Synthesis of heterobimetallic Ru-Mn complexes and the coupling reactions of epoxides with carbon dioxide catalyzed by these complexes

Article abstract of DOI:10.1002/chem.200500780

The heterobimetallic complexes [(η⁵-C₅H ₅)Ru(CO)(μ-dppm)Mn(CO)₄] and [(η⁵-C ₅Me₅)Ru(μ-dppm)(μ-CO)₂Mn(CO) ₃] (dppm= bisdiphenylphosphinomethane) have been prepared by reacting the hydridic complexes [(η⁵-C₅H₅)Ru(dppm) H] and [(η-C₅Me₅)Ru(dppm)H], respectively, with the protonic [HMn(CO)₅] complex. The bimetallic complexes can also be synthesized through metathetical reactions between [(η⁵-C ₅R₅)Ru-(dppm)Cl] (R = H or Me) and Li⁺ [Mn(CO)₅]^-. Although the complexes fail to catalyze the hydrogenation of CO₂ to formic acid, they catalyze the coupling reactions of epoxides with carbon dioxide to yield cyclic carbonates. Two possible reaction pathways for the coupling reactions have been proposed. Both routes begin with heterolytic cleavage of the Ru-Mn bond and coordination of an epoxide molecule to the Lewis acidic ruthenium center. In Route I, the Lewis basic manganese center activates the CO₂ by forming the metallocarboxylate anion which then ring-opens the epoxide: subsequent ring-closure gives the cyclic carbonate. In Route II, the nucleophilic manganese center ring-opens the ruthenium-attached epoxide to afford an alkoxide intermediate; CO₂ insertion into the Ru-O bond followed by ring-closure yields the product. Density functional calculations at the B3LYP level of theory were carried out to understand the structural and energetic aspects of the two possible reaction pathways. The results of the calculations indicate that Route II is favored over Route I.

Full text of DOI:10.1002/chem.200500780

DOI: 10.1002/chem.200500780
ꢀ
Synthesis of Heterobimetallic Ru Mn Complexes and the Coupling
Reactions of Epoxides with Carbon Dioxide Catalyzed by these Complexes
[
a]
[b]
[a]
[a]
[a]
Man Lok Man, King Chung Lam, Wing Nga Sit, Siu Man Ng, Zhongyuan Zhou,
[
b]
[a]
Zhenyang Lin,* and Chak Po Lau*
Abstract: The heterobimetallic com-
coupling reactions of epoxides with
carbon dioxide to yield cyclic carbo-
nates. Two possible reaction pathways
for the coupling reactions have been
proposed. Both routes begin with het-
erolytic cleavage of the RuꢀMn bond
forming the metallocarboxylate anion
which then ring-opens the epoxide;
subsequent ring-closure gives the cyclic
carbonate. In Route II, the nucleophilic
manganese center ring-opens the ruthe-
nium-attached epoxide to afford an
alkoxide intermediate; CO2 insertion
into the RuꢀO bond followed by ring-
5
plexes
[(h -C H )Ru(CO)(m-
5 5
5
dppm)Mn(CO) ] and [(h -C Me )Ru(m-
4
5
5
dppm)(m-CO) Mn(CO) ] (dppm= bis-
2
3
diphenylphosphinomethane) have been
prepared by reacting the hydridic com-
5
plexes [(h -C H )Ru(dppm)H] and
and coordination of an epoxide mole-
cule to the Lewis acidic ruthenium
center. In Route I, the Lewis basic
5
5
5
[
(h -C Me )Ru(dppm)H], respectively,
5 5
with the protonic [HMn(CO) ] com-
closure yields the product. Density
functional calculations at the B3LYP
level of theory were carried out to un-
derstand the structural and energetic
aspects of the two possible reaction
pathways. The results of the calcula-
tions indicate that Route II is favored
over Route I.
5
plex. The bimetallic complexes can also
manganese center activates the CO by
2
be synthesized through metathetical re-
5
actions
(
[
between
[(h -C R )Ru-
5
5
Keywords: coupling reactions · cy-
clic carbonates · density functional
+
dppm)Cl] (R=H or Me) and Li
Mn(CO) ] . Although the complexes
ꢀ
5
calculations
·
heterobimetallic
fail to catalyze the hydrogenation of
complexes · reaction mechanisms
CO to formic acid, they catalyze the
2
[
2]
Introduction
cal and catalytic reactions. Heterobimetallic complexes are
of particular interest since it is relatively easy to introduce
metalꢀmetal bond polarity into these systems, which can
Bimetallic complexes have attracted much attention because
it is believed that with two metal centers in proximity, the
reactivity of the individual metal atoms might complement
each other and give rise to so-called cooperative reactivity.
Moreover, the chemistry of these systems is potentially
unique and so they are promising candidates for new chemi-
lead to bifunctional activity and direct selectivity in sub-
strate–system interactions. Furthermore, heterolytic cleavage
of the polar metalꢀmetal bond in the course of a reaction
[1]
might generate a metal nucleophile and electrophile pair;
the former could act as a Lewis base to activate a substrate
and the latter as a Lewis acid to activate a second one. The
pair might also activate a polar substrate in a concerted
[
a] Dr. M. L. Man, W. N. Sit, S. M. Ng, Prof. Z. Zhou, Prof. C. P. Lau
Department of Applied Biology and Chemical Technology
The Hong Kong Polytechnic University
Hung Hom, Kowloon, Hong Kong (China)
Fax : (+852)2364-9932
[3]
manner.
The utilization of carbon dioxide as a feedstock in the
production of chemical products has attracted much atten-
[4]
tion for economic and environmental reasons. One of the
promising methodologies in chemical CO2 fixation is the
coupling of carbon dioxide with epoxides to synthesize
cyclic carbonates which are valuable as aprotic polar sol-
vents, fine chemical intermediates, and starting material for
E-mail: bccplau@polyu.edu.hk
[
b] K. C. Lam, Prof. Z. Lin
Department of Chemistry
The Hong Kong University of Science and Technology
Clear Water Bay, Kowloon, Hong Kong (China)
Fax : (+852)2358-1594
[5]
the synthesis of polymers and engineering plastics. Various
catalysts have been explored for use in such coupling reac-
E-mail: chzlin@ust.hk
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author. Optimized geo-
metries of all species calculated.
[6]
tions. Some previous reports have suggested that parallel
Lewis base activation of CO and Lewis acid activation of
2
1004
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1004 – 1015

FULL PAPER
[
6a–d]
epoxides is important for the success of the reaction.
For
complex. The T (min) values of the hydride ligands of
1
III
example, it has been proposed that in the [Cr salen]/(4-di-
[CpRu(dppm)H] and [Cp*Ru(dppm)H] in [D ]chloro-
5
methylamino)pyridine (DMAP)-catalyzed CO /epoxide cou-
benzene were measured to be 1139 ms at 240 K and 924 ms
at 244 K, respectively; these values were lowered only
slightly to 1099 ms at 247 K and 900 ms at 246 K, respective-
2
III
pling reactions, the starting [Cr salen] complex acts as a
III
Lewis acid to activate the epoxide and the [Cr salen]·D-
III
MAP complex, in which the Cr center is rendered more
ly, upon addition of one equivalent of [HMn(CO) ] to the
5
electron-rich by the coordination of the DMAP molecule,
solutions.
activates the CO by forming a metallocarboxylate interme-
Despite the seeming absence of stable dihydrogen-bonded
species in the solution containing [Cp’Ru(dppm)H] (Cp’=
2
[6a]
diate. It is also likely that the catalytic activity of MgꢀAl
mixed oxides in the coupling of carbon dioxide with epox-
ides originates from the cooperative action of neighboring
Cp, Cp*) and [HMn(CO) ], it was, however, learned that H/
5
D exchange occurred upon addition of one equivalent of
[6b]
basic and acidic sites on the surface of the catalyst.
We
[HMn(CO) ] to a solution of [Cp’Ru(dppm)D]; an equilibri-
5
herein report the synthesis, characterization, and a reactivity
um in which the deuterium was distributed equally between
the two hydride species was established within 30 minutes.
With H/D exchange occurring between [Cp’Ru(dppm)D]
study of a pair of RuꢀMn heterobimetallic complexes; the
catalysis of the carbon dioxide/epoxide coupling reactions
with these complexes has also been investigated.
and [HMn(CO) ], we anticipated that spin-saturation trans-
5
fer between the two hydride complexes should be observa-
ble. It was, however, found that in a solution containing
Results and Discussion
equimolar amounts of [Cp’Ru(dppm)H] and [HMn(CO) ],
5
irradiation of the ruthenium hydride signal did not lead to
any enhancement of the hydride signal of the manganese
complex. Conversely, the intensity of the ruthenium hydride
signal was unaltered when the hydride signal of the manga-
nese complex was irradiated. The hydride exchange between
the two complexes is probably much too slow to render the
spin-saturation transfer observable.
5
Synthesis and characterization of [(h -C H )Ru(CO)(m-
5
5
5
dppm)Mn(CO)4] (1a) and [(h -C Me )Ru(m-CO) (m-
5
5
2
dppm)Mn(CO) ] (1b): We envision that the reaction of the
3
relatively acidic manganese carbonyl hydride [HMn(CO) ]
5
[7]
(
(
pK (aq scale)=7.2) with the hydride complex [Cp’Ru-
a
dppm)H] (Cp’=Cp, Cp*; dppm= bis-diphenylphosphino-
methane; the pK values (aq scale) of the conjugate acids
A mechanism for the H/D exchange between [Cp’Ru-
a
+
+
[
CpRu(dppm)(H )] and [Cp*Ru(dppm)(H )] are 7.3 and
(dppm)D] and [HMn(CO) ] is proposed and shown in
2
2
5
[8]
8.8, respectively) would generate, by elimination of a dihy-
Scheme 1. The protonic hydrogen of [HMn(CO) ] attacks
5
drogen molecule, the heterobi-
metallic complex. However,
stirring a THF solution of equi-
molar amounts of [HMn(CO)5]
and [Cp’Ru(dppm)H] at room
temperature did not seem to
lead to the formation of any bi-
metallic complex. The reaction
of the two hydrides in [D ]THF
8
was therefore monitored by
1
NMR spectroscopy.
H
and
31
1
P{ H} NMR spectroscopy,
however, showed that the two
hydrides remained unchanged
over a period of several hours.
The hydride signals of the two
hydride complexes remained
sharp over a temperature range
of 213–293 K, indicative of the
absence of stable dihydrogen-
bonded bimetallic species Ruꢀ
[
9]
H···HꢀMn.
The absence of
these stable dihydrogen-bonded
species in the solution mixture
was corroborated by the varia-
ble-temperature T1 relaxation
time measurements for the hy-
Scheme 1. Proposed mechanism for the H/D exchange between [Cp’Ru(dppm)D] and [HMn(CO)
5
]. R=H,
3
dride ligand of the ruthenium CH .
Chem. Eur. J. 2006, 12, 1004 – 1015
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1005

C. P. Lau, Z. Lin et al.
the deuteride ligand of [Cp’Ru(dppm)D] and H/D exchange
proceeds rapidly via the transient intermediates of the Ruꢀ
2
D···HꢀMn species and the h -HD complex. It has been
shown that the kinetic products of the protonation reactions
2
of [Cp’Ru(L )H] are the h -dihydrogen complexes; depend-
2
ing on the ligands L , in some cases, intramolecular tautome-
2
rization of the dihydrogen complexes occurs to give the
transoid dihydride form or a mixture of dihydrogen and di-
2
hydride complexes, while in other cases the h -dihydrogen
form persists and does not tautomerize to give the dihydride
[
10]
form. Although [Cp’Ru(dppm)H] (Cp’=Cp or Cp*) and
HMn(CO) ] did not seem to react at room temperature
a pseudo-halide that forms a dative Mn!Ru bond with a
II
ꢀI
[
formulation of Ru /Mn .
5
3
1
1
over a period of several hours, it was, however, found that
after a [D ]THF solution of [CpRu(dppm)H]/[HMn(CO) ]
The P{ H} NMR spectrum of 1a exhibits a pair of dou-
2
blets at d=54.9 and 56.6 ppm [ J(P,P)=91.2Hz]. The meth-
8
5
(
1:1) had been allowed to stand at room temperature in a
ylene hydrogen atoms of the dppm ligand appear as a triplet
at d=2.90 ppm [J(H,P)=9.91 Hz] in the H NMR spectrum.
1
sealed NMR tube for eight days, the two hydrides had react-
ed completely to yield the metalꢀmetal-bonded bimetallic
These hydrogen atoms should, in principle, be diastereotop-
ic, they are magnetically equivalent and have basically iden-
tical coupling constants to the two phosphorus atoms, proba-
bly by coincidence. Complex 1a exhibits three carbonyl
peaks at 247.0, 225.6, and 222.5 ppm (relative intensities,
complex [CpRu(CO)(m-dppm)Mn(CO) ] (1a) and
H
2
4
[
Eq. (1)]. On a preparative scale, 1a can be prepared by re-
fluxing equimolar amounts of the two hydrides in THF for
5 h. In this reaction the chelating dppm ligand of [CpRu-
dppm)H] unwinds upon reaction with [HMn(CO) ] to yield
1
1
3
(
2:2:1) in the C NMR spectrum. The IR spectrum (KBr) of
the complex shows, in addition to the bands at 1896, 1938,
5
the dppm-bridged complex 1a.
ꢀ
1
and 2000 cm due to terminal carbonyl groups, a relatively
ꢀ
1
low-energy CO stretching frequency at 1710 cm . The pres-
ence of this low CO stretching frequency indicates that a
bridging or semibridging carbonyl group is present in the bi-
metallic complex. Our recently reported RuꢀMo and RuꢀW
heterobimetallic complexes, which contain semibridging car-
bonyl ligands, exhibit low-energy CO stretching frequencies
ꢀ
1 [12]
at 1777–1792cm
.
Similar to 1a, the pentamethylcyclopentadienyl analog,
5
[
{h -C (CH ) }Ru(m-CO) (m-dppm)Mn(CO) ] (1b) (vide
5
3
5
2
3
infra) was prepared by the reaction of the two hydride pre-
3
1
1
cursors or by the metathetical reaction. The P{ H} NMR
2
Not unexpectedly, 1a can also be conveniently prepared
by the reaction of the ruthenium chloro complex [CpRu-
spectrum of 1b shows two doublets at d=48.1 [ J(P,P)=
2
105.0 Hz] and 51.2ppm [ J(P,P)=105.0 Hz]. Similar to those
(
dppm)Cl] with lithium manganese pentacarbonyls [Eq. (2)].
of 1a, the methylene hydrogen atoms of the bridging dppm
ligand of 1b also appear as a triplet [d=2.35 ppm; J(H,P)=
9.1 Hz] in the H NMR spectrum. The complex shows only
Similar metathetical reactions have been employed to pre-
[11]
1
pare bimetallic complexes containing metalꢀmetal bonds,
including the RuꢀMo and RuꢀW bimetallic complexes that
two carbonyl peaks at d=269.8 and 225.6 ppm (relative in-
[12]
13
we recently reported.
heterobimetallic complexes
RhMH(CO) (m-dppm) ] (M=Fe, Ru, Os), [RhM(CO) (m-
It has been suggested that in the
tensities, 3:2) in the C NMR spectrum. The IR spectrum
[RhCo(CO) (m-dppm) ],
(KBr) of 1b, in addition to the bands due to terminal car-
3
2
[
bonyl groups, exhibits
1710 cm , which might be due to semibridging or bridging
carbonyl groups.
a
low-energy CO stretch at
3
2
4
ꢀ
1
dppm) ] (M=Mn, Re), and [RhMH(CO) (m-dppm) ] (M=
Cr, W), the metalꢀmetal bonds are M!Rh dative bonds.
It has also been reported that the heterobimetallic complex
formed by the metathetical reaction of Li [h -C H P(C H -
p-CH ) Mo(CO) ] with [{(C H -p-CH )PCH }RhCl] con-
2
4
2
I
[13]
+
5
Molecular structures of 1a and 1b: The metalꢀmetal-
bonded bimetallic structure of 1a was confirmed by X-ray
crystallography. The molecular structure of 1a is shown in
Figure 1 (the solvent molecule CH Cl , which is disordered,
5
4
6
4
ꢀ
3
2
4
6
4
3
2
2
d+
dꢀ
tains a highly polarized Rh ꢀMo bond; changing the do-
nating phosphine ligands on rhodium to carbonyls led to a
2
2
[14]
reduction of the metalꢀmetal-bond polarity. The bimetal-
lic complex [(PEt ) (CO)RhꢀCo(CO) ] has been shown to
is not shown). The crystal data and refinement details are
given in Table 1. Selected bond distances and angles are
given in Table 2. The RuꢀMn bond distance of 2.8524(7) Š
in 1a is comparable to the metalꢀmetal bond lengths mea-
3
2
4
possess a polar metalꢀmetal bond which structurally and
I
ꢀI
chemically is best described as a Rh ꢀCo complex in which
ꢀ
[3f]
the [Co(CO) ] group behaves as a pseudo-halide.
It
sured in other RuꢀMn bimetallic complexes that contain
4
5
seems reasonable to regard the manganese moiety in 1a as
bridging ligands, for example, [RuMn(m-H)(m-PPh )(h -
2
1006
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1004 – 1015

Heterobimetallic RuꢀMn Complexes
FULL PAPER
Table 2. Selected bond lengths and angles for [(C
dppm)Mn(CO) ] (1a).
5 5
H )Ru(CO)-
(
4
interatomic distances [Š]
Ru1ꢀMn1
Mn1ꢀP2
2.8524(7)
2.2894(11)
1.801(5)
1.793(5)
1.158(6)
1.130(5)
1.157(5)
Ru1ꢀP1
Ru1ꢀC6
Mn1ꢀC8
Mn1ꢀC10
O2ꢀC7
2.2842(10)
1.832(5)
1.839(5)
1.832(4)
1.145(5)
1.152(5)
Mn1ꢀC7
Mn1ꢀC9
O1ꢀC6
O3ꢀC8
O4ꢀC9
O5ꢀC10
intramolecular angles [8]
C35-P1-Ru1
112.32(12)
171.7(4)
176.3(5)
167.3(4)
C35-P2-Mn1
O2-C7-Mn1
O4-C9-Mn1
113.75(12)
176.0(6)
176.1(4)
O1-C6-Ru1
O3-C8-Mn1
O5-C10-Mn1
Figure 1. X-ray structure of [(C
5
H
5
)Ru(CO)(m-dppm)Mn(CO)
4
] (1a).
C H )(CO) ], in which the RuꢀMn bond length is
[15]
5
5
5
2
.894(1) Š; it is, however, shorter than those of the Ruꢀ
Mn bimetallic complexes that have no bridging ligands, such
as the a-diimine RuꢀMn bimetallic complex [(CO) Mnꢀ
Table 1. Crystal data and structure refinement for complexes
a·0.5CH Cl and 1b.
5
1
2
2
Ru(Me)(CO) (a-diimine)] [a-diimine=pyridine-2-carbalde-
2
hyde-N-isopropylimine (iPr-PyCa)], in which the RuꢀMn
1
a·0.5CH
2
Cl
2
1b
[16]
bond distance was found to be 2.9875(8) Š. Note that for
one of the carbonyl ligands attached to the manganese
center, the Mn-C-O angle [Mn1-C10-O5, 167.3(4)8] deviates
more from linearity than those of the other CO ligands on
the manganese atom. Moreover, the distance of the carbon
atom of this less linear carbonyl ligand on manganese from
the ruthenium center measures 2.656(4) Š; this relatively
short distance is indicative of the presence of a weak inter-
action between this CO group and the ruthenium center. In
a ZrꢀRu bimetallic complex, the zirconium-bound CO,
empirical formula
formula weight
temperature [K]
wavelength [Š]
crystal system
space group
unit cell dimensions
a [Š]
b [Š]
c [Š]
a [8]
b [8]
C
787.98
294(2)
0.71073
monoclinic
35.5
H
28ClMnO
5
P
2
Ru
40 5 2
C H37mnO P Ru
815.65
294(2)
0.71073
orthorhombic
P2
P2
1
/c
1 1 1
2 2
18.813(3)
10.5259(14)
19.633(3)
90
90
90
3617.5(11)
4
1.429
0.955
1588
11.7144(15)
13.1309(18)
24.014(3)
90
90
90
3693.8(8)
4
1.467
0.880
1664
g [8]
volume [Š ]
which is slightly bent (Zr-C-O, 1678), semibridges the ruthe-
3
nium center and the carbon atom of the bent CO is 2.70 Š
Z
[17]
from the ruthenium center. Moreover, in each of the Ruꢀ
ꢀ
3
1
calcd [Mgm
]
ꢀ
1
M (M=Mo, W) bimetallic complexes, one of the metal-
bound CO ligands is a semibridging carbonyl, the M-C-O
angle deviates significantly from linearity, and the distance
of the carbon atom of this carbonyl ligand from the rutheni-
m [mm
]
F(000)
3
crystal size [mm ]
q range [8] for
data collection
index ranges
0.22”0.20”0.14
2.11–27.54
0.30”0.16”0.14
2.48–27.52
[12]
um center falls in the range of 2.744–2.906 Š.
Figure 2shows the X-ray structure of 1b. The crystal data
and refinement details are included in Table 1. Selected
bond lengths and angles are given in Table 3. An obvious
difference between the structure of 1b and that of 1a is that
the former contains two bridging carbonyl groups, whilst the
latter contains only one semibridging CO. Both bridging car-
bonyl ligands in 1b lean slightly towards the ruthenium
center. The RuꢀMn bond length in 1b is, as expected, short-
ꢀ
ꢀ
ꢀ
23%h%24
13%k%13
25%l%10
ꢀ12%h%15
ꢀ17%k%13
ꢀ31%l%30
25195
reflections collected
24254
independent reflections 8410 [R(int)=0.0363] 8468 [R(int)=0.0365]
completeness to
q=27.648 [%]
absorption correction
99.6
99.7
empirical
empirical
0.8867 and 0.7782
max. and min. transmis- 0.8779 and 0.8174
sion
er than that of 1a (2.7777(5) Š versus 2.8524(7) Š) as a
result of the presence of two bridging carbonyl groups. The
CꢀO bond lengths of the bridging carbonyls are significantly
refinement method
full-matrix least-
squares on F
8410/6/417
full-matrix least-
squares on F
8468/0/447
2
2
data/restraints/parame-
ters
goodness-of-fit on F
longer than those of the terminal CO ligands in the com-
plex.
2
1.0321.019
final R indices [I>2s(I)]
R
1
=0.0468,
wR =0.129
=0.0742,
wR =0.1439
0.858 and ꢀ0.436
R
1
=0.0320,
wR =0.0548
=0.0434,
wR =0.0575
0.596 and ꢀ0.416
2
2
R indices (all data)
R
1
R
1
Reactions of 1a and 1b with H /CO : We have studied dihy-
2
2
2
2
drogen-bonding interactions in aminocyclopentadienylruthe-
nium complexes and have learned that complexes containing
intramolecular RuꢀH···HꢀN dihydrogen bonds catalyze CO2
largest diff. peak and
ꢀ3
hole [eŠ
]
Chem. Eur. J. 2006, 12, 1004 – 1015
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1007

C. P. Lau, Z. Lin et al.
Scheme 2.
[
20]
lyst
and the chiral “metal/NH” catalysts reported by
[21]
[22]
Figure 2. X-ray structure of [{C
1b).
5
(CH
3
)
5
}Ru(m-CO)
2
(m-dppm)Mn(CO)
3
]
Noyori and Morris and their co-workers. We therefore
monitored the reactions of 1a and 1b with H by P{ H}
(
31
1
2
NMR spectroscopy. It was, however, found that after heat-
ing a C D solution of 1a or 1b at 1008C in a high-pressure
6
6
Table 3. Selected bond lengths and angles for [{C
dppm)Mn(CO) ] (1b).
5 3 5 2
(CH ) }Ru(m-CO) (m-
NMR tube under about 35 atm of H for 45 h, the complex
2
3
remained unchanged. Attempted CO hydrogenation (CO /
2
2
interatomic distances [Š]
Ru1-Mn1
Mn1-P2
H =35 atm/35 atm; 1008C for 45 h) with 1a or 1b in the
2.7777(5)
2.3296(9)
Ru1-P1
Ru1-C11
2.2969(8)
1.994(3)
2
presence of Et N in an autoclave was also unsuccessful, that
3
Ru1-C121.950(3) .0 9M6 (n3 1) -C11
2
is, no HCOOH·Et N adduct was detected.
3
.151(3)
Mn1-C1 23 2
Mn1-C14
O1-C11
1.804(4)
1.820(3)
1.178(3)
1.153(4)
1.153(3)
Mn1-C15
O2-C12
O4-C14
1.792(3)
1.190(3)
1.136(3)
Carbon dioxide/epoxide coupling reactions with 1a and 1b:
Although 1a and 1b are not catalytically active in the hy-
drogenation of carbon dioxide, it was, however, found that
they are active in catalyzing the coupling reactions of
carbon dioxide with epoxides to give cyclic carbonates. The
results of these reactions are shown in Table 4. The catalytic
O3-C13
O5-C15
intramolecular angles [8]
P1-Ru1-Mn1
Ru1-C12-Mn1
O1-C11-Ru1
93.55(2)
85.13(11)
137.0(2)
141.1(2)
P2-Mn1-Ru1
P2-C40-P1
O1-C11-Mn1
O2-C12-Mn1
93.09(2)
112.78(15)
136.7(2)
O2-C12-Ru1
133.6(2)
reactions were carried out in neat epoxides and no CO /ep-
2
oxide copolymer was formed in any of the reactions. After
the removal of the product and the unreacted substrate
1
31
1
from the catalytic reaction mixture, H and P{ H} NMR
spectroscopy showed that the bimetallic complex was recov-
ered unchanged.
Note that the presence of electron-withdrawing groups on
the epoxides leads to higher conversions (Table 4, entries 1–
4). The failure of styrene oxide and cyclohexene oxide to
hydrogenation to yield formic acid, albeit in low yields.
During the catalytic reaction, the dihydrogen-bonded
moiety plays an important role in transferring the hydrogen
[18]
atoms of H to the CO molecule. More recently we stud-
2
2
ied the promoting effects of water and alcohols on CO hy-
2
drogenation reactions catalyzed by the hydrotris(pyrazolyl)-
couple with CO is probably due to steric congestion. In
2
borato (Tp) ruthenium hydride complex [TpRu(PPh )-
general, complex 1b has a lower catalytic activity than 1a;
the lower activity of 1b might be attributable to greater
steric hindrance and the presence of two bridging carbonyl
groups which render the cleavage of the metalꢀmetal bond
3
(
CH CN)H]; supported by theoretical calculations, we pro-
3
posed that the active species is the aquo or alcohol hydride
complex [TpRu(PPh )(ROH)H] (R=H or alkyl), which is a
3
bifunctional catalyst that transfers the metal hydride and the
proton of the coordinated ROH molecule to the carbon and
a more demanding step (vide infra).
We have also studied the catalytic activity of the individu-
oxygen atoms of the CO molecule, respectively, in a con-
al metallic moieties of the complexes in CO /epoxide cou-
2
2
certed manner; that is, the CO molecule does not have to
pling reactions. It was found that the ruthenium complexes
2
[19]
5
5
coordinate to the metal center.
One of our interests in
[(h -C H )Ru(CO)(PPh )(CH CN)]OTf
and
[(h -
5
5
3
3
+
ꢀ
this work was to study the reactivity of the bimetallic com-
C H )Ru(CO)(PPh )(Cl)]/Ag OTf were inactive in the re-
5
5
3
plexes towards H in the hope of generating dihydrogen-
action, however, the manganese complex Li[Mn(CO)4-
2
bonded bimetallic species that might act as bifunctional cat-
(PPh )] (1c) was found to be active, its activity in general
being lower than that of 1a but comparable to that of 1b.
3
+
ꢀ
alysts capable of delivering a H and a H in a concerted
process (Scheme 2). The bimetallic species are reminiscent
of metal–ligand bifunctional catalysts such as the Shvo cata-
The results of the 1c-catalyzed CO /epoxide coupling reac-
2
tions are also included in Table 4. In general, the activities
1008
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1004 – 1015

Heterobimetallic RuꢀMn Complexes
FULL PAPER
[
a]
2
Table 4. Catalytic coupling reactions of CO and epoxides.
[
b]
[c]
[b]
[c]
Entry
1
Substrate
Catalyst
TON
TOF
Entry
Substrate
Catalyst
TON
TOF
epifluorohydrin
1a
1a
1a
1a
1a
1a
1a
1a
1b
1b
1b
1b
1b
8640
8000
6450
1490
trace
2800
480
trace
7050
5300
4200
450
216
200
161
37
14
15
16
17
18
19
butadiene monoxide
1,2-epoxyhexane
cyclohexene oxide
epifluorohydrin
epichlorohydrin
epibromohydrin
1b
1b
1b
1c
1c
1c
1c
1c
1c
1c
1c
1c
1940
120
48
3
2
3
4
5
6
7
8
9
1
1
1
1
epichlorohydrin
epibromohydrin
propylene oxide
propylene oxide
butadiene monoxide
1,2-epoxyhexane
cyclohexene oxide
epifluorohydrin
epichlorohydrin
epibromohydrin
trace
7020
5400
4100
440
trace
trace
1795
110
trace
176
135
103
11
trace
trace
45
[
d]
trace
70
0
122 propylene oxide
trace
176
[
d]
21
22
propylene oxide
propylene oxide
[
e]
0
1
3
1322 butadiene monoxide
105
11
24
25
1,2-epoxyhexane
cyclohexene oxide
3
2propylene oxide
trace
trace
[
d]
3
propylene oxide
trace
trace
[
a] Typical reaction conditions: 3.5 mmol catalyst, 31.5 mmol substrate (S/C=9000), 40 bar CO
of moles of product/no. of moles of catalyst. [c] Turnover number frequency (TOF)=TON/time(h). [d] 7.0 mmol of CH
12]crown-4 added.
2
pressure, 1008C, 40 h. [b] Turnover number (TON)=no.
3
CN added. [e] 7.0 mmol of
[
III [6a]
II [6m]
II [6m]
[24]
of 1a and 1b are similar to those of Cr , Zn ,
and Co
Cu ,
ring-opening of the former. The proposed epoxide com-
plex and the ring-opened species in Route I of Scheme 3 are
probably transient intermediates because we have not been
able to detect either of these species in NMR-monitored
II[6m]
[6o]
salen-type complexes and [Re(CO) Br]. Com-
5
plexes 1a and 1b, however, exhibit much higher catalytic ac-
tivities in the coupling reactions of epihalohydrins with CO2.
Note that in general the catalytic activity of the less well-de-
fined [Ni(PPh ) Cl ]/PPh /Zn/n-Bu NBr system
than an order of magnitude higher than those of 1a and 1b.
catalytic CO /propylene oxide coupling reactions carried out
in 10 mm sapphire high-pressure NMR tubes. We have also
failed to isolate or detect any epoxide complex in independ-
ent studies involving the reactions of [(h -C H )Ru-
(PPh )(CO)(CH CN)] and [(h -C H )Ru(PPh )(CO)(Cl)]/
3 3 5 5 3
2
[6k]
is more
3
2
2
3
4
5
5
5
+
5
Proposed mechanism for the catalytic CO /expoxide cou-
2
+
ꢀ
pling reaction: It has been proposed that the coupling of ep-
oxides with carbon dioxide to yield cyclic carbonates proba-
bly requires the activation of both substrates; the former by
a Lewis acid and the latter by a Lewis base.
Scheme 3 shows a possible mechanism for the 1a-catalyzed
Ag OTf with propylene oxide. The fact that the addition
of a small amount of CH CN, which is a much better coordi-
3
nating ligand to ruthenium than propylene oxide, completely
quenches the catalytic reaction (Table 4, entry 5) lends sup-
port to the notion that activation of the epoxide by the elec-
trophilic ruthenium center is crucial to the success of the
coupling reaction. The 1b-catalyzed coupling reaction could
probably proceed by the same mechanism, although the
cleavage of the RuꢀMn metalꢀmetal bond, which is flanked
[
6a–d]
Route I of
CO /epoxide coupling reactions. Heterolytic cleavage of the
2
metalꢀmetal bond generates an electrophilic ruthenium
fragment and a nucleophilic manganese moiety. An epoxide
molecule then coordinates to the Lewis acidic ruthenium
center, whilst the Lewis basic manganese center activates
the carbon dioxide by forming a metallocarboxylate anion.
Although not isolated, the man-
by two bridging carbonyl groups, might be a more demand-
ing step. Moreover, 1b is more hindered than 1a.
ganese carboxylate [Mn(CO) -
4
ꢀ
(
PPh )(CO )] was believed to
3
2
be the intermediate in the reac-
tion of K[CpFe(CO)(PPh )-
3
(
CO )]
with
[Mn(CO)5-
2
(
PPh )]BF followed by the ad-
3
4
dition of CH3I to afford
[
[
CpFe(CO) (PPh )]BF
4
and
Nu-
2
3
[23]
Mn(CO) (PPh )(CH )].
4
3
3
cleophilic ring-opening of the
ruthenium-attached epoxide by
the manganese carboxylate in
Scheme 3 generates A which
then extrudes the cyclic carbon-
ate by ring-closure. It is widely
accepted that coordination of
an epoxide molecule to a Lewis
acid facilitates nucleophilic Scheme 3.
Chem. Eur. J. 2006, 12, 1004 – 1015
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1009

C. P. Lau, Z. Lin et al.
An alternative mechanism for the CO /epoxide coupling
reaction is also proposed (Scheme 3, Route II). In this pro-
posed mechanism, the manganese fragment, instead of form-
Computational study: To understand the structural and en-
ergetic aspects of the possible reaction pathways proposed
above for the carbon dioxide/epoxide coupling reactions cat-
alyzed by RuꢀMn heterobimetallic complexes, theoretical
2
ing a metallocarboxylate with CO , ring-opens the epoxide,
2
which is activated by O-coordination to the ruthenium frag-
calculations at the B3LYP level of density functional theory
were carried out. In our calculations, the model catalyst
ment, to form the cyclic alkoxide B. CO then inserts into
2
5
the RuꢀO bond to form the cyclic metal carbonate C, which
[(h -C H )Ru(CO)(m-dppm)Mn(CO) ] was used in which
5
5
4
then extrudes the cyclic carbonate. The insertion of CO
the phenyl groups in the dppm ligand were replaced by hy-
drogen atoms. The two proposed reaction pathways (Rou-
tes I and II in Scheme 3) were studied. For the convenience
of our discussion, all the calculated structures of the inter-
mediates, reactants, and transition states are numbered and
the transition states are labelled with TS.
2
into a metalꢀalkoxide bond to form a metal carbonate spe-
[25]
cies is well-documented.
The lithium salt of the manganese tetracarbonylate anion
Li[Mn(CO) (PPh )] (1c) was shown to be an active catalyst
4
3
in the coupling reactions, although, in general, its activity is
lower than that of 1a (Table 4). The lithium cation of 1c is
probably capable of activating the epoxide by attaching to
the oxygen atom of the latter. The fact that the addition of
acetonitrile (Table 4, entry 21) or 12-crown-4 (Table 4,
Coupling reaction of carbon dioxide and ethylene oxide:
Figure 3 shows the two possible reaction pathways (Routes I
and II) for the carbon dioxide/epoxide coupling reaction;
the relative free energies and electronic energies (in paren-
theses) are also shown. To take into account the effect of
entropy, we use the free energies rather than the electronic
energies in our discussion because two or more molecules
are involved in the reactions studied herein. For the readerꢁs
information, the relative electronic energies are also shown
in parentheses in Figure 3.
+
entry 22), which is able to solvate or encapsulate Li , re-
spectively, practically quenches the activity of 1c gives cre-
dence to this premise. It has been reported that benzo[15]-
crown-5 acts as a deactivator in sodium halide catalyzed
CO /epoxide coupling reactions; the crown ether is a good
2
[6j]
host for the sodium cation. The proximity of the metal
centers in 1a is an advantage over 1c.
Figure 3. Schematic illustration of the two reaction pathways studied in the coupling reaction of carbon dioxide with ethylene oxide. The calculated rela-
ꢀ
1
tive free energies (kcalmol ) and the relative electronic energies (in parentheses) of the species involved in the reaction are given. The relative energies
5
5 5 4 2 2 4
of all species are given relative to [(h -C H )Ru(CO)(m-dppm)Mn(CO) ], CO , and C H O.
1010
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1004 – 1015

Heterobimetallic RuꢀMn Complexes
FULL PAPER
ꢀ
1
Both Routes I and II begin with a bimetallic complex 1.
After heterolytic cleavage of the RuꢀMn bond, an epoxide
(53.91 kcalmol , 1!TS3–4) to the first major step. In the
second major step, ring-closure in 5 to yield the product
molecule (cyclic carbonate) again leads to charge separa-
molecule coordinates to the electrophilic ruthenium center
through the O(epoxide) atom to afford complex 2 via the transi-
tion state TS1–2. In Route I, carbon dioxide then coordinates
to the nucleophilic manganese center through the electro-
philic carbon atom to form complex 3. Ring-opening of the
epoxide in 3 to form 4 takes place via the transition state
TS3–4. In this step, one of the two nucleophilic oxygen atoms
of the carboxylate moiety attacks one of the carbon atoms
of the coordinated epoxide ring, which behaves as an elec-
trophile, to afford a relatively stable intermediate 4. Inter-
mediates 4 and 5 are rotational isomers which differ in their
O-C-C-O dihedral angles, being ꢀ72.5 and 59.38, respective-
ly. We were unable to locate the rotational transition state
because of the flatness of the potential energy surface near
the transition state, however, we expect that the rotational
barrier is small. From the rotational isomer 5, ring-closure
occurs via TS5–6 to give 6 in which the product molecule
ꢀ
1
tion. This step (5!TS ) has a barrier of 35.93 kcalmol .
5–6
Route II involves three major steps. 1) Coordination of
the epoxide to the Lewis acidic ruthenium center with heter-
olytic cleavage of the RuꢀMn bond and manganese-nucleo-
philic ring-opening of the epoxide to give 8. 2) Insertion of
CO into the RuꢀO bond in 8 to give 10. 3) Ring-closure in
2
10 to yield the cyclic carbonate and regeneration of the cata-
lyst. The first major step has an overall energy barrier of
ꢀ
1
44.04 kcalmol , which is less than the overall barrier calcu-
lated for the first major step of Route I. The energy re-
quired for coordination of the epoxide and heterolytic cleav-
age of the RuꢀMn bond is the same as that in Route I. The
smaller overall barrier here is a result of a smaller barrier to
manganese-nucleophilic ring-opening than that for the met-
allocarboxylate-nucleophilic ring-opening of Route I. By ex-
amining the energy changes for the steps 2!TS and 2!
2–8
(
cyclic carbonate) is coordinated to the ruthenium metal
TS , we can conclude that the unfavorable metallocarboxy-
3
–4
center. The last step involves the dissociation of the cyclic
carbonate from the ruthenium center and regeneration of
late-nucleophilic ring-opening in Route I is mainly related
to an entropy effect. In Route II, ring-opening occurs imme-
diately after the heterolytic RuꢀMn bond cleavage. Howev-
the catalyst via transition state TS6–7
.
In Route II, after coordination of the epoxide to the
ruthenium center to give complex 2, the nucleophilic manga-
nese center attacks one of the carbon atoms of the rutheni-
um-coordinated epoxide and opens the epoxide ring to
afford a stable alkoxide intermediate 8 via transition state
TS2–8. Carbon dioxide interacts with the oxygen atom
bonded to the ruthenium center to form 9. Insertion of the
carbon dioxide molecule into the RuꢀO bond generates the
er, the ring-opening in Route I occurs after 2 has taken up
one more molecule, CO . The insertion of CO into 8 in the
2
2
second major step does not cost much energy with an
ꢀ
1
energy barrier of 24.68 kcalmol . In the third major step,
ring-closure in 10 to yield the product molecule (cyclic car-
bonate), similar to the second major step in Route I, has a
ꢀ
1
large barrier of 44.59 kcalmol (from 10 to TS11–6). Again,
formation of 6 causes charge separation between the two
metal centers, contributing to the large barrier. As the dif-
ference in the overall energy barriers between the first and
third major steps is small, we expect that these two steps are
important in determining the reaction rate.
cyclic metal carbonate 10 via the transition state TS . In-
9
–10
termediates 10 and 11 are rotational isomers with different
Ru-O-C=O and O=C-O-C dihedral angles. The Ru-O-C=O
dihedral angles of 10 and 11 are 139.9 and 13.48, respective-
ly, and the O=C-O-C dihedral angles are ꢀ7.2and ꢀ173.48,
By comparing the energetics of Routes I and II described
above, one finds that Route II is favored over Route I. The
experiments described in the preceding section show that
the presence of electron-withdrawing groups on the epox-
ides leads to higher conversions (Table 4). It is expected that
electron-withdrawing groups, which increase the electrophi-
licity of the epoxide carbon atoms, should reduce the barrier
to the manganese-nucleophilic ring-opening step in Rou-
te II. Electron-withdrawing groups should also facilitate the
ring-closure in 11 because this step is also related to the
electrophilic attack of one of the epoxide carbon atoms on
the ruthenium-bonded oxygen in 11.
respectively. Ring-closure of 11 occurs via TS
to give 6
1–6
1
with the cyclic carbonate (the product molecule) coordinat-
ed to the ruthenium center through the oxygen atom. Final-
ly, dissociation of the cyclic carbonate from 6 and formation
of the RuꢀMn bond regenerates the bimetallic catalyst.
Energetic aspects of Routes I and II: On the basis of the
energy profiles shown in Figure 3, we can see that Route I
involves two major steps. 1) Coordination of the epoxide to
the Lewis acidic ruthenium center with heterolytic cleavage
of the RuꢀMn bond and metallocarboxylate-nucleophilic
ring-opening of the epoxide. 2) Ring-closure of intermediate
Note that the reaction barriers calculated for both Routes
I and II are very high. As mentioned above and as will be
discussed in more detail below, the reaction paths involve
heterolytic RuꢀMn bond cleavage which causes charge sepa-
5
to yield the product molecule (cyclic carbonate) and re-
generation of the catalyst. Coordination of the epoxide to
the ruthenium center and formation of the metallocarboxy-
late 3 occur sequentially in the first major step leading to a
significant decrease in entropy. The RuꢀMn heterolytic
ration. It is well recognized that gas-phase calculations,
which are now commonly carried out in computational
chemistry, for such charge separation processes always pro-
cleavage causes charge separation, giving ruthenium a
formal charge of +1 and manganese a charge of ꢀ1. The
charge separation, entropy loss, and opening of the epoxide
ring, all together, contribute to a very large barrier
[26]
duce very high reaction barriers. Since we are interested
in the comparison of Routes I and II, the relative barrier
heights are more important than the absolute barriers. Note
Chem. Eur. J. 2006, 12, 1004 – 1015
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1011

C. P. Lau, Z. Lin et al.
also that intermediates 8–10 were predicted by the calcula-
tions to be stable. However, we did not observe these spe-
cies experimentally. We suspect that the calculations might
have overestimated the electrostatic interactions between
ruthenium and oxygen and between manganese and carbon
atoms in the RuꢀO and MnꢀC bonds of the intermediates,
vored route (Route II) are shown in Figure 4. Complex 1
can be described as being composed of a square pyramidal
ꢀ
I
8
18-electron Mn d ML anion coordinated to a 16-electron
5
II
6
!
Ru d -CpML cation fragment through a dative Ru Mn
2
bond. The calculated bond length of RuꢀMn in 1 is 2.933 Š,
which is slightly longer than the corresponding bond length
(2.852 Š) in the X-ray crystal structure reported in Table 2.
The metalꢀphosphine and metalꢀcarbonyl distances are
again because gas-phase models were used.
Structures of the species in Route II: Structural details of
well-reproduced. The calculated bond lengths and bond
the optimized intermediates and transition states of the fa-
angles of 1 are in reasonably good agreement with the ex-
ꢀ
1
Figure 4. B3LYP-optimized structures for the species shown in Figure 3 (Route II). The free energies (kcalmol ) relative to the reactants are given in
parentheses. Bond lengths are given in angstroms.
1012
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1004 – 1015

Heterobimetallic RuꢀMn Complexes
FULL PAPER
perimental values. In 2, the RuꢀMn distance is considerably
lengthened to 4.803 Š, indicating that the RuꢀMn bond is
Experimental Section
[27]
completely broken. The calculated NBO natural charges
All experiments were carried out under dry nitrogen using standard
Schlenk techniques. All solvents were distilled and degassed prior to use.
Dichloromethane was distilled from calcium hydride. Tetrahydrofuran,
diethyl ether, toluene, and hexane were distilled from sodium-benzophe-
none ketyl. Methanol and ethanol were distilled from magnesium and
iodine. [Mn (CO) ] was purchased from Strem. Li(C H ) BH was pur-
of the ruthenium and manganese centers are 0.12and ꢀ0.86,
respectively, suggesting that 2 more closely resembles a
ruthenium cation/manganese anion pair. Heterolytic bond
cleavage in the gas-phase requires a huge amount of energy,
therefore, the high activation barrier for the process 1!2 is
2
10
2
5 3
[
28]
[29]
5
chased from Aldrich. [Mn
2
(CO)
8
(PPh
3
)
2
]
,
Li[Mn(CO)
5
],
[(h -
[
30]
5
[31]
5
C
5
H
5
)Ru(dppm)Cl],
[(h -C
(CH ]Ru(dppm)H],
3 4
)Ru(CO)(PPh )(CH CN)]BF
5
H
5
)Ru(dppm)H],
[h -C
5
(CH
3
)
5
]Ru-
reasonable. In the transition state TS , the O
ꢀC
2
–8
(epoxide)
(epoxide)
[8]
5
[8]
5
(
(
dppm)Cl],
[h -C
5
3
)
5
[(h -C
5
H
5
)Ru(CO)-
bond is lengthened to 1.927 Š and the C(epoxide)···Mn distance
is reduced to 3.700 Š. These features indicate that TS2–8 is
an early transition state. The ruthenium and manganese cen-
ters in 8 are bridged by an alkoxide group. In the transition
state TS9–10, the C(CO2)ꢀO(epoxide) and RuꢀO(CO2) distances are
[32]
5
[33]
dppm)]I, and [(h -C
5
H
5
3
were prepared
according to published procedures. [HMn(CO) ] was synthesized accord-
5
2 5 3
ing to a literature procedure except that Li(C H ) BH was used instead
[
34]
of Na/Hg. Propylene oxide and butadiene monoxide were purchased
from Aldrich. Epifluorohydrin, epichlorohydrin, styrene oxide, cyclohex-
ene oxide, isobutylene oxide, and 1,2-epoxyhexane were purchased from
Acros. All substrates were dried with molecular sieves before use.
shortened to 1.486 and 2.524 Š, respectively, and the C
ꢀ
(
CO2)
O(CO2) and RuꢀO
bonds are lengthened to 1.290 and
(epoxide)
Infrared spectra were recorded with a Bruker Vector 22 FT-IR spectro-
photometer. H NMR spectra were recorded with a Bruker DPX 400
1
2
.636 Š, respectively. These geometrical features indicate
that TS9–10 is a concerted four-center transition state. In the
intermediate 10, the ruthenium and manganese centers are
bridged by the carbonate group. From 10 to 11, the RuꢀOꢀ
spectrometer at 400.13 MHz. Chemical shifts (d, ppm) were measured
relative to the proton residue of the deuteriated solvent ([D
8
]THF: d=
: d=7.40 ppm). P{ H} NMR spectra were recorded with
a Bruker DPX-400 spectrometer at 161.98 MHz. The chemical shifts are
3
1
1
1
6 6
.85 ppm, C D
C=O dihedral angle changes from 139.9 to 13.48, so that the
lone pairs of the oxygen atom, which is bonded to the ruthe-
nium atom, are ready to interact with one of the carbon
atoms of the epoxide in the transition state TS11–6 in the
ring-closure process. In the transition state TS11–6, the Mnꢀ
13
1
referenced to external 85% H
spectra were recorded with
3
PO
a
4
in D
2
O (d=0.0 ppm). C{ H} NMR
Bruker DPX-400 spectrometer at
1
00.63 MHz. High-pressure NMR studies were carried out in a sapphire
NMR tube; the 10 mm sapphire NMR tube was purchased from Saphi-
kon, Milford, NH, USA, and the titanium high-pressure valve was con-
structed at the ISSECC-CNR, Firenze, Italy. Mass Spectrometry was car-
ried out with a Finnigan MAT 95S mass spectrometer. Elemental analy-
C(epoxide) distance is lengthened to 3.112Š and the C (epoxide)
O(CO2) distance shortened to 1.769 Š, typical of a late transi-
tion state. In 6, the MnꢀC and RuꢀMn distances are
ꢀ
ses were performed by M-H-W Laboratories, Phoenix, AZ, USA.
5
[(h -C
(
5
H
5
)Ru(CO)(m-dppm)Mn(CO)
] (0.032g, 0.163 mmol) was transferred
into a Schlenk flask equipped with a water condenser and loaded with a
4 2
] (1a) by H elimination: A THF
(
epoxide)
15 mL) solution of [HMn(CO)
5
4
.446 and 4.804 Š, respectively, indicating that there is no
bonding interaction between the ruthenium and manganese
5
5 5
sample of [(h -C H )Ru(dppm)H] (0.090 g, 0.163 mmol). The resulting
[27]
fragments. The calculated NBO natural charges
of the
mixture was refluxed for 24 h. After cooling to room temperature, the
solvent was removed under vacuum to afford an orange paste. Hexane
ruthenium and manganese centers are 0.10 and ꢀ0.88, re-
spectively. Similar to the process of 1!2, heterolytic bond
cleavage occurs in the 11!6 process, requiring a high activa-
(
5 mL) was added, with stirring, to obtain an orange solid which was
washed with diethyl ether (1 mL) and hexane (2mL) and then dried in
vacuo for 6 h. Yield: 0.099 g (82%). Elemental analysis calcd (%) for
tion barrier. In the transition state TS6 , the RuꢀMn dis-
–7
35 27 5 2
C H O P RuMn: C 56.39, H 3.65; found: C 56.29, H 3.61; IR (KBr):
tance is shortened to 4.493 Š and the RuꢀO distance is
lengthened to 2.545 Š. This transition state is related to dis-
sociation of the product molecule (cyclic carbonate) and re-
generation of the catalyst.
ꢀ
1
1
n˜ (CꢁO)=1710 (m), 1896 (s), 1938 (s), and 2000 cm (s); H NMR
(400.13 MHz, C , 2 58 C): d=2.90 (t, J(H,P)=9.91 Hz, 2H; PCH P),
.02 (s, 5H; Cp), 7.72–7.13 ppm (m, 20H of dppm); P{ H} NMR
161.98 MHz, C , 2 58 C): d=54.9 (d, J(P,P)=91.2Hz), 56.5 ppm (d,
6
D
6
2
3
1
1
5
(
6 6
D
+
J(P,P)=91.2Hz); ESI-MS (CH
2
Cl
2
/MeOH as solvent): m/z: 746 [M] .
5
[
(h -C
5
H
5
)Ru(CO)(m-dppm)Mn(CO)
4
+
] (1a) by metathetical reaction: A
ꢀ
5
] (0.060 g, 0.295 mmol)
THF solution (10 mL) solution of Li [Mn(CO)
was transferred with a cannula into a Schlenk flask equipped with a
water condenser and loaded with a sample of [(h -C
Conclusions
5
5 5
H )Ru(dppm)Cl]
(
0.173 g, 0.295 mmol). The mixture was refluxed for 24 h. After cooling
This work reports catalytic CO /epoxide coupling reactions
2
the solution to room temperature, the solvent was removed under
vacuum to yield a crude orange solid. Toluene (8 mL) was added to the
solid and the resulting mixture was filtered through Celite to remove the
salt. The solvent of the filtrate was removed by vacuum to give an
orange paste which was washed with diethyl ether (1 mL) and hexanes
with well-defined heterobimetallic complexes. Our study in-
dicates that cooperative participation of the metal centers of
the complexes occurs during the catalytic process. Theoreti-
cal calculations seem to support a reaction pathway involv-
ing heterolytic cleavage of the RuꢀMn bond and epoxide
(
0
2mL) and dried in vacuum for 6 h to afford the pure product. Yield:
.176 g (80%). The IR, NMR, and mass spectrometric data of the prod-
coordination to the Lewis acidic ruthenium center, ring-
opening of the epoxide by the Lewis basic manganese
uct were identical to those of the product obtained by the synthetic
method described above.
center followed by CO insertion into the RuꢀO bond to
5
2
[{h -C (CH ) }Ru(m-CO) (m-dppm)Mn(CO) ] (1b) by H2 elimination:
This complex was prepared by using the same procedure as described
above for the preparation of 1a except [{h -C
used in place of [(h -C
analysis calcd (%) for C40
5
3
5
2
3
afford the carbonato intermediate, which then undergoes
ring-closure to yield the cyclic carbonate product. The heter-
olytic metalꢀmetal bond cleavage and the ring-closure steps,
5
5
(CH
3 5
) }Ru(dppm)H] was
5
5 5
H )Ru(dppm)H]. Yield: 0.059 g (83%). Elemental
H
37
O
5
P
2
RuMn: C 58.90, H 4.57; found: C 58.77,
both of which cause charge separations, have high energy
barriers.
ꢀ1
H 4.61; IR (KBr): n˜ (CꢁO)=1710 (m), 1892(s), 1912(s), 1989 cm
(s);
1
6 6
H NMR (C D , 400.13 MHz, 258C): d=1.76 (s, 15H; methyls of Cp*),
Chem. Eur. J. 2006, 12, 1004 – 1015
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1013

C. P. Lau, Z. Lin et al.
[
37]
2
.35 (t, J(H,P)=9.1 Hz, 2H; PCH
2
P), 7.66–7.04 ppm (m, 20H of dppm);
of Hay and Wadt with a double-z valence basis set (LanL2DZ) were
3
1
1
P{ H} NMR (C
6
D
6
, 161.98 MHz, 258C): d=48.1 (d, J(P,P)=105.0 Hz),
used to describe ruthenium, manganese, and phosphorus atoms. For all
the other atoms, the standard 6-31G basis set was used. Polarization
+
[38]
5
1.2ppm (d, J(P,P)=105.0 Hz); ESI-MS (CH
2
Cl
2
/MeOH): m/z: 816 [M] .
5
functions were added for the ruthenium [z (Ru)=1.235], manganese
[
{h -C
5
(CH
3
)
5
}Ru(m-CO)
2
(m-dppm)Mn(CO)
3
] (1b) by metathetical reac-
f
[
39]
[40]
f d
[z (Mn)=2.195], and phosphorus [z (P)=0.340] atoms. All calcula-
tion: Complex 1b was synthesized by using the same procedure as de-
scribed above for the preparation of 1a by the same method except that
[
41]
tions were performed by using the Gaussian 03 software package on
PC Pentium IV computers.
5
5
[
{h -C
Yield: 0.109 g (83%).
H/D exchange between [(h -C
5 3 5 5 5
(CH ) }Ru(dppm)Cl] was used instead of [(h -C H )Ru(dppm)Cl].
CCDC-276203 (1a) and CCDC-276204 (1b) contain the supplementary
crystallographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
5
5
R
5
)Ru(dppm)D] (R=H, CH
]: In a typical experiment, the ruthenium deuteride complex
0.006 mmol) was loaded into a 5-mm NMR tube which was then sealed
3
) and
[
(
HMn(CO)
5
with a rubber septum. The tube was purged and filled with nitrogen. De-
gassed [D ]THF (0.4 mL) was added through a syringe to dissolve the
complex. A [D ]THF solution (0.4 mL) of [HMn(CO) ] (0.006 mmol)
8
8
5
1
was added to the tube using a syringe and a needle. The H NMR spec-
trum of the mixture was recorded immediately at room temperature.
Acknowledgements
Li[Mn(CO)
.17 mmol) was dissolved in THF (10 mL) in a 50 mL Schlenk flask.
Excess Li(C BH (1.0m solution in THF, 0.44 mL, 0.44 mmol,
.5 equiv) was added slowly to this solution, which was cooled to 08C,
4 3 2 8 3 2
(PPh )] (1c): A sample of [Mn (CO) (PPh ) ] (0.15 g,
We thank the Hong Kong Research Grant Council (Project Nos. PolyU
0
5
282/02P, PolyU 5006/03P, and HKUST6023/04P) for financial support.
2
5 3
H )
2
using a syringe and a needle over a period of 20 min. The solution was
stirred for 2.5 h, during which time the temperature of the reaction mix-
ture gradually increased to room temperature. The solvent was then re-
moved under vacuum to afford a crude yellow solid which was washed
with diethyl ether (3 mL). The residue was then extracted with toluene
[
1] See, for example: a) F. Torres, E. Sola, A. Elduque, A. R. Martinez,
F. J. Lohoz, L. A. Oro, Chem. Eur. J. 2000, 6, 2120–2128; b) Y.
Yuan, M. V. JimØnez, E. Sola, F. J. Lahoz, L. A. Oro, J. Am. Chem.
Soc. 2002, 124, 752–753; c) R. C. Mathews, D. K. Howell, W.-J.
Peng, S. G. Train, W. D. Treleaven, G. G. Stanley, Angew. Chem.
(
5 mL) and the solvent of the extract was removed under vacuum to
1
996, 108, 2402–2405; Angew. Chem. Int. Ed. Engl. 1996, 35, 2253–
yield a yellow solid which was washed with hexane (5 mL) and dried in
2
256; d) M. E. Broussard, B. Juma, S. G. Train, W. Peng, S. A. Lane-
vacuo. Yield: 0.10 g (74%). IR (KBr): n˜ (CꢁO)=1890 (sh), 1904 (s),
ꢀ
1
1
man, G. G. Stanley, Science 1993, 260, 1784–1788; e) J. R. Torkelson,
F. H. Antwi-Nsiah, R. McDonald, M. Cowie, J. G. Pruis, K.-J. Jalka-
nen, R. L. DeKock, J. Am. Chem. Soc. 1999, 121, 3666–3683; f) J. R.
Torkelson, R. McDonald, M. Cowie, J. Am. Chem. Soc. 1998, 120,
1
7
2
996 cm
(m);
8
H NMR (400.13 MHz, [D ]THF, 258C): d=7.44–
3
1
1
.84 ppm (m, H atoms of PPh
58C): d=74.67 ppm (s); ESI-MS (CH
with epoxides: The reactions were
3
); P{ H} NMR (161.98 MHz, [D
8
]THF,
+
2
Cl
2
/MeOH): m/z: 42 9 [M ꢀLi] .
Catalytic coupling reactions of CO
2
4
047–4048; g) M. M. Dell’Anna, S. J. Trepanier, R. McDonald, M.
carried out in a 40-mL stainless steel autoclave. In a typical run, the com-
plex (3.5 mmol) was dissolved in the epoxide (31.5 mmol) and the solu-
tion was heated under 40 bar of CO at 1008C for 45 h. The reactor was
2
Cowie, Organometallics 2001, 20, 88–99; h) Y. Ohki, H. Suzuki,
Angew. Chem. 2000, 112, 3605–3607; Angew. Chem. Int. Ed. 2000,
3
9, 3463–3465; i) T. Shima, H. Suzuki, Organometallics 2000, 19,
2420–2422; j) K. Tada, M. Oishi, H. Suzuki, Organometallics 1996,
5, 2422–2424; k) M. D. Fryzuk, S. A. Johnson, B. O. Patrick, A. Al-
binati, S. A. Mason, T. F. Koetzle, J. Am. Chem. Soc. 2001, 123,
960–3973.
cooled rapidly in an ice-bath and carefully vented. The cyclic carbonates
1
formed were isolated by vacuum distillation and analyzed by H NMR
1
spectroscopy.
5
Crystallographic analysis of [(h -C
5
H
5
)Ru(CO)(m-dppm)Mn(CO)
] (1b): Crystals of 1a
and 1b suitable for X-ray diffraction studies were obtained by layering
hexane on CH Cl solutions of the complexes. A suitable crystal of 1a or
b was mounted on a Bruker CCD area detector diffractometer and sub-
jected to MoKa radiation (l=0.71073 Š) from a generator operating at
0 kV and 30 mA. The intensity data of 1a and 1b were collected in the
range of 2q=3–558 with oscillation frames of f and w in the range of 0–
808; 1321 frames were recorded in four shells. An empirical absorption
4
] (1a)
3
5
5 3 5 2 3
and [{h -C (CH ) }Ru(m-CO) (m-dppm)Mn(CO)
[
[
2] a) R. D. Adams, F. A. Cotton, Catalysis by Di- and Polynuclear
Metal Complexes, Wiley-VCH, New York, 1998; b) P. Braunstein, J.
Rose in Comprehensive Organometallic Chemistry, Vol. 10, 2nd ed.
2
2
1
(
Eds.: E. W. Abel, F. G. A. Stone, G. Wilkinson), Pergamon Press,
Oxford, 1995, Chapter 7.
5
3] a) L. H. Gade, Angew. Chem. 2000, 112, 2768–2789; Angew. Chem.
Int. Ed. 2000, 39, 2659–2678; b) L. H. Gade, H. Memmler, U.
Kauper, A. Schneider, S. Fabre, I. Bezongli, M. Lutz, C. Galka, I. J.
Scowen, M. McPartlin, Chem. Eur. J. 2000, 6, 692–708; c) S. Tsutsu-
minai, N. Komine, M. Hirano, S. Komiya, Organometallics 2003, 22,
1
correction based on Fourier coefficient fitting was applied using the
SADABS program (Sheldrick, 1996). The crystal structures were deter-
mined by direct methods, which yielded the positions of some of the non-
hydrogen atoms, and subsequent difference Fourier syntheses were em-
ployed to locate all of the remaining non-hydrogen atoms that did not
show up in the initial structure. Hydrogen atoms were located based on
difference Fourier syntheses connecting geometrical analysis. All non-hy-
drogen atoms were refined anisotropically with a weight function of w=
4
2
238–4247; d) K. Uehara, S. Hikichi, M. Akita, Organometallics
001, 20, 5002–5004; e) W. C. Mercer, R. R. Whittle, E. W. Bur-
khardt, G. L. Geoffroy, Organometallics 1985, 4, 68–74; f) D. A.
Roberts, W. C. Mercer, S. M. Zahurak, G. L. Geoffroy, C. W. De-
Brosse, M. E. Cass, C. G. Pierpont, J. Am. Chem. Soc. 1982, 104,
9
10–913.
2
2
2
2
2
1
o o c
/[s (F )+0.1000p] +0.0000p, where p=(F +2F )/3. Hydrogen atoms
[
[
4] a) W. Leitner, Coord. Chem. Rev. 1996, 155, 257–284; b) T. J. Marks,
Chem. Rev. 2001, 101, 953–996.
5] a) A. Behr, Angew. Chem. 1988, 100, 681–698; Angew. Chem. Int.
Ed. Engl. 1988, 27, 661–678; b) A.-A. Shaikh, S. Sivaram, Chem.
Rev. 1996, 96, 951–976.
were refined with fixed individual displacement parameters. All experi-
ments and computations were performed with a Bruker CCD area detec-
tor diffractometer and a PC computer using the Bruker Smart and
Bruker SHELXTL packages.
Computational details: Density functional theory calculations at the
[6] See, for example: a) R. L. Paddock, S. T. Nguyen, J. Am. Chem. Soc.
2001, 123, 11498–11499; b) K. Yamaguchi, K. Ebitani, T. Yoshida,
H. Yoshida, K. Kaneda, J. Am. Chem. Soc. 1999, 121, 4526–4527;
c) T. Yano, H. Matsui, T. Koiki, H. Ishiguro, H. Fujihara, M. Yoshi-
hara, T. Maeshima, Chem. Commun. 1997, 1129–1130; d) D. J.
Darensbourg, M. W. Holtcamp, Coord. Chem. Rev. 1996, 153, 155–
174; e) T. Fujinami, T. Suzuki, M. Kamiya, S. Fukuzawa, S. Sakai,
Chem. Lett. 1985, 199–200; f) H. S. Kim, J. J. Kim, B. G. Lee, O. S.
[
35]
Becke3LYP (B3LYP) level of theory were used to optimize the geome-
tries of all the reactants, intermediates and transition states. Frequency
calculations at the same level of theory were also performed to identify
all stationary points as minima (zero imaginary frequency) or transition
[
36]
states (one imaginary frequency). Intrinsic reaction coordinates (IRC)
were also calculated for the transition states to confirm that such struc-
tures indeed connect two minima. The effective core potentials (ECPs)
1014
www.chemeurj.org
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2006, 12, 1004 – 1015

Heterobimetallic RuꢀMn Complexes
FULL PAPER
Jung, H. G. Jang, S. O. Kang, Angew. Chem. 2000, 112, 4262–4264;
Angew. Chem. Int. Ed. 2000, 39, 4096–4098; g) W. J. Kruper, D. V.
Deller, J. Org. Chem. 1995, 60, 725–727; h) V. Caló, A. Nacci, A.
Monopoli, A. Fanizzi, Org. Lett. 2002, 4, 2561–2563; i) H. Kawana-
mi, Y. Ikushima, Chem. Commun. 2000, 2089–2090; j) N. Kihara, N.
Hara, T. Endo, J. Org. Chem. 1993, 58, 6198–6202; k) F. Li, C. Xia,
L. Xu, W. Sun, G. Chen, Chem. Commun. 2003, 2042–2043; l) X.-B.
Lu, B. Liang, Y.-J. Zhang, Y.-Z. Tian, Y.-M. Wang, C.-X. Bai, H.
Wang, R. Zhang, J. Am. Chem. Soc. 2004, 126, 3732–3733; m) Y.-M.
Shen, W.-L. Duan, M. Shi, J. Org. Chem. 2003, 68, 1559–1562; n) F.
Li, L. Xiao, C. Xia, B. Hu, Tetrahedron Lett. 2004, 45, 8307–8310;
o) J.-L. Jiang, F. Gao, R. Hua, X. Qiu, J. Org. Chem. 2005, 70, 381–
Chem. 2001, 15, 141–144; d) V. Mahaderan, Y. D. Y. L. Getzler,
G. W. Coates, Angew. Chem. 2001, 113, 2211–2214; Angew. Chem.
Int. Ed. 2001, 40, 2781–2784; e) see reference [6f]; f) H. S. Kim, J. J.
Kim, S. D. Lee, M. S. Lah, D. Moon, H. G. Jang, Chem. Eur. J. 2003,
9, 678–686.
[25] a) T. Tsuda, S. I. Sanada, K. Ueda, T. Saegusa, Inorg. Chem. 1976,
15, 2329–2332; b) D. J. Darensbourg, M. W. Holtcamp, G. E. Struck,
M. S. Zimmer, S. A. Niezgoda, P. Rainey, J. B. Robertson, J. D.
Draper, J. H. Reibenspies, J. Am. Chem. Soc. 1999, 121, 107–116.
[26] J. G. Cordaro, R. G. Bergman, J. Am. Chem. Soc. 2004, 126, 16912–
16929.
[27] E. D. Glendening, A. E. Reed, J. E. Carpenter, F. Weihold, NBO,
Version 3.1.
3
83.
[
7] S. S. Kristjµndóttir, J. R. Norton, Transition Metal Hydrides (Ed.: A.
Dedieu), VCH, Weinheim, 1992.
[28] D. Drew, D. J. Darensbourg, M. Y. Darensbourg, Inorg. Chem. 1975,
14, 1579–1584.
[
[
8] G. Jia, R. H. Morris, J. Am. Chem. Soc. 1991, 113, 875–883.
9] For dihydrogen bonding, see: a) R. H. Crabtree, P. E. M. Siebbahn,
O. Eisenstein, A. L. Rheingold, T. F. Koetzle, Acc. Chem. Res. 1996,
[29] J. A. Gladysz, G. M. Williams, W. Tam, D. L. Johnson, D. W. Parker,
J. C. Selover, Inorg. Chem. 1979, 18, 553–558.
[30] a) M. I. Bruce, C. Hameisten, A. G. Swincer, R. C. Wallis, Inorg.
Synth. 1982, 21, 78–84; b) R. B. King, F. G. A. Stone, Inorg. Synth.
1963, 7, 99–115.
2
9, 348–354; b) R. H. Crabtree, Science 1998, 282, 2000–2001; c) R.
Custelcean, J. E. Jackson, Chem. Rev. 2001, 101, 1963–1980.
10] M. S. Chinn, D. M. Heinekey, J. Am. Chem. Soc. 1990, 112, 5166–
175.
[
[
[31] L. Ballester, A. Gutierrez, M. F. Perpinan, J. Chem. Educ. 1989, 66,
777–778.
5
11] a) H. Matsuzaka, K. Ichikawa, T. Ishii, M. Kondo, S. Kitagana,
Chem. Lett. 1998, 1125–1126; b) L. Carlton, W. E. Lindsell, K. J.
McCullough, P. N. Preston, J. Chem. Soc. Chem. Commun. 1982,
[32] N. J. Coville, E. A. Darling, J. Organomet. Chem. 1984, 260-278,
105–111.
[33] P. M. Treichel, D. A. Komer, Synth. React. Inorg. Met.-Org. Chem.
1980, 10, 205–218.
1
001–1003; c) C. P. Casey, Y. Wang, R. S. Tanke, P. N. Hazin, E. W.
Rutter, Jr., New. J. Chem. 1994, 18, 43–50.
12] M. L. Man, Z. Zhou, S. M. Ng, C. P. Lau, Dalton Trans. 2003, 3727–
[34] E. A. McNeill, F. R. Scholer, J. Am. Chem. Soc. 1977, 99, 6243–
6249.
[
3
735.
[35] a) A. D. Becke, Phys. Rev. A 1988, 38, 3098–3100; b) A. D. Becke, J.
Chem. Phys. 1993, 98, 5648–5652; c) B. Miehlich, A. Savin, H. Stoll,
H. Preuss, Chem. Phys. Lett. 1989, 157, 200–206; d) C. T. Lee, W. T.
Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785–789.
[
[
13] D. M. Antonelli, M. Cowie, Organometallics 1990, 9, 1818–1826.
14] C. P. Casey, R. M. Bullock, F. Nief, J. Am. Chem. Soc. 1983, 105,
7
574–7580.
[
[
[
[
[
15] A. J. M. Caffyn, M. J. Mays, P. R. Raithby, J. Chem. Soc. Dalton
Trans. 1991, 2349–2356.
16] H. A. Nieuwenhuis, A. V. Loon, M. A. Moraal, D. J. Stufkens, A.
Oskam, K. Goubitz, Inorg. Chim. Acta 1995, 232, 19–25.
17] C. P. Casey, R. E. Palermo, R. F. Jordan, J. Am. Chem. Soc. 1985,
[36] a) K. Fukui, J. Phys. Chem. 1970, 74, 4161–4163; b) K. Fukui, Acc.
Chem. Res. 1981, 14, 363–368.
[37] a) P. J. Hay, W. R. Wadt, J. Chem. Phys. 1985, 82, 270–283; b) W. R.
Wadt, P. J. Hay, J. Chem. Phys. 1985, 82, 284–298; c) P. J. Hay, W. R.
Wadt, J. Chem. Phys. 1985, 82, 299–310.
[38] a) M. S. Gordon, Chem. Phys. Lett. 1980, 76, 163–168; b) P. C. Hari-
haran, J. A. Pople, Theor. Chim. Acta 1973, 28, 2 13–2 2 2 ; c) R. C.
Binning, Jr., L. A. Curtiss, J. Comput. Chem. 1990, 11, 1206–1216.
[39] A. W. Ehlers, M. Bohme, S. Dapprich, A. Gobbi, A. Hollwarth, V.
Jonas, K. F. Kohler, R. Stegmann, A. Veldkamp, G. Frenking, Chem.
Phys. Lett. 1993, 208, 111–114.
1
07, 4597–4599.
18] H. S. Chu, C. P. Lau, K. Y. Wong, W. T. Wong, Organometallics 1998,
7, 2768–2777.
1
19] a) C. Yin, Z. Xu, S.-Y. Yang, S. M. Ng, K. Y. Wong, Z. Lin, C. P.
Lau, Organometallics 2001, 20, 1216–1222; b) S. M. Ng, C. Yin,
C. H. Yeung, T. C. Chan, C. P. Lau, Eur. J. Inorg. Chem. 2004, 1788–
1
793.
20] a) Y. Blum, D. Czarkie, Y. Rahamin, Y. Shvo, Organometallics 1985.
, 1459–1461; b) Y. Shvo, D. Czarkie, Y. Rahamin, J. Am. Chem.
Soc. 1986, 108, 7400–7403; c) N. Menashe, Y. Shvo, Organometallics
991, 10, 3885–3891; d) N. Menashe, E. Salant, Y. Shvo, J. Organo-
[40] S. Huzinaga, Gaussian Basis Sets for Molecular Calculations, Elsevi-
er Science, Amsterdam, 1984.
[
4
[41] Gaussian 03 (Revision B05), M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgom-
ery, T. Vreven, Jr., K. N. Kudin, J. C. Burant, J. M. Millam, S. S.
Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani,
N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda,
O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,
J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y.
Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg,
V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O.
Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Fores-
man, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski,
B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L.
Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Na-
nayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen,
M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian, Inc., Pittsburgh,
PA, 2003.
1
met. Chem. 1996, 514, 97–102; e) C. P. Casey, S. W. Singer, D. R.
Powell, R. K. Hayashi, M. Kavana, J. Am. Chem. Soc. 2001, 123,
1
Bäckvall, J. Am. Chem. Soc. 1999, 121, 1645–1650; g) G. Csjernyik,
A. H. Éll, L. Fadini, B. Pugin, J. E. Bäckvall, J. Org. Chem. 2002, 67,
1
090–1100; f) B. A. Persson, A. L. E. Larsson, M. LeRay, J. E.
657–1662.
[
[
21] a) K.-J. Haack, S. Hashiguchi, A. Fujii, T. Ikariya, R. Noyori,
Angew. Chem. 1997, 109, 297–300; Angew. Chem. Int. Ed. Engl.
1
997, 36, 285–288; b) M. Yamakawa, I. Yamada, R. Noyori, Angew.
Chem. 2001, 113, 2900–2903; Angew. Chem. Int. Ed. 2001, 40, 2818–
821.
2
22] K. Abdar-Rashid, M. Faatz, A. J. Lough, R. H. Morris, J. Am. Chem.
Soc. 2001, 123, 7473–7474.
[
[
23] D. H. Gibson, T.-S. Ong, J. Am. Chem. Soc. 1987, 109, 7191–7193.
24] a) L. E. Martínez, J. L. Leighton, D. H. Carsten, E. N. Jacobsen, J.
Am. Chem. Soc. 1995, 117, 5897–5898; b) K. B. Hansen, J. L. Leight-
on, E. N. Jacobsen, J. Am. Chem. Soc. 1996, 118, 10924–10925; c) P.
Tascedda, M. Weidmann, E. Dinjus, E. DuÇach, Appl. Organomet.
Received: July 6, 2005
Published online: October 24, 2005
Chem. Eur. J. 2006, 12, 1004 – 1015
ꢀ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
1015