Efficient synthesis of ruthenium(II) η5-dienyl compounds starting from Di-μ-chlorodichloro-bis[(1-3η:6-8η)-2,7-dimethyloctadienediyl] diruthenium(IV). Versatile precursors for enantioselective hydrogenation catalysts

Article abstract of DOI:10.1021/om0007015

The dimeric complex di-μ-chlorodichloro-bis[(1-3η:6-8η)-2,7-dimethyloctadienediyl] diruthenium(IV) in the presence of base reacts with cyclic and acyclic dienes to the corresponding bis(η⁵-dienyl)ruthenium(II) compounds. Crystalline yellow comp

Full text of DOI:10.1021/om0007015

Organometallics 2000, 19, 5471-5476
5471
Efficien t Syn th esis of Ru th en iu m (II) η5-Dien yl
Com p ou n d s Sta r tin g fr om Di-µ-ch lor od ich lor o-
bis[(1-3η:6-8η)-2,7-d im eth ylocta d ien ed iyl]d ir u th en iu m (IV).
Ver sa tile P r ecu r sor s for En a n tioselective Hyd r ogen a tion
Ca ta lysts
Andre´ Bauer, Ulli Englert, Stefan Geyser, Frank Podewils, and Albrecht Salzer*
Institut fu¨r Anorganische Chemie der RWTH Aachen, D 52056 Aachen, Germany
Received August 14, 2000
The dimeric complex di-µ-chlorodichloro-bis[(1-3η:6-8η)-2,7-dimethyloctadienediyl]diru-
thenium(IV) in the presence of base reacts with cyclic and acyclic dienes to the corresponding
bis(η5-dienyl)ruthenium(II) compounds. Crystalline yellow compounds have been isolated
in high yields for dienyl ) cyclopentadienyl, pentamethylpentadienyl, cycloheptadienyl,
indenyl, dimethylpentadienyl, and trimethylpentadienyl. The analogous reaction of cyclohexa-
1,3-diene gives the ruthenium(0) compound (η6-benzene)(η4-cyclohexa-1,3-diene)ruthenium.
The “open” bis(dienyl)ruthenium complexes can be converted into half-sandwich complexes
through protonation and subsequent ligand exchange. These compounds can be used as
precursors for efficient enantioselective hydrogenation catalysts.
Sch em e 1
In tr od u ction
Organometallic ruthenium complexes are becoming
increasingly important in homogeneous catalysis such
as metathesis, the Murai reaction, hydrogenation, and
hydrogen transfer.1 The preparation of the necessary
ruthenium catalysts most often starts from RuCl3‚nH2O,
[Ru(H2O)6]2+, RuCl2(PPh3)3, [(cyclooctadiene)RuCl2]n, or
[(cymene)RuCl2]n.2
For the synthesis of diolefin and dienyl complexes, two
general methods have evolved: the so-called “Fischer-
Mu¨ller synthesis” where RuCl3‚nH2O is treated with an
isopropyl Grignard reagent and irradiated in the pres-
ence of a diolefin,3 and the "Vitulli method" where
RuCl3‚nH2O is treated with zinc in the presence of
diolefines.4 Both methods suffer from unpredictable
yields and are difficult to reproduce. This may be due
to the uncertain nature of commercial RuCl3‚nH2O as
well as the poorly understood mechanism of such
conversions (vide infra).
were unable to prepare them following traditional
methods.6
Resu lts a n d Discu ssion
Cox and Roulet have described an alternate method
for the preparation of bis(2,4-dimethylpentadienyl)-
ruthenium derivatives starting from di-µ-chlorodichloro-
bis[(1-3η:6-8η)-2,7-dimethyloctadienediyl]diruthenium-
(IV) (1). Their method involves silver tetrafluoroborate
and produces the cation [(C7H11)2RuH]+.7 Following this
procedure we tried to prepare this compound but
isolated to our surprise the [(C7H11)Ru(toluene)]+ cation
(2) in good yields. It turned out that the source of
toluene most likely was the ethanol used, which con-
tained small amounts of toluene as a denaturizing
agent. On repeating the reaction with purified ethanol
in the presence of added benzene or toluene we were
able to prepare [(C7H11)Ru(benzene)]+ (3) and [(C7H11)-
Ru(toluene)]+ in very high yields (Scheme 1).
In continuation of our studies on open and half-open
ruthenocenes,5 we therefore sought a rational high-yield
synthesis for this class of compounds, as we ourselves
(1) (a) Murahashi, S.-I.; Naota, T.; Takaya, H. Chem. Rev. 1998, 98,
2599. (b) Beller, M.; Bolm, C. Transition Metals for Organic Synthesis;
VCH: Weinheim, 1998. (c) Schwab, P.; Ziller, J . W.; Grubbs, R. H. J .
Am. Chem. Soc. 1996, 118, 100. Murai, S.; Kakiuchi, F.; Sekine, S.;
Tanaka, Y.; Kamatani, A.; Sonoda, M.; Chatani, N. Pure Appl. Chem.
1994, 66, 1527. (d) Noyori, R. Acta Chem. Scand. 1996, 113, 8518. (e)
Noyori, R.; Hashiguchi, S. Acc. Chem. Res. 1997, 30, 97.
(2) (a) Ko¨lle, U. In Encyclopedia of Inorganic Chemistry; King, R.
B., Ed.; J ohn Wiley: Chichester, 1994; Vol. 7, p 3533. (b) Bruce, M. I.;
Bennett, M. A.; Matheson, T. W. In Comprehensive Organometallic
Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon
Press: Oxford, 1982, 1994. (c) Bu¨rgi, H.-B.; Ludi, A.; Salzer, A.; Stebler-
Ro¨thlisberger, M. Organometallics 1986, 5, 298-302.
(5) (a) Bosch, H. W.; Hund, H.-U.; Nietlispach, D. Organometallics
1992, 11, 2087. (b) Bertling, U.; Englert, U.; Salzer, A. Angew. Chem.
1994, 106, 1026; Angew. Chem., Int. Ed. Engl. 1994, 33, 1003. (c)
Englert, U.; Podewils, F.; Schiffers, I.; Salzer, A. Angew. Chem. 1998,
110, 2196; Angew. Chem., Int. Ed. Engl. 1998, 37, 2134.
(6) Ernst, R. D.; Stahl, L. Organometallics 1983, 2, 1229.
(7) Cox, D. N.; Roulet, R. J . Chem. Soc., Chem Commun. 1988, 951.
(3) Mu¨ller, J .; Kreiter, C. G.; B. Mertschenk, B.; Schmitt, S. Chem.
Ber. 1975, 108, 273-282.
(4) (a) Partici, P.; Vitulli, G.; Paci, M.; Porri, L. J . Chem. Soc., Dalton
Trans. 1980, 1961-1964. (b) Dahlenburg, L.; Frosin, K.-M. Inorg.
Chim. Acta 1990, 167, 83-89.
10.1021/om0007015 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 11/08/2000

5472 Organometallics, Vol. 19, No. 25, 2000
Bauer et al.
Ta ble 1. Yield of 4 w ith Differ en t Alk a li Ca r bon a te
Ba ses
Sch em e 3
solid base
yield (%)
K2CO3
Na2CO3
Li2CO3
48
72
95
Sch em e 2
This reaction is similar to the reaction conditions of
Ludi where [Ru(H2O)6]2+ in the presence of dienes and
arenes gives high yields of the arene cation.2c Using
high- purity ethanol and AgBF4 leads as described by
Cox and Roulet to the protonated open ruthenocene.
As we however sought a procedure to prepare neutral
bis(pentadienyl)ruthenium complexes, we modified the
Cox/Roulet method extensively. We first optimized the
preparation on the dimeric starting material 1 by
changing the solvent to a 1:3 mixture of 2-methoxy-
ethanol and isoprene in the procedure described by Cox
and Roulet.8 This improved the yield to 95%. In a second
step, we treated 1 with 1 equiv of acetonitrile to form
the monomeric species8 and to make the compound more
soluble. Instead of using AgBF4 for dehalogenation, we
used different bases to neutralize the 2 equiv of HCl
that must be formed during the reaction. There is a
striking dependence of the yield of this reaction on the
solid base used, for which we currently have no expla-
nation (Table 1). In this way, open ruthenocene (C7H11)2-
Ru (4) could be prepared in almost quantitative yield,
avoiding the use of expensive AgBF4 and the protona-
tion of the product. This method also allows the reduc-
tion of the amount of ligand to a 2-fold excess per
ruthenium, while the Vitulli method always requires a
large excess (>20-fold) of the diolefinic ligand (Scheme
2). We have extensively varied the type of base used
but found that only nonsoluble, nonnucleophilic bases
such as the carbonates give satisfactory results. Other
bases such as sodium amide, pyridine, or sodium
methanolate either destroy the bis(allyl) starting mate-
rial or break up the dimeric structure of 1 and form
stable adducts, as observed by Cox and Roulet.8 Even
acetonitrile can only be used in equimolar amounts, as
otherwise yields of 4 are drastically reduced. The
increase in yields going from potassium to sodium to
lithium may possibly be due to the increasing solubility
of the alkali halides in ethanol in this order.
surprising that in the Roulet method the open ru-
thenocene immediately is protonated by HBF4 formed
during the reaction, as no base is present.
In further experiments we have found that bis(dienyl)
complexes not sensitive to the presence of strong acids
such as HCl and HBr can be directly prepared from
RuCl3‚nH2O. Refluxing of RuCl3‚nH2O in the presence
of cyclopentadiene (CpH) in 2-propanol but without zinc
dust also produces ruthenocene in 61% yield. The
success of this method is probably due to the fact that
Cp2Ru is less sensitive to strong acids and is not easily
protonated. In this case, the reduction of Ru(III) (if this
is assumed to be the predominant oxidation state of
“RuCl3‚nH2O”) is most likely performed by 2-propanol,
which is oxidized to acetone. When Li2CO3 is used, the
yield is increased to 98% and therefore higher than in
the Vitulli method in the presence of zinc dust.
The presence of solid bases is essential for the
synthesis of other dienyl complexes of ruthenium. We
were able to prepare a whole series of ruthenium(II) and
ruthenium(0) complexes 4-11 in good to excellent yields
(Scheme 3).
The reaction conditions were optimized for (C7H11)2-
Ru; modified reaction conditions may give better yield
for the other dienyl complexes. These complexes thus
prepared served as highly useful starting materials for
a variety of ruthenium(II) complexes.
It was possible to protonate bis(cycloheptadienyl)-
ruthenium (C7H9)2Ru (6) similar to (C7H11)2Ru in 80%
yield. At room temperature, nearly all protons are
equivalent on the NMR time scale. These scrambling
processes are similar to those previously described for
similar protonated olefin complexes (Scheme 4).9 On
cooling (-100 °C), we observed that some of the rear-
rangements are significantly slowed and the limiting
spectrum observed at that temperature is that of a bis-
The method described here also indicates that the role
of zinc in the Vitulli method most probably is that of
an HCl quencher and not of a reducing agent, in
contrast to the assumption of Vitulli.4a In our method,
the fate of the various agents can easily be explained.
The octadienediyl ligand is eliminated by reductive
coupling leading to 1,6-dimethyl-1,5-cyclooctadiene, which
was detected spectroscopically, while the two molar
equivalents of HCl are absorbed by the base. It is not
(9) Buchmann, B.; Piantini, U.; von Philipsborn, W.; Salzer, A. Helv.
Chim. Acta 1987, 70, 1487.
(8) Cox, D. N.; R. Roulet, R. Inorg. Chem. 1990, 29, 1360-1365.

Synthesis of Ruthenium(II) η5-Dienyl Compounds
Organometallics, Vol. 19, No. 25, 2000 5473
Sch em e 4
Sch em e 5
F igu r e 1. Molecular structure and crystallographic num-
bering scheme for compound 13 (PLATON representation).
Ellipsoids are scaled to enclose 30% probability. Hydrogen
atoms are drawn with arbitrary radii.
Ta ble 2. Selected Bon d Len gth s (Å)a a n d An gles
(d eg)a for Com p ou n d 13
Ru-I
2.7446(8)
2.213(4)
2.211(3)
2.198(4)
2.188(4)
2.245(4)
2.167(4)
2.179(4)
2.170(4)
2.246(4)
1.401(5)
C(2)-C(3)
1.434(5)
1.408(6)
1.38.9(5)
1.408(6)
1.413(6)
1.408(6)
Ru-C(1)
Ru-C(2)
Ru-C(3)
Ru-C(4)
Ru-C(11)
Ru-C(12)
Ru-C(13)
Ru-C(14)
Ru-C(15)
C(1)-C(2)
C(3)-C(4)
C(11)-C(12)
C(12)-C(13)
C(13)-C(14)
C(14)-C(15)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(11)-C(12)-C(13)
C(12)-C(13)-C(14)
C(13)-C(14)-C(15)
118.0(4)
118.2(4)
123.2(4)
124.3(4)
125.5(4)
a
Estimated standard deviations in the least-squares significant
figure are given in parentheses.
(heptadienyl)ruthenium hydrido cation in which the
agostic hydride bond rapidly interchanges between the
four equivalent positions of the terminal carbons of the
dienyl moieties.5a,10
Sch em e 6
This protonated species is highly susceptible to ligand
exchange similar to the protonated open ruthenocenes10,11
We treated [(C7H9)2RuH]BF4 (12) with KI as a halide
source in the presence of dimethylbutadiene and ob-
tained the neutral half-sandwich complex (C7H9)Ru-
(C6H10)I (13) (Scheme 5). This compound was charac-
terized by an X-ray structure analysis (Figure 1, Table
2).
The analogous pentadienyl ruthenium dimethylbuta-
diene complex (15) previously described by Cox and
Roulet11 reacts with TlCp to give the half-open ru-
thenocene (C5H5)Ru(C7H11) (16) in almost quantitative
yields (Scheme 6).
Starting from [(C7H9)2RuH]BF4 (12) and [(C7H11)2-
RuH]BF4 (14), we were able to prepare the cationic
BINAP complexes [(C7H11)Ru(BINAP)(acetonitrile)]BF4
(17) and [(C7H9)Ru(BINAP)(acetonitrile)]BF4 (18)
(Scheme 7).
These BINAP complexes react under hydrogen atmo-
sphere in acetone to an identical solvated hydrido
species [Ru(BINAP)H(solv)x]+ with facile loss of the
second dienyl ligand. This species apparently is identical
to that described by Bergens,12 which was shown to be
a highly efficient catalyst for the enantioselective hy-
drogenation of R,â-unsaturated esters. We were able to
hydrogenate various unsaturated ester derivatives in
(10) Newbound, T. D.; Stahl, L.; Ziegler, M. L.; Ernst, R. D.
Organometallics 1990, 9, 2962.
(11) (a) Cox, D. N.; Lumini, T.; Roulet, R.; Schenk, K. J . Organomet.
Chem. 1992, 434, 363. (b) Cox, D. N.; Lumini, T.; Roulet, R. J .
Organomet. Chem. 1992, 438, 195.
(12) (a) Bergens, S. H.; Wiles, J . A. Organometallics 1998, 17, 2228.
(b) Wiles, J . A.; Lee, C. E.; McDonald, R.; Bergens, S. H. Organome-
tallics, 1996, 15, 3782. (c) Wiles, J . A.; Bergens, S. H.; Young, V. G. J .
Am. Chem. Soc. 1997, 119, 2940. (d) Daley, C. J . A.; Wiles, J . A.;
Bergens, S. H. Can. J . Chem. 1998, 76, 1447.

5474 Organometallics, Vol. 19, No. 25, 2000
Bauer et al.
Sch em e 7
and closed dienyl complexes of ruthenium, making in
particular “open” and “half-open” ruthenocene available
for the first time in almost quantitative yields. Open
ruthenocenes were used by us among other reactions
for the unprecedented synthesis of the first bis(metalla-
benzene)ruthenium sandwich complexes.5c After proto-
nation of open ruthenocenes, these are readily and
quantitatively converted into half-sandwich complexes,
which in turn are an efficient source for enantioselective
hydrogenation catalysts of ruthenium(II).
Exp er im en ta l Section
All reactions were carried out under nitrogen using standard
Schlenck techniques. Solvents were dried and deoxygenated
by standard methods. NMR spectra were recorded on a Varian
1
Mercury 200 (200 MHz, H; 50 MHz, 13C; 81 MHz, 31P) and a
Varian Unity 500 (500 MHz, 1H; 125 MHz, 13C; 202 MHz, 31P)
at ambient temperature. Chemical shifts (δ) are given in ppm
relative to SiMe4. Mass spectra were obtained with a Finnigan
MAT 95 spectrometer. Elemental analyses were obtained on
a Carlo Erba element analyzer, model 1106. Isoprene, 1,3-
cyclohexadiene, 1,3-cyclooctadiene, indene, ruthenium chloride,
Sch em e 8
.
HBF4 Et2O (54% in diethyl ether), KI, tetraethylammonium
chloride, (S)-BINAP, and (R)-p-tol-BINAP were purchased
from Fluka, Merck, J ohnson Matthey, or Strem and used as
received. Monomeric C5H6 was obtained from commercial
dicyclopentadiene (Fluka) by dropping into hot Decaline and
distillation through a vigreux column and was stored under
nitrogen at -80 °C. The compounds 2,4-dimethylpentadiene,
2,3,4-trimethylpentadiene, pentamethylcyclopentadiene, cy-
cloheptadiene, and TlCp were prepared by standard methods.
X-r a y Str u ctu r e Deter m in a tion of 13. Geometry and
intensity data were collected with Mo KR radiation at 203 K
on an Enraf-Nonius CAD4 diffractometer equipped with a
graphite monochromator (λ ) 0.7107 Å). Crystal data: mono-
clinic space group P21/n (14), a ) 8.206(3) Å, b ) 15.291(7) Å,
c ) 10.643(2) Å, â ) 104.23(2)°, V ) 1294.6(8) Å3, Z ) 4, dc )
2.069 g cm-3, µ ) 35.18 cm-1, F(000) ) 776. Intensity data
(3910) were in the range 2.0 < θ < 27.0° on a yellow rod of
approximate dimensions 0.4 × 0.2 × 0.2 mm3. An empirical
absorption correction based on azimuthal scans14 was applied
before averaging over symmetry equivalent data. The structure
was solved by direct methods15 and refined16 on F with
anisotropic displacement parameters for all non-hydrogen and
isotropic displacement parameters for H atoms. Independent
observations (2589) with I > 1.0 σ(I) for 193 variables resulted
in R ) 0.027, Rw ) 0.032 (GOF ) 1.060). Crystallographic data
(excluding structure factors) for the structure reported in this
paper have been deposited with the Cambridge Crystal-
lographic Data Centre as supplementary publication No.
CCDC-149752. Copies of the data can be obtained free of
charge on application to The Director, CCDC 12 Union Road,
Cambridge CB2 1EZ, U.K. (FAX, int. +1223/336-033; E-mail,
teched@chemcrys.cam.ac.uk).
good agreement with results of Bergens with very high
enantioselectivities (Scheme 8).12
A similar hydrogenation catalyst with DUPHOS and
J OSIPHOS ligands obtained by other routes has also
very recently found industrial application in the cata-
lytic hydrogenation of jasmonates.13
Our method of obtaining these hydrogenation cata-
lysts seems to be superior to the published or patented
methods,12,13 as all synthetic conversions described in
this paper starting from RuCl3‚nH2O and isoprene are
nearly quantitative. The catalyst can be prepared
directly in situ from the protonated “open” ruthenocene
14 without prior isolation of any intermediates.
Dich lor o-b is-µ-ch lor o-b is[(1-3η:6-8η)-2,7-d im et h yl-
octa d ien ed iyl]d ir u th en iu m (II) (1). A solution of ruthenium
chloride in a mixture of isoprene (400 mL) and 2-methoxy-
ethanol (160 mL) was refluxed for 10 days. The purple
crystalline product was collected in a sintered glass funnel,
washed with diethyl ether, and dried in vacuo; yield 95%.
1H NMR (250 MHz, CDCl3): 5.72, 5.37, 5.22, (s, 2H, H-1,
H-8), 4.65 (m, 2H, H-3, H-6), 4.49 (m, 4H, H-1, H-3, H-6, H-8),
2.7-2.4 (m, 8H, H-4, H-5), 2.37 (s, 6H, H-9, H-10), 2.28 (s, 6H,
Con clu sion s
We have demonstrated that the easily accessible
dimeric di-µ-chlorodichloro-bis[(1-3η:1-3η)-2,7-dime-
thyloctadienediyl]diruthenium(IV) compound is an al-
most universal reagent for the rational synthesis of open
(14) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.
1968, A24, 351.
(13) Dobbs, D. A.; Vanhessche, K. P. M.; Brazi, E.; Rautenstrauch,
V.; Lenoir, J .-Y.; Geneˆt, J .-P.; Wiles, J . A.; Bergens, S. H. Angew. Chem.
2000, 112, 2080-2083; Angew. Chem., Int. Ed. Engl. 2000, 39, 1992.
(15) Sheldrick, G. M. SHELX97, Program for Crystal Structure
Determination; University of Go¨ttingen, 1997.
(16) ENRAF-Nonius. SDP Version 5.0, 1989.

Synthesis of Ruthenium(II) η5-Dienyl Compounds
Organometallics, Vol. 19, No. 25, 2000 5475
H-9, H-10).13C NMR (125 MHz, CDCl3): 124.33 (C-2, C-7),
119.32 (C-2, C-7), 96.12 (C-3, C-6), 94.57 (C-3, C-6), 84.58 (C-
1, C-8), 80.96 (C-1, C-8), 33.97 (C-4, C-5), 32.36 (C-4, C-5), 19.81
(η6-Ben zen e)(η4-cycloh exa d ien e)r u th en iu m (7). A solu-
tion of 1 (0.24 g, 0.4 mmol) and Li2CO3 (0.29 g, 4.0 mmol) in a
mixture of 10 mL of ethanol, 26 µL (0.5 mmol) of acetonitrile,
and freshly distilled cyclohexadiene (0.24 g, 3.1 mmol) was
refluxed for 4 h. After evaporation of the solvents, the yellow-
brown crude product was extracted with diethyl ether, filtered
over a pad of alumina, and cooled to -80 °C. 7 was obtained
as yellow crystals; yield 69%. 1H NMR (250 MHz, C6D6): 4.92
(s, 6H, C6H6), 4.86 (dd, 2H, CH)CHCH2,H-2), 3.20 (m, 2H,
CHdCHCH2 H-3), 1.70 (m, 4H, CHdCHCH2 H-4). Anal. Calcd
(Found) for C12H14Ru: C, 55.58 (55.11); H, 5.44 (5.19).
1
(C-9, C-10), 19.01 (C-9, C-10) for the Ci-isomer of 1. H NMR
(250 MHz, CDCl3): 6.09, 5.07, 4.87, (s, 2H, H-1, H-8), 4.73 (m,
4H, H-1, H-3, H-6, H-8), 4.45 (m, 2H, H-3, H-6), 2.7-2.4 (m,
8H, H-4, H-5), 2.47 (s, 6H, H-9, H-10), 2.24 (s, 6H, H-9, H-10).
13C NMR (125 MHz, CDCl3): 124.10 (C-2, C-7), 120.16 (C-2,
C-7), 96.50 (C-3, C-6), 94.57 (C-3, C-6), 86.75 (C-1, C-8), 78.83
(C-1, C-8), 33.91 (C-4, C-5), 32.92 (C-4, C-5), 19.75 (C-9, C-10),
19.25 (C-9, C-10) for the C2-isomer of 1. Anal. Calcd (Found)
for C20H32Cl4Ru2: C, 38.97 (39.00), H, 5.23 (5.19). MS (EI)
m/z: 616 (M+). These NMR data are basically identical to those
reported in the literature.8
Bis(η5-in d en yl)r u th en iu m (8). The orange compound was
prepared as described for 7 substituting cyclohexadiene for
1
indene; yield 46%. H NMR (200 MHz, C6D6): δ ) 6.52-6.69
3
3
(η6-Tolu en e)(η5-2,4-d im et h ylp en t a d ien yl)r u t h en iu m
Tet r a flu or ob or a t e (2). To a solution of silver tetrafluoro-
borate (0.77 g, 4.0 mmol) in 20 mL of ethanol, 2,4-dimethyl-
penta-1,3-diene (0.62 g, 6.5 mmol) and 2 mL toluene were
added. This solution was added dropwise and under vigorous
stirring to 1 (0.61 g, 2.0 mmol) dissolved in 15 mL of methylene
chloride. Silver chloride was separated by centrifugation and
washed with 5 mL of methylene chloride. The combined
solutions were concentrated, and the orange product was
(m, 8H, H-1,2), 4.80 (d, J ) 2.4 Hz, 4H, H-3), 4.46(t, J ) 2.4
Hz, 2H, H-4). MS (EI) m/z: 332 (M+, 100%), 217 (M+ - indene,
20%). Anal. Calcd (Found) for C18H14Ru: C, 65.25 (65.02); H,
4.26 (4.19).
Bis(η5-p en ta m eth ylcyclop en ta d ien yl)r u th en iu m (9).
The off-white crystalline compound was isolated as described
for 7 substituting cyclohexadiene for pentamethylcyclopenta-
diene; yield 47%. 1H NMR (200 MHz, C6D6): 1.64 (s, Me) ppm.
13C NMR (50 MHz, C6D6): 82.9 (CCH3), 10.5 (CCH3) ppm. MS
(EI) m/z: 372 (M+, 100%). Anal. Calcd (Found) for C20H30Ru:
C, 64.66 (65.01); H, 8.14 (8.19).
Bis(η5-m eth ylcyclop en ta d ien yl)r u th en iu m (10). The
off-white crystalline compound was isolated as described for
7 substituting cyclohexadiene for methylcyclopentadiene; yield
50%. 1H NMR (200 MHz, C6D6): 4.39 (m, Cp), 1.81 (s, Me).
13C NMR (50 MHz, C6D6): 86.5, 72.7, 70.3 (Cp), 14.7 (Me). MS
1
precipitated by addition of diethyl ether; yield 67%. H NMR
(500 MHz, CD2Cl2): 6.18 (td, 2H, J ) 6.0/1.0 Hz, toluene), 6.14
(tt, 1H, J ) 5.8/0.9 Hz, toluene), 6.02 (d, 2H, J ) 5.8 Hz,
toluene), 3.53 (d, 2H, 3.4 Hz, CH2,endo), 2.31 (s, 3H, CH3), 2.10
(s, 6H, 2 CH3), 1.03 (d, 2H, 3.05, CH2,endo). 13C NMR (75 MHz,
CD2Cl2): 108.3 (CCH3, toluene), 105.8 (2 CCH3), 97.6 (1 CH),
92.0 (2 CH, toluene), 91.4 (CH, toluene), 53.4 (2 CH2), 26.3 (2
CH3), 20.0 (CH3). Anal. Calcd (Found) for C14H19RuBF4: C,
44.82 (44.99); H, 5.10 (4.92).
(η6-Ben zen e)(η5-2,4-d im et h ylp en t a d ien yl)r u t h en iu m
Tetr a flu or obor a te (3). The orange crystalline compound was
isolated as described for 2 substituting toluene for benzene;
yield 75%. 1H NMR (250 MHz, CD2Cl2): 6.36 (s, 6H, benzene),
3.53 (d, 2H, J ) 4 Hz, CH2,exo), 2.16 (s, 6H, CH3), 1.15 (d, 2H,
J ) 4 Hz, CH2,endo).13C NMR (75 MHz, CD2Cl2): 106.3 (2
CCH3), 97.9 (1 CH), 92.7 (6 CH), 51.6 (2 CH2), 25.7 (2 CH3).
Anal. Calcd (Found) for C13H17RuBF4: C, 43.24 (43.29); H, 4.74
(4.67).
Bis(η5-2,4-d im eth ylp en ta d ien yl)r u th en iu m (4). A solu-
tion of 1 (0.31 g, 0.5 mmol) and Li2CO3 (0.15 g, 2.0 mmol) in a
mixture of 10 mL of ethanol, 26 µL (0.5 mmol) of acetonitrile,
and 2,4-dimethylpenta-1,3-diene (0.38 g, 4.0 mmol) was re-
fluxed for 4 h. After evaporation of the solvents, the brown
crude product was purified by sublimation and 4 was obtained
as yellow crystals. On a larger scale, it is more convenient to
extract the dry brown crude product with diethyl ether and to
filter the solution over a pad of alumina prior to sublimation;
yield 95%. 1H NMR (250 MHz, C6D6): 4.63 (s, 1H), 2.71 (s,
2H, J ) 2 Hz), 1.73 (s, 6H), 0.86 (s, 2H, J ) 2 Hz). 13C NMR
(62.9 MHz, C6D6): 100.3 (C-2), 97.8 (C-3), 46.8 (C-1), 26.3 (C-
4). These NMR data are basically identical to those reported
in the literature.6 Anal. Calcd (Found) for C14H22Ru: C, 57.71
(57.99); H, 7.61 (7.82).
Bis(η5-2,3,4-tr im eth ylp en ta d ien yl)r u th en iu m (5). The
yellow crystalline compound was isolated as described for 4
substituting 2,4-dimethyl-1,3-pentadiene for 2,3,4-trimethyl-
1,3-pentadiene; yield 62%. 1H NMR (250 MHz, C6D6): 2.73 (s,
4H, H-1exo), 1.53 (s, 12H, H-4), 1.46 (s, 6H, H-5), 0.86 (s, 4H,
H-1endo). 13C NMR (62.9 MHz, C6D6): 105.9 (C-3), 96.26 (C-2),
49.0 (C-1), 25.2 (C-4), 16.4 (C-5). Anal. Calcd (Found) for
(EI) m/z: 259 (M+, 100%), 245 (M+ - CH3, 20%), 181 (M+
-
CpMe, 14%), 102 (M+ - 2CpMe, 4%). Anal. Calcd (Found) for
C
12H14Ru: C, 55.56 (56.11); H, 5.44 (5.31).
Bis(η5-cyclop en ta d ien yl)r u th en iu m (11). The off-white
crystalline compound was isolated as described for 7 substitut-
ing cyclohexadiene for cyclopentadiene; yield 98%. 1H NMR
(200 MHz, C6D6): 4.46 (s, Cp). 13C NMR (50 MHz, C6D6): 70.4
(Cp). MS (EI) m/z: 232 (M+, 100%), 169 (M+ - Cp, 20%). Anal.
Calcd (Found) for C10H10Ru: C, 51.94 (50.99); H, 4.36 (4.41).
Bis(η5-cycloh ep ta d ien yl)h yd r id or u th en iu m Tetr a flu o-
r obor a te (12). A solution of 6 (0.16 g, 0.56 mmol) in 40 mL of
diethyl ether was cooled to -78 °C, and HBF4‚Et2O (0.1 mL,
0.61 mmol) was added with stirring. A yellow precipitate was
immediately formed. The reaction mixture was slowly warmed
to room temperature, and after removal of the magnetic
stirring bar the yellow precipitate settled out of the solution.
The supernatant liquid was removed, and the solid was
1
washed with diethyl ether and dried in vacuo; yield 99%. H
NMR (500 MHz, 296.2 K, CD2Cl2): 4.1 (br s), 1.5 (br s) ppm.
1H NMR (500 MHz, 183.2 K, CD2Cl2): 5.9 (CH), 5.1 (CH), 4.4
(CH), 2.1 (CH2,exo), 1.4 (CH2,endo), -6.0 (RuH) ppm.
(η4-2,3-Dim et h ylb u t a d ien e)(η5-cycloh ep t a d ien yl)r u -
th en iu m Iod id e (13). To a solution of the hydrido complex
12 (0.205 g, 0.55 mmol) in 20 mL of acetone, potassium iodide
(0.095 g, 0.57 mmol) and dimethylbutadiene (0.898 g, 10.9
mmol) dissolved in acetone were added dropwise at -78 °C.
The reaction mixture was stirred and slowly warmed to room
temperature over a period of 16 h. The product was isolated
as a yellow solid after cooling to -30 °C for 24 h; yield 90%.
1H NMR (500 MHz, CD2Cl2): 4.58-4.53 (m, 3H, CH), 4.32 (dd,
J ) 6.1 Hz/8.6 Hz, 2H, CH), 2.71 (d, J ) 1.8 Hz, 2H, CHexo,diene),
2.60 (m, 2H, CHexo), 1.82 (s, 6H, CH3,diene), 1.75 (m, 2H, CHendo
)
1.4 (d, J ) 1.8 Hz, CHendo,diene), 13C NMR (125 MHz, CD2Cl2):
C
16H26Ru: C, 60.16 (60.09); H, 8.20 (8.11).
Bis(η5-cyloh ep ta d ien yl)r u th en iu m (6). The yellow crys-
102.1 (C), 96.28 (CH), 95.6 (CH), 80.5 (CH), 52.2 (CH2), 33.2
-
(CH2), 17.7 (CH3_). MS (EI): 403 (M+), 322 (M+ dimethyl-
butadiene), 277 (M+ - I), 195 (M+ - I - dimethylbutadiene).
Anal. Calcd (Found) for C13H19RuI: C, 38.72 (39.02); H, 4.75
(4.79).
talline compound was isolated as described for 4 substituting
2,4-dimethyl-1,3-pentadiene for 1,3-cycloheptadiene; yield 80%.
1H NMR (250 MHz, C6D6): 5.01 (t, 2H, H-1), 4.37 (dd, 4H, H-2),
3.88 (m, 4H, H-3), 2.15, 1.66 (m, 8H, H-4). 13C NMR (62.9 MHz,
C6D6): 94.56 (C-1); 88.21 (C-2); 64.88 (C-3); 34.95 (C-4). Anal.
Calcd (Found) for C14H18Ru: C, 58.52 (57.99); H, 6.31 (6.21).
Bis(η5-2,4-dim eth ylpen tadien yl)h ydr idor u th en iu m Tet-
r a flu or obor a te (14). This compound was obtained by a
synthesis previously described by Ernst and co-workers.10
A

5476 Organometallics, Vol. 19, No. 25, 2000
Bauer et al.
well-stirred solution of 4 (0.97 g, 3.3 mmol) in 50 mL of diethyl
ether was cooled to -75 °C, and over a period of 15 min a 54%
solution of HBF4 in ether (0.45 mL) was added dropwise. The
product precipitated as a yellow solid and was collected in a
sintered glass funnel, washed with diethyl ether, and dried
in vacuo; yield 99%. 1H NMR (250 MHz, CD2Cl2): 5.61 (s,
1H,CH), 2.09 (s, 6H, CH3), 1.3 (b, 5H, Ru-H/CH2). 13C NMR
(62.9 MHz, CD2Cl2): 100.05 (CCH3), 98.65 (CH), 47.19 (CH2),
25.33 (CH3).
and ®-BINAP (0.220 g, 0.35 mmol) in 10 mL of methylene
chloride and 20 mL of acetonitrile was stirred for 16 h at room
temperature. The solution was concentrated, and the product
was precipitated by addition of diethyl ether; yield 82%. 1H
NMR (500 MHz, CD2Cl2): 8.20-5.90 (m, 32H, aromatic), 5.12,
4.91, 4.49, 4.45, 3.50 (m, 1H, CH), 2.97 (s, 3H, NCCH3) 1.34,
1.01, 0.66, 0.38 (m, 1H, CH2).13C NMR (125 MHz, CD2Cl2):
116.9 (NCCH3), 106.0, 93.7 (CH), 94.0 (d, J ) 24.7 Hz, CH),
75.2 (d, J ) 20.3, CH), 59.9 (s, C-H) 33.3, 25.5 (CH2), 2.0
(NCCH3). 31P NMR (202 MHz, CD2Cl2): 46.5 (J ) 34.6 Hz),
37.5 (J ) 34.6 Hz). Anal. Calcd (Found) for C13H19RuI: C, 67.38
(68.02); H, 4.69 (4.72).
(η4-2,3-Dim et h ylb u t a d ien e)(η5-2,4-d im et h ylp en t a d i-
en yl)iod or u th en iu m (15). This compound was obtained by
a synthesis previously described by Cox and Roulet. A solution
of 14 (1.3 g, 3.3 mmol) in 30 mL of acetone was added dropwise
to a solution of 2,3-dimethylbutadiene (5.7 g, 69.0 mmol) and
potassium iodide (0.6 g, 3.6 mmol) at -78 °C. The mixture
was stirred for 16 h and allowed to warm to room temperature.
The product precipitated and was collected in a sintered glass
funnel and dried in vacuo, yield 93%. 1H NMR (250 MHz, CD2-
Cl2): 4.85 (s, 1H, H-3), 3.80 (d, J ) 0.9 Hz, 2H, H-1exo), 2.65
(d, J ) 2.5 Hz, 2H, H-1′exo), 1.89 (s, 6H, H-3′), 1.83 (s, 6H, H-4),
1.72 (d, J ) 2.5 Hz, 2H, H-1′exo), 1.67 (d, J ) 0.9 Hz, 2H, H-1exo).
13C NMR (62.9 MHz, CD2Cl2): 106.05 (C-2), 100.37 (C-2′), 93.30
(C-3), 60.57 (C-1′), 52.64 (C-1), 22.93 (C-4), 20.03 (C-3′).
(η5-Cyclop en ta d ien yl)(η5-2,4-d im eth ylp en ta d ien yl)r u -
th en iu m (16). To a suspension of 15 (1.25 g, 3.1 mmol) in 50
mL of toluene TlCp (0.91 g, 3.4 mmol) was added, and the
suspension was refluxed for 16 h. The solvent was removed,
and the brown residue was extracted three times with 30 mL
of hexane. The solution was concentrated, and the yellow crude
product was purified by sublimation in vacuo (80 °C); yield
99%. 1H NMR (250 MHz, C6D6): 5.31 (s, 1H, H-3), 4.46 (s, 5H,
H-5), 2.93 (s, 2H, H-1exo), 1.83 (s, 6H, H-4), 0.17 (s, 2H, H-1endo).
13C NMR (62,9 MHz, C6D6): 92.64 (C-3), 92.19 (C-2), 78.11 (C-
5), 40.75 (C-1), 28.02 (C-4).
Ca ta lytic Hyd r ogen a tion s. A glass pressure reactor (Bu¨-
chi) was charged with 1.0 mmol of the substrate [(Z)-methyl-
R acetamidocinnamate, tiglic acid, dimethyl itaconate] dis-
solved in 20 mL of acetone and with a solution of the catalyst
(1 mol %) in 5 mL of acetone under an atmosphere of nitrogen
gas. The catalyst is formed by stirring a solution of the open
ruthenocene 4 with (S)-BINAP or (R)-p-tol-BINAP, respec-
tively, in 5 mL of acetone for 16 h at room temperature. In
the case of tiglic acid, methanol was used as solvent instead
of acetone. The reaction vessel was flushed with dihydrogen
gas (three cycles). The reactor was pressurized to 5 bar, heated
to 40 °C, and allowed to react for 3 h while stirring. After
complete conversion, confirmed by GC (CP-Sil-8, 10.9 psi H2,
T ) 100 °C, 5 min, then 20 K/min up to 250 °C), the catalyst
was separated by filtration over a thin pad of alox. The
resulting solution was analyzed by GC without further puri-
fication. Enantiomeric excesses were determined by GC (Chira-
sil-Val-L, 14.9 psi H2, T ) 50 °C, 5 min, then 10 K/min up to
100 °C), and the absolute configuration was assigned by
comparison to commercial samples of the optically pure
products.
[Ru (a ceton itr ile)((R)-BINAP )(η5-2,4-d im eth ylp en ta d i-
en yl)][BF 4] (17). A solution of the hydrido complex 14 (0.129
mg, 0.34 mmol) and (R)-BINAP (0.220 g, 0.35 mmol) in 10 mL
of methylene chloride and 20 mL of acetonitrile was stirred
for 16 h at room temperature. The solution was concentrated,
and the product was precipitated by addition of diethyl ether;
Ack n ow led gm en t. The authors gratefully acknowl-
edge financial support by the Deutsche Forschungsge-
meinschaft DFG within the Collaborative Research
Center (SFB) 380: “Asymmetric Syntheses with Chemi-
cal and Biological Means” and by the “Fonds der
Deutschen Chemischen Industrie”. We also thank C.
Vermeeren from the Group of Prof. Gais, RWTH Aachen,
for performing the GC analyses.
1
yield 82%. H NMR (500 MHz, CD2Cl2): 8.20-5.90 (m, 32H,
aromatic), 5.21 (s, 1H, CH), 3.17, 2.57 (bs, 1H each, CHexo) 2.11
(s, 3H, NCCH3), 1.60 (s, 3H, CH3), 1.06 (d, J ) 3 Hz, 3H, CH3),
-0.34, -0.80 (bs, 1H each, CHendo).13C NMR (125 MHz, CD2-
Cl2): 116.9 (NCCH3), 106.0, 93.7 (C-2,2′), 94.0 (d, J ) 24.7 Hz,
C-1), 75.2 (d, J ) 20.3, C-3/3′), 59.9 (s, C-3, 3′) 33.3, 25.5 (C-4,
4′), 2.0 (NCCH3). 31P NMR (202 MHz, CD2Cl2): 46.5 (J ) 34.6
Hz), 37.5 (J ) 34.6 Hz). Anal. Calcd (Found) for C13H19RuI:
C, 67.38 (68.02); H, 4.69 (4.72).
Su p p or tin g In for m a tion Ava ila ble: Tables with crystal
data, atomic coordinates, anisotropic displacement parameters,
and listings of interatomic distances and angles. This material
is available free of charge via the Internet at http://pubs.acs.org.
[Ru (MeCN)((R-BINAP )(η5-cycloh eptadien yl)][BF4] (18).
A solution of the hydrido complex 12 (0.129 mg, 0.34 mmol)
OM0007015