Ruthenium complexes with novel tridentate N,P,N ligands containing a phosphonite bridge between two chiral oxazolines. Catalytic activity in cyclopropanation of olefins and transfer hydrogenation of acetophenone

Article abstract of DOI:10.1021/om991034m

We compare the coordination behavior of the new chiral ligand (S,S)-bis[1-(4-isopropyl-4,5-dihydrooxazol-2-yl)-1-methylethyl] phenylphosphonite (V), abreviated NOPON^iPr and referred to as bis(oxazolinyl) phenylphosphonite, toward Ru(II) with that of NOPON^Me(2) (IV). Although the similarity between IV and V led to the expectation that they would coordinate in a similar manner, considerable differences were observed. Whereas reaction of [RuCl₂-(η⁶-p-cymene)]₂ with IV afforded the pentacoordinated complex [RuCl₂(NOPON^Me(2))] 1, the chiral ligand V led instead to the dinuclear, chloride-bridged complex [Ru(μ-Cl)Cl(NOPON^iPr)]₂ (3). The crystal structures of 1 and 3 have been determined by X-ray diffraction. The mer arrangement of the NOPON^Me(2) ligand in 1 results from the presence of the four methyl groups, two of which would point toward each other and lead to a steric clash if a fac geometry were adopted. Preliminary theoretical calculations on 1 at the EHT level indicated that coordination of ethylene parallel to the RuCl₂P plane would result in a stable situation and it is for steric reasons that ethylene does not coordinate to the metal, either parallel or perpendicular to the RuCl₂P plane. Coordination of CO to 1 was found to be reversible, whereas bulkier ligands do not coordinate to Ru. Complex 3 is a rare example of a fully characterized complex in which a tridentate chiral bis(oxazoline)-type ligand coordinates in a non-mer fashion. It was evaluated in catalytic reactions such as asymmetric cyclopropanation of styrene with ethyl diazoacetate and transfer hydrogenation of acetophenone in propan-2-ol.

Full text of DOI:10.1021/om991034m

2676
Organometallics 2000, 19, 2676-2683
Ru th en iu m Com p lexes w ith Novel Tr id en ta te N,P ,N
Liga n d s Con ta in in g a P h osp h on ite Br id ge betw een Tw o
Ch ir a l Oxa zolin es. Ca ta lytic Activity in
Cyclop r op a n a tion of Olefin s a n d Tr a n sfer
Hyd r ogen a tion of Acetop h en on e†
Pierre Braunstein* and Fre´de´ric Naud
Universite´ Louis Pasteur, Laboratoire de Chimie de Coordination (UMR 7513 CNRS),
4, rue Blaise Pascal, F-67070 Strasbourg Cedex, France
Andreas Pfaltz
Department of Chemistry, University of Basel, St. J ohanns-Ring 19,
CH-4056 Basel, Switzerland
Steven J . Rettig‡
Department of Chemistry, University of British Columbia, 2036 Main Mall,
Vancouver, British Columbia, Canada V6T 1Z1
Received December 27, 1999
We compare the coordination behavior of the new chiral ligand (S,S)-bis[1-(4-isopropyl-
4,5-dihydrooxazol-2-yl)-1-methylethyl] phenylphosphonite (V), abreviated NOPONiPr and
referred to as bis(oxazolinyl) phenylphosphonite, toward Ru(II) with that of NOPONMe (IV).
2
Although the similarity between IV and V led to the expectation that they would coordinate
in a similar manner, considerable differences were observed. Whereas reaction of [RuCl2-
(η6-p-cymene)]2 with IV afforded the pentacoordinated complex [RuCl2(NOPONMe )] 1, the
2
chiral ligand V led instead to the dinuclear, chloride-bridged complex [Ru(µ-Cl)Cl(NOPO-
NiPr)]2 (3). The crystal structures of 1 and 3 have been determined by X-ray diffraction. The
mer arrangement of the NOPONMe ligand in 1 results from the presence of the four methyl
2
groups, two of which would point toward each other and lead to a steric clash if a fac geometry
were adopted. Preliminary theoretical calculations on 1 at the EHT level indicated that
coordination of ethylene parallel to the RuCl2P plane would result in a stable situation and
it is for steric reasons that ethylene does not coordinate to the metal, either parallel or
perpendicular to the RuCl2P plane. Coordination of CO to 1 was found to be reversible,
whereas bulkier ligands do not coordinate to Ru. Complex 3 is a rare example of a fully
characterized complex in which a tridentate chiral bis(oxazoline)-type ligand coordinates in
a non-mer fashion. It was evaluated in catalytic reactions such as asymmetric cyclopropa-
nation of styrene with ethyl diazoacetate and transfer hydrogenation of acetophenone in
propan-2-ol.
In tr od u ction
The design of new ligands leading to high reactivity
and enantioselectivity in metal-catalyzed asymmetric
synthesis is a field of constant ongoing research activity.
In the past decade, oxazoline-based bidentate ligands
have proven very valuable in asymmetric catalysis,
mainly as heteroditopic ligands, such as the phosphino-
oxazoline I1-6 or as bis(oxazoline) ligands with or
without a coordinating connecting group.7 However, few
groups only have reported on the design of tridentate
bis(oxazolinyl)-type ligands where the two oxazolines
are linked by a coordinating phosphorus, nitrogen, or
* To whom correspondence should be addressed. E-mail: braunst@
chimie.u-strasbg.fr.
† Part of the Doctoral thesis of F.N. (ULP Strasbourg, 1999).
‡ Deceased, October 27, 1998.
(1) Helmchen, G. J . Organomet. Chem. 1999, 576, 203.
(2) Kudis, S.; Helmchen, G. Angew. Chem., Int. Ed. 1998, 37, 3047.
(3) Lightfoot, A.; Schnider, P.; Pfaltz, A. Angew. Chem., Int. Ed.
1998, 37, 2897.
(6) Nishibayashi, Y.; Takei, I.; Uemura, S.; Hidai, M. Organome-
tallics 1999, 18, 2291.
(4) Pfaltz, A. Synlett 1999, 51, 835.
(5) Williams, J . M. J . Synlett 1996, 705.
(7) Ghosh, A. K.; Mathivanan, P.; Cappiello, J . Tetrahedron: Asym-
metry 1998, 9, 1.
10.1021/om991034m CCC: $19.00 © 2000 American Chemical Society
Publication on Web 06/03/2000

Ru Complexes with Tridentate N,P,N Ligands
Organometallics, Vol. 19, No. 14, 2000 2677
oxygen atom or by a phenyl group susceptible to
subsequent metalation.8-13 A possible difficulty in using
chiral tridentate ligands is that, in comparison to their
bidentate analogues, they can offer a larger diversity
of binding modes and this requires the coordination
geometry of their metal complexes to be characterized
with great care. An exact knowledge of the structure of
a catalyst precursor is most helpful in order to gain a
better insight into the overall reaction and allow sub-
sequent fine-tuning of the catalytic system, although it
is intrinsically difficult to identify the active species in
a catalytic process. Chiral tridentate ligands have been
less extensively used in asymmetric catalysis than their
bidentate analogues. Nevertheless, they appear to be
effective promoters for asymmetric catalysis11,14-22 and
Nishiyama et al. have developed the chiral tridentate
ligand bis(oxazolinyl)pyridine (Pybox; II), which has
been successfully used in Cu-catalyzed Diels-Alder
reactions, Rh-catalyzed hydrosilylation of ketones, and
Ru-catalyzed cyclopropanation of olefins with diazo-
acetates.23-25
with metals that have an octahedral coordination
geometry.26
Here we report on the coordination behavior of IV
toward Ru(II) and compare it to that of the new ligand
V, the synthesis of which is also described. Although
the similarity between IV and V led to the expectation
that they would coordinate in a similar manner, con-
siderable differences were observed. We also performed
catalytic reactions such as asymmetric cyclopropanation
of styrene with ethyl diazoacetate and transfer hydro-
genation of acetophenone.
Resu lts
Syn th esis, Ch a r a cter iza tion , a n d Rea ctivity of
Liga n d V a n d Its Ru Com p lexes. The synthesis of
(S,S)-bis[1-(4-isopropyl-4,5-dihydrooxazol-2-yl)-1-meth-
ylethyl] phenylphosphonite, abreviated NOPONiPr and
referred to as bis(oxazolinyl) phenylphosphonite in the
following, is straightforward and was achieved by fol-
lowing the methodology previously developed for IV26
by using enantiomerically pure 4-isopropyl-2-(1-hy-
droxy-1-methylethyl)-4,5-dihydrooxazole (eq 1). The 1H
We have recently shown that ligand III readily binds
octahedral Ru centers to form active catalytic precursors
for transfer hydrogenation of ketones.12 In contrast to
and 13C NMR spectra are consistent with the lack of
any symmetry element in the molecule. The four OC-
(CH3)2 methyl groups appear as four singlet resonances
1
in the H NMR spectrum. The IR spectrum of the pure
oil in a capillary tube exhibits a strong band at 1665
cm-1 assigned to the CdN vibration.
When a THF solution containing 1 equiv of [RuCl2-
(η6-p-cymene)]2 and 2 equiv of IV (NOPONMe ) was
2
brought to reflux, quantitative formation of the complex
III, ligand IV can form two six-membered chelates in
square-planar Pd(II) complexes and could potentially
adopt meridional (mer) or facial (fac) coordination modes
[RuCl2(NOPONMe )] (1) was observed and the complex
2
was isolated in 75% yield (Scheme 1). The 1H NMR
spectrum of 1 is very similar to that of the free ligand,
except that the chemical shifts for the complex are
downfield with respect to those of IV. It exhibits four
singlets for the eight methyl groups and an AB spin
system for the methylenic protons. This is indicative of
the coordination of both oxazoline arms of the ligand
and of the existence in solution of a mirror plane on the
NMR time scale, which includes the phenyl ring and
the phosphorus and ruthenium atoms. The far-infrared
(FIR) spectrum of complex 1 shows an intense ν(Ru-
Cl) absorption band at 321 cm-1, suggestive of a trans
arrangement of the two chloride ligands, whereas no
absorption was observed in the 290-250 cm-1 region,
where the stretching vibrations of a cis-RuCl2 moiety
(8) Denmark, S. E.; Stavenger, R. A.; Faucher, A.-M.; Edwards, J .
P. J . Org. Chem. 1997, 62, 3375.
(9) J iang, Y.; J iang, Q.; Zhang, X. J . Am. Chem. Soc. 1998, 120, 3817.
(10) Motoyama, Y.; Makihara, N.; Mikami, Y.; Aoki, K.; Nishiyama,
H. Chem. Lett. 1997, 951.
(11) J iang, Y.; J iang, Q.; Zhu, G.; Zhang, X. Tetrahedron Lett. 1997,
38, 215.
(12) Braunstein, P.; Fryzuk, M. D.; Naud, F.; Rettig, S. J . J . Chem.
Soc., Dalton Trans. 1999, 589.
(13) Kanemasa, S.; Oderaotoshi, Y.; Yamamoto, H.; Tanaka, J .;
Wada, E.; Curran, D. P. J . Org. Chem. 1997, 62, 6454.
(14) Hawkins, J . M.; Sharpless, K. B. Tetrahedron Lett. 1987, 28,
2825.
(15) Burk, M. J .; Feaster, J . E.; Harlow, R. L. Tetrahedron: Asym-
metry 1991, 2, 569.
(16) Gorla, F.; Togni, A.; Venanzi, L. M.; Albinati, A.; Lianza, F.
Organometallics 1994, 13, 1607.
(17) de Vries, E. F. J .; Brussee, J .; Kruse, C. G.; van der Gen, A.
Tetrahedron Asymmetry 1994, 5, 377.
(18) Christenson, D. L.; Tokar, C. J .; Tolman, W. B. Organometallics
1995, 14, 2148.
(19) J iang, Q.; van Plew, D.; Murtuza, S.; Zhang, X. Tetrahedron
Lett. 1996, 37, 797.
(22) Sablong, R.; Osborn, J . A. Tetrahedron Lett. 1996, 37, 4937.
(23) Evans, D. A.; Murry, J . A.; von Matt, P. V.; Norcross, R. D.;
Miller, S. J . Angew. Chem., Int. Ed. Engl. 1995, 34, 798.
(24) Nishiyama, H.; Kondo, M.; Nakamura, T.; Itoh, K. Organome-
tallics 1991, 10, 500.
(20) Zhu, G.; Terry, M.; Zhang, X. J . Organomet. Chem. 1997, 547,
97.
(21) Barbaro, P.; Bianchini, C.; Togni, A. Organometallics 1997, 16,
3004.
(25) Nishiyama, H.; Itoh, Y.; Sugawara, Y.; Matsumoto, H.; Aoki,
K.; Itoh, K. Bull. Chem. Soc. J pn. 1995, 68, 1247.
(26) Braunstein, P.; De Cian, A.; Naud, F.; Rettig, S. J . Manuscript
in preparation.

2678 Organometallics, Vol. 19, No. 14, 2000
Braunstein et al.
Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Ru Cl2(NOP ONMe2)] (1)
Ru(1)-Cl(1)
Ru(1)-Cl(2)
Ru(1)-P(1)
2.3806(6)
2.3849(6)
2.0883(6)
Ru(1)-N(1)
Ru(1)-N(2)
2.085(2)
2.093(2)
N(1)-C(4)
C(4)-C(1)
C(1)-O(1)
O(1)-P(1)
O(2)-C(4)
1.272(3)
1.511(3)
1.455(2)
1.602(2)
1.359(2)
N(2)-C(12)
C(12)-C(9)
C(9)-O(3)
O(3)-P(1)
O(4)-C(12)
1.268(3)
1.523(3)
1.450(3)
1.615(2)
1.359(3)
Cl(1)-Ru(1)-Cl(2) 157.30(2)
Cl(1)-Ru(1)-P(1) 101.57(2)
Cl(2)-Ru(1)-P(1) 101.06(2)
Cl(2)-Ru(1)-N(1)
Cl(2)-Ru(1)-N(2)
86.43(5)
85.59(5)
N(1)-Ru(1)-N(2) 170.92(7)
Cl(1)-Ru(1)-N(1)
N(1)-Ru(1)-P(1)
91.29(5)
91.58(5)
Cl(1)-Ru(1)-N(2)
N(2)-Ru(1)-P(1)
97.74(5)
85.72(5)
Ru(1)-N(1)-C(4) 124.9(2)
Ru(1)-N(2)-C(12) 125.9(2)
N(1)-C(4)-C(1)
C(4)-C(1)-O(1)
C(1)-O(1)-P(1)
O(1)-P(1)-Ru(1)
C(5)-N(1)-C(4)
O(2)-C(4)-N(1)
O(2)-C(4)-C(1)
131.1(2)
111.6(2)
125.36(14) C(9)-O(3)-P(1)
116.61(6)
107.3(2)
116.8(2)
112.1(2)
N(2)-C(12)-C(9)
C(12)-C(9)-O(3)
131.9(2)
114.3(2)
124.28(14)
111.99(6)
O(3)-P(1)-Ru(1)
C(13)-N(2)-C(12) 107.7(2)
F igu r e 1. ORTEP view of the structure of [RuCl2-
N(2)-C(12)-O(4)
O(4)-C(12)-C(9)
116.9(2)
111.2(2)
(NOPONMe )] (1).
2
Sch em e 1
P-O angle of 4° and an opening of the chelate central
backbone O-C-C angle of 2°. The geometry around the
phosphorus atom (angles and bond distances) remains
unchanged when compared to the structure of the free
ligand IV.26
The IR spectrum of 1 in KBr shows two absorption
bands at 1641 and 1626 cm-1, which is again in
agreement with the absence of any symmetry element
in the molecule in the solid state.
Complex 1 is thus an unsaturated pentacoordinated
16-electron species. From its X-ray structure, it appears
that the accessibility to the sixth, vacant coordination
site is fairly hindered due to the close proximity of the
chloride atoms and methyl groups. In fact, triph-
enylphosphine, triphenyl phosphite, nor ethylene react
with 1. However, treating a CDCl3 solution of 1, in an
NMR tube, with 1 atm of CO at room temperature
yielded [RuCl2(CO)(NOPONMe )] (2) within 1 min (eq 2).
2
would be expected.27,28 A single-crystal X-ray diffraction
study of 1 established that the tridentate ligand adopts
a meridional (mer) coordination mode with the two
chlorides in a transoid arrangement (Figure 1). Selected
bond distances and angles are given in Table 1.
The Cl-Ru-Cl angle of 157.30(2)° is intermediate
between the ideal angles in the equatorial plane of a
trigonal bipyramid (120°) and of a square-based pyramid
(180°). The two P-Ru-Cl angles are nearly identical
and equal to 101.57(2)° and 101.06(2). The two nitrogen
donor atoms are in a trans arrangement with a N-Ru-N
angle of 170.92(7)°. These data lead to a description of
the geometry of this pentacoordinated complex as
distorted square pyramidal, as expected for a Ru(II) d6
complex. Interestingly, the solid-state structural fea-
tures of the two six-membered ring chelates are not
identical. The N(1)-Ru-P and N(2)-Ru-P bite angles
are of 91.58(5) and 85.72(5)°, respectively. This decrease
in the bite angle is accompanied by a pinch of the Ru-
The coordination of the terminal CO ligand was ob-
served by IR (ν(CO) 1988 cm-1 in CH2Cl2) and ac-
companied by an upfield shift of 35 ppm in the 31P{1H}
NMR. This large shift is consistent with the coordina-
tion of the CO molecule trans to the phosphorus atom.29
1
The H NMR spectrum of 2 is identical with that of its
precursor, except for a slight upfield shift of the meth-
ylene protons (0.10 ppm) and an upfield shift of 0.15
ppm of two methyl groups on the oxazoline backbone.
The reversibility of the CO coordination upon standing
or under reduced pressure prevented isolation of pure
2 in the solid state, and therefore, no satisfactory
elemental analysis could be obtained.
(27) Lupin, M. S.; Shaw, B. L. J . Chem. Soc. A 1968, 741.
(28) Mague, J . T.; Mitchener, J . P. Inorg. Chem. 1972, 11, 2714.
(29) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev.
1973, 10, 335.

Ru Complexes with Tridentate N,P,N Ligands
Organometallics, Vol. 19, No. 14, 2000 2679
Ch a r t 1a
a
i
Methyls from Pr and OC(CH3)2 omitted for clarity.
We then prepared complexes analogous to 1 and 2 but
containing the chiral ligand V. Reaction of 2 equiv of V
with 1 equiv of [RuCl2(η6-p-cymene)]2 in refluxing THF
resulted in the formation of [Ru(µ-Cl)Cl(NOPONiPr)]2
(3), which was further purified by crystallization (60%
F igu r e 2. ORTEP view of the structure of [Ru(µ-Cl)Cl-
(NOPONiPr)]2 (3).
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for [Ru (µ-Cl)Cl(NOP ONiP r )]2 (3)
1
yield) (Scheme 1). The H and 13C{1H} NMR spectra of
Ru(1)-Cl(1)
Ru(1)-Cl(2)
Ru(1)-Cl(3)
Ru(2)-Cl(1)
Ru(2)-Cl(2)
2.6018(10)
2.3988(11)
2.4125(11)
2.6032(11)
2.4123(10)
Ru(2)-Cl(4)
Ru(1)-N(1)
Ru(1)-N(2)
Ru(1)-P(1)
2.4224(11)
2.113(3)
2.077(3)
3 showed that the proton and carbon nuclei are chemi-
cally and magnetically inequivalent. In the 1H NMR
spectrum in C6D6, the oxazoline protons show a similar
pattern for the two arms but their chemical shifts are
very different from each other (up to 1.45 ppm), indicat-
ing that the oxazoline moieties are placed in very
different chemical environments, consistent with a fac
coordination mode. This feature is in contrast to the
NMR data of complex 1.
2.1278(11)
N(1)-C(4)
C(4)-C(1)
C(1)-O(1)
1.273(5)
1.516(5)
1.432(5)
O(1)-P(1)
O(2)-C(4)
1.610(3)
1.366(5)
Cl(1)-Ru(1)-Cl(2) 82.78(3) Ru(1)-Cl(1)-Ru(2) 92.22(3)
Cl(1)-Ru(2)-Cl(2) 82.50(4) Ru(1)-Cl(2)-Ru(2) 102.47(4)
Cl(2)-Ru(1)-P(1)
P(1)-Ru(1)-N(2)
N(2)-Ru(1)-Cl(1)
Cl(3)-Ru(1)-N(1) 176.58(10) C(1)-O(1)-P(1)
Cl(1)-Ru(1)-P(1) 175.50(4) O(1)-P(1)-Ru(1)
Cl(2)-Ru(1)-N(2) 174.76(10) O(2)-C(4)-N(1)
P(1)-Ru(1)-N(1)
P(1)-Ru(1)-Cl(3)
92.80(4) Ru(1)-N(1)-C(4)
90.42(9) N(1)-C(4)-C(1)
94.04(9) C(4)-C(1)-O(1)
127.5(3)
132.5(4)
113.3(3)
132.1(3)
117.14(10)
116.8(3)
110.7(3)
All protons of the ligand were assigned using 1H
homonuclear decoupling and 2D COSY NMR experi-
ments. Of particular interest are the oxazoline protons,
abbreviated Ha-Hd (Chart 1). The resonance of proton
Hb could be easily assigned by virtue of its complexity;
89.94(9) O(2)-C(4)-C(1)
90.19(4)
this proton couples to Ha (3J ba ) 9.4 Hz), to Hc (3J bc
)
3.6 Hz), and to Hd (3J bd ) 2.4 Hz). Proton Hb is strongly
deshielded (6.90 ppm), since it lies above the plane
defined by the chloride bridges. Proton Hd is pointing
toward the opposite direction, and its chemical shift is
very similar to that of the free ligand. The OCH2 protons
Ha and Hc could be distinguished by the different
magnitudes of their vicinal scalar couplings to Hb,
remembering that in planar five-membered rings, cis-
vicinal couplings are greater than trans-vicinal cou-
plings.30 Protons He-Hh were similarly assigned, and
the downfield chemical shift of Hh is consistent with its
proximity to a terminal chloride.
The far-IR spectrum of 3 did not show any absorption
clearly assignable to a ν(Ru-Cl) vibration. A single-
crystal X-ray diffraction study of 3 (Figure 2) showed
the complex to be a neutral dinuclear Ru(II) species with
two bridging chlorides. Selected bond distances and
angles are given in Table 2.
Ru-Cl bond lengths of the chloride trans to P are much
longer (2.6013(10), 2.6032(11) Å) than the mean value
of 2.423 Å found for Ru-Cl distances (Cambridge
Crystal Data Base search). Note that although the
skeleton formed by the donor set exhibits a C2 axis of
symmetry along the two bridging chlorides, the crystal
structure has no symmetry element, due to the folding
of the PN chelate, as exemplified by the positions of O(3)
and O(5).
Due to our interest in the reactivity of Ru complexes
with multidentate heterotopic ligands that contain
oxazoline unit(s) and a phosphorus donor atom,12 we
undertook preliminary studies on asymmetric cyclopro-
panation of styrene using ethyl diazoacetate and on the
asymmetric transfer hydrogenation of acetophenone in
propan-2-ol catalyzed by 3 (see Discussion and Table 3
for results and details).
Ligand V coordinates in a fac mode, and the terminal
and bridging chlorides are in a mutually cis arrange-
ment. Each ruthenium center has an octahedral geom-
etry, and each chloride bridge is symmetric, although
the Ru-Cl bonds trans to the P atom are much longer
than those trans to N, consistent with the respective
trans influences of the P and N donor atoms.29,31 The
Discu ssion
The synthesis of complex [RuCl2(NOPONMe )] (1) from
2
RuCl2(η6-p-cymene)]2 according to Scheme 1 was com-
pleted after 6 h in refluxing THF (in situ 31P{1H} NMR
monitoring), while it took 3 days in CH2Cl2 at room
temperature. The behavior of NOPONMe is therefore
2
analogous to that of Pybox but contrasts with that of
III, which does not displace p-cymene but instead forms
mono- and dicationic complexes in which it is bidentate
(30) Abraham, R. J .; Fisher, J .; Loftus, P. Introduction to NMR
Spectroscopy; Wiley: New York, 1988.
(31) Hartley, F. R. Chem. Soc. Rev. 1973, 2, 163.

2680 Organometallics, Vol. 19, No. 14, 2000
Braunstein et al.
Ta ble 3. Tr a n sfer Hyd r ogen a tion of Acetop h en on e
in P r op a n -2-ol Ca ta lyzed by 3a
Ch a r t 2
Ru/ketone/base
molar ratio
run
1
temp (°C) time (h) yield (%)b ee (%)c
1/200/24
reflux
0.5
1
0.5
1
1
27
95
98
84
98
16
32
29
94
27
26
22
21
45
41
6
2
3
4
1/200/4
1/200/4
1/200/4d
reflux
room temp
reflux
0.5
8
4
a
Reactions were carried out in propan-2-ol using 0.1 M sub-
i
strate concentration and a 0.1 M solution of PrONa as a base.
b Chemical yields determined by GC analysis on the crude reaction
mixture at the reported time. c Determined by GC analysis (Li-
podex A, 25 m × 0.25 mm); absolute configurations (S in all cases)
were determined by comparing optical rotations of isolated 1-phen-
d
ylethanol with literature data. Experiment run with 1 equiv of
This indicates that coordination of the ethylene paral-
lel to the RuCl2P plane would represent the most stable
situation. Similar calculations were then performed on
added PPh3.
and tridentate, respectively. This was established by
comparison with the NMR data for the benzene com-
plexes [RuCl(η6-benzene)(NPN-N,P)](O3SCF3) and [Ru-
(η6-benzene)(NPN-N,P,N)](O3SCF3)2.12 Therefore, the
size of the chelate (five- vs six-membered) and/or the
nature of the phosphorus atom (phosphonite vs phos-
phine) appear to play an important role for the substi-
tution of the p-cymene ligand. Full characterization of
the coordinatively unsaturated complex 1 is interesting,
since a similar species with the Pybox ligand II was
suggested by Nishiyama to be a key in situ cyclopropa-
nation catalyst but could not be isolated.32 Attempts to
coordinate ethylene to 1 or to introduce it during the
synthesis by using a procedure similar to that of
Nishiyama et al. for compound 4a (1 equiv of [RuCl2-
(η6-p-cymene)]2, 2 equiv of ligand, CH2Cl2, room tem-
perature, 1 atm of ethylene, 1 h) either failed or led only
to the formation of 1 after 3 days.25
the hypothetical complex [RuCl2(ethylene)(NOPONMe )],
2
with a fixed orientation of the ethylene parallel to the
RuCl2P plane, which is electronically and intuitively
also sterically the most favorable situation. In compari-
son to 1, this complex is stabilized by the coordination
of the ethylene, since while the energy level of the
HOMO remains in the same energy range, -10.83 eV
in 1 and -10.50 eV in [RuCl2(ethylene)(NOPONMe )],
2
the energy gap between the HOMO and the LUMO
increases from 1.46 to 2.15 eV. This is the result of the
2
destabilization of the dz orbital (LUMO in 1) through
interactions with the filled pz ethylene orbitals. How-
ever, the energy gain based on electronic criteria is
counterbalanced by the fact that in this structure the
ethylene protons show contacts with the oxazoline
methyls as short as 1.40 Å, which are repulsive in
nature. Thus, it is for steric reasons that the ethylene
does not bind the Ru center either parallel nor perpen-
dicular to the RuCl2P plane.
However, a sterically much less demanding “rodlike”
molecule such as CO easily coordinates to ruthenium
at room temperature. In the IR spectrum of compound
4b the ν(CO) vibration appears at 1965 cm-1, while in
2 it is shifted toward higher energy (1988 cm-1), thus
indicating that the M-CO bond in 4b is stronger than
that in [RuCl2(CO)(NOPONMe )]. This is consistent with
2
the stability of 4b, while 2 easily loses its CO ligand.
The phosphorus atom and the CO ligand in 2 both have
a high trans influence and interact with the same metal
orbitals, while in 4b the nitrogen trans to CO has
considerably less trans influence, thus resulting in an
increased strength of the M-CO bond. This difference
This is, however, consistent with Nishiyama’s findings
that a compound analogous to 4a with an achiral Pybox-
dimethyl ligand could not be obtained “due to the small
mono-vacant site of the RuCl2(Pybox-dimethyl) moiety
which does not have sufficient space to capture one
ethylene molecule on the ruthenium center”.25 Further-
more, preliminary theoretical calculations on [RuCl2-
between the RuCl2(NOPONMe ) and RuCl2(Pybox) moi-
2
eties underlines the importance of the electronic effect
induced by the multidonor ligand on the reactivity of
the complex.
(NOPONMe )] at the EHT level of theory have revealed
2
We could not obtain a compound analogous to 1 with
the chiral ligand V by following the same procedure as
for 1. Instead, we obtained the dinuclear complex [Ru-
(µ-Cl)Cl(NOPONiPr)]2 (3). Monitoring of the reaction by
31P{1H} NMR spectroscopy showed complete consump-
tion of the ligand V. Even though the modes of prepara-
tion are the same, 1 and 3 are very different, since the
latter contains two bridging chlorides and two tridentate
ligands exhibiting a fac coordination mode. This differ-
that the two ruthenium metal orbitals dyz and dxz, which
could interact with the vacant π* orbital of the ethylene
ligand, are almost of the same energy: -10.88 and
-11.09 eV, respectively (see Chart 2).33-35
(32) Nishiyama, H.; Itoh, Y.; Matsumoto, H.; Park, S.-B.; Itoh, K.
J . Am. Chem. Soc. 1994, 116, 2223.
(33) Hoffmann, R.; Lipscomb, W. N. J . Chem. Phys. 1962, 37, 2872.
(34) Hoffmann, R.; Lipscomb, W. N. J . Chem. Phys. 1962, 36, 3179.
(35) Hoffmann, R. J . Chem. Phys. 1963, 39, 1397.

Ru Complexes with Tridentate N,P,N Ligands
Organometallics, Vol. 19, No. 14, 2000 2681
Nishiyama’s catalysts,25 but they are comparable to
those of other Ru catalysts.39 It is possible that the fac
coordination mode of our ligand prevents the formation
of an efficient stereo-demanding chiral pocket around
the metal. Nevertheless, enantioselectivity remains
always difficult to rationalize.
Ch a r t 3
Complex 3 was also used for preliminary catalytic
studies on asymmetric transfer hydrogenation of ke-
tones by propan-2-ol (eq 4). There is considerable
ence should be related to the nature of the substituents
on each oxazoline. These are methyl groups in IV, while
i
in V there is one Pr group with an S configuration on
each oxazoline so that when the two oxazolines are
current research activity around this reaction in order
both to develop new classes of catalysts and to under-
stand the different steps involved in the overall catalytic
process.40-42
placed in close proximity, as in a fac coordination mode,
i
the Pr groups can avoid each other (Chart 3).
If ligand IV were to adopt such a fac coordination
mode, two of the four methyl groups would have to point
toward each other and thus create an unfavorable steric
clash. This is not the case in a mer situation. It therefore
appears that the coordination mode of our bis(oxazoli-
nyl) phenylphosphonite ligands is controlled by the
nature of the oxazoline substituents. Moreover, the fact
that no compound of the type [RuCl2(mer-NOPONiPr)]
could be detected indicates that, when given the choice,
this new class of ligands prefers to bind in a fac
coordination mode.
Ca ta lytic Stu d ies. The reactivity of [Ru(µ-Cl)Cl-
(NOPONiPr)]2 (3) was tested toward asymmetric cyclo-
propanation of styrene using ethyl diazoacetate. The
metals of choice for this reaction are usually Pd, Rh,
and Cu, and only a limited number of catalysts based
on ruthenium have been reported.25,36-38 Preliminary
studies have shown that, under standard reaction
conditions, complex 3 mainly catalyzes the dimerization
of ethyl diazoacetate to fumarate and maleate and
produces low yields of the cyclopropanation products (eq
3).
To allow comparisons with literature data, acetophe-
none was chosen as a prochiral substrate. Since the
conversion rate is dependent on substrate concentration,
all experiments were performed using a 0.1 M concen-
tration of substrate.43,44 The best combination of yield
and enantiomeric excess was obtained in refluxing
propan-2-ol after 1 h (98% conversion, 26% ee) (Table
3, run 1). Reducing the amount of base moderately slows
down the turnover frequency of the reaction, but the
final conversion remains identical and the enantiomeric
excess decreases from 26 to 21%. When the reaction was
performed at room temperature, the enantioselectivity
increased up to 45% but the conversion was only 16%.
Two studies with Ru-based catalysts for asymmetric
transfer hydrogenation of ketones have shown that 1
equiv of PPh3 per ruthenium is needed in the enanti-
oselective step.9,45 When our catalytic experiment was
performed in the presence of 1 equiv of added PPh3
(Table 3, run 4), we found a slower conversion and a
drastically decreased enantiomeric excess (8 h, 94%
yield, 4% ee). To gain some insight into the overall
catalytic process and to explain the low stereoselectivity,
we studied the feasibility of the backward reaction,
namely the oxidation of 1-phenylethanol. Exposure of
a racemic mixture of 1-phenylethanol in acetone to
complex 3 in the presence of i-PrONa ([alcohol] ) 0.1
M, Ru/alcohol/base ) 1/200/4, reflux) led to a 3%
conversion to acetophenone after 15 h. Thus, it appears
that the reverse process is, for kinetic reasons, unlikely
to account for the low stereoselectivity obtained with
the complex [Ru(µ-Cl)Cl(NOPONiPr)]2 (3).
Whereas high conversions and enantiomeric excesses
have recently been obtained with chiral diamine or
phosphino-oxazoline bidentate ligands and with po-
Running the experiments under more dilute condi-
tions slightly improved the conversion to the cyclopro-
panation products (15% yield). The trans/cis selectivity
is low (70:30) and no significant chiral induction was
observed. These results are in sharp contrast to the good
to excellent trans/cis stereoselectivities observed with
(39) Lee, H. M.; Bianchini, C.; J ia, G.; Barbaro, P. Organometallics
1999, 18, 1961.
(40) Zassinovich, G.; Mestroni, G.; Gladiali, S. Chem. Rev. 1992, 92,
1051.
(41) Noyori, R.; Hashiguchi, S. Acc. Chem. Res. 1997, 30, 97.
(42) Aranyos, A.; Csjernyik, G.; Szabo´, K. J .; Ba¨ckvall, J .-E. Chem.
Commun. 1999, 351.
(36) Park, S.-B.; Sakata, N.; Nishiyama, H. Chem. Eur. J . 1996, 2,
303.
(37) Song, J .-H.; Cho, D.-J .; J eon, S.-J .; Kim, Y.-H.; Kim, T.-J .; J eong,
J .-H. Inorg. Chem. 1999, 38, 893.
(43) Hashiguchi, S.; Fujii, A.; Takehara, J .; Ikariya, T.; Noyori, R.
J . Am. Chem. Soc. 1995, 117, 7562.
(44) de Graauw, C. F.; Peters, J . A.; van Bekkum, H.; Huskens, J .
Synthesis 1994, 1007.
(38) Uchida, T.; Irie, R.; Katsuki, T. Synlett 1999, 1163.
(45) Sammakia, T.; Stangeland, E. L. J . Org. Chem. 1997, 62, 6104.

2682 Organometallics, Vol. 19, No. 14, 2000
Braunstein et al.
[Ru Cl2(NOP ONMe )] (1). In a Schlenk tube were placed
together the ligand I26 (0.108 g, 0.257 mmol) and [RuCl2(η6-
p-cymene)]2 (0.078 g, 0.126 mmol) in THF (15 mL), and the
reddish solution was refluxed for 6 h. The mixture was cooled
to room temperature, and the solvent was removed under
vacuum. The reddish solid was washed with a 1/3 Et2O/
pentane mixture (2 × 15 mL) and dried in vacuo (0.115 g, 75%).
IR (KBr): ν (cm-1) 1641 s (CdN), 1626 s (CdN). Far-IR
(polyethylene): ν (cm-1) 321 vs (trans-RuCl2). 1H NMR (CDCl3,
300.13 MHz): δ 1.55 (s, 6 H, NC(CH3)(CH3)), 1.60 (s, 6 H, NC-
(CH3)(CH3)), 1.80 (s, 6 H, OC(CH3)(CH3)), 2.05 (s, 6 H, OC-
(CH3)(CH3)), AB spin system δA 4.10 (d, 2J HH ) 8.1 Hz, OCHH),
tentially tridentate chiral ligands,9,11,19,46 in transfer
hydrogenation of ketones in propan-2-ol (up to 95% yield
and >99% ee for acetophenone),6,41,43,47 there are only
very few studies with chiral tridentate ligands where
their coordination mode has been firmly established.21,48,49
Among the latter, our catalyst is of comparable activity
but has lower enantioselectivity than the best reported
system (99% yield, 71.7% ee),21 in which the dicationic
Ru2+ complexes were found to be highly superior to their
neutral, dichloro precursor complexes. We are currently
investigating the synthesis and characterization of
dicationic Ru(II) complexes starting from [Ru(µ-Cl)Cl-
(NOPONiPr)]2.
2
2
δB 4.25 (d, J HH ) 8.1 Hz, OCHH), 7.35 (m, 3 H, aryl), 7.70
(m, 2 H, aryl). 13C{1H} NMR (CDCl3, 75.4 MHz): δ 25.2 (s,
3
NC(CH3)2) 27.4 (s, NC(CH3)2), 27.9 (d, J PC ) 5.2 Hz, OC-
(CH3)2), 29.3 (s, OC(CH3)2), 70.9 (s, NC(CH3)2), 79.4 (d, J PC
2
)
Exp er im en ta l Section
5.6 Hz, OC(CH3)2), 81.2 (s, OCH2), 125.2-132.0 (m, aryl), 171.0
(s, CdN). 31P{1H} NMR (CDCl3, 121.5 MHz): δ 196.9. Anal.
Calcd for C22H33ClN2O4PRu: C, 44.60; H, 5.61; N, 4.73.
Found: C, 44.57; H, 5.40; N, 4.53.
All reactions were performed under purified nitrogen.
Solvents were purified and dried under nitrogen by conven-
1
tional methods. The H NMR spectra were recorded at 300.13
[Ru Cl2(CO)(NOP ONMe )] (2). CO was bubbled through a
MHz, 31P{1H} NMR spectra at 81.0 or 121.5 MHz, and 13C-
{1H} NMR spectra at 75.4 MHz on a FT Bruker AC200 or
AC300 instrument; IR spectra were recorded in the 4000-400
cm-1 range on a Bruker IFS66 FT spectrometer and far-IR
spectra in the region 500-90 cm-1 on a Bruker ATS 83
spectrometer. All the complexes are air-stable for a short
period of time but are best kept under an inert atmosphere.
The compound [Ru(µ-Cl)Cl(η6-p-cymene)]2 was prepared ac-
cording to the literature procedure.50,51
2
CDCl3 solution of [RuCl2(NOPONMe )] (0.015 g in 0.5 mL) for
2
1 min in an NMR tube. The solution went from reddish to light
orange within 30 s. IR (CH2Cl2): ν (cm-1) 1988 (CO). 1H NMR
(CDCl3, 300.13 MHz): δ 1.35 (s, 6 H, NC(CH3)(CH3)), 1.55 (s,
6 H, NC(CH3)(CH3)), 1.70 (s, 6 H, OC(CH3)(CH3)), 1.90 (s, 6
2
H, OC(CH3)(CH3)), AB spin system δA 3.85 (d, J HH ) 8.1 Hz,
OCHH), δB 4.15 (d, 2J HH ) 8.1 Hz, OCHH), 7.40 (m, 3 H, aryl),
8.05 (m, 2 H, aryl). 31P{1H} NMR (CDCl3, 121.5 MHz): δ 161.2.
[Ru (µ-Cl)Cl(NOP ONiP r )]2 (3). In a Schlenk tube were
placed together the ligand V (0.213 g, 0.475 mmol) and [RuCl2-
(η6-p-cymene)]2 (0.145 g, 0.237 mmol) in THF (15 mL), and
the reddish solution was refluxed for 3 h. The mixture was
cooled to room temperature, and the solvent was removed in
vacuo to afford a brown-yellow powder which was washed with
2 × 10 mL of pentane. Recrystallization from a 1/3 THF/
Syn th esis of th e Liga n d NOP ONiP r (V). 4-Isopropyl-2-
(1-hydroxy-1-methylethyl)-4,5-dihydrooxazole52,53 (0.845 g, 4.94
mmol) and triethylamine (2.1 mL, 15 mmol) were mixed in a
100 mL Schlenk flask. The solution was cooled to -78 °C, and
dichlorophenylphosphine (0.335 mL, 2.47 mmol) was quickly
injected, affording an immediate white precipitate. The reac-
tion mixture was slowly warmed to room temperature over 4
h and was stirred further for 8 h. The THF was removed under
reduced pressure, and the pale yellow oil obtained was
dissolved in 70 mL of toluene. The white suspension was
filtered off over Celite, and the solution was evaporated to
dryness, affording a pale yellow oil. Purification by column
chromatography (silica, eluent 1/6 ethyl acetate/pentane, Rf
0.6) gave the ligand in its pure form: yield 0.830 g, 75%. IR
(capillary): ν (cm-1) 1665 (CdN). 1H NMR (CDCl3, 300.13
hexane mixture gave pure 3 (0.177 g, 60%). IR (KBr): ν (cm-1
)
1639 (CdN). 1H NMR (C6D6, 300.13 MHz): δ 0.55 (d, 3 H, 3J HH
3
) 7.1 Hz, CH(CH3)2), 0.90 (d, 3 H, J HH ) 6.8 Hz, CH(CH3)2),
1.00 (d, 3 H, J HH ) 7.1 Hz, CH(CH3)2), 1.15 (d, 3 H, J HH
6.8 Hz, CH(CH3)2), 1.40 (s, 3 H, OC(CH3)(CH3)), 1.60 (s, 3 H,
OC(CH3)(CH3)), 1.65 (s, 3 H, OC(CH3)(CH3)), 1.67 (s, 3 H, OC-
3
3
)
3
3
b
(CH3)(CH3)), 2.15 (sept of d, 1 H, J HH ) 7.1 Hz, J HH ) 2.4
Hz, CHd(CH3)2), 3.75 (dd with appearance of t, 1 H, J H
)
)
2
e
g
H
3
8.7 Hz, 3J H H (cis) ) 8.9 Hz, OCHH ), 3.95 (dd, 1 H, J H H
e
2
e
f
c
a
MHz): δ 0.80 (d, 6 H, J HH ) 6.8 Hz, CH(CH3)2), 0.85 (d, 6 H,
3J HH ) 6.8 Hz, CH(CH3)2), 1.54 (s, 3 H, OC(CH3)2), 1.57 (s, 3
H, OC(CH3)2), 1.66 (s, 3 H, OC(CH3)2), 1.69 (s, 3 H, OC(CH3)2),
1.70 (sept, 2 H, 3J HH ) 6.8 Hz, CH(CH3)2), 3.80 (m, 2 H, NCH),
3.85 (m, 2 H, OCHH), 4.15 (m, 2 H, OCHH), 7.25-7.35 (m, 3
H, aryl H), 7.60-7.70 (m, 2 H, aryl). 13C{1H} NMR (CDCl3,
75.4 MHz): δ 17.4 (s, CH(CH3)2), 17.5 (s, CH(CH3)2), 18.4 (s,
CH(CH3)2), 18.5 (s, CH(CH3)2), 26.7-28.1 (m, OC(CH3)2), 32.0
(s, CH(CH3)2), 32.1 (s, CH(CH3)2), 69.6 (s, OCH2), 69.7 (s,
OCH2), 71.6 (s, NCH(CH3)2), 71.7 (s, NCH), 75.3 (m, OC(CH3)2),
127.2-130.0 (m, aryl), 143.7 (d, J PC ) 11.5 Hz, ipso-C of aryl),
168.4 (s, CdN). 31P{1H} NMR (CDCl3, 81.0 MHz): δ 150.6.
Anal. Calcd for C24H37N2O4P: C, 64.27; H, 8.31; N, 6.25.
Found: C, 64.21; H, 8.26; N, 6.19.
3
c
2
c
b
g
e
8.2 Hz, J H H (trans) ) 3.6 Hz, OCH H), 4.10 (dd, 1 H, J H
H
) 8.7 Hz, 3J H H (trans) ) 2.0 Hz, OCH H), 4.20 (sept of d, 1 H,
g
g
f
3
3
2
a
c
J HH ) 6.8 Hz, J HH ) 1.8 Hz, CH(CH3)2), 5.40 (dd, 1 H, J H
H
3
a
a
b
) 8.2 Hz, J H (cis) ) 9.4 Hz, OCHH ), 5.45 (m with appear-
H
ance of dt, 3J H H (cis) ) 8.9 Hz, J H H (trans) ) 2.0 Hz, J H
)
3
3
f
e
f
g
g
h
H
1.8 Hz, NCHg), 6.90 (m with appearance of dt, 3J H (cis) )
b
a
H
9.4 Hz, J H (trans) ) 3.6 Hz, J H
) 2.4 Hz, NCHb), 7.05-
3
3
b
c
b
d
H
H
7.25 (m, 3 H, aryl), 8.65-8.75 (m, 2 H, aryl). 13C{1H} NMR
(C6D6, 75.4 MHz): δ 15.0 (s, CH(CH3)2), 15.5 (s, CH(CH3)2),
19.2 (s, CH(CH3)2), 19.8 (s, CH(CH3)2), 28.3 (d, J PC ) 5.8 Hz,
OC(CH3)2), 29.6 (d, J PC ) 5.4 Hz, OC(CH3)2), 29.9 (s, OC-
3
3
(CH3)2), 30.3 (d, 3J PC ) 7.4 Hz, OC(CH3)2), 68.4 (s, OCH2), 69.7
(s, OCH2), 72.5 (s, NCH(CH3)2), 73.9 (s, NCH(CH3)2), 77.0 (s,
OC(CH3)2), 77.1 (d, 2J PC ) 5.4 Hz, OC(CH3)2), 126.5-134.0 (m,
aryl), 140.5 (d, J PC ) 80.0 Hz, i-C of aryl), 168.2 (s, CdN), 171.7
(s, CdN). 31P{1H} NMR (C6D6, 121.5 MHz): δ 191.1. Anal.
Calcd for C24H37Cl2N2O4PRu: C, 46.46; H, 6.01; N, 4.51.
Found: C, 46.40; H, 5.99; N, 4.16.
(46) J iang, Y.; J iang, Q.; Zhu, G.; Zhang, X. Tetrahedron Lett. 1997,
38, 6565.
(47) Langer, T.; Helmchen, G. Tetrahedron Lett. 1996, 37, 1381.
(48) Bianchini, C.; Farnetti, E.; Glendenning, L.; Graziani, M.;
Nardin, G.; Peruzzini, M.; Rocchini, E.; Zanobini, F. Organometallics
1995, 14, 1489.
(49) Yang, H.; Alvarez-Gressier, M.; Lugan, N.; Mathieu, R. Orga-
nometallics 1997, 16, 1401.
(50) Bennett, M. A.; Smith, A. K. J . Chem. Soc., Dalton Trans. 1974,
233.
X-r a y St r u ct u r a l An a lyses.54 Crystals of [RuCl2-
(NOPONMe )](1) suitable for X-ray diffraction were obtained
2
from a 1/3 CH2Cl2/pentane mixture and those of [Ru(µ-Cl)Cl-
(NOPONiPr)]2 (3) from a 1/3 THF/hexane mixture. The struc-
tures were solved by heavy-atom Patterson methods and
(51) Bennett, M. A.; Huang, T.-N.; Matheson, T. W.; Smith, A. K.
Inorg. Synth. 1982, 21, 74.
(52) Allen, J . V.; Williams, J . M. J . Tetrahedron: Asymmetry 1994,
5, 277.
(53) Pridgen, L. N.; Miller, G. J . Heterocycl. Chem. 1983, 20, 1223.
(54) Fu, T. Y.; Liu, Z.; Rettig, S. J .; Scheffer, J . R.; Trotter, J . Acta
Crystallogr., Sect. C 1997, 53, 1577.

Ru Complexes with Tridentate N,P,N Ligands
Organometallics, Vol. 19, No. 14, 2000 2683
Ta ble 4. Cr ysta llogr a p h ic Da ta for th e Str u ctu r a l
An a lysis of Com p lexes 1 a n d 3
a CH2Cl2 solution of ethyl diazoacetate (1.5 mmol, ca. 1 M)
through a microsyringe controlled by a mechanical feeder for
8 h under argon. After it was stirred for an additional 8 h, the
mixture was passed through a 1 cm silica gel column to remove
metal impurities. Conversion and enantioselectivity were
determined by gas chromatography using a â-CD No. 8 column
(0.5 bar of H2, 90 °C, 0.3 °C/min).
Tr a n sfer Hyd r ogen a tion . A typical procedure for catalytic
transfer hydrogenation of acetophenone is as follows: in a 50
mL two-neck round-bottom flask fitted with a reflux condenser
was dissolved 3 (0.0062 g, 0.01 mmol) in 19.5 mL of i-PrOH.
Acetophenone (0.234 mL, 2.0 mmol) was added, and the yellow
solution was brought to the desired temperature. The solution
was stirred for 10 min, and a solution of i-PrONa in i-PrOH
(0.1 M) was added. Note that the volume of i-PrOH was
adjusted so that all catalytic runs are performed with an initial
concentration in acetophenone of 0.1 M.
1
3
empirical formula
C22H33Cl2N2O4PRu C48H74Cl4N4O8P2Ru2
fw
592.46
1241.03
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/a (No. 14)
15.425(2)
9.4508(13)
12.6782(14)
103.3545(5)
2606.6(4)
4
monoclinic
P21 (No. 4)
11.5291(13)
17.329(2)
14.4236(4)
104.6653(5)
2787.7(4)
2
â (deg)
V (Å3)
Z
D
calcd (g cm-3
)
1.51
1.478
radiation; λ (Å)
Mo KR; 0.710 69
Mo KR; 0.710 69
F(000)
1216
1280
µ (cm-1
)
8.97
8.43
cryst size (mm)
θ range (deg)
temp (K)
0.10 × 0.20 × 0.30 0.40 × 0.35 × 0.20
2.0 < θ < 30
2.0 < θ < 30
180
180
Ack n ow led gm en t. We are grateful to Prof. M. D.
Fryzuk (Vancouver, BC, Canada) for stimulating
discussions and hospitality toward F.N. and to Dr.
Marie-Madeleine Rohmer (Strasbourg, France) for as-
sistance with the theoretical calculations. The Centre
National de la Recherche Scientifique (Paris, France)
and the Max-Planck Institut fu¨r Kohlenforschung (Mu¨l-
heim an der Ruhr, Germany) are gratefully acknowl-
edged for a visiting grant to F.N., and the Ministe`re
de l’Enseignement Supe´rieur et de la Recherche (Paris)
is acknowledged for a Ph.D. grant to F.N.
scan mode
ω
ω
no. of rflns (I > 3σ(I)) 4472
7443
no. of variables
289
0.027; 0.023
612
0.028; 0.0604
1.436
residuals (R; Rw)a
goodness of fit (GOF)a 1.27
max peak in final
0.86
1.01
diff map (e/Å3)
a
R
) ∑hkl(||Fo| - |Fc||)/∑hkl|Fo|; Rw ) [∑hklw(|Fo| - |Fc|)2/
2
∑
n
hklwFo
]
1/2, w ) 1/σ2(Fo); GOF ) [∑hklw(|Fo| - |Fc|)2/(ndata
-
variables)]1/2
.
expanded Fourier techniques. The non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were fixed in calcu-
lated positions with C-H ) 0.98 Å. The numbers of reflections
and parameters and the values of the residuals are given in
Table 4.
Ca ta lytic Exp er im en ts. Cyclop r op a n a tion . A typical
procedure for cyclopropanation of styrene and ethyl diazoac-
etate is as follows: to a solution of 3 (0.0093 g, 0.015 mmol)
and styrene (0.85 mL, 7.5 mmol) in 10 mL of CH2Cl2 was added
Su p p or tin g In for m a tion Ava ila ble: Tables giving de-
tails of the structure determination, atomic coordinates,
including those of the hydrogen atoms, anisotropic thermal
parameters, and all bond distances and angles for complexes
1 and 3, respectively. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM991034M