)-(1,1′- binaphthalene)-2,2′-diylbis[1,1-bis(3,5-dimethylphenyl)phosphane] (xylbinap); diamine = (R,R)-1,2-diphenylethylenediamine (dpen) or (R,R)-l,2-diaminocyclohexane (dach)), obtained by the treatment of 2 with the diphosphane and the 1,2-diamine in toluene at reflux temperature. Compounds 3-5 in ethanol and in the presence of NaOEt catalyze the reduction of methyl aryl, dialkyl, and diaryl ketones and aldehydes with H₂ at low pressure (5 atm), with substrate/catalyst (S/C) ratios of 10000-200000 and achieving turnover frequencies (TOFs) of up to 3.0x 10⁵ h^-1 at 70°C. By employment of the chiral compounds 6-9, different ketones, including alkyl aryl, bulky tertbutyl, and cyclic ketones, have successfully been hydrogenated with enantioselectivities up to 99% and with S/C ratios of 5000-100000 and TOFs of up to4.1xl0⁴h^-1at 60°C.

Full text of DOI:10.1002/chem.200902809

FULL PAPER
DOI: 10.1002/chem.200902809
Chiral and Nonchiral [OsX2(diphosphane)ACHTUNGRTNEUNG(diamine)] (X: Cl, OCH2CF3)
Complexes for Fast Hydrogenation of Carbonyl Compounds
Walter Baratta,* Cinzia Barbato, Santo Magnolia, Katia Siega, and Pierluigi Rigo[a]
Dedicated to Professor Fausto Calderazzo on the occasion of his 80th birthday
Abstract: The osmium complexes
trans-[OsCl2A(dppf)(diamine)] (dppf:
1,1’-bis(diphenylphosphino)ferrocene;
diamine: ethylenediamine in 3, propy-
lenediamine in 4) were prepared by the
dimethoxy(1,1’-biphenyl)-2,2’-diyl]bis-
[1,1-bis(3,5-dimethylphenyl)phosphane]
(xylMeObiphep) or (R)-(1,1’-binaph-
thalene)-2,2’-diylbis[1,1-bis(3,5-dime-
thylphenyl)phosphane] (xylbinap); di-
amine=(R,R)-1,2-diphenylethylenedi-
amine (dpen) or (R,R)-1,2-diaminocy-
clohexane (dach)), obtained by the
treatment of 2 with the diphosphane
and the 1,2-diamine in toluene at
reflux temperature. Compounds 3–5 in
ethanol and in the presence of NaOEt
catalyze the reduction of methyl aryl,
dialkyl, and diaryl ketones and alde-
hydes with H2 at low pressure (5 atm),
with substrate/catalyst (S/C) ratios of
10000–200000 and achieving turnover
frequencies (TOFs) of up to 3.0ꢀ
105 hÀ1 at 708C. By employment of the
chiral compounds 6–9, different ke-
tones, including alkyl aryl, bulky tert-
butyl, and cyclic ketones, have success-
fully been hydrogenated with enantio-
selectivities up to 99% and with S/C
ratios of 5000–100000 and TOFs of up
to 4.1ꢀ104 hÀ1 at 608C.
G
E
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
reaction of [OsCl2ACHTUNGTRENNUNG(PPh3)3] (1) with the
ferrocenyl diphosphane, dppf and the
corresponding diamine in dichlorome-
thane. The reaction of derivative 3 with
NaOCH2CF3 in toluene afforded the
alkoxide
(ethylenediamine)] (5). The novel pre-
cursor [Os2Cl4(P(m-tolyl)3)5] (2) allows
cis-[OsACHTUNGTRENNUNG(OCH2CF3)2ACHTUNGERTN(NUNG dppf)-
ACHTUNGTRENNUNG
Keywords: amino ligands · asym-
metric catalysis · hydrogenation ·
osmium · phosphane ligands
the synthesis of the chiral complexes
trans-[OsCl2(diphosphane)(1,2-di-
amine)] (6–9; diphosphane: (R)-[6,6’-
Introduction
count of the structural diversity of ketones, so a high level
of selectivity has been attained through fine tuning of the
stereoelectronic properties of the diphosphanes and dia-
mines. By contrast, the influence of the nature of the metal
The
ruthenium
system
trans-[RuCl2(diphosphane)-
ACHTUNGTRENNUNG(diamine)], developed by Noyori et al. for the catalytic re-
duction of simple ketones to chiral alcohols,[1] represents
one of the most significant breakthroughs of both academic
and industrial relevance in transition-metal-mediated asym-
metric hydrogenation.[2] In addition to the most frequently
in the system [MCl2(diphosphane)ACHTGNUTERNNU(G diamine)] has not been
investigated, with the chiral and achiral Fe and Os com-
plexes being unexplored. It is worth noting that the PPh3
osmium derivative [OsHCl
described by Clapham and Morris, was found to catalyze the
hydrogenation[6] of acetophenone.
comparative DFT
(PPh3)2(NH2CMe2CMe2NH2)],[5]
ACHTUNGTRENNUNG
used
(1,1’-binaphthalene)-2,2’-diylbis(1,1-diphenylphos-
phane) (binap) diphosphane and (R,R)-1,2-diphenylethyle-
A
À
nediamine (dpen) N H diamine ligands, a large number of
study on the hydrogenation of acetone with M–PH3–ethyle-
nediamine complexes (M: Fe, Ru, or Os) has also been re-
ported.[7] Although osmium-based catalysts are usually con-
sidered less active than the ruthenium analogues,[8] we re-
cently found that Os complexes containing the 1-(pyridin-2-
yl)methanamine motif[9] are highly efficient catalysts for
both the hydrogenation and transfer hydrogenation of ke-
tones, with the CNN pincer complexes being active in enan-
tioselective hydrogenation.[9a] Preliminary experiments
bidentate chiral P and N ligands have been developed to
achieve both high enantioselectivity and productivity, as
well as broad scope.[3,4] No universal catalysts exist on ac-
[a] Prof. W. Baratta, Dr. C. Barbato, Dr. S. Magnolia, Dr. K. Siega,
Prof. P. Rigo
Dipartimento di Scienze e Tecnologie Chimiche
Universitꢁ di Udine, Via Cotonificio 108, 33100 Udine (Italy)
Fax : (+39)0432-558803
showed that the system comprising [OsCl2ACHTNUGTRENUNG(PPh3)3] (1)/di-
À
E-mail: inorg@uniud.it
phosphane/N H diamine shows catalytic activity in the hy-
Chem. Eur. J. 2010, 16, 3201 – 3206
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3201

drogenation of ketones, so the chemistry of the diphos-
phane/diamine–osmium species has been investigated.
stitution, as inferred from NMR spectroscopy measure-
ments. The problem of synthesizing the chiral derivatives
We describe herein
[OsX2(diphosphane)(diamine)] (X: Cl, OR), which were
successfully prepared from and the new precursor
[Os2Cl4(P(m-tolyl)3)5] (2); this gives access to the chiral
complexes. These derivatives were found to be the most
active and productive osmium catalysts reported to date for
the hydrogenation of simple ketones and aldehydes (turn-
over frequency (TOF) and substrate/catalyst (S/C) values of
up to 3ꢀ105 hÀ1 and 2ꢀ105, respectively) at low dihydrogen
pressure. With chiral diphosphanes and diamines, the asym-
metric hydrogenation of ketones has been achieved with up
to 99% enantiomeric excess (ee).
a
novel class of complexes
trans-[OsCl2(diphosphane)
through the preparation of novel precursor 2, which contains
the bulkier P(m-tolyl)3 phosphane that allows higher reactiv-
ity. The orange osmium(II) compound 2 was obtained in
75% yield from the reaction of [(NH4)2OsCl6] with P(m-
ACHTUNGTNER(NUNG diamine)] has been overcome
ACHTUNGTRENNUG
1
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
tolyl)3 in a tBuOH/H2O mixture at reflux temperature
(1 day; Scheme 2).
The 31P{1H} NMR spectrum of 2 in C6D6 shows two dou-
blets at d=À15.4 and À16.8 ppm (2J
ACHTUNGTREN(NUGN P,P)=17.2 Hz) and
three triplets at d=À13.4, À18.1, and À19.6 ppm (2J
ACHTUNGTRENNUNG(P,P)=
11.5 Hz); this is consistent with the proposed arrangement
and in agreement with the related ruthenium complexes
[Ru2Cl
[Os2Cl4(L)ACTHNUGENRTN(UG PPh3)4] (L: H2O, =C=CH[C(OH)Ph2]) have been
(PR3)5].[12] For osmium, the related dinuclear species
4ACHTUNGTRENNUNG
Results and Discussion
reported.[13] Compound 2 reacts cleanly with several diphos-
phanes and diamines in toluene (T>908C), as established
by 31P NMR spectroscopy. On the basis of the catalytic re-
sults carried out by using in situ generated catalysts (see
below), the derivatives containing xylbinap-type diphos-
phanes and 1,2-diamines have been isolated. The reaction of
precursor 2 with (R)-xylMeObiphep in toluene at reflux
temperature for 4 h followed by treatment with (R,R)-dpen
(1 h) led to the complex trans-[OsCl2((R)-xylMeObiphep)-
Preparation of [OsX2(diphosphane)
ACHTUNGTRENNUNG
The thermally stable complex trans-[OsCl CHTUNGTRENNUNG
dppf: 1,1’-bis(diphenylphosphino)ferrocene, en: ethylenedia-
mine) was easily obtained in 86% yield by treatment of 1
with the flexible diphosphane dppf[10] in dichloromethane at
408C (3 h), followed by the addition of ethylenediamine
(1 h; Scheme 1).
Derivative 4 was obtained similarly to 3 by using 1,3-pro-
pylenediamine. The trans configuration of both complexes
was confirmed by the presence of one singlet in the
31P NMR spectra. Treatment of 3 in toluene with two equiv-
alents of NaOCH2CF3, prepared from 2,2,2-trifluoroethanol
and NaOEt, afforded the osmium alkoxide[9a,11] cis-[Os-
ACHTUNGTREN(NUNG (R,R)-dpen)] (6), which was isolated in 54% yield
(Scheme 2). In a similar way, derivatives 7–9 were obtained
(47–66% yields) by using the appropriate ligands. The
31P NMR spectra of derivatives 6–9 containing C2 symmetry
ligands show one singlet and are consistent with a trans ge-
ometry.
ACHTUNGTRENNUNG(OCH2CF3)2ACHTUNGTRENNUNG(dppf)(en)] (5), according to the presence of
two doublets at d=1.6 and À20.6 ppm (2J
(P,P)=19.8 Hz) in
Catalytic results: The osmium complexes 3–5 in basic etha-
nol are extremely active and productive catalysts for the hy-
drogenation of ketones and aldehydes at low H2 pressure
(5 atm). Acetophenone (10a; 0.5m) is rapidly and quantita-
tively converted into 1-phenylethanol in 10 min at 708C, by
using 3 with a S/C ratio of 10000 and in the presence of
1 mol% NaOEt (Scheme 3; Table 1).
the 31P NMR spectrum and two singlets at d=À34.5 and
À36.1 ppm in the 19F NMR spectrum (Scheme 1).
The reaction of 1 with more rigid and bulkier chiral di-
phosphanes, such as (R)-[6,6’-dimethoxy(1,1’-biphenyl)-2,2’-
diyl]bis(1,1-diphenylphosphane) (MeObiphep) or (R)-binap
and 1,2-diamines resulted in the formation of a mixture of
trans-[OsCl2(diphosphane)
N
and
trans-[OsCl2-
At higher S/C ratios (50000–100000), the reduction is
straightforward, and complete conversion of 10a was at-
A
CHTUNGTRENNUNG
Scheme 1. Synthesis of the complexes [OsX2ACTHNUTRGENN(UG dppf)ACHUTNGTREN(NGUN diamine)] (X: Cl, OR).
3202
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Chem. Eur. J. 2010, 16, 3201 – 3206

Osmium Catalysts for the Hydrogenation of Carbonyl Compounds
FULL PAPER
Scheme 2. Synthesis of the novel osmium precursor 2 and the chiral complexes trans-6–9.
active osmium species. These high
values of rate and productivity of
Os in hydrogenation are unprece-
dented[5,6,9a,b] and rely on a combi-
À
nation of the accelerating N H
effect[1] with the robust metal
frame. In the absence of H2 in
ethanol, these osmium complexes
led to poor conversion of 10a
(less than 30% after 2 h), in ac-
cordance with the unfavorable
redox potential of ethanol for
ketone reduction,[14] which indi-
cates that transfer hydrogenation
is a less important pathway when
H2 is used. Complex 3 has been
proven to efficiently catalyze the
hydrogenation of linear and cyclic
aliphatic ketones 10b and 10c (S/
C=50000) and the diaryl ketone
10d (S/C=10000) in less than
1 h. Also, the aromatic and ali-
phatic aldehydes 10e and 10 f
were easily and quantitatively re-
Scheme 3. Hydrogenation of ketones and aldehydes 10 with the trans and cis Os complexes 3–9 (S/C=10000–
200000).
tained within 2 h at S/C=200000 (TOF=2.3ꢀ105 hÀ1),
which indicates that deactivation is retarded. Derivative 4,
containing the 1,3-diamine, shows a higher rate with a TOF
value of 3.0ꢀ105 hÀ1 (S/C=50000). The alkoxide 5 of cis
configuration displays a similar activity to that of the trans-
configured chloride 3 (TOF=1.5ꢀ105 and 1.7ꢀ105 hÀ1, re-
spectively); this suggests that, under these catalytic condi-
tions, both precursors rapidly generate the catalytically
duced to primary alcohols within 10 min at 608C by using
0.5 mol% NaOEt.
The chiral complexes 6–9 rapidly catalyze the enantiose-
lective hydrogenation of 10a in EtOH at 608C in the pres-
ence of 1 mol% NaOEt. With derivative 6, containing (R)-
xylMeObiphep, (S)-1-phenylethanol (90% ee) has been ob-
tained with S/C=10000–100000, without deactivation or
erosion of enantioselectivity (Table 2). An increase in the ee
Chem. Eur. J. 2010, 16, 3201 – 3206
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3203

W. Baratta et al.
Table 1. Catalytic hydrogenation of ketones and aldehydes (0.5m) in the
presence of 3–5 and NaOEt (1 mol%) in ethanol under 5 atm H2.
10n and 10o is lower than that with the other substrates, the
related complexes trans-[RuCl2ACTHNUGRTNEUNG(binap)(1,2-diamine)] were
shown to be poorly active and enantioselective,[16] which in-
dicates that the Os system is more active for bulky keto-
nes[9b] than the Ru system. In addition, the configurationally
labile a-substituted ketone 10p has been hydrogenated to
(1S,2S)-2-phenylcyclohexanol with high diastereoselectivity
(cis/trans=97:3) and an ee value of 92%.[1a] These are the
highest ee values to date for asymmetric ketone hydrogena-
tion based on Os catalysts,[9a] a field that has been practically
unexplored.
Complex Substrate S/C
T
[8C]
Conv.
[%][a]
t
TOF
[b]
[min]
[hÀ1
]
3
3
3
3
4
4
5
3
10a
10a
10a
10a
10a
10a
10a
10b
10c
10d
10e
10 f
10000 70
>99
99
98
10
30
60
120
10
30
10
60
60
30
10
10
1.7ꢀ105
1.8ꢀ105
1.5ꢀ105
2.3ꢀ105
1.8ꢀ105
3.0ꢀ105
1.5ꢀ105
8.0ꢀ104
9.0ꢀ104
3.0ꢀ104
9.0ꢀ104
5.7ꢀ104
50000 70
100000 70
200000 70
10000 70
50000 70
10000 70
50000 60
50000 60
10000 60
10000 60
10000 60
98
>99
>99
98
95
97
>99
99
>99
3
3
The complexes trans-[OsCl2(diphosphane)ACTHNURTGNEU(GN diamine)] can
3[c]
3[c]
also be generated in situ from 2 and the appropriate ligands.
Thus, complex 8, prepared by the treatment of 2 with (R)-
xylbinap in toluene at 1108C (3 h) and (R,R)-dpen (1 h),
catalyzes the hydrogenation of 10a to the corresponding
(S)-alcohol in EtOH at 608C (S/C=10000, TOF=
20000 hÀ1, 96% ee) with much the same activity as that of
the isolated complex. Employment of (R)-binap in place of
(R)-xylbinap afforded the S enantiomer with 89% ee. In ad-
dition, if (S)-xylbinap is combined with (R,R)-dpen, com-
pound 10a is reduced to the (R)-alcohol at a lower rate and
with lower enantioselectivity (TOF=15000 hÀ1, 54% ee). Fi-
nally, attempts to prepare 8 in situ from 1 instead of 2 result-
ed in the incomplete formation of 8 (about 40% conversion)
and the hydrogenation of 10a to the (S)-alcohol with
60% ee.
With regard to the catalytic cycle, it is likely that the
trans-dichloride complexes react with sodium ethoxide in
the presence of dihydrogen to afford the catalytically active
osmium dihydride species[5] through a mechanism similar to
that reported for the related ruthenium complexes.[17]
The stronger bonding and different electronic properties
of the 5d metal osmium, with respect to the 4d metal ruthe-
nium, result in the formation of more stable catalysts, which
can work at higher temperature, in more protic solvents
(ethanol versus 2-propanol), and with less base. This sug-
gests that the chiral complexes trans-[OsCl2(diphosphane)-
[a] The conversion were determined by GC analysis. [b] Turnover fre-
quency (moles of ketone converted into alcohol per mole of catalyst per
hour) at 50% conversion. [c] With 0.5 mol% NaOEt.
Table 2. Catalytic asymmetric hydrogenation of ketones (0.5m) in the
presence of 6–9 and NaOEt (1 mol%) in ethanol under 5 atm H2 at
608C.
Complex Ketone S/C
Conv.
[%][a]
t
TOF
ee [%][a]
[b]
[h]
[hÀ1
]
6
10a
10a
10a
10a
10a
10a
10g
10h
10i
10j
10k
10l
10m
10n
10o
10p
10000
50000
100000
10000
10000
10000
10000
10000
10000
10000
10000
10000
10000
10000
10000
5000
96
94
90
0.5
2
15
2
0.5
0.5
2
2.0ꢀ104
2.1ꢀ104
1.0ꢀ104
1.8ꢀ104
2.5ꢀ104
4.1ꢀ104
7.0ꢀ103
1.0ꢀ104
2.0ꢀ104
2.0ꢀ104
1.2ꢀ104
1.9ꢀ104
5.0ꢀ103
1.0ꢀ103
1.2ꢀ103
2.5ꢀ103
90 (S)
90 (S)
90 (S)
86 (S)
97 (S)
94 (S)
90 (S)
99 (S)
99 (S)
95 (S)
87 (R)
99 (S)
99 (S)
90 (S)
71 (R)
92 (1S,2S);
cis/
6[c]
6[c,d]
7
>99
>99
99
>99
>99
>99
99
>99
>99
99
8
9
8
8
8
8
8
8
8
8
8
8
1
0.5
0.3
1
0.5
3
24
15
2
85
92
>99
trans=97:3
AHCTUNGTREG(NNNU diamine)], despite the higher metal cost, may be a valid
complement to the analogous Ru derivatives.
[a] The conversion and ee value were determined by GC analysis.
[b] Turnover frequency (moles of ketone converted into alcohol per mole
of catalyst per hour) at 50% conversion. [c] With 2 mol% NaOEt.
[d] T=508C.
Conclusion
value (97 and 94% ee, respectively) was observed with the
(R)-xylbinap derivatives 8 and 9, containing (R,R)-dpen and
(R,R)-dach, with 9 being more rapid (TOF=4.1ꢀ104 hÀ1).
With complex 8, several methyl aryl ketones, namely,
10g–j, are efficiently reduced to the corresponding (S)-alco-
hols in 0.3–2 h with 90, 99, 99, and 95% ee, respectively (S/
C=10000 and TOF values of up to 2.0ꢀ104 hÀ1). The
ketone 10k, containing the electron-withdrawing CF3 group,
is also quickly reduced to the R enantiomer (87% ee). Inter-
estingly, the alkyl aryl ketones 10l[15] and 10m and the tert-
butyl substrates 10n and 10o are hydrogenated to the corre-
sponding alcohols with 99, 99, 90, and 71% ee, respectively.
It is worth noting that although the catalytic activity of 8 for
We have prepared a novel class of osmium(II) complexes,
trans- and cis-[OsX2(diphosphane)
Whereas the derivatives with the flexible diphosphane dppf
were prepared from [OsCl2A(PPh3)3], the synthesis of the
ACHTUNGERTN(NUNG diamine)] (X: Cl, OR).
CTHUNGTRENNUNG
complexes containing more rigid chiral diphosphanes (such
as the binap type) has been achieved by using the novel pre-
cursor [Os2Cl4(PACHTUNRGTNE(UNG m-tolyl)3)5]. These complexes exhibit re-
markably high activity and productivity in the hydrogena-
tion of ketones and aldehydes (S/C and TOF values of up to
2.0ꢀ105 and 3.0ꢀ105 hÀ1, respectively). The enantioselective
reduction of ketones (up to 99%) has been performed with
the correctly matched chiral diphosphane and diamine li-
gands. The straightforward preparation and high modularity
3204
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Chem. Eur. J. 2010, 16, 3201 – 3206

Osmium Catalysts for the Hydrogenation of Carbonyl Compounds
FULL PAPER
Synthesis of 5: Sodium ethoxide (0.25 mmol), obtained by evaporation of
a 0.25m solution of NaOEt in ethanol (1 mL), was treated with 2,2,2-tri-
fluoroethanol (42 mL, 0.576 mmol) and trans-[OsCl2ACTHNUTRGNEUNG(dppf)(en)] (100 mg,
of the system [OsX2(diphosphane)ACTHUNTGRNEUNG(diamine)] holds promise
for the broad application of osmium in asymmetric hydroge-
nation.
0.114 mmol) in toluene (4 mL). The suspension was stirred at 1008C for
1 h. The resulting dark orange solution was kept at À208C for 4 h; this
afforded precipitation of NaCl, which was then removed by filtration
through Celite. The filtrate was concentrated (1 mL) and addition of pen-
tane (4 mL) afforded a yellow-orange precipitate, which was filtered and
Experimental Section
1
dried under reduced pressure (91 mg, 80%). H NMR (200.1 MHz, C6D6,
General: All reactions were carried out under an argon atmosphere by
using standard Schlenk techniques. The solvents and ketones were care-
fully dried by standard methods and distilled under argon before use.
The diphosphane ligands and all other chemicals were purchased from
Aldrich and Strem and used without further purification. Compound 1
was prepared according to the literature procedure.[18] NMR spectroscopy
measurements were recorded on a Bruker AC200 spectrometer and the
chemical shifts (in ppm) are relative to tetramethylsilane for 1H and
13C{1H} spectra and to 85% H3PO4 for 31P{1H} spectra. Elemental analy-
ses (C, H, N) were carried out with a Carlo Erba 1106 elemental ana-
lyzer, whereas the GC analyses were performed with a Varian GP-3380
gas chromatograph equipped with a MEGADEX-ETTBDMS-b chiral
column.
208C): d=8.26 (pseudo t, JACHTUNTGRNEUNG(H,H)=8.6 Hz, 3H; Ph), 7.71 (brs, 1H; Ph),
7.31–6.98 (m, 15H; Ph), 6.74 (s, 1H; Ph), 4.69 (s, 1H; C5H4), 4.57 (m,
1H; OCH2), 4.35–4.25 (s, 2H; C5H4 and CH2), 3.81–3.47 (s, 10H; C5H4,
CH2 and NH2), 3.24 (t, J
ACHTUNGTREN(NNUG H,H)=10.1 Hz, 1H; CH2), 2.93–1.51 ppm (brm,
5H; CH2 and NH2); 13C{1H} NMR (50.3 MHz, C6D6, 208C): d=142.7 (d,
J
J
C
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
127.0 (m; aromatic carbon atoms and CF3), 85.2 (d, J
ipso C5H4), 82.1 (d, J
C5H4), 74.8 (d, J
71.6 (d, J
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
N
ACHTUNGTRENNUNG
N
ACHTUNGTRENNUNG
J
J
C
JACHTUNGTRENNUNG
ACHTUNGTRENNUNG
Synthesis of 2: [(NH4)2OsCl6] (1.50 g, 3.42 mmol) and PACHTUNTRGNE(GNU m-tolyl)3 (4.20 g,
(d, J
ACHTUNGTRENNUNG
13.8 mmol) were added to a solution of tert-butanol (130 mL) and water
(55 mL). The suspension was heated at reflux temperature for 24 h to
afford an orange precipitate, which was washed with water (2ꢀ15 mL),
heptane (3ꢀ15 mL), and pentane (1ꢀ15 mL) and then dried under re-
duced pressure (2.61 g, 75%). 1H NMR (200.1 MHz, C6D6, 208C): d=
9.72 (m, 1H; aromatic proton), 8.82 (brs, 1H; aromatic proton), 8.24 (t,
1.6 (d, 2J
(P,P)=19.8 Hz), À20.6 ppm (d, 2J
ACHTUNGTRENNUNG
(188.3 MHz, C6D6, 208C): d=À34.5 (s), À36.1 ppm (s); elemental analy-
sis calcd (%) for C40H40F6FeN2O2OsP2: C 47.91, H 4.02, N 2.79; found: C
48.01, H 4.10, N 2.74.
Synthesis of 6: Complex 2 (100 mg, 0.049 mmol) and (R)-xylMeObiphep
(75 mg, 0.108 mmol) were dissolved in toluene (1 mL) and the solution
was heated at reflux temperature for 4 h. After addition of (R,R)-dpen
(23 mg, 0.108 mmol), the solution was heated at reflux for 1 h. The sol-
vent was evaporated, then heptane (5 mL) was added to the product, and
was subsequently evaporated. Addition of heptane afforded a yellow pre-
cipitate, which was washed with cold heptane and dried under reduced
pressure (62 mg, 54%). 1H NMR (200.1 MHz, C6D6, 208C): d=8.04 (brt,
JACHTUNGTRENNUNG(H,H)=5.4 Hz, 1H; aromatic proton), 8.10–5.95 (m, 57H; aromatic pro-
tons), 2.26 (s, 3H; Me), 2.15–1.81 (m, 33H; Me), 1.71 (s, 3H; Me), 1.67
(s, 3H; Me), 1.26 ppm (s, 3H; Me); 13C{1H} NMR (50.3 MHz, C6D5CD3,
208C): d=141.9–124.2 (m; aromatic carbon atoms), 22.5–20.9 ppm (m;
Me); 31P{1H} NMR (81.0 MHz, C6D6, 208C): d=À13.4 (t, 2J
ACHTUNGTRNE(NUNG P,P)=
11.5 Hz), À15.4 (d, 2J
G
E
(brt 2J
(P,P)=11.5 Hz), À19.6 ppm (t, 2J
ACHTUNGTRNE(NUNG P,P)=11.5 Hz); elemental analy-
sis calcd (%) for C105H105Cl4OsP5: C 61.70, H 5.18; found: C 61.90, H
JACHTUNGTRENNUNG
5.23; ESI-MS (MeOH): m/z (%): 2042.8 (100) [MÀCl+MeOH]+, 1139.3
AHCTUNGTRENNUNG
(26) [OsCl(PACHTUNGTRENNUNG
(m-tolyl)3)3]+.
aromatic protons), 4.54 (brs, 2H; CH), 4.08 (brs, 4H; NH2), 3.03 (s, 6H;
OMe), 2.11 (s, 12H; CMe), 2.08 ppm (s, 12H; CMe); 13C{1H} NMR
Synthesis of 3: Complex
1 (150 mg, 0.143 mmol) and dppf (87 mg,
0.157 mmol) were dissolved in dichloromethane (3.0 mL) and the solu-
tion was heated at 408C for 3 h. Ethylenediamine (9.6 mL, 0.143 mmol)
was added at room temperature and the solution was heated at reflux for
1 h. The resulting solution was concentrated (1.5 mL) and the addition of
diethyl ether (4 mL) afforded a yellow precipitate, which was washed
with diethyl ether (2ꢀ3 mL) and dried under reduced pressure (108 mg,
86%). 1H NMR (200.1 MHz, CD2Cl2, 208C): d=7.79–7.28 (m, 20H; Ph),
4.58 (m, 4H; C5H4), 4.16 (t, J=1.7 Hz, 4H; C5H4), 3.12 (brs, 4H; CH2),
2.65 ppm (brs, 4H; NH2); 13C{1H} NMR (50.3 MHz, CD2Cl2, 208C): d=
(50.3 MHz, C6D6, 208C): 158.1 (pseudo t, JACTHNGUTERN(UNG C,P)=5.3 Hz, COMe), 143.3–
109.9 (m; aromatic carbon atoms), 64.1 (s; NCH), 54.3 (s; OMe), 21.6 (s;
CMe), 21.5 ppm (s; CMe); 31P{1H} NMR (81.0 MHz, C6D6, 208C): d=
À12.9 ppm (s); elemental analysis calcd (%) for C60H64Cl2N2O2OsP2: C
61.69, H 5.52, N 2.40; found: C 61.35, H 5.64, N 2.40.
Synthesis of 7: Complex 7 was prepared by following the procedure used
for 6, with (R,R)-dach (12 mg, 0.105 mmol) in place of (R,R)-dpen
(69 mg, 66%). 1H NMR (200.1 MHz, C6D6, 208C): d=8.01 (m, 6H; aro-
matic protons), 7.43–6.69 (m, 10H; aromatic protons), 5.98 (d, JACHTUNGTRENNUNG(H,H)=
140.7 (dd, J
129.0 (t, J(C,P)=0.9 Hz; Ph), 127.4 (pseudo t, J
(d, J(C,P)=55.5 Hz; ipso C5H4), 76.3 (t, J(C,P)=3.8 Hz; C5H4), 70.2 (t,
(C,P)=2.9 Hz; C5H4), 44.0 ppm (s; CH2); 31P{1H} NMR (81.0 MHz,
A
ACHTUNGTREN(NUGN C,P)=4.9 Hz; Ph),
8.1 Hz, 2H; aromatic protons), 3.45 (m, 2H; NHH), 2.99 (s, 6H; OMe),
2.67 (m, 2H; NHH), 2.31 (m, 2H; CHN), 2.16 (s, 12H; CMe), 2.11 (s,
12H; CMe), 0.92 (m, 4H; CH2), 0.49 ppm (m, 4H; CH2); 13C{1H} NMR
(50.3 MHz, C6D6, 208C): 158.2 (m; COMe), 136.8–109.9 (m; aromatic
carbon atoms), 57.0 (s; NCH), 54.2 (s; OMe), 35.5 (s; CH2), 24.8 (s;
CH2), 21.7 (s; CMe), 21.2 ppm (s; CMe); 31P{1H} NMR (81.0 MHz, C6D6,
208C): d=À14.3 ppm (s); elemental analysis calcd (%) for
C52H62Cl2N2O2OsP2: C 58.36, H 5.84, N 2.62; found: C 59.00, H 5.87, N
2.84.
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
JACHTUNGTRENNUNG
CD2Cl2, 208C): d=À10.1 ppm (s); elemental analysis calcd (%) for
C36H36Cl2FeN2OsP2: C 49.38, H 4.14, N 3.20; found: C 48.86, H 4.10, N
3.18.
Synthesis of 4: Complex 4 was prepared by following the procedure used
for 3, with 1,3-propylenediamine (12 mL, 0.144 mmol) in place of ethyle-
nediamine (111 mg, 87%). 1H NMR (200.1 MHz, CD2Cl2, 208C): d=
7.75–7.28 (m, 20H; Ph), 4.57 (m, 4H; C5H4), 4.15 (t, J=1.8 Hz, 4H;
C5H4), 3.32 (brs, 4H; NCH2), 2.81 (brs, 4H; NH2), 1.68 ppm (brm, 2H;
Synthesis of 8: Complex 8 was prepared by following the procedure used
for 6, with (R)-xylbinap (79 mg, 0.108 mmol) in place of (R)-xylMeObi-
phep (56 mg, 47%). 1H NMR (200.1 MHz, C6D6, 208C): d=8.86 (t,
CH2); 13C{1H} NMR (50.3 MHz, CD2Cl2, 208C): d=139.0 (dd, J
51.8, 8.6 Hz; ipso Ph), 135.0 (t, J(C,P)=4.8 Hz; Ph), 129.2 (t, J
0.9 Hz; Ph), 127.4 (pseudo t, J(C,P)=4.4 Hz; Ph), 88.6 (dd, J(C,P)=61.8,
5.5 Hz; ipso C5H4), 76.2 (t, J(C,P)=3.8 Hz; C5H4), 70.4 (t, J(C,P)=
ACHTUNGTRENNUNG
JACTHNUTRGENN(UG H,H)=6.9 Hz, 2H; aromatic protons), 8.16 (d, JACHTUNGTRNE(NUGN H,H)=9.2 Hz, 4H; ar-
A
ACHTUNGTRENNUNG
omatic protons), 7.94–6.48 (m, 26H; aromatic protons), 5.94 (s, 2H; aro-
matic protons), 4.53 (brm, 2H; NCH), 3.96 (brm, 2H; NH2), 3.84 (brm,
2H; NH2), 2.08 (s, 12H; CMe), 1.82 ppm (s, 12H; CMe); 13C{1H} NMR
(50.3 MHz, C6D6, 208C): d=135.2–123.9 (m; aromatic carbon atoms),
63.9 (s; NCH), 21.5 (s; CMe), 21.3 ppm (s; CMe); 31P{1H} NMR
(81.0 MHz, C6D6, 208C): d=À12.7 ppm (s); elemental analysis calcd (%)
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
2.9 Hz; C5H4), 38.6 (s; NCH2), 29.1 ppm (s; CH2); 31P{1H} NMR
(81.0 MHz, CD2Cl2, 208C): d=À10.5 ppm (s); elemental analysis calcd
(%) for C37H38Cl2FeN2OsP2: C 49.95, H 4.31, N 3.15; found: C 49.99, H
4.47, N 2.98.
Chem. Eur. J. 2010, 16, 3201 – 3206
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3205

W. Baratta et al.
for C66H64Cl2N2OsP2: C 65.61, H 5.34, N 2.32; found: C 65.47, H 5.12, N
2.25.
[3] a) W. P. Hems, M. Groarke, A. Zanotti-Gerosa, G. A. Grasa, Acc.
Chem. Res. 2007, 40, 1340; b) N. B. Johnson, I. C. Lennon, P. H.
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Studer, Adv. Synth. Catal. 2003, 345, 103; b) W. Tang, X. Zhang,
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Synthesis of 9: Complex 9 was prepared by following the procedure used
for 6, with (R)-xylbinap (79 mg, 0.108 mmol) and (R,R)-dach (12 mg,
0.105 mmol) in place of (R)-xylMeObiphep and (R,R)-dpen, respectively
(64 mg, 59%). 1H NMR (200.1 MHz, C6D6, 208C): d=8.85 (t, J
ACHTUNGTRENNUNG
[5] S. E. Clapham, R. H. Morris, Organometallics 2005, 24, 479.
[6] For osmium hydrogenation catalysts, see: a) M. Rosales, A. Gon-
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Vol. 1 (Eds.: J. G. de Vries, C. J. Elsevier), Wiley-VCH, Weinheim,
2007, p. 45; b) M. A. Esteruelas, A. M. López, M. Olivꢄn, Coord.
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Chem. 2008, 120, 4434; Angew. Chem. Int. Ed. 2008, 47, 4362; b) W.
Baratta, M. Ballico, A. Del Zotto, K. Siega, S. Magnolia, P. Rigo,
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7.9 Hz, 2H; aromatic protons), 8.11 (d, JACTHUNGTRENNUNG
protons), 7.91–6.43 (m, 16H; aromatic protons), 5.95 (s, 2H; aromatic
protons), 3.38 (m, 2H; NHH), 2.54 (m, 2H; NHH), 2.30 (m, 2H; CHN),
2.17 (s, 12H; Me), 1.81 (s, 12H; Me), 0.89 (m, 4H; CH2), 0.46 ppm (m,
4H; CH2); 13C{1H} NMR (50.3 MHz, C6D6, 208C): d=135.2–123.3 (m; ar-
omatic carbon atoms), 57.0 (s; NCH), 35.4 (s; CH2), 24.8 (s; CH2), 21.7
(s; CMe), 21.2 ppm (s; CMe); 31P{1H} NMR (81.0 MHz, C6D6, 208C): d=
À13.7 ppm (s); elemental analysis calcd (%) for C58H62Cl2N2OsP2: C
62.75, H 5.63, N 2.52; found: C 62.47, H 5.84, N 2.42.
Typical procedure for the catalytic hydrogenation of ketones: The
osmium complex (1.7 mmol) was dissolved in ethanol (2 mL). The ketone
(4.3 mmol), NaOEt (0.043 mmol from a 0.25m standard solution), and
the osmium solution (500 mL, 0.43 mmol) were added to the ethanol (final
volume of 8.6 mL). The resulting solution was transferred into a thermo-
stated reactor at 608C, and dihydrogen was introduced at a pressure of
5 atm to reduce the ketone (S/Os=10000, 1 mol% NaOEt, 0.5m
ketone). The samples were withdrawn from the reactor at regular time
intervals (2, 5, 10, 20, 30 min, and longer reaction times), in accordance
with the S/C ratio and the conversion of the ketone. The solution was
quickly quenched by the addition of diethyl ether (1:1 v/v), filtered over
a short silica pad, and analyzed by chiral GC. The TOF values were ob-
tained by interpolating the data at 50% conversion.
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This work was supported by the Ministero dellꢃUniversitꢁ e della Ricerca
(MIUR) and the Regione Friuli Venezia Giulia. We thank Solvias for a
generous supply of xylMeObiphep and Mr. P. Polese for carrying out the
elemental analyses.
[15] After this hydrogenation procedure, (S)-1-phenylpropan-1-ol (ee=
99%) was isolated in 91% yield from 10l.
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Received: October 12, 2009
Published online: January 28, 2010
3206
www.chemeurj.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 3201 – 3206