Preparation and characterization of chiral zerovalent organoruthenium aqua complexes

Article abstract of DOI:10.1021/om050664n

Enantiopure organoruthenium aqua complexes, Ru(dppe)(dmfm) ₂(H₂O) (1) [dmfm = dimethyl fumarate] and Ru(QUINAP)(dmfm)₂(H₂O) (2) [QUINAP = 1-(2- diphenylphosphino-1-naphthyl)isoquinoline], were prepared and the absolute structures were determined by X-ray crystallography. In the crystals of these complexes, the water molecule is captured in the chiral coordination environment assisted by two different hydrogen bonds; that is, a chiral center is generated on the coordinated oxygen of water. The behavior of the coordinated water in 1 and 2 was monitored by variable-temperature ¹HNMR measurement. At lower than -60 to -70 °C, the nonequivalency of the geminal protons in the coordinated water molecule was observed even in solution. On the basis of the VT NMR data and DFT study, the behavior of the coordinated water was discussed. Complex 1 reacts with ammonia to give Ru(dppe)(dmfm)₂(NH3) (4), which is the first example of the isolated mononuclear Ru(0) ammonia complex. Complex 4 was reversibly converted into 1 by the reaction with water.

Full text of DOI:10.1021/om050664n

5724
Organometallics 2005, 24, 5724-5731
Preparation and Characterization of Chiral Zerovalent
Organoruthenium Aqua Complexes
Yasuyuki Ura,† Fumiaki Tsunawaki,† Kenji Wada,† Masashi Shiotsuki,†
Teruyuki Kondo,† Syuhei Yamaguchi,‡ Hideki Masuda,‡ Atsushi Ohnishi,§ and
Take-aki Mitsudo*,†
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering,
Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan, Department of Applied Chemistry,
Faculty of Engineering, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan,
and CPI Company, Life Science Development Center, Daicel Chemical Industries, Ltd.,
Tsukuba, Ibaraki 305-0841, Japan
Received August 2, 2005
Enantiopure organoruthenium aqua complexes, Ru(dppe)(dmfm)2(H2O) (1) [dmfm )
dimethyl fumarate] and Ru(QUINAP)(dmfm)2(H2O) (2) [QUINAP ) 1-(2-diphenylphosphino-
1-naphthyl)isoquinoline], were prepared and the absolute structures were determined by
X-ray crystallography. In the crystals of these complexes, the water molecule is captured in
the chiral coordination environment assisted by two different hydrogen bonds; that is, a
chiral center is generated on the coordinated oxygen of water. The behavior of the coordinated
1
water in 1 and 2 was monitored by variable-temperature H NMR measurement. At lower
than -60 to -70 °C, the nonequivalency of the geminal protons in the coordinated water
molecule was observed even in solution. On the basis of the VT NMR data and DFT study,
the behavior of the coordinated water was discussed. Complex 1 reacts with ammonia to
give Ru(dppe)(dmfm)2(NH3) (4), which is the first example of the isolated mononuclear
Ru(0) ammonia complex. Complex 4 was reversibly converted into 1 by the reaction with
water.
Introduction
categories: (A) complexes where either of the geminal
protons is fixed by one intramolecular hydrogen bond;2-11
(B) complexes where the water molecule is fixed by two
intramolecular hydrogen bonds and stands in the chiral
coordination site.12 However, in solution the nonequiva-
lency of the geminal protons is lost due to the vigorous
motion of H2O and/or the rapid exchange with external
protons; therefore, to the best of our knowledge, inten-
sive investigation of the nonequivalency in solution has
not yet been successful.
Investigation of the behavior of a water molecule in
organometallic aqua complexes is of great interest since
it offers fundamental information useful for the metal
complex-catalyzed organic synthesis in aqueous media
or the reactions using H2O as a reagent.1 A large
number of organometallic aqua complexes have been
synthesized and investigated to date, some of which
have chemically nonequivalent geminal protons of the
coordinated H2O connected to adjacent ligand(s) through
intramolecular hydrogen bonding in the solid state, as
revealed by their X-ray crystallography.2-12 Such aqua
complexes can be classified into either of the following
We previously reported the synthesis of a racemic
zerovalent ruthenium aqua complex, Ru(dppe)(dmfm)2-
(H2O) (1) [dppe ) 1,2-bis(diphenylphosphino)ethane,
dmfm ) dimethyl fumarate], by reacting rac-Ru(η6-cot)-
13
(dmfm)2 [cot ) 1,3,5-cyclooctatriene] with H2O and
* To whom correspondence should be addressed. Phone: +81 75 383
2506. Fax: +81 75 383 2507. E-mail: mitsudo@scl.kyoto-u.ac.jp.
† Kyoto University.
dppe, where H2O is captured in the chiral coordination
environment (eq 1).14 Complex 1 belongs to category B;
‡ Nagoya Institute of Technology.
§ Daicel Chemical Industries, Ltd.
(1) For reviews, see: (a) Joo´ F. In Catalysis by Metal Complexes:
Aqueous Organometallic Catalysis 23; James, B. R., P., van Leeuwen,
W. N. M., Eds.; Kluwer Academic Publishers: Dordrecht, 2001; p 300.
(b) Cornils, B.; Herrmann, W. A. In Aqueous-Phase Organometallic
Catalysis: Concept and Applications, 2nd & rev. ed.; Wiley-VCH:
Weinheim, Germany, 2004; p 750. (c) Koelle, U. Coord. Chem. Rev.
1994, 135/136, 623. (d) Li, C.-J.; Chan, T.-H. In Organic Reactions in
Aqueous Media; John Wiley & Sons: New York, 1997; p 199. (e) Auge,
J.; Beletskaya, I. P.; Cheprakov, A. V.; Fringuelli, F.; Gajewski, J. J.;
Garner, P. P.; Grieco, P. A.; Kobayashi, S.; Lubineau, A.; Parker, D.
T.; Piermatti, O.; Pizzo, F.; Quenau, Y. In Organic Synthesis in Water;
Grieco, P. A., Ed.; Thomson Science: London, 1998; p 310. (f) Grundler,
P. V.; Laurenczy, G.; Merbach, A. E. Helv. Chim. Acta 2001, 84, 2854.
(2) Zhao, Q.; Wang, X.; Fang, R.; Tiekink, E. R. T. Acta Crystallogr.
2003, E59, m719.
(5) Fettouhi, M.; Khaled, M.; Waheed, A.; Golhen, S.; Ouahab, L.;
Sutter, J.; Kahn, O. Inorg. Chem. 1999, 38, 3967.
(6) Cucciolito, M. E.; Panunzi, A.; Ruffo, F.; Albano, V. G.; Monari,
M. Organometallics 1999, 18, 3482.
(7) Halfen, J. A.; Bodwin, J. J.; Pecoraro, V. L. Inorg. Chem. 1998,
37, 5416.
(8) Sobolev, A. N.; Miminoshvili, E. B.; Miminoshvili, K. E.; Sak-
varelidze, T. N. Acta Crystallogr. 2003, E59, m836.
(9) Koman, M.; Baloghova, Z.; Valigura, D. Acta Crystallogr. 1998,
C54, 1277.
(10) Clegg, W.; Straughan, B. P. Acta Crystallogr. 1989, C45, 1992.
(11) Bailey, A.; Griffith, W. P.; Leung, D. W. C.; White, A. J. P.;
Williams, D. J. Polyhedron 2004, 23, 2631.
(12) Kuznetsov, V. F.; Yap, G. P. A.; Alper, H. Organometallics 2001,
20, 1300.
(3) Hokelek, T.; Necefoglu, H. Acta Crystallogr. 1999, C55, 545.
(4) Zhang, X.; Fan, C.; Wang, W.; Chen, C.; Liu, Q. Acta Crystallogr.
2002, E58, m688.
(13) Mitsudo, T.; Suzuki, T.; Zhang, S.-W.; Imai, D.; Fujita, K.;
Manabe, T.; Shiotsuki, M.; Watanabe, Y.; Wada, K.; Kondo, T. J. Am.
Chem. Soc. 1999, 121, 1839.
10.1021/om050664n CCC: $30.25 © 2005 American Chemical Society
Publication on Web 10/14/2005

Chiral Zerovalent Organoruthenium Aqua Complexes
Organometallics, Vol. 24, No. 23, 2005 5725
the coordinated H2O is bound by the two nonequivalent
intramolecular hydrogen bonds, and thus the oxygen
atom of H2O becomes a chiral center. We report here
the synthesis of enantiopure zerovalent organoruthe-
nium aqua complexes and the successful observation of
the nonequivalent geminal protons of the coordinated
H2O in solution. The detailed behavior of the coordi-
nated H2O and further reaction of 1 with ammonia will
be discussed.
Results and Discussion
Optical Resolution and Solid-State Structures
of Enantiomeric Complexes 1a and 1b. The racemic
aqua complex 1 was prepared as reported previously.14
Spontaneous resolution of rac-1, which occurred during
recrystallization from chlorobenzene/pentane, enabled
the isolation of each enantiomer 1a and 1b in pure form.
The solid-state structures of 1a and 1b determined by
X-ray crystallography are shown in Figure 1, and their
absolute configurations were confirmed by the values
of the Flack parameters,15 0.00(4) for 1a and 0.03(4) for
1b, as refined by least-squares techniques. The water
protons (H1, H2) could be found on the basis of Fourier
maps. As clearly shown, the oxygen atom of H2O (O1)
is bound to ruthenium, and the two hydrogen atoms are
located close to the carbonyl oxygen atoms of dimethyl
fumarate ligands (O2, O3). The distances of O1‚‚‚O2
(2.652(5) Å) and O1‚‚‚O3 (2.643(5) Å) for 1a and
O1‚‚‚O2 (2.657(6) Å) and O1‚‚‚O3 (2.627(6) Å) for 1b
reflect the existence of intramolecular hydrogen bonds
H1‚‚‚O2 and H2‚‚‚O3. The coordinative directions of the
two dimethyl fumarate ligands differ from each other;
in 1a the dimethyl fumarate ligands coordinate to
ruthenium by the (re, re)-enantioface, and in 1b by the
(si, si)-enantioface. Thus, the water protons H1 and H2
are fixed in different chemical environments, and a
chiral center is generated on O1, in each enantiomer.
Optical resolution of 1a and 1b by HPLC equipped with
a chiral column was also successfully performed to give
1a in 98% ee and 1b in 92% ee. CD spectra of these
separated complexes measured in CHCl3 clearly showed
an enantiomeric relation (Figure 2).
Figure 1. Molecular structures of 1a (top) and 1b (bot-
tom). Thermal ellipsoids are set at 50% probability. Solvent
and all hydrogen atoms except water are omitted for clarity.
Dashed bonds between water protons (H1, H2) and oxygen
atoms of dimethyl fumarates (O2, O3) exhibit hydrogen
bonds.
meric ligand, (S)-QUINAP [QUINAP ) 1-(2-diphen-
ylphosphino-1-naphthyl)isoquinoline],16 instead of dppe,
we obtained Ru((S)-QUINAP)(dmfm)2(H2O) (2a) in 29%
yield as a single enantiomer (eq 2). However, fine single
crystals suitable for X-ray analysis could not be obtained
by recrystallization of 2a. Further investigation revealed
that rac-2, which was synthesized by the reaction of rac-
Ru(η6-cot)(dmfm)2 with rac-QUINAP in the presence of
H2O, was successfully recrystallized from chlorobenzene/
pentane to give fine yellow single crystals. The X-ray
structure corresponding to the enantiomer 2a is exhib-
ited in Figure 3. The space group (P21/n) indicated that
the crystals are racemic. Again, the water protons (H1,
H2) were located on the basis of the Fourier map.
Complex 2 also has a distorted trigonal bipyramidal
structure like 1. The phosphorus atom of QUINAP
Synthesis and Solid-State Structure of Novel
Zerovalent Ruthenium QUINAP Aqua Complex 2.
By using an optically active P-N bidentate atropiso-
(14) Shiotsuki, M.; Miyai, H.; Ura, Y.; Suzuki, T.; Kondo, T.; Mitsudo,
T. Organometallics 2002, 21, 4960.
(15) Flack, H. D.; Bernardinelli, G. J. Appl. Crystallogr. 2000, 33,
1143.
(16) Lim, C. W.; Tissot, O.; Mattison, A.; Hooper, M. W.; Brown, J.
M.; Cowley, A. R.; Hulmes, D. I.; Blacker, A. J. Org. Process Res. Dev.
2003, 7, 379.

5726 Organometallics, Vol. 24, No. 23, 2005
Ura et al.
Figure 3. Molecular structure of 2 (the structure corre-
sponding to 2a is shown). Thermal ellipsoids are set at
50% probability. Solvent and all hydrogen atoms except
water are omitted for clarity. Dashed bonds between water
protons (H1, H2) and oxygen atoms of dimethyl fumarates
(O2, O3) exhibit hydrogen bonds. Selected bond distances
(Å) and angles (deg): Ru1-P1 ) 2.2469(9), Ru1-O1 )
2.222(2), Ru1-C1 ) 2.115(3), Ru1-C2 ) 2.167(3), Ru1-
C3 ) 2.219(3), Ru1-C4 ) 2.140(3), Ru1-N1 ) 2.196(3),
C1-C2 ) 1.461(5), C3-C4 ) 1.435(5), P1-Ru1-N1 )
81.17(7), O1-Ru1-N1 ) 88.85(9), C1-Ru1-C4 ) 90.6(1),
C2-Ru1-N1 ) 105.0(1), C3-Ru1-N1 ) 86.7(1).
Figure 2. CD spectra of 1a (c ) 2.5 × 10-5 M) and 1b (c
) 3.7 × 10-5 M) in CHCl3. For 1a: λmax 270 nm (∆ꢀ +45),
381 (-5). For 1b: λ 268 nm (∆ꢀ -41), 378 (+5).
occupies an axial position and is trans to the water
molecule, and the nitrogen atom is located at an
equatorial position. The QUINAP ligand coordinates to
ruthenium to avoid steric hindrance by the carbomethoxy
groups of dimethyl fumarates located at equatorial
positions. The distance O1-O2 (2.677(3) Å) is similar
to those for 1a and 1b, while O1-O3 (2.581(3) Å) is
slightly shorter, by ca. 0.04-0.06 Å.
1
Variable-Temperature H NMR Study of Com-
plexes 1 and 2: Observation of the Nonequivalent
Geminal Protons of the Coordinated H2O and
Their Positional Exchange in Solution. The behav-
ior of H2O in rac-1 was examined by variable-temper-
ature 1H NMR spectroscopic analysis in CD2Cl2 (Figure
4a, left). The signal for the water protons appears as a
broad singlet at 4.68 ppm at 25 °C. As the temperature
was lowered, the broad singlet gradually sharpened (0
to -40 °C) with the appearance of a small shoulder
peak at a slightly lower magnetic field, and the top of
the signal began to split into two peaks at -70 °C.
Further splitting was observed by cooling to -80 °C,
with peaks at 4.64 and 4.52 ppm. This splitting indicates
that the geminal protons of the coordinated H2O are
observed nonequivalently and their positional exchange
is slowed by a decrease in temperature. The small
shoulder peak observed below -40 °C may be due to
the flip of the carbomethoxy group of the dmfm ligand.
This flip can also be one possible reason for the
broadening of the signal at 25 to ∼0 °C as well as other
Figure 4. Experimental 1H NMR spectra of 1 (a; left) and
2 (b; left) in CD2Cl2 at temperatures of 25 to -80 °C, and
1
simulated H NMR spectra of 1 (a; right) and 2 (b; right)
at -40 to -80 °C. Chemical shifts are referenced to internal
solvent resonances and reported relative to SiMe4. The
signal at 5.3 ppm in (b, left) derives from the solvent.
factors such as an exchange of the water molecule with
external ones, which will be discussed later.
1
For rac-2, the H NMR signal of the water protons
appeared as a broad singlet at 3.98 ppm at 25 °C,
overlapping with another peak (Figure 4b, left). The
singlet peak comparatively shifted to lower magnetic
field and broadened by cooling, in contrast to that of 1.
Two broad singlets appeared again at around 5.7 and
4.8 ppm at -60 °C, respectively, the shapes of which

Chiral Zerovalent Organoruthenium Aqua Complexes
Organometallics, Vol. 24, No. 23, 2005 5727
Scheme 1. Possible Positional Exchange Process of the Water Protons via Rotation and Inversion
became sharper by further cooling to -80 °C. A 1H-1H
COSY spectrum of 2 measured at -90 °C clearly showed
the correlation between the two split singlets, re-
vealing that these signals are assigned to the non-
equivalent geminal protons of the identical water mol-
ecule (Figure 5).
coordination of the water molecule can also explain the
positional exchange of the water protons,17 whereas it
seems to be unlikely (vide infra).
Density Functional Study on the Positional
Exchange Process of the Water Protons: (a) Water
Rotation and Inversion. On the basis of the as-
sumption depicted in Scheme 1, the exchange process
was investigated theoretically by the DFT method.
Ru(dmpe)(dmfm)2(H2O) (A) [dmpe ) 1,2-bis(dimeth-
ylphosphino)ethane] was used as a model complex. The
geometries of complex A, intermediate B (corresponding
to 3 in Scheme 1), and transition states for the rotation
(TSrot) and the inversion (TSinv) were optimized by the
B3LYP method with the basis set composed of the com-
bination of SDD for Ru, the 6-31G(d,p) basis set for all
oxygen and phosphorus atoms as well as two hydrogen
atoms of coordinated water, and the 6-31G basis set for
all other hydrogen and carbon atoms (see Experimental
Section for details). The energetic profile and the
optimized structures for A, B, TSrot, and TSinv are
exhibited in Figure 6. The upper structures correspond
to the side views, and the lower ones the bottom views.
The geometries around the coordinated H2O for A,
TSrot, B, and TSinv are shown in Figure 7. As H2O in A
rotates clockwise on the Ru1-O1 axis, both hydrogen
bonds are weakened gradually, and in TSrot, the original
O3‚‚‚H2 hydrogen bond is greatly lengthened. At this
stage, the O1‚‚‚O3 distance (2.856 Å) is longer by ca.
0.2 Å than that in A (2.670 Å). Although the distance
of O1‚‚‚O2 also becomes slightly longer (2.713 Å) than
that in A (2.626 Å), the angle of H1-O1-H2 is consid-
erably smaller than that in A. The theoretical energy
barrier for the water rotation (13.6 kcal mol-1 based on
∆E0) is moderately consistent with the activation en-
thalpy for 1 obtained experimentally (10.8 kcal mol-1).
Another rotation barrier, TSrot′ (counterclockwise direc-
Figure 5. 1H-1H COSY spectrum of 2 measured at -90
°C. The correlation between the two split singlets of the
water protons (5.71 and 4.79 ppm) can be observed clearly
(indicated by arrows).
Line-shape analysis of the 1H NMR spectra measured
at -40 to -80 °C for 1 and 2 was performed by
computer simulation (Figure 4a and 4b, right). The
obtained activation parameters based on the Eyring plot
were ∆Hq ) 10.8 kcal mol-1 and ∆Sq ) 4.3 cal mol-1
K-1 for 1 and ∆Hq ) 7.5 kcal mol-1 and ∆Sq ) -10.9
cal mol-1 K-1 for 2. The slightly positive ∆Sq value for
1 indicates that the positional exchange of water protons
occurs in an intramolecular manner. On the other hand,
the negative ∆Sq value for 2 implies that another
molecule such as a solvent (CD2Cl2) may participate in
the transition state to lower the energy barrier. This
exchange occurs even at -80 °C at a rate of ∼30 Hz for
1 and ∼50 Hz for 2.
tion), is slightly higher than TSrot, 15.5 kcal mol-1
,
because of the cleavage of the stronger hydrogen bond
O2‚‚‚H1. In the next step from TSrot to the intermediate
B, complete loss of the hydrogen bonds O3‚‚‚H2 and
O2‚‚‚H1 occurs; instead, a new strong hydrogen bond
O2‚‚‚H2 is formed. The distance of O1‚‚‚O3 (3.010 Å),
where no hydrogen bond exists, is further lengthened
by 0.15 Å than that in TSrot. The hydrogen bond
O2‚‚‚H2 formed in B is maintained in TSinv. The
position of H1 is somewhat shifted to be close to the
carbonyl oxygen O3; thus, the distance of O3‚‚‚H1 in
TSinv is fairly shorter than that in B. The O1‚‚‚O3
distance is also shortened from 3.010 to 2.933 Å. The
angles around the water molecule (H1-O1-H2,
Ru1-O1-H1, and Ru1-O1-H2) are all increased by
It is assumed that this process proceeds via both the
rotation of H2O around the Ru-O axis and the inversion
(Scheme 1). The rotation by ∼120° occurs to give the
intermediate 3, along with the dissociation of the
hydrogen bonds HA‚‚‚OA and HB‚‚‚OB and the formation
of a new hydrogen bond HB‚‚‚OA. The inversion of H2O
along with the formation of another hydrogen bond
HA‚‚‚OB completes the intramolecular positional ex-
change of the water protons. The dissociation/re-
(17) Helm, L.; Merbach, A. E. Chem. Rev. 2005, 105, 1923.

5728 Organometallics, Vol. 24, No. 23, 2005
Ura et al.
Figure 6. Energetic profile for the positional exchange of water protons via rotation and inversion.
Figure 7. Simplified side and bottom views for A, TSrot, B, and TSinv. Selected bond distances (Å) and angles (deg) are
shown.
4-10° in TSinv (111.2°, 124.7°, and 108.0°) compared
with those in B (107.0°, 115.0°, and 103.2°). The
Ru-OH2 moiety in TSinv has an intermediate structure
between pyramidal and trigonal planar, and the inver-
sion from B to A seems to proceed smoothly with nearly
no barrier.
energy barrier of the associative pathway for A is ca.
18 kcal mol-1, still somewhat greater than the experi-
mentally obtained ∆Hq for 1 and 2.
(c) Flipping Motion of the Carbomethoxy Groups.
The flip of the carbomethoxy groups of dmfm ligands
having hydrogen bonds with the water protons was
also theoretically investigated. By rotating one of the
carbomethoxy groups by ca. 180° to have a hydrogen
bond between the water proton and the methoxy oxy-
gen atom, the formed complexes were destabilized by
2.6-5.8 kcal mol-1, and the rotation barriers were
estimated to be 13.4-17.8 kcal mol-1. The aqua complex
having hydrogen bonds with both methoxy oxygen
atoms was unstable by 8.9 kcal mol-1 compared with
the stable structure of complex A.
Reaction of Aqua Complex 1 with Ammonia. The
coordinated H2O in 1 has been found to be labile. For
example, the reaction of 1 with 1 atm of CO dissociates
the water;14 the amount of the liberated water was
exactly determined by the Karl Fischer method,18 and
85% of the theoretical amount of water was detected.
Further investigations on the reactivity of 1 were
(b) Possibility for the Exchange of the Coordi-
nated H2O with an External H2O. As alternative
mechanisms for the positional exchange of the water
protons, dissociative and associative exchange of the
coordinated H2O with an external one can be considered.
The dissociation of H2O from A affords a coordinatively
unsaturated 16-electron species, Ru(dmpe)(η2-dmfm)2,
which is more thermodynamically unstable by 30.8 kcal
mol-1 than A according to the calculation. A coordina-
tively saturated isomer of Ru(dmpe)(η2-dmfm)2, where
a carbonyl oxygen atom of dmfm occupies the coordina-
tion site, was also calculated to be considerably more
unstable than A, by 29.4 kcal mol-1. These values are
fairly greater than the observed ∆Hq for 1 and 2
obtained by the line-shape analysis. Judging from the
observed ∆Sq, both the dissociative and associative
mechanisms are unlikely below -40 °C. DFT calcula-
tions at the B3LYP/LANL2DZ level show that the
(18) Scholz, E. Karl Fischer Titration; Springer-Verlag: Berlin, 1984.

Chiral Zerovalent Organoruthenium Aqua Complexes
Organometallics, Vol. 24, No. 23, 2005 5729
complexes 1 and 2 by ca. 0.13-0.19 Å. Although a low-
temperature 1H NMR measurement of 4 was also
performed, no clear peak splitting of the ammonia
protons was observed even at -90 °C. The calculated
energy barrier for ammonia rotation in Ru(dmpe)-
(dmfm)2(NH3) is 4.6 kcal mol-1, which is lower than that
for the water rotation by 9.0 kcal mol-1. These results
are all consistent with decrease of the binding energy
of the hydrogen bonds, compared with those in 1 and 2.
The ligand displacement reaction shown in eq 3 was
revealed to be reversible by the NMR spectra; that is,
complex 4 readily reacts with an excess amount of water
to afford aqua complex 1 again.
Conclusion
Enantiopure organoruthenium aqua complexes 1a,
1b, and 2a were synthesized, and the nonequivalent
geminal protons of the coordinated H2O in solution were
successfully observed. The positional exchange of the
geminal protons was strongly suggested to involve the
rotation and inversion of H2O by DFT calculation; the
rotation has a higher energy barrier and the value was
moderately consistent with that of the activated en-
thalpy obtained experimentally, and the inversion pro-
ceeded very smoothly. The Ru(0) ammonia complex 4
was successfully synthesized by reacting 1 with am-
monia, and the energy barrier for the ammonia rotation
was calculated, which was fairly lower than that for the
water rotation. The information obtained here would
assist in understanding the behavior of water molecules
in general organometal aqua complexes, which leads to
the development of the chemistry of water and related
fields.
Figure 8. Molecular structure of 4 (the structure corre-
sponding to 4a is shown). Thermal ellipsoids are set at 50%
probability. Solvent and all hydrogen atoms except am-
monia are omitted for clarity. Dashed bonds between
ammonia protons (H1, H2) and oxygen atoms of dimethyl
fumarates (O1, O2) exhibit hydrogen bonds. Selected bond
distances (Å) and angles (deg): Ru1-P1 ) 2.3064(9), Ru1-
P2 ) 2.3841(9), Ru1-C1 ) 2.150(3), Ru1-C2 ) 2.192(3),
Ru1-C3 ) 2.212(3), Ru1-C4 ) 2.152(3), Ru1-N1 ) 2.200-
(3), C1-C2 ) 1.440(5), C3-C4 ) 1.445(5), P1-Ru1-P2 )
82.54(3), P2-Ru1-N1 ) 94.13(8), P2-Ru1-C2 ) 89.91-
(9), P2-Ru1-C3 ) 102.71(9), C1-Ru1-C4 ) 92.1(1).
carried out, where displacement of the water moiety was
expected. Among the small polar molecules, ammonia
in dioxane readily reacted with rac-1 at ambient tem-
perature (eq 3). After removal of the solvent, a green
solid of a novel ammonia complex, rac-Ru(dppe)(dmfm)2-
(NH3) (4), was obtained in 88% isolated yield, and the
single crystals were obtained by recrystallization from
chloroform/pentane as racemates (the space group was
P1h). The X-ray structure is shown in Figure 8. Com-
plex 4 is the first example of the isolated mononuclear
Ru(0) ammonia complex, whereas a large number of Ru
ammonia complexes in higher oxidation states have
been reported so far. Low-valent transition metal am-
monia complexes are intriguing, since oxidative addition
of ammonia may take place to afford amido hydride
complexes.19 In 4, a chiral center is generated on the
nitrogen atom of the coordinated NH3.
Experimental Section
General Methods. All manipulations were performed in
an argon atmosphere using standard Schlenk techniques.
Racemic complex 1 was prepared by the reported procedure.14
All solvents were distilled under argon over appropriate drying
reagents (sodium, calcium hydride, sodium-benzophenone, and
calcium chloride). NMR spectra were recorded on JEOL
EX-400 (FT, 400 MHz (1H), 100 MHz (13C), 162 MHz (31P))
spectrometers. Chemical shift values (δ) for 1H and 13C are
referenced to internal solvent resonances and reported relative
to SiMe4. Chemical shifts for 31P are referenced to an external
P(OMe)3 resonance and reported relative to H3PO4. IR spectra
were recorded on a Nicolet Impact 410 FT-IR spectrometer.
Melting points were determined under argon on a Yanagimoto
micro melting point apparatus. HR-MS spectra were recorded
on JEOL SX102A spectrometers with m-nitrobenzyl alcohol
(m-NBA) as a matrix. Elemental analyses were performed at
the Microanalytical Center of Kyoto University. Circular
dichroism spectra were recorded on a JASCO J-750 spectropo-
larimeter.
Spontaneous Resolution of Aqua Complex 1. Racemic
complex 1 (ca. 3 mg) was dissolved in chlorobenzene (ca. 0.3
mL), and pentane (5 mL) was placed on the chlorobenzene
solution. After 1 day, several crystals were formed. Unfortu-
nately each enantiomer could not be separated even under
microscope. Some of the crystals were confirmed to be 1a and
others were 1b, respectively, by means of X-ray crystal-
lography.
(19) (a) Zhao, J.; Goldman, A. S.; Hartwig, J. F. Science 2005, 307,
1080. (b) Casalnuovo, A. L.; Calabrese, J. C.; Milstein, D. Inorg. Chem.
1987, 26, 971. (c) Hillhouse, G. L.; Bercaw, J. E. J. Am. Chem. Soc.
1984, 106, 5472. (d) Bryan, E. G.; Johnson, B. F. G.; Lewis, J. J. Chem.
Soc., Dalton Trans. 1977, 1328.
The distances N1-O1 (2.791(3) Å) and N1-O2 (2.815-
(2) Å) are longer than the corresponding ones in aqua

5730 Organometallics, Vol. 24, No. 23, 2005
Ura et al.
Optical Resolution of 1. Racemic complex 1 (20 mg) was
dissolved in chloroform (1 mL), and 2 mL of a hexane/acetone/
THF mixture (85/10/5) was added. The solution was injected
in four portions into a chiral column (CHIRALPAK IA, Daicel
Chemical Industry, φ 2.0 × 25 cm). Elution with a mixture of
hexane/acetone/THF (85/10/5) and subsequent evaporation of
the obtained fractions and drying under vacuum afforded
enantiomers 1a (7 mg) in 98% ee and 1b (6 mg) in 92% ee.
Preparation of Aqua Complex 2. Ru(η6-cot)(dmfm)2 (1.07
g, 2.16 mmol)13 in distilled 1,2-dichloroethane (6 mL)/H2O (9
mL) solution was stirred at 60 °C for 1 h. rac-QUINAP (952
mg, 2.16 mmol)16 in distilled 1,2-dichloroethane (10 mL) was
then added dropwise, and the mixture was stirred at 60 °C
for 2 h. After the solvent and water were evaporated, the
residue was dissolved in distilled chloroform and then chro-
matographed on alumina (φ 2.0 × 30 cm, Merck No. 1.01097,
activity II-III). Elution with chloroform gave an orange
solution, from which the solvent was evaporated. The brown
residue was dissolved in chloroform (6 mL), and then pentane
(150 mL) was added. The resulting orange precipitate was
collected by filtration, washed with pentane (10 mL × 2), and
dried under vacuum to give 2 (704 mg, 0.83 mmol, 38%).
Ru(rac-QUINAP)(dmfm)2(H2O) (2). Mp: 129-131 °C
(dec). IR (KBr disk): 3058, 2949, 1691, 1655, 1433, 1317, 1172
cm-1. 1H NMR (400 MHz, CD2Cl2): δ 9.20 (d, 1H, J ) 6.3 Hz),
7.94 (d, 1H, J ) 8.3 Hz) 7.87 (d, 1H, J ) 7.8 Hz), 7.78 (d, 1H,
J ) 7.8 Hz), 7.66 (d, 1H, J ) 6.3 Hz), 7.62 (d, 1H, J ) 8.3 Hz),
7.52-7.47 (m, 3H), 7.40-7.27 (m, 4H), 7.08 (dt, 1H, J ) 1.0,
7.8 Hz) 6.95 (t, 1H, J ) 7.8 Hz), 6.79 (d, 1H, J ) 7.8 Hz), 6.62
(d, 1H, J ) 8.3 Hz), 6.54 (d, 1H, J ) 8.0 Hz), 6.52 (d, 1H, J )
8.0 Hz), 6.48 (t, 1H, J ) 7.6 Hz), 6.30 (t, 2H, J ) 7.6 Hz), 4.99
(br s, 2H, H2O), 3.95 (d, 1H, J ) 9.8 Hz, CH of dmfm), 3.73
(dd, 1H, J ) 3.2, 9.5 Hz, CH of dmfm), 3.69 (s, 3H, OCH3 of
dmfm), 3.60 (s, 3H, OCH3 of dmfm), 3.31 (s, 3H, OCH3 of
dmfm), 2.95 (d, 1H, J ) 9.8 Hz, CH of dmfm), 2.90 (s, 3H,
OCH3 of dmfm), 2.73 (dd, 1H, J ) 1.5, 9.3 Hz, CH of dmfm).
13C NMR (100 MHz, CD2Cl2): δ 178.9 (CdO, 2C), 178.6
(CdO, 2C), 162.8, 148.4, 139.5, 139.0, 137.9 (d, J ) 13.3 Hz),
136.0, 135.8, 135.7, 134.6 (d, J ) 9.2 Hz), 133.8, 133.4 (d,
J ) 7.4 Hz), 133.3, 133.2, 131.2, 130.1, 129.7, 128.9 (2C),
128.4, 128.1, 127.6 (2C), 127.5, 127.3, 126.6 (2C), 126.2,
126.1, 126.0, 124.5, 120.2, 52.9 (s, dCH), 52.3 (d, J ) 2.5 Hz,
dCH), 51.4 (OMe), 51.3 (OMe), 50.9 (d, J ) 4.2 Hz, dCH),
50.8 (OMe), 50.5 (OMe), 42.8 (s, dCH). 31P NMR (162 MHz,
CD2Cl2): δ 63.0. HR-MS(FAB-mNBA): m/z 847.1497, calcd for
C43H40NO9PRu 847.1484. Anal. Calcd for C43H40NO9PRu: C,
60.99; H, 4.76; N, 1.65. Found: C, 60.82; H, 4.78; N, 1.42.
Complex 2a was prepared by a manner similar to that for
2. In place of rac-QUINAP, (s)-QUINAP was used to give 2a
in 29% yield.
(d, J ) 2.5 Hz), 127.7, 127.7, 127.1, 127.1, 51.4 (OMe), 51.4
(OMe), 51.1 (OMe), 51.0 (dd, J ) 1.7, 6.7 Hz, CH of dmfm),
50.7 (OMe), 49.1 (dd, CH of dmfm, J ) 2.5, 10.0 Hz), 46.6 (dd,
CH of dmfm, J ) 1.7, 5.8 Hz), 45.0 (dd, olefin of dmfm, J )
2.5, 3.3 Hz), 29.3 (dd, PCH2, J ) 18.8, 13.3 Hz), 23.7 (dd, PCH2,
J ) 9.2, 19.2 Hz). 31P NMR (162 MHz, CD2Cl2): δ 61.2, 45.5.
Anal. Calcd for C38H43NO8P2Ru‚0.5CHCl3: C, 53.49; H, 5.07;
N, 1.62. Found: C, 53.39; H, 5.09; N, 1.32.
Crystallographic Study for 1a, 1b, 2, and 4. Crystals
stable for X-ray diffraction measurements obtained by recrys-
tallization from chlorobenzene/pentane were mounted on glass
fibers. The diffraction data were collected with a Rigaku
Mercury CCD area detector using graphite-monochromated
Mo KR radiation (λ ) 0.71069 Å) with the oscillation technique.
Crystal data and experimental details are listed in Table 1.
All structures were solved by a combination of direct methods
and Fourier techniques. Non-hydrogen atoms were anisotro-
pically refined by full-matrix least squares calculations. Hy-
drogen atoms were located from the difference Fourier maps
but not refined. Refinements were continued until all shifts
were smaller than one-tenth of the standard deviations of the
parameters involved. Atomic scattering factors and anomalous
dispersion terms were taken from the International Tables for
X-ray Crystallography.20 All calculations were carried out with
a Japan SGI workstation computer using the CrystalStructure
crystallographic software package.21,22
Dynamic NMR Simulation for 1 and 2. The multispin
dynamic NMR simulations were performed using the WinD-
NMR program package.23 For complex 1, the simulation
pattern of 2×2-spin was selected, in which two independent
sets of exchangeable protons, HA-HB and HA′-HB′, were
considered. For both sets, the differences of chemical shifts of
two exchangeable protons were set to be 41.5 Hz. Both sets of
protons were postulated to be exchange at the same rate, kab.
The exchange between HA and HA′ (or HB and HB′) was not
considered at temperatures below -40 °C. The signal of the
HA′ (or HB′) proton was located at the lower field than that of
HA (or HB) by 11.5 Hz, and the ratio of HA plus HB versus
HA′ plus HB′ protons was set to be 0.83/0.17. For complex 2,
the simple 2-spin simulation pattern was employed. The
natural line width for each spectrum was determined on the
basis of the measurement of nonexchanging peaks of the
complexes.
Theoretical Calculations. To consistently compare the
single-point energies of model complexes, calculations were
carried out using density functional theory (DFT) optimized
geometries. Calculations were performed using the Gaussian
03 RevB.0424 implementation of B3LYP [Becke three-param-
(20) Ibers, J. A., Hamilton, W. C., Eds. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, UK, 1974; Vol. IV.
(21) CrystalStructure 3.6.0, Crystal Structure Analysis Package;
Rigaku and Rigaku/MSC, 2000-2004.
(22) Watkin, D. J.; Prout, C. K.; Carruthers, J. R.; Betteridge, P.
W. CRYSTALS Issue 10; Chemical Crystallography Laboratory: Ox-
ford, UK, 1996.
(23) Reich, H. J. WinDNMR; Dynamic NMR Spectra for Windows
J. Chem. Educ. Software 3D2.
Preparation of Ammonia Complex 4. Complex 1 (80 mg,
0.10 mmol) was reacted with 0.5 M NH3 in dioxane (4.0 mL,
2.0 mmol) at room temperature for 12 h. The color of the
solution changed from yellow to green during the course of
the reaction. Removal of the solvent followed by recrystalli-
zation from chloroform/pentane afforded green microcrystals
(79 mg, 0.088 mmol, 88%).
(24) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson,
G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai,
H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken,
V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev,
O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P.
Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas,
O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.;
Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov,
B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.;
Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.;
Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.;
Gonzalez, C.; Pople, J. A. Gaussian 03, revision B.04; Gaussian, Inc.:
Pittsburgh, PA, 2003.
Ru(dppe)(dmfm)2(NH3) (4). Mp: 147-151 °C (dec). IR
(KBr disk): 3047, 2944, 1701, 1683, 1647, 1434, 1314, 1165
cm-1 1H NMR (400 MHz, CD2Cl2): δ 7.51-7.31 (m, 15H),
.
7.08-7.23 (m, 3H), 6.82 (t, 2H, J ) 8.8 Hz), 3.75-3.80 (m, 1H,
CH of dmfm), 3.77 (s, 3H, OCH3 of dmfm), 3.54 (s, 3H, OCH3
of dmfm), 3.19 (s, 3H, OCH3 of dmfm), 3.08 (ddd, 1H, J ) 1.0,
2.9, 4.9 Hz, CH of dmfm), 2.95 (s, 3H, OCH3 of dmfm), 2.72-
2.84 (m, 2H, CH2 of PCH2), 2.13-2.27 (m, 4H, CH2 of PCH2
and CH of dmfm), 1.93 (br s, 3H, NH3). 13C NMR (100 MHz,
CD2Cl2): δ 181.2 (d, CdO, J ) 5.0 Hz), 180.6 (CdO), 180.4 (d,
CdO, J ) 2.5 Hz), 177.9 (d, CdO, J ) 5.8 Hz), 139.6 (d, J )
30.0 Hz), 138.7 (d, J ) 30.0 Hz), 138.5, 138.1, 133.7, 133.7,
132.7, 132.6, 131.3, 131.2, 129.9, 129.8, 129.6 (d, J ) 1.7 Hz),
129.5 (d, J ) 1.7 Hz), 129.0, 128.9, 128.8, 128.8, 128.8, 128.3

Chiral Zerovalent Organoruthenium Aqua Complexes
Organometallics, Vol. 24, No. 23, 2005 5731
Table 1. Summary of Crystal Data, Collection Data, and Refinement of 1a, 1b, 2, and 4
1a
1b
2
4
formula
C
38H42O9P2Ru‚C6H5Cl
C38H42O9P2Ru‚C6H5Cl
C43H40NO9PRu‚C6H5Cl
959.39
C38H43NO8P2Ru‚0.5CHCl3
864.47
fw
918.32
918.32
cryst color
habit
cryst size, mm
cryst syst
space group
a, Å
yellow
yellow
yellow
green
platelet
0.20 × 0.10 × 0.05
orthorhombic
P212121 (#19)
8.9549(13)
12.856(2)
36.668(5)
90
platelet
0.10 × 0.10 × 0.05
orthorhombic
P212121 (#19)
8.947(2)
12.850(3)
36.617(7)
90
platelet
block
0.35 × 0.20 × 0.05
monoclinic
P21/n (#14)
13.2604(4)
23.9503(9)
13.5294(5)
90
0.50 × 0.25 × 0.10
triclinic
P1h (#2)
8.9268(4)
11.6343(4)
19.467(1)
104.400(2)
100.860(2)
93.692(1)
1910.0(2)
2
b, Å
c, Å
R, deg
â, deg
90
90
90
90
93.164(2)
90
4290.3(3)
4
1.485
-100
γ, deg
V, Å3
4221.2(11)
4
1.445
-100
4209.7(14)
4
1.449
-100
Z
D(calcd), g cm-3
data collection
temp, °C
µ(Mo KR), cm-1
2θ max, deg
no. of measd reflns
no. of unique reflns
no. of obsd reflns
no. of variables
Ra
1.503
-130
5.65
55.0
33 752
9685 (Rint ) 0.058)
5414 (I > 2.00σ(I))
484
0.033 (I > 2.00σ(I))
0.042 (I > 2.00σ(I))
1.052
5.67
55.0
32 681
9606 (Rint ) 0.059)
5062 (I > 2.00σ(I))
530
0.038 (I > 2.00σ(I))
0.043 (I > 2.00σ(I))
1.09
5.25
55.0
34 574
9808 (Rint ) 0.034)
5556 (I > 3.00σ(I))
612
0.031 (I > 3.00σ(I))
0.030 (I > 3.00σ(I))
1.00
6.52
54.7
16 220
8110 (Rint ) 0.030)
7035 (I > 3.00σ(I))
530
0.040 (I > 3.00σ(I))
0.118 (I > 3.00σ(I))
1.190
a
Rw
GOF
2
1/2
a R ) ∑||Fo| - |Fc||/∑|Fo|; Rw ) [∑w(|Fo| - |Fc|)2/∑wFo
] .
eter exchange functional (B3)25 and the Lee-Yang-Parr
correlation functional (LYP)26] on Intel PIV computers at Kyoto
University. The basis set composed of the combination of the
Stuttgart-Dresden-Bonn energy-consistent pseudopotential
(SDD)27 for Ru, the 6-31G(d,p) basis set for all oxygen and
phosphorus atoms as well as two hydrogen atoms of coordi-
nated water, and the 6-31G basis set for all other hydrogen
and carbon atoms were used. No constraints were imposed for
all the systems. Frequency calculations on optimized species
established that the energy minima possessed only real
frequencies and the transition states possessed a single
imaginary frequency. Zero-point energy and thermodynamic
functions were computed at standard temperature (298.15 K)
and pressure (1 atm). Spatial plots of the optimized geometries
and frontier orbitals were obtained from Gaussian 03 output
using Cambridge Soft Corporation’s Chem 3D Pro v4.0 and
Fujitsu WinMOPAC v3.5.
Acknowledgment. This work was supported in part
by Grants-in-Aid for Scientific Research (A and B) and
Scientific Research on Priority Areas from the Japan
Society for the Promotion of Science and the Ministry
of Education, Culture, Sports, Science and Technology,
Japan. T.K. acknowledges financial support from the
Sumitomo Foundation and Japan Chemical Innovation
Institute. We thank Dr. M. Shiro (Rigaku Corp.) for
supporting our X-ray crystallography.
Supporting Information Available: The results of the
dynamic NMR simulation for 1 and 2 and the theoretical
calculations. This material is available free of charge via the
Internet at http://pubs.acs.org.
(25) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
(26) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. 1988, B37, 785.
(27) Dolg, M. In Modern Methods and Algorithms of Quantum
Chemistry; Grotendorst, J., Ed.; John von Neumann Institute for
Computing: Zu¨lich, 2000; Vol. 1, pp 479-508.
OM050664N