Hydrogen-transfer catalyzed by half-sandwich Ru(II) aminophosphine complexes

Article abstract of DOI:10.1039/b104128m

The syntheses of and catalytic studies on some Ru(II) complexes bearing the aminophosphine ligands N,N-dimethyl-2-diphenylphosphinoethylamine (PN), optically pure (R_C,S_pl)-2-{1-(N,N-dimethylamino)ethyl}-1- diphenylphosphinoferrocene(PPFA), and N,N-dimethyl-2-diphenylphosphinoaniline (DBD) are described, [RuCp(CH₃CN)₃]⁺ reacts with these ligands to give the cationic complexes [RuCp(PN-κN,κP)(CH₃CN)]⁺ (1a), [(S_Ru,R_C,S_pl)-RuCp(PPFA-κN,κP) (CH₃CN)]⁺ (1b), and [RuCp(DBD-κN,κP)(CH₃CN)]⁺ (1c), respectively, in high yields. From these, in turn, the residual CH₃CN ligand can be replaced by Br^- upon addition of NEt₄Br in CH₂Cl₂, resulting in the formation of the neutral complexes RuCp(PN)Br (2a), (S_Ru,R_C,S_pl)-RuCp(PPFA)Br (2b), and RuCp(DBD)Br (2c), again in good yields. Similarly, [Ru(η⁶-p-cymene)Cl₂]₂ reacts with 1 equiv. of PN or PPFA to give Ru(η⁶-p-cymene)(PN-κP)Cl₂ (3a) and Ru(η⁶-p-cymene)(PPFA-κP)Cl₂ (3b). Furthermore, treatment of 3 with TlCF₃SO₃ in THF at room temperature affords the cationic complexes [Ru(η⁶-p-cymene)(PN-κN,κP)Cl]CF₃SO ₃ (4a) and [(R_Ru,R_C,S_pl)-Ru (η⁶-p-cymene)-(PPFA-κN,κP)Cl]CF₃SO ₃ (4b). The absolute configuration at the metal center of 2b and 4b′ (BPh₄^- salt of 4b) was determined by X-ray crystallography. Catalytic studies were performed with the racemic complexes 1a, 2a, 2c, and 4a and the diastereopure complexes 1b, 2b, and 4b. All of these proved to be excellent precatalysts for the transfer hydrogenation of acetophenone and derivatives thereof, and cyclohexanone. With the enantiomerically pure systems 2b and 4b, only racemic products were obtained. This testifies to the hemilabile nature of the aforementioned aminophosphine ligands giving transient κ-P-bonding coordination. Since diastereoface selection of incoming substrates is based on the planar chirality of the ferrocene moiety, rather than the metal centered chirality, no enantioselective reaction takes place.

Full text of DOI:10.1039/b104128m

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Hydrogen-transfer catalyzed by half-sandwich Ru(II)
aminophosphine complexes†
Christina Standfest-Hauser,a Christian Slugovc,a Kurt Mereiter,b Roland Schmid,a
Karl Kirchner,*a Li Xiaoc and Walter Weissensteiner*c
a Institute of Inorganic Chemistry, Vienna University of Technology, Getreidemarkt 9,
A-1060 Vienna, Austria
b Institute of Mineralogy, Crystallography, and Structural Chemistry, Vienna University of
Technology, Getreidemarkt 9, A-1060 Vienna, Austria
c Institute of Organic Chemistry, University of Vienna, Währinger Straße 38, A-1090 Wien,
Austria
Received 10th May 2001, Accepted 10th August 2001
First published as an Advance Article on the web 1st October 2001
The syntheses of and catalytic studies on some Ru() complexes bearing the aminophosphine ligands N,N-dimethyl-
2-diphenylphosphinoethylamine (PN), optically pure (RC,Spl)-2-{1-(N,N-dimethylamino)ethyl}-1-diphenylphos-
phinoferrocene(PPFA),andN,N-dimethyl-2-diphenylphosphinoaniline(DBD)aredescribed,[RuCp(CH3CN)3]ϩ reacts
with these ligands to give the cationic complexes [RuCp(PN-κN,κP)(CH3CN)]ϩ (1a), [(SRu,RC,Spl)-RuCp(PPFA-
κN,κP)(CH3CN)]ϩ (1b), and [RuCp(DBD-κN,κP )(CH3CN)]ϩ (1c), respectively, in high yields. From these, in turn,
the residual CH3CN ligand can be replaced by BrϪ upon addition of NEt4Br in CH2Cl2, resulting in the formation of
the neutral complexes RuCp(PN)Br (2a), (SRu,RC,Spl)-RuCp(PPFA)Br (2b), and RuCp(DBD)Br (2c), again in good
yields. Similarly, [Ru(η6-p-cymene)Cl2]2 reacts with 1 equiv. of PN or PPFA to give Ru(η6-p-cymene)(PN-κP)Cl2 (3a)
and Ru(η6-p-cymene)(PPFA-κP)Cl2 (3b). Furthermore, treatment of 3 with TlCF3SO3 in THF at room temperature
affords the cationic complexes [Ru(η6-p-cymene)(PN-κN,κP)Cl]CF3SO3 (4a) and [(RRu,RC,Spl)-Ru(η6-p-cymene)-
(PPFA-κN,κP)Cl]CF3SO3 (4b). The absolute configuration at the metal center of 2b and 4bЈ (BPh4Ϫ salt of 4b) was
determined by X-ray crystallography. Catalytic studies were performed with the racemic complexes 1a, 2a, 2c, and
4a and the diastereopure complexes 1b, 2b, and 4b. All of these proved to be excellent precatalysts for the transfer
hydrogenation of acetophenone and derivatives thereof, and cyclohexanone. With the enantiomerically pure systems
2b and 4b, only racemic products were obtained. This testifies to the hemilabile nature of the aforementioned
aminophosphine ligands giving transient κ-P-bonding coordination. Since diastereoface selection of incoming
substrates is based on the planar chirality of the ferrocene moiety, rather than the metal centered chirality, no
enantioselective reaction takes place.
some Ru() Cp and p-cymene complexes featuring the phos-
phinoamine ligands N,N-dimethyl-2-diphenylphosphinoethyl-
Introduction
Transition metal complexes containing chelating ligands with
amine (PN), optically pure (RC,Spl)-2-{1-(N,N-dimethylamino)-
different donor atoms such as C, N, O, and P can induce
ethyl}-1-diphenylphosphinoferrocene (PPFA), and N,N-di-
increased selectivity due to the different electronic properties
methyl-2-diphenylphosphinoaniline (DBD) and whether these
compounds are suitable precatalysts for the transfer hydro-
of these atoms which are relayed to the reactive metal site.1
We 2 and others3 have previously shown that aminophosphine
genation of prochiral ketones such as acetophenone and deriva-
ligands are readily introduced into RuCp, RuTp, and Ru(arene)
systems. In the case of optically pure aminophosphine ligands,
Ϫ
tives thereof, and cyclohexanone.4–7 The counterions are PF6
Ϫ
and CF3SO3 for the RuCp and Ru(p-cymene) complexes,
diastereopure complexes are often obtained in a single step with
respectively.
de’s >98%. Consequently, such complexes could be useful pre-
catalysts for various organic reactions. One has to keep in mind,
however, that aminophosphines are hemilabile, particularly if
the nitrogen site is sufficiently bulky (NMe2 < NEt2 < N-i-Pr2).
These soft/hard assemblies are able to coordinate reversibly to
a metal center providing, or protecting temporarily, a vacant
coordination site, a feature very desirable for catalysts. On the
other hand, this very property may result in the loss of chiral
information in the vicinity of a prochiral substrate and con-
sequently rendering enantioselective reactions impossible or at
least very difficult.
Results and discussion
Synthesis and characterization of ruthenium(II) Cp and p-cymene
complexes
We have recently shown8,9 that the cationic complexes [RuCp-
(PN-κN,κP)(CH3CN)]ϩ (1a) and [(SRu,RC,Spl)-RuCp(PPFA-
κN,κP)(CH3CN)]ϩ (1b) are formed in high yields by the reac-
tion of [RuCp(CH3CN)3]ϩ with the phosphinoamine ligands
PN and PPFA, respectively. Most notably, the formation of 1b
is highly diastereoselective (de > 98%). Complex [RuCp(DBD-
κP,κN)(CH3CN)]PF6 (1c), not previously reported, is obtained
in a similar fashion.
In the present contribution, we report on the synthesis of
† Electronic supplementary information (ESI) available: experimental
details and NMR data for 1c and 2c. See http://www.rsc.org/suppdata/
dt/b1/b104128m/
Upon addition of NEt4Br to a solution of 1 in CH2Cl2, the
color is immediately changed from yellow to orange to afford,
DOI: 10.1039/b104128m
J. Chem. Soc., Dalton Trans., 2001, 2989–2995
This journal is © The Royal Society of Chemistry 2001
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on workup, the neutral complexes RuCp(PN)Br (2a),
(SRu,RC,Spl)-RuCp(PPFA)Br (2b), and RuCp(DBD)Br (2c)
(Scheme 1) in good yields.
Fig. 1 Structural view of one of the two independent Ru complexes in
(SRu,RC,Spl)-RuCp(PPFA-κN,κP)BrؒCHCl3 (2bؒCHCl3) showing 20%
thermal ellipsoids. Priority for the assignment of the absolute con-
figuration at Ru: Br > Cp > PPh2 > NMe2. Selected bond lengths (Å)
and angles (Њ): Ru–C(31–35)av 2.176(7), Ru–P 2.288(2), Ru–N 2.269(6),
Ru–Br 2.589(2); P–Ru–N 92.3(1), N–Ru–Br 87.3(1), Br–Ru–P 94.7(1).
by H, 13C{1H}, and 31P{1H} NMR spectroscopies as well as
elemental analysis. In the H NMR spectra of 3a and 3b, the
1
1
Scheme 1
NMe2 group of the coordinated ligand displays a singlet at a
δ value nearly that of the ‘free’ ligand, indicating that the ligand
is monodentate P-bonded. The 31P{1H} NMR spectra exhibit a
singlet at 21.6 and 23.3 ppm, respectively.
1
All complexes have been characterized by H, 13C{1H}, and
31P{1H} NMR spectroscopies and elemental analysis. The
formation of the bromide complex 2b is again highly diastereo-
selective (de > 98%), with retention of configuration at
ruthenium, as established by X-ray crystallography (Fig 1).
Selected bond distances and angles are reported in the caption.
Accordingly, 2b (in the form of its crystalline CHCl3 solvate)
adopts a three-legged piano stool conformation with Br and the
N and P atoms of the bidentate PPFA ligand as the legs. There
are two independent, but stereochemically similar, complexes in
the asymmetric unit of the monoclinic cell. Their mean Ru–Br,
Ru–N, and Ru–P bond lengths are 2.604(2), 2.266(6), and
2.287(2) Å, respectively, with Br–Ru–N, Br–Ru–P, and N–Ru–P
angles of 87.5(1), 96.6(1), and 91.9(1)Њ. The Ru-bonded Cp
rings are essentially planar with C–C bond distances in the
range 1.32(1)–1.45(1) Å, giving a mean value of 1.39(1) Å.
The Ru–C distances range from 2.147(7) to 2.222(7) Å [mean
2.183(7) Å].
Treatment of 3 with TlCF3SO3 (1 equiv.) in THF at room
temperature affords, on workup, the cationic complexes [Ru(η6-
p-cymene)(PN-κN,κP)Cl]CF3SO3 (4a) and [(RRu,RC,Spl)-Ru-
(η6-p-cymene)(PPFA-κN,κP)Cl]CF3SO3 (4b) in 52 and 86%
isolated yield (Scheme 2). Characterization of these complexes
1
was again accomplished by H, 13C{1H}, and 31P{1H} NMR
spectroscopies as well as elemental analysis. In the 31P{1H}
NMR, the phosphorus atom of the κN,κP-coordinated
phosphinoamine displays a singlet at 59.0 and 28.2 ppm
(cf. 21.6 and 23.3 ppm in 3a and 3b, respectively, where the
phosphinoamine ligand is κP-coordinated). It is also evident
from 31P{1H} NMR spectroscopy that, in the case of 4b, only
one diastereoisomer is formed. In order to assign the absolute
configuration at the metal center, an X-ray diffraction study of
Ϫ
4bЈ (BPh4 salt of 4b) has been undertaken. The structure is
Treatment of [Ru(η6-p-cymene)Cl2]2 with 1 equiv. of PN
and PPFA in THF at room temperature afforded Ru(η6-p-
cymene)(PN-κP)Cl2 (3a) and Ru(η6-p-cymene)(PPFA-κP)Cl2
(3b) in 80 and 87% isolated yields (Scheme 2) as orange air-
stable complexes. Complexes 3a and 3b have been characterized
depicted in Fig. 2, with selected bond distances and angles
reported in the caption.
Complex 4bЈ (in the form of its crystalline acetone–diethyl
ether solvate) adopts a typical three-legged piano stool con-
formation with Cl and the N and P atoms of the bidentate
PPFA ligand as the legs. The configuration at the Ru atom is R.
As in 2bؒCHCl3, there are two independent but stereo-
chemically similar complexes in the asymmetric part of the
unit cell. Their Ru–Cl, Ru–N, and Ru–P distances average to
2.388(2), 2.289(5), and 2.346(2) Å, respectively, with Cl–Ru–N,
Cl–Ru–P, and N–Ru–P angles of 85.9(1), 87.5(1), and 90.0(1)Њ.
The p-cymene rings show C–C arene bond distances in the
range 1.381(9)–1.438(8) Å, giving a mean value of 1.411 Å.
The Ru–C distances range from 2.186(6) to 2.324(6) Å (mean
2.250 Å).
Catalytic transfer hydrogenation of ketones
Catalytic studies with the racemic complexes 1a, 2a, 2c, and 4a
and the diastereo- and enantiopure complexes 1b, 2b, and 4b
Scheme 2
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Table 1 Reduction of acetophenone by 1, 2, and 4 with i-PrOH/i-
Table 2 Reduction of various ketones by 2a (4a) with i-PrOH/i-
PrONa as the reducing agenta
PrONa as the reducing agenta
Substrate
Precatalyst
T /ЊC
Time/h
Yield (%)
Product
Yield (%)
>99
1a
1a
1b
1b
2a
2a
2b
2b
2c
2c
4a
4a
4b
4b
25
82
25
82
25
82
25
82
25
82
25
82
25
82
24
2.5
24
2.5
24
2.5
24
48
24
2.5
24
24
24
48
>99
>99
no reaction
<5
>99
>99
no reaction
>99
no reaction
27
<5
78 (>99)
75 (>99)
62 (>99)
>99
no reaction
>99
a 0.1 M 2-propanol solution of acetophenone containing 5 mg of the
precatalyst (acetophenone : precatalyst : i-PrONa = 200 : 1 : 2).
>99
>99
61 (>99)
>99
78 (>99)
33 (72)
Fig. 2 Structural view of one of the two independent Ru complexes
in
[(RRu,RC,Spl)-Ru(η6-p-cymene)(PPFA-κN,κP)Cl]BPh4ؒ½(CH3)2-
COؒ½(C2H5)2O (4bЈؒ½(CH3)2COؒ½(C2H5)2O) showing 20% thermal
ellipsoids. Priority for the assignment of the absolute configuration
at Ru: p-cymene > Cl > PPh2 > NMe2. Selected bond lengths (Å)
and angles (Њ): Ru–C(31–36)av 2.249(6), Ru–P 2.346(2), Ru–N 2.293(5),
Ru–Cl 2.383(2); P–Ru–N 89.6(1), N–Ru–Cl 86.1(1), Cl–Ru–P 87.4(1).
45 (>99)
>99
for the transfer hydrogenation of acetophenone revealed that
the RuCp and Ru(p-cymene) complexes with the simple PN
ligand are much more effective than those with PPFA or DBD
(Table 1). For instance, while 1a and 2a convert acetophenone
to 1-phenylethanol quantitatively at room temperature after
24 h, compounds 1b, 2b, 2c, 4a, and 4b require both prolonged
reaction times (24 h or longer) and elevated temperatures
(82 ЊC). At 82 ЊC the reduction of acetophenone with 1a and 2a
as precatalysts is already complete after 2.5 h. By and large,
complexes 2a and 4a are excellent precatalysts for the transfer
hydrogenation of acetophenone derivatives and cyclohexanone
in boiling 2-propanol for 48 h, as shown in Table 2. In most
cases, the conversion to the respective alcohols is essentially
quantitative.
50 (80)
>99 (80)b
>99
Expanding the transfer hydrogenation of acetophenone and
its derivatives to the optically pure systems 2b and 4b revealed
that at elevated temperatures these complexes are also efficient
precatalysts, comparable in reactivity to 2a and 4a. However, in
all cases only racemic products were obtained. Racemization
a 0.1 M 2-propanol solution of the ketone containing 5 mg of 2a (4a)
(ketone : cat : i-PrONa = 200 : 1 : 2), T = 82 ЊC, t = 48 h. b t = 92 h.
J. Chem. Soc., Dalton Trans., 2001, 2989–2995
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of the final products seems not to take place since treatment of
an optically pure sample of (R)-1-phenylethanol under the
same reaction conditions did not result in racemization. Thus,
we suggest that the aminophosphine ligands are hemilabile
under the reaction conditions, forming reactive intermediates
with κP-bonded aminophosphine ligands, an observation per-
opening has to occur is further supported by the fact that the
monophosphine complex [RuCp(PPh3)(CH3CN)2]ϩ is an even
more efficient precatalyst for the above reductions than 1a
and 2a.
In conclusion, we have shown that ruthenium() half-
sandwich complexes containing aminophosphine ligands are
excellent precatalysts for the transfer hydrogenation of aceto-
phenone derivatives and cyclohexanone. However, due to the
hemilability of these ligands, there is no longer a discrimination
between the two diastereofaces of the chiral complexes (the
planar chirality of the PPFA ligand is important). Con-
sequently, at least at elevated temperatures, such ligand systems
are not suitable for enantioselective transfer hydrogenations.
In fact, analogous complexes with monodentate phosphine
ligands are much better suited for these types of reactions.
1
haps not too surprising. However, since H or 31P{1H} NMR
spectra of 2a (the most reactive complex) in CD3NO2 at 100 ЊC
did not significantly change as compared to the room tempera-
ture spectra, there was no indication of any dynamic processes.
In fact, the presence of two 1H signals due to the diastereotopic
NMe2 groups is very indicative of a κN,κP coordination and a
species with a monodentate P-bonded ligand must be present
only in very small concentrations.
A reasonable mechanism for the transfer hydrogenation of
ketones is summarized in Scheme 3 (exemplified for RuCp
aminophosphine complexes). After BrϪ dissociation, which is
favored in polar solvents such as 2-propanol, the alkoxide anion
attacks the metal center giving complex A. β-Elimination from
A yields the hydride complex B and acetone. This process
already requires an additional vacant coordination site. DFT
calculations on related ruthenium arene systems revealed that
β-elimination could involve ring slippage.10,11 On the other
hand, in our systems, Ru–N bond cleavage may occur as well,
leading to reactive monodentate P-bonded intermediates. The
decrease in reactivity on going from PN to DBD and PPFA
may be partially explained by such a ring opening process.
PPFA and DBD are certainly more rigid than PN due to their
aromatic backbone. Furthermore, PPFA is sterically more
demanding than both PN and DBD. In the following step, the
substrate has to coordinate to B, requiring again a vacant
coordination site. Accordingly, Ru–N bond cleavage or η5 to
η3 ring slippage of the Cp ligand (in the case of arenes η6 to η4
ring slippage) has to take place, leading to intermediates C and/
or D, respectively. However, since the two diastereopure PPFA
systems were not enantioselective in the hydrogenation of 15
different substrates (Table 2), it is most likely that the catalytic
reaction involves Ru–N bond cleavage. Thus, since diastereo-
face selection of incoming labile substrates is based on the
planar chirality of the ferrocene moiety, rather than the metal
centered chirality, as has been shown previously,9 no enantio-
selective reaction takes place. On the other hand, in the case
of ring slippage, even if the enantioselectivities are poor, there
still should be some discrimination between the two diastereo-
faces of complexes 2b and 4b. The assumption that ring
Experimental
All manipulations were performed under an inert atmosphere
of argon by using Schlenk techniques. All chemicals were
standard reagent grade and used without further purification.
The solvents were purified according to standard procedures.12
The deuterated solvents were purchased from Aldrich and dried
over 4 Å molecular sieves. [RuCp(CH3CN)3]PF6 and [RuCp-
(PPh3)(CH3CN)2]PF6,8,13 [RuCl2(η6-p-cymene)]2,14 [RuCp(PN-
κN, κP)(CH3CN)]PF6 (1a), and [(SRu,RC,Spl)-RuCp(PPFA-κN,
κP)(CH3CN)]PF6 (1b)9 were prepared according to the litera-
ture. 1H, 13C{1H}, and 31P{1H} NMR spectra were recorded on
a Bruker AC-250 spectrometer operating at 250.13, 62.86, and
101.26 MHz, respectively, and were referenced to SiMe4
and H3PO4 (85%). IR spectra were recorded on a Perkin-Elmer
16PC FTIR spectrometer. For analytical HPLC runs a
Hewlett Packard HP1090 liquid chromatograph was used. The
enantiomeric excess was determined by HPLC on Daicel
Chiralcel OB (250 × 4.6 mm) column. Separation conditions:
flow 0.5 mL/minϪ1, column temperature: 25 ЊC, eluent: hexane–
isopropanol 9 : 1, c = 20 mg mLϪ1, sample volume: 5 µl; tR
12.4 and 18.2 min.
=
Synthesis
RuCp(PN-ꢀN,ꢀP)Br (2a). To a solution of 1a (100 mg,
0.164 mmol) in CH2Cl2 (3 mL), NEt4Br (50.5 mg, 0.328 mmol)
was added and the mixture was stirred for 20 h at room
temperature. On addition of Et2O, a precipitate of NEt4PF6
Scheme 3
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J. Chem. Soc., Dalton Trans., 2001, 2989–2995

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1
was formed which was removed by filtration over Na2SO4. The
solvent of the remaining dark red solution was then removed
under reduced pressure and a red precipitate was obtained
which was collected on a glass frit, washed with Et2O and
petroleum ether (1 : 5), and dried under vacuum. Yield: 68.1 mg
(82.3%). C21H25BrNPRu requires: C, 50.11; H, 5.01; N, 2.78.
Found: C, 50.29; H, 5.06; N, 2.90%. 1H NMR (δ, CDCl3, 20 ЊC):
7.88 (m, 2H, Ph), 7.49–7.30 (m, 8H, Ph), 4.15 (s, 5H, Cp), 3.38
(s, 3H, NMe2), 3.05 (s, 3H, NMe2), 2.99–1.90 (m, 4H). 13C{1H}
2.03%. H NMR (δ, CDCl3, 20 ЊC): 8.05–7.96 (m, 2H, Ph),
7.79–7.68 (m, 2H, Ph), 7.50–7.39 (m, 3H, Ph), 7.31–7.16 (m,
3H, Ph), 5.67–5.56 (m, 2H, Cy), 5.09–5.04 (m, 1H, FeCps),
5.04–4.96 (m, 2H, Cy), 4.63–4.59 (m, 1H, FeCps), 4.48–4.45 (m,
1H, FeCps), 4.03 (s, 5H, FeCp), 3.17 (q, JHH = 6.8 Hz, 1H,
CH(Me)NMe2), 2.68 (m, JHH = 6.9 Hz, 1H, Cy–CHMe2), 1.96
(s, 3H, Cy–CH3), 1.73 (s, 6H, CH(Me)NMe2), 1.23 (d, JHH
3
3
=
3
7.1 Hz, 3H, CH(Me)NMe2), 1.11 (d, JHH = 7.13 Hz, 3H, Cy–
CHMe2), 1.05 (d, JHH = 6.56 Hz, 3H, Cy–CHMe2). 13C{1H}
3
NMR (δ, CDCl3, 20 ЊC): 142.1 (d, JCP = 42.9 Hz, 1C, Ph1),
NMR (δ, CDCl3, 20 ЊC): 136.2 (d, JCP = 10.5 Hz, 2C, Ph2,6),
1
2
135.0 (d, 2JCP = 11.4 Hz, 2C, Ph2,6), 132.5 (d, 1JCP = 40.1 Hz, 1C,
135.8 (d, 2JCP = 8.6 Hz, 2C, Ph2Ј,6Ј), 134.3 (d, 1JCP = 49.6 Hz, 1C,
Ph1), 133.7 (d, 1JCP = 48.6 Hz, 1C, Ph1Ј), 130.8 (d, 4JCP = 1.9 Hz,
1C, Ph4), 129.4 (d, 4JCP = 3.8 Hz, 1C, Ph4Ј), 127.7 (d, 3JCP = 9.5
Hz, 2C, Ph3,5), 126.0 (d, 3JCP = 9.5 Hz, 2C, Ph3Ј,5Ј), 107.1 (s, 1C,
2
4
Ph1Ј), 131.1 (d, JCP = 10.5 Hz, 2C, Ph2Ј,6Ј), 130.1 (d, JCP = 1.9
Hz, 1C, Ph4), 129.1 (d, 4JCP = 1.9 Hz, 1C, Ph4Ј), 128.6 (d, 3JCP
=
8.6 Hz, 2C, Ph3,5), 128.2 (d, 3JCP = 10.5 Hz, 2C, Ph3Ј,5Ј), 73.0 (d,
2JCP = 2.9 Hz, 5C, Cp), 61.7 (d, 2JCP = 7.6 Hz, 1C, PCH2CH2N),
58.0 (s, 1C, NMe2), 57.8 (s, 1C, NMe2), 29.6 (d, 1JCP = 18.1 Hz,
PCH2CH2N). 31P{1H} NMR (δ, CDCl3, 20 ЊC): 64.9 (PPh2)
Cy), 95.5 (s, 1C, Cy), 92.8 (d, JCP = 32.4 Hz, 1C, FeCp1), 91.3
1
(s, 1C, Cy), 88.9 (s, 1C, Cy), 86.4 (d, JCP = 4.8 Hz, 1C, Cy), 85.6
(d, JCP = 3.8 Hz, 1C, Cy), 78.0 (d, JCP = 17.2 Hz, 1C, FeCp2),
70.2 (d, JCP = 18.1 Hz, 1C, FeCps), 69.9 (d, JCP = 2.9 Hz, 1C,
FeCps), 69.2 (d, JCP = 7.6 Hz, 1C, FeCps), 54.7 (s, 2C, NMe2),
39.9 (s, 1C, CH(Me)NMe2), 30.4 (s, 1C, Cy–CHMe2), 23.1
(s, 1C, Cy–CHMe2), 22.4 (s, 1C, Cy–CHMe2), 18.0 (s, 1C, Cy–
CH3), 9.8 (s, 1C, CH(Me)NMe2). 31P{1H} NMR (δ, CDCl3,
20 ЊC): 23.3 (PPh2).
(SRu,RC,Spl)-RuCp(PPFA-ꢀN,ꢀP)Br (2b). This complex has
been prepared analogously to 2a with 1b (300 mg, 0.391 mmol)
and NEt4Br as the starting materials. Yield: 0.216 mg (84%).
C31H33BrFeNPRu requires: C, 54.17; H, 4.83; N, 2.04. Found:
C, 54.29; H, 4.95; N, 2.10%. 1H NMR (δ, CD2Cl2, 20 ЊC): 8.39–
8.27 (m, 2H, Ph), 7.53–7.44 (m, 3H, Ph), 7.20–7.11 (m, 3H,
3
Ph), 6.98–6.87 (m, 2H, Ph), 5.38 (q, JHH = 6.78 Hz, 1H,
[Ru(ꢁ6-p-cymene)(PN-ꢀN,ꢀP)Cl]CF3SO3 (4a). To a solution
of 3a (200 mg, 0.355 mmol) in THF (10 mL), TlCF3SO3
(150 mg, 0.426 mmol) was added and stirred for 30 min at room
temperature. The reaction mixture was evaporated to dryness
and the residue redissolved in CH2Cl2 (1 mL). Insoluble
materials (TlCl) were then removed by filtation over Na2SO4.
Upon addition of Et2O (4 mL), a red precipitate was formed
which was collected on a glass frit, washed with Et2O (3 ×
2 mL), and dried in vacuo. Yield: 116 mg (52%). C27H34ClF3-
NO3PRuS requires: C, 47.89; H, 5.06; N, 2.07. Found: C, 47.81;
CH(Me)NMe2), 4.42–4.40 (m, 1H, FeCps), 4.39–4.34 (m,
2H, FeCps), 3.79 (s, 5H, RuCp), 3.70 (s, 5H, FeCp), 3.46 (s, 3H,
3
NMe2), 2.45 (s, 3H, NMe2), 1.25 (d, JHH = 7.00 Hz, 3H,
CH(Me)NMe2). 13C{1H} NMR (δ, CD2Cl2, 20 ЊC): 148.2 (d,
1
1JCP = 48.8 Hz, 1C, Ph1), 137.5 (d, JCP = 42.7 Hz, 1C, Ph1Ј),
137.4 (d, 2JCP = 12.2 Hz, 2C, Ph2,6), 131.4 (d, 2JCP = 9.2 Hz, 2C,
Ph2Ј,6Ј), 130.2 (d, 4JCP = 2.3 Hz, 1C, Ph4), 127.9 (d, 4JCP = 1.5 Hz,
1C, Ph4Ј), 127.5 (d, 3JCP = 9.2 Hz, 2C, Ph3,5), 127.5 (d, 3JCP = 10.7
2
Hz, 2C, Ph3Ј,5Ј), 94.7 (d, JCP = 22.9 Hz, 1C, FeCp2), 75.5 (d,
JCP = 2.3 Hz, 1C, FeCps), 74.3 (d, 2JCP = 3.0 Hz, 5C, CpRu), 74.3
H, 5.11; N, 2.13%. H NMR (δ, CDCl3, 20 ЊC): 7.75–7.40 (m,
1
(d, 1JCP = 27.5 Hz, 1C, FeCp1), 71.0 (s, 5C, FeCp), 70.2 (d, JCP
=
10H, Ph), 6.25 (d, JHH = 5.8 Hz, 1H, Cy), 5.99 (d, JHH = 6.5 Hz,
1H, Cy), 5.36–5.16 (m, 2H, Cy), 3.22 (s, 3H, NMe2), 3.16 (s, 3H,
NMe2), 3.04–2.47 (m, 4H, PCH2CH2N), 3.04–2.47 (m, 1H, Cy–
CHMe2), 1.27 (d, 3JHH = 6.5 Hz, 3H, Cy–CHMe2), 1.20 (s, 3H,
3.8 Hz, 1C, FeCps), 70.0 (d, JCP = 9.2 Hz, 1C, FeCps), 59.0 (d,
3
3JCP = 1.5 Hz, 1C, CH(Me)NMe2), 56.1 (d, JCP = 2.3 Hz,
3
1C, NMe2), 48.6 (d, JCP = 1.5 Hz, 1C, NMe2), 10.3 (s, 1C,
CH(Me)NMe2). 31P{1H} NMR (δ, CD2Cl2, 20 ЊC): 37.4 (PPh2).
Cy–CH3), 1.10 (d, JHH = 6.9 Hz, 3H, Cy–CHMe2). 13C{1H}
3
NMR (δ, CDCl3, 20 ЊC): 134.6 (d, JCP = 9.9 Hz, 2C, Ph2,6),
2
Ru(ꢁ6-p-cymene)(PN-ꢀP)Cl2 (3a). A solution of [RuCl2(η6-p-
cymene)]2 (250 mg, 0.410 mmol) in THF (10 mL) was treated
with PN (0.211 g, 0.820 mmol) for 3 h at room temperature.
After removal of the solvent under reduced pressure, the solid
was collected on a glass frit, washed with Et2O, and dried under
vacuum. Yield: 0.201 g (80%). C26H34Cl2NPRu requires: C,
55.42; H, 6.08; N, 2.49. Found: C, 55.50; H, 6.02; N, 2.43%. 1H
134.0 (d, JCP = 47.6 Hz, 1C, Ph1), 133.3 (d, JCP = 9.9 Hz, 2C,
1
2
Ph2Ј,6Ј), 133.1 (d, JCP = 47.6 Hz, 1C, Ph1Ј), 131.8 (d, JCP = 2.7
1
4
Hz, 1C, Ph4), 131.6 (d, 3JCP = 9.0 Hz, 2C, Ph3,5), 131.5 (d, 4JCP
=
2.7 Hz, 1C, Ph4Ј), 129.4 (d, JCP = 9.9 Hz, 2C, Ph3Ј,5Ј), 97.3 (s,
1C, Cy), 92.8 (s, 1C, Cy), 89.8 (d, JCP = 8.9 Hz, 1C, Cy), 89.5
(d, JCP = 3.6 Hz, 1C, Cy), 87.9 (s, 1C, Cy), 87.0 (d, JCP = 5.4 Hz,
3
2
1C, Cy), 61.2 (d, JCP = 3.6 Hz, 1C, PCH2CH2N), 58.9 (s,
NMR (δ, CDCl3, 20 ЊC): 7.90–7.50 (m, 10H, Ph), 5.25 (d, JHH
=
1C, NMe2), 57.4 (s, 1C, NMe2), 31.0 (s, 1C, Cy–CHMe2), 22.3
(d, 1JCP = 28.7 Hz, 1C, PCH2CH2N), 20.7 (s, 1C, Cy–CHMe2),
18.0 (s, 1C, Cy–CHMe2), 15.9 (s, 1C, Cy–CH3). 31P{1H} NMR
(δ, CDCl3, 20 ЊC): 59.0 (PPh2).
5.3 Hz, 2H, Cy), 5.11 (d, JHH = 6.0 Hz, 2H, Cy), 2.84–2.81 (m,
2H, PCH2CH2N), 2.11 (s, 6H, NMe2), 2.30–2.09 (m, 2H,
PCH2CH2N), 2.60 (m, JHH = 7.1 Hz, 1H, Cy–CHMe2), 1.91 (s,
3H, Cy–CH3), 0.90 (d, 3JHH = 6.9 Hz, 6H, Cy–CHMe2). 13C{1H}
2
NMR (δ, CDCl3, 20 ЊC): 133.3 (d, JCP = 9.9 Hz, 4C, Ph2,6),
[(RRu,RC,Spl)-Ru(ꢁ6-p-cymene)(PPFA-ꢀN,ꢀP)Cl]CF3SO3
(4b). This complex has been prepared analogously to 4a using
3b (200 mg, 0.268 mmol) as starting material. Yield: 198 mg
(86%). C37H42ClF3FeNO3PRuS requires: C, 51.61; H, 4.92; N,
1.63. Found: C, 51.84; H, 5.13; N, 1.76%. 1H NMR (δ, CDCl3,
20 ЊC): 8.17–8.07 (m, 2H, Ph), 7.64–7.53 (m, 3H, Ph), 7.46–7.36
(m, 3H, Ph), 7.10–6.97 (m, 2H, Ph), 6.46–6.43 (m, 1H, Cy),
1
4
132.9 (d, JCP = 42.2 Hz, 2C, Ph1), 130.9 (d, JCP = 1.8 Hz,
2C, Ph4), 128.6 (d, JCP = 9.9 Hz, 4C, Ph3,5), 108.8 (s, 1C, Cy),
3
94.4 (s, 1C, Cy), 90.4 (d, JCP = 3.6 Hz, 2C, Cy), 85.9 (d, JCP
=
5.4 Hz, 2C, Cy), 53.6 (m, 1C, PCH2CH2N), 44.6 (s, 2C, NMe2),
30.2 (s, 1C, Cy–CHMe2), 21.6 (s, 2C, Cy–CHMe2), 21.1 (d,
1JCP = 29.6 Hz, 1C, PCH2CH2N), 17.6 (s, 1C, Cy–CH3).
31P{1H} NMR (δ, CDCl3, 20 ЊC): 21.6 (PPh2).
3
6.14–6.08 (m, 1H, Cy), 5.44 (q, JHH = 6.8 Hz, 1H, CH(Me)-
NMe2), 5.27–5.20 (m, 1H, Cy), 4.91–4.85 (m, 1H, Cy), 4.56–
4.50 (m, 1H, FeCps), 4.45–4.40 (m, 1H, FeCps), 4.38–4.33 (m,
1H, FeCps), 3.68 (s, 5H, FeCp), 3.45 (s, 3H, CH(Me)NMe2),
(RC,Spl)-Ru(ꢁ6-p-cymene)(PPFA-ꢀP)Cl2 (3b). A solution of
[RuCl2(η6-p-cymene)]2 (250 mg, 0.410 mmol) in THF was
treated with PPFA (361 mg, 0.820 mmol) for 1 h at room
temperature. During that time, an orange precipitate began to
form. After removal of the solvent under reduced pressure,
the solid was collected on a glass frit, washed with Et2O, and
dried under vacuum. Yield: 0.529 g (87%). C36H42Cl2FeNPRu
requires: C, 57.84; H, 5.66; N, 1.87. Found: C, 58.65; H, 5.80; N,
3
2.79 (m, JHH = 6.8 Hz, 1H, Cy–CHMe2), 2.57 (s, 3H, CH-
3
(Me)NMe2), 1.39 (d, JHH = 6.68 Hz, 3H, Cy–CHMe2), 1.34
3
3
(d, JHH = 7.2 Hz, 3H, CH(Me)NMe2), 1.31 (d, JHH = 7.0 Hz,
3H, Cy–CHMe2), 0.93 (s, 3H, Cy–CH3). 13C{1H} NMR (δ, CD2-
Cl2, 20 ЊC): 140.4 (d, JCP = 53.4 Hz, 1C, Ph1), 136.2 (d, JCP
=
1
2
10.5 Hz, 2C, Ph2,6), 133.6 (d, 1JCP = 56.3 Hz, 1C, Ph1Ј), 133.5 (d,
J. Chem. Soc., Dalton Trans., 2001, 2989–2995 2993

View Article Online
Table 3 Crystallographic data for 2bؒCHCl3 and 4bЈؒ½(CH3)2COؒ½(C2H5)2O
2bؒCHCl3
4bЈؒ½(CH3)2COؒ½(C2H5)2O
Formula
Fw
Crystal system
Space group
a/Å
b/Å
c/Å
C32H34BrCl3FeNPRu
806.75
C63.5H70BClFeNOPRu
1097.36
Monoclinic
P21 (no. 4)
13.439(6)
23.913(11)
17.169(8)
90.84(3)
5517(4)
4
Monoclinic
P21 (no. 4)
9.542(6)
34.54(2)
10.164(6)
109.67(3)
3155(3)
4
β/Њ
V/Å3
Z
T /K
223(2)
2.53
31779
10891
223(2)
0.66
79805
23774
µ(Mo-Kα)/mmϪ1
Measured rflns
Indep rflns
2θmax/Њ
49.8
54
No. of params
R1 [I > 2σ(I )]a
R1 (all data)a
wR2 (all data)b
722
0.043
0.049
0.102
1271
0.045
0.054
0.118
2
½
a R1 = Σ||Fo| Ϫ |Fc||/Σ|Fo|. b wR2 = [Σ{w(Fo2 Ϫ Fc2)2}/Σ{w(Fo )2}]
2JCP = 8.6 Hz, 2C, Ph2Ј,6Ј), 132.1 (d, 4JCP = 2.9 Hz, 1C, Ph4), 131.1
(d, 4JCP = 2.9 Hz, 1C, Ph4Ј), 128.9 (d, 3JCP = 10.5 Hz, 2C, Ph3,5),
128.5 (d, 2JCP = 10.5 Hz, 2C, Ph3Ј,5Ј), 96.8 (d, 1JCP = 21.0 Hz, 1C,
crystallographically independent Ru complexes of similar
stereochemistry and conformation, but with differing
environments, e.g. by the two independent CHCl3 molecules.
4bЈؒ½(CH3)2COؒ½(C2H5)2O also contains two crystallographi-
cally independent Ru complexes of similar comformation
arranged in a pseudo-21-like fashion along the c-axis of the
monoclinic unit cell. This compound stands out in containing
two different but well-ordered solvent molecules.
2
FeCp1), 96.6 (s, 1C, Cy), 93.4 (d, JCP = 20.0 Hz, 1C, FeCp2),
93.4 (s, 1C, Cy), 91.8 (s, 1C, Cy), 91.6 (s, 1C, Cy), 88.7 (d, JCP
=
3.8 Hz, 1C, Cy), 85.3 (s, 1C, Cy), 72.1 (d, JCP = 14.3 Hz, 1C,
FeCps), 71.6 (s, 5C, FeCp), 71.4 (d, JCP = 4.8 Hz, 1C, FeCps),
71.3 (d, JCP = 1.9 Hz, 1C, FeCps), 57.8 (s, 1C, NMe2), 57.3
(s, 1C, NMe2), 49.5 (d, 1JCP = 1.9 Hz, 1C, CH(Me)NMe2), 31.7
(s, 1C, Cy–CHMe2), 22.4 (s, 1C, Cy–CHMe2), 20.7 (s, 1C, Cy–
CHMe2), 15.0 (s, 1C, Cy–CH3), 10.2 (s, 1C, CH(Me)NMe2).
31P{1H} NMR (δ, CDCl3, 20 ЊC): 28.2 (PPh2). The BPh4Ϫ salt of
4b, [(RRu,RC,Spl)-Ru(η6-p-cymene)(PPFA-κN,κP)Cl]BPh4 (4bЈ),
has been prepared by anion metathesis with NaBPh4 in MeOH
as the solvent.
CCDC reference numbers 164452 and 164453.
Seehttp://www.rsc.org/suppdata/dt/b1/b104128m/forcrystal-
lographic data in CIF or other electronic format.
Acknowledgements
Financial support by the “Fonds zur Förderung der wissen-
schaftlichen Forschung” (project no. P13571 and P14681) and
“Österreichische Nationalbank” (project no. 7516) is gratefully
acknowledged. A PhD grant from the “Bundesministerium
für Auswärtige Angelegenheiten (Nord-Süd-Dialog Stipendien-
programm)” is gratefully acknowleged by L. X.
Hydrogen transfer catalysis with the precatalysts 1a–c, 2a–c, 4a,
and 4b
In a typical procedure, to a 0.1 M solution of the ketone in
2-propanol, the precatalyst (5 mg) and i-PrONa were added
(ketone : precatalyst : i-PrONa = 200 : 1 : 2) to a Schlenk tube
and heated in an oil bath at 82 ЊC for 48 h (see Tables 1 and 2).
After that time, the solvent was removed under reduced
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pressure and the product distribution was determined by H
NMR spectroscopy. In the case of chiral precatalysts the
enantiomeric excess was determined by HPLC.
X-Ray structure determination for 2bؒCHCl3 and 4bЈؒ½(CH3)2-
COؒ½(C2H5)2O
Crystals of 2b and 4bЈ in the form of their solvates 2bؒCHCl3
and 4bЈؒ½(CH3)2COؒ½(C2H5)2O were obtained by liquid phase
diffusion of petroleum ether into CHCl3 solutions and by gas
phase diffusion of Et2O into acetone solutions, respectively.
Crystal data and experimental details are given in Table 3.
X-Ray data were collected on a Bruker SMART CCD area
detector diffractometer (graphite monochromated Mo-Kα
radiation, λ = 0.71073 Å, 0.3Њ ω-scan frames covering complete
spheres of the reciprocal space). Corrections for Lorentz
and polarization effects, for crystal decay, and for absorption
were applied. Both structures were solved by direct methods
using the program SHELXS97.15 Structure refinement on F 2
was carried out with program SHELXL97.16 All non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were
inserted in idealized positions and were refined riding with
the atoms to which they were bonded. 2bؒCHCl3 contains two
2994
J. Chem. Soc., Dalton Trans., 2001, 2989–2995

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J. Chem. Soc., Dalton Trans., 2001, 2989–2995
2995