Ruthenium(II) complexes containing optically active hemilabile P,N,O-tridentate ligands. Synthesis and evaluation in catalytic asymmetric transfer hydrogenation of acetophenone by propan-2-ol

Article abstract of DOI:10.1021/om960955j

The trifunctional ligands (R)-1-(diphenylphosphino)-2-((1R,2S,5R)-menthoxy)-1-(2-pyridyl)-ethane (2R), (S)-1-(diphenylphosphino)-2-((1R,2S,5R)-menthoxy)-1-(2-pyridyl)ethane (2S), and (S)-(phenyl(2-anisyl)phosphino)(2-pyridyl)methane (3) have been synthesized, as well as the corresponding RuCl₂(PPh₃)(L) complexes. The complexes RuCl₂(PPh₃)(2R) (5) and RuCl₂(PPh₃)(2S) (6) were isolated as mixtures of two isomers, 5a and 5b and 6a and 6b, respectively. In each of these isomers, the ligands 2 are η³-(P,N,O) bound. They differ by the position of the triphenylphosphine, which is either in a trans position relative to the pyridyl ring (5a or 6a) or in a trans position relative to the ether function (5b or 6b). Variable temperature NMR experiments have shown that the hemilabile character in solution of the ligands 2 is through their pyridyl arm in the isomers a or their ether arm in b. The complexes 6b and RuCl₂(PPh₃)(S) (9) were characterized by X-ray diffraction. The complexes 5, 6, and 9 are very active catalysts for the transfer hydrogenation of acetophenone by propan-2-ol in basic media, the higher activity being observed for 9 (turnovers frequency 48 900 h^-1). The enantioselectivity is modest and dependent on the reactions conditions. The best result has been observed for 5, with an ee of 60%.

Full text of DOI:10.1021/om960955j

Organometallics 1997, 16, 1401-1409
1401
Ru th en iu m (II) Com p lexes Con ta in in g Op tica lly Active
Hem ila bile P ,N,O-Tr id en ta te Liga n d s. Syn th esis a n d
Eva lu a tion in Ca ta lytic Asym m etr ic Tr a n sfer
Hyd r ogen a tion of Acetop h en on e by P r op a n -2-ol
Hong Yang, Marie Alvarez-Gressier, Noe¨l Lugan, and Rene´ Mathieu*,†
Laboratoire de Chimie de Coordination du CNRS, UPR 8241, 205 route de Narbonne,
31077 Toulouse Cedex 4, France
Received November 8, 1996X
The trifunctional ligands (R)-1-(diphenylphosphino)-2-((1R,2S,5R)-menthoxy)-1-(2-pyridyl)-
ethane (2R), (S)-1-(diphenylphosphino)-2-((1R,2S,5R)-menthoxy)-1-(2-pyridyl)ethane (2S),
and (S)-(phenyl(2-anisyl)phosphino)(2-pyridyl)methane (3) have been synthesized, as well
as the corresponding RuCl2(PPh3)(L) complexes. The complexes RuCl2(PPh3)(2R) (5) and
RuCl2(PPh3)(2S) (6) were isolated as mixtures of two isomers, 5a and 5b and 6a and 6b,
respectively. In each of these isomers, the ligands 2 are η3-(P,N,O) bound. They differ by
the position of the triphenylphosphine, which is either in a trans position relative to the
pyridyl ring (5a or 6a ) or in a trans position relative to the ether function (5b or 6b). Variable
temperature NMR experiments have shown that the hemilabile character in solution of the
ligands 2 is through their pyridyl arm in the isomers a or their ether arm in b. The complexes
6b and RuCl2(PPh3)(3) (9) were characterized by X-ray diffraction. The complexes 5, 6, and
9 are very active catalysts for the transfer hydrogenation of acetophenone by propan-2-ol in
basic media, the higher activity being observed for 9 (turnovers frequency 48 900 h-1). The
enantioselectivity is modest and dependent on the reactions conditions. The best result has
been observed for 5, with an ee of 60%.
In tr od u ction
RuCl2(1)2 complex, the ligand 1 is P,N bonded. In polar
solvent it evolves to [RuCl(1)2]+Cl-, in which one of the
ligands is P,N,O bonded, the ether arm being weakly
bonded to ruthenium.9 More recently, we have observed
the easy formation of the complex RuCl2(PPh3)(1) by the
reaction of 1 equiv of 1 with RuCl2(PPh3)3. We have
shown the later complex to be, to the best of our
knowledge, the most efficient ruthenium-based catalyst
for the transfer hydrogenation of ketones by propan-2-
ol.10
In recent years, the design of so-called hemilabile
ligands containing one functional group strongly bound
to a late transition metal and another coordinatively
labile has been of considerable interest and developed
by several groups.1-3 The weakly bound functional
group plays the role of an intramolecular solvent
molecule assuring the stability of the complex and
possibly improving its stoichiometric reactivity4-6 or
catalytic activity.7
This prompted us to investigate the asymmetric
version of this reaction by using ruthenium complexes
bearing optically active tridentate ligands with P,N,O
donor atoms. In this paper, we report the synthesis of
three ligands closely related to 1, (R)-1-(diphenylphos-
phino)-2-((1R,2S,5R)-menthoxy)-1-(2-pyridyl)ethane (2R),
(S)-1-(diphenylphosphino)-2-((1R,2S,5R)-menthoxy)-1-
(2-pyridyl)ethane (2S), and a ligand in which the chiral
center is the phosphorus atom, (S)-(phenyl(2-anisyl)-
phosphino)(2-pyridyl)methane (3). These ligands have
been coordinated to ruthenium in complexes of the type
RuCl2(PPh3)(L) (L ) 1, 2, 3). These complexes have
been used as catalyst precursors for the transfer hy-
drogenation of acetophenone by propan-2-ol. A prelimi-
nary account of this work has been published.10
For our part, we have tried to apply this concept to
tridentate ligands, which are expected to exert more
control on the coordination sphere of a metal than
bidentate ligands, with a possible effect on the catalytic
properties of the resulting complexes.8 This led us to
synthesize the ligand 1-(diphenylphosphino)-2-ethoxy-
1-(2-pyridyl)ethane (1), which associates phosphorus to
a hard donor center, the oxygen of an ether function,
and a quite soft donor center, the nitrogen of a pyridine
cycle. We have previously shown that in the all cis-
† E-mail: mathieu@lcc-toulouse.fr.
X Abstract published in Advance ACS Abstracts, March 1, 1997.
(1) Bader, A.; Lindner, E. Coord. Chem. Rev. 1991, 108, 27.
(2) Lindner, E.; Haustein, M.; Mayer, H. A.; Gierling, K.; Fawzi, R.;
Steimann, M. Organometallics 1995, 14, 2246 and references therein.
(3) Higgins, T. B.; Mirkin, C. A. Inorg. Chim. Acta 1995, 240, 347
and references therein.
Resu lts a n d Discu ssion
(4) Chadwell, S. J .; Coles, S. J .; Edwards, P. G.; Hursthouse, M. B.
J . Chem. Soc., Dalton Trans. 1995, 3551 and references therein.
(5) Lindner, E.; Grepa¨gs, M.; Gierling, K.; Fawzi, R.; Steimann, M.
Inorg. Chem. 1995, 34, 6106.
(6) Werner, H.; Stark, A.; Steinert, P.; Gru¨nwald, G.; Wolf, J . Chem.
Ber. 1995, 128, 49.
Syn th esis of th e Ligan ds. The synthesis of 1-(diphe-
nylphosphino)-2-ethoxy-1-(2-pyridyl)ethane (1) from
(7) (a) Lindner, E.; Sickinger, A.; Wegner, P. J . Organomet. Chem.
1988, 349, 75. (b) Allgeier, A. M.; Singewald, E. T.; Mirkin, C. A.; Stern,
C. L. Organometallics 1994, 13, 2928.
(9) Alvarez, M.; Lugan, N.; Mathieu, R. J . Chem. Soc., Dalton Trans.
1994, 2755.
(10) Yang, H.; Alvarez, M.; Lugan, N.; Mathieu, R. J . Chem. Soc.,
Chem. Commun. 1995, 1721.
(8) Cotton, F. A.; Hong, B. Prog. Inorg. Chem. 1992, 40, 179.
S0276-7333(96)00955-7 CCC: $14.00 © 1997 American Chemical Society

1402 Organometallics, Vol. 16, No. 7, 1997
Yang et al.
Sch em e 1
Sch em e 2
2-((diphenylphosphino)methyl)pyridine has been previ-
ously reported.9 The parent 1-(diphenylphosphino)-2-
(1R,2S,5R)-menthoxy)-1-(2-pyridyl)ethane (2) has been
synthesized following the same strategy, as illustrated
in Scheme 1. Successive addition of n-butyllithium and
chloromethyl-(1R,2S,5R)-menthyl ether to 2-((diphe-
nylphosphino)methyl)pyridine leads to 2 in a 70% yield
as a mixture of two diastereoisomers in a 1:1 ratio. Only
after complexation with borane could the two diaster-
eomers 2R‚BH3 and 2S‚BH3 be separated by chroma-
tography on silica gel. The free ligands (R)-1-(diphenyl-
ph osph in o)-2-((1R,2S ,5R)-m en t h oxy)-1-(2-pyr idyl)-
ethane (2R) and (S)-1-(diphenylphosphino)-2-((1R,2S,5R)-
menthoxy)-1-(2-pyridyl)ethane (2S) have subsequently
been liberated by reaction with morpholine at 70 °C and
isolated in a 26% and 41% yield, respectively. The
absolute configuration of these ligands has been deduced
from the X-ray structure determination of RuCl2(PPh3)-
(2S) (vide infra).
first step, the addition of 2-anisyllithium to (2R,4S,5R)-
3,4-dimethyl-2,5-diphenyl-1,3,2-oxazaphospholidine12 af-
fords the aminophosphine-borane complex 3a (Scheme
2). A subsequent acidic methanolysis at room temper-
ature gives the phosphinite-borane complex 3b, and a
final reaction with (2-pyridylmethyl)lithium at -20 °C
leads to the phosphine borane complex 3‚BH3. The
ligand 3 is then liberated from its borane complex by
morpholine at 70 °C. It has been isolated in a 70%
overall yield.
Syn th esis a n d Ch a r a cter iza tion of th e Ru Cl2-
(P P h 3)(L) Com p lexes (L ) 1, 2R, 2S, 3). The com-
plexes RuCl2(PPh3)(L) (L ) 1, 2R, 2S, 3) have been
obtained by the addition at room temperature of 1 equiv
of the ligand L to RuCl2(PPh3)2 in dichloromethane
solution, according to the general equation shown below.
RuCl2(PPh3)3 + L f RuCl2(PPh3)(L) + 2PPh3
The enantiomerically pure (S)-(phenyl(2-anisyl)phos-
phino)(2-pyridyl)methane (3) has been synthesized fol-
lowing a procedure developed by J uge´ et al.11-14 In the
Ch a r a cter iza tion of th e Com p lex Ru Cl2(P P h 3)-
(1) (4). The complex RuCl2(PPh3)(1) (4) has been
isolated in a 73% yield as a yellow powder. It has been
characterized by the usual spectroscopic techniques. 31P-
{1H} NMR in benzene solution shows an AB system (δA
(11) J uge´, S.; Genet, J .-P. Tetrahedron Lett. 1989, 30, 2783.
(12) J uge´ S.; Wakselman, M.; Stephan, M.; Genet, J .-P. Tetrahedron
Lett. 1990, 31, 4443.
(13) J uge´, S.; Stephan, M.; Lafitte, J .-A.; Genet, J .-P. Tetrahedron
Lett. 1990, 31, 6357.
(14) J uge´, S.; Stephan, M.; Merdes, R.; Genet, J .-P.; Halut-Desportes,
S. J . Chem. Soc., Chem. Commun. 1993, 531.

Ruthenium(II) Complexes
Organometallics, Vol. 16, No. 7, 1997 1403
) 63.3, δB ) 61.2), and the J PP coupling constant of 39
Hz indicates that the two phosphorus atoms are in a
cis position. The room temperature 1H NMR spectra
in CD2Cl2 solution show the expected signals for the
alkyl part of the ligand 1 (see Experimental Section).
Noteworthy is the deshielding by 0.82 ppm of the
resonance of the methylene group of the ethoxy group
compared to that of the free ligand, which shows that
the ether function is coordinated to ruthenium. The
protons of the pyridyl group appear as a very broad
resonance at 8 ppm. This suggests a fluxional process
within the molecule, and variable temperature NMR
experiments have been performed in CD2Cl2 solution.
In this solvent, a single resonance is now observed at δ
) 62.2 in the 31P{1H} spectrum and it is only by
lowering the temperature to 203 K that an AB pattern
is observed (δA ) 66.7, δB ) 64.7, J PP ) 39 Hz). In the
same temperature range, the most salient feature in the
1H NMR spectrum is in the 6-10 ppm area and,
peculiarly, the replacement of the broad resonance
observed at 8 ppm at 298 K by an ill-resolved triplet at
9.69 ppm, characteristic of the hydrogen in the 6-posi-
tion on a coordinated pyridyl ring.15 1H{31P} NMR
decoupling experiments transform this signal into a
doublet. Taken altogether, these results indicate that
the fluxionality of the molecule is certainly related to
the reversible coordination of the pyridyl ring. This is
a quite surprising observation as the ether function is
a harder base than the pyridine and a reversible
opening of the Ru-O was expected.
F igu r e 1. CAMERON drawing of compound 6b with 50%
thermal ellipsoids.
diastereoisomers a while the menthyl ether group does
and that the reverse situation is occurring in diastere-
oisomers b. For 5a and 6a , a lowering of the temper-
ature to 193 K induces the same type of changes as for
4 (vide supra). Indeed, the broad resonances observed
at 8.45 and 8.39 ppm at 298 K shift to 9.73 and 9.74
ppm, respectively, and become ill-resolved triplets.
These observations show that 5a and 6a experience the
same fluxional process in solution as complex 4, i.e., a
reversible opening of the Ru-N bond.
The behavior in solution of diastereoisomers 5b and
6b is less clear. Indeed, the two resonances which could
be sensitive to the mode of bonding of the N and O
donating centers are not greatly affected. The most
significant differences concern the resonance of the
hydrogen bonded to the chiral carbon in the R-position
relative to the phosphorus that moves by about 0.3 ppm
to high field at 193 K. No clear conclusions about the
mode of bonding of the ligands 2R and 2S in 5b and 6b
could, however, be deduced.
The structure of complex 4 will be presented later,
along with the structure of the complexes RuCl2(PPh3)-
(2R) (5) and RuCl2(PPh3)(2S) (6).
Ch a r a cter iza tion of th e Com p lexes Ru Cl2(P P h 3)-
(2R) (5) a n d Ru Cl2(P P h 3)(2S) (6). The reaction of 2R
or 2S with RuCl2(PPh3)3 leads to the formation of
complexes RuCl2(PPh3)(2R) (5) and RuCl2(PPh3)(2S) (6),
respectively. 31P{1H} NMR indicates that complexes 5
and 6 form as a mixture of two isomers, 5a and 5b and
6a and 6b. Each of the four complexes is characterized
by an AB pattern in the 31P{1H} spectra, with a J PP
coupling constant characteristic of two phosphorus
nuclei being in a cis position. In each reaction, the ratio
between the two isomers varies when allowed to stand
in solution, until 5b or 6b remains as the sole observable
1
complex. The most significant features in the H NMR
Crystals of 6b suitable for an X-ray structure deter-
mination have been obtained. A CAMERON perspec-
tive view of the complex is shown in Figure 1. Table 1
contains a selection of bond distances and angles of
interest.
spectra concern the resonances for the hydrogen in the
6-position on the pyridyl ring and in the 1-position on
the menthyl group. At room temperature, the hydrogen
in the 6-position on the pyridyl ring is observed as a
broad signal at 8.45 and 8.39 ppm for the isomers 5a
and 6a , respectively and as a thin doublet at 9.42 and
9.43 ppm for the isomers 5b and 6b, respectively. The
hydrogen in the 1-position on the menthyl group ap-
pears as a complex multiplet at 4.41 and 4.50 ppm for
5a and 6a and at 2.79 and 2.91 ppm for 5b and 6b. First
of all, these data indicate that 5a and 6a and 5b and
6b are diastereoisomers. Secondly, the comparison of
the chemical shifts of the protons in the 6-position on
the pyridyl ring, and in the 1-position on the menthyl
group with the corresponding ones in the free ligand
(8.49 and 2.89 ppm, respectively) suggests that the
pyridyl group is not firmly coordinated to ruthenium in
In complex 6b, the ligand 2S is P,N,O bound to
ruthenium. The chlorine atoms are mutually cis and
the triphenylphosphine ligand is in the trans position
relative to the oxygen atom of the ether function. The
geometry around the ruthenium atom is a distorted
octahedron, due to the tridentate mode of bonding of
2S. Bond distances illustrate the trans influence of the
phosphorus ligands in this molecule. Indeed, the Ru-
(1)-Cl(2) bond (2.4634(8) Å) trans to P(1) is significantly
longer than the Ru(1)-Cl(1) bond (2.4420(8) Å) trans
to N(1). Moreover, the Ru(1)-O(1) bond trans to P(2)
(2.311(2) Å) is one of the longest distances observed for
ruthenium complexes with P,O ligands in which the
oxygen atom is in a trans position to a phosphorus
atom.16-19 This last result suggests that the fluxionality
(15) Deeming, A. J .; Smith, M. B. J . Chem. Soc., Chem. Commun.
1993, 844.

1404 Organometallics, Vol. 16, No. 7, 1997
Yang et al.
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Ru Cl2(P P h 3)(2S) (6b), w ith Esd in
P a r en th eses
Sch em e 3
Ru(1)-Cl(1)
Ru(1)-Cl(2)
Ru(1)-P(1)
Ru(1)-P(2)
Ru(1)-N(1)
Ru(1)-O(1)
P(1)-C(1)
P(1)-C(21)
P(1)-C(31)
P(2)-C(41)
P(2)-C(51)
P(2)-C(61)
N(1)-C(3)
N(1)-C(7)
O(1)-C(2)
O(1)-C(8)
2.4420(8)
2.4634(8)
2.2609(8)
2.2437(9)
2.125(3)
2.311(2)
1.858(4)
1.836(4)
1.855(3)
1.860(4)
1.851(4)
1.835(4)
1.366(4)
1.360(4)
1.439(4)
1.459(4)
C(1)-C(2)
1.515(5)
1.527(5)
1.378(5)
1.376(6)
1.392(6)
1.394(5)
1.535(5)
1.522(5)
1.508(6)
1.515(6)
1.553(6)
1.527(6)
1.537(6)
1.560(6)
1.538(7)
1.529(7)
C(1)-C(7)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
C(6)-C(7)
C(8)-C(9)
C(8)-C(13)
C(9)-C(10)
C(10)-C(11)
C(10)-C(14)
C(11)-C(12)
C(12)-C(13)
C(13)-C(15)
C(15)-C(16)
C(15)-C(17)
Cl(1)-Ru(1)-Cl(2)
Cl(1)-Ru(1)-P(1)
Cl(2)-Ru(1)-P(1)
91.48(3) Cl(1)-Ru(1)-P(2)
97.29(3) Cl(2)-Ru(1)-P(2)
166.88(3) P(1)-Ru(1)-P(2)
93.35(3)
89.21(3)
99.96(3)
Cl(1)-Ru(1)-N(1) 165.83(8) C(41)-P(2)-C(51) 102.6(2)
Cl(2)-Ru(1)-N(1)
P(1)-Ru(1)-N(1)
P(2)-Ru(1)-N(1)
Cl(1)-Ru(1)-O(1)
Cl(2)-Ru(1)-O(1)
P(1)-Ru(1)-O(1)
P(2)-Ru(1)-O(1)
N(1)-Ru(1)-O(1)
Ru(1)-P(1)-C(1)
Ru(1)-P(1)-C(21) 124.7(1)
C(1)-P(1)-C(21) 104.9(2)
Ru(1)-P(1)-C(31) 125.8(1)
C(1)-P(1)-C(31) 103.5(2)
87.94(8) Ru(1)-P(2)-C(61) 117.8(1)
81.16(7) C(41)-P(2)-C(61) 107.2(2)
100.80(8) C(51)-P(2)-C(61)
90.07(6) Ru(1)-N(1)-C(3)
89.14(5) Ru(1)-N(1)-C(7)
81.14(5) C(3)-N(1)-C(7)
176.24(6) Ru(1)-O(1)-C(2)
95.5(2)
127.4(2)
115.4(2)
116.7(3)
113.6(2)
126.9(2)
117.9(2)
107.2(2)
107.2(2)
110.4(3)
105.8(3)
114.7(3)
To evaluate the consequence of the lability of the
various bonds in these complexes, we have investigated
the reactivity of 4 toward carbon monoxide. At room
temperature, the reaction is instantaneous and infrared
spectroscopy shows a main absorption at 1980 cm-1 and
another one at 1962 cm-1. The 31P{1H} NMR spectrum
indicates that two complexes are formed. The most
abundant one, 7, is characterized by two doublets at 40.4
and 25.5 ppm (J PP ) 27.6 Hz) and the other, 8, by two
doublets at 61.2 and 18.8 ppm (J PP ) 354.5 Hz). When
the complexes remain in solution, the ratio between the
two complexes varies and after 1 h in the NMR tube,
only 8 remains observable and, at this stage, only the
absorption at 1962 cm-1 is noticed in the IR spectrum.
This shows complex 7 to be the kinetic product of the
reaction. As the 31P{1H} NMR data show that the two
phosphine ligands are mutually cis and the ν(CO) value
indicates the CO ligand is in a trans position to a
phosphine ligand,20 we propose the structure shown in
Scheme 4 for 7. It is very likely that the first step of
the reaction is an opening of the Ru-N bond in 4, in
agreement with its observed labile character, which
allows the coordination of CO. Subsequent intramo-
lecular substitution of the pyridyl group for the ethoxy
group would lead to 7, the ligand 1 going from an η2-
(P,O) to an η2-(P,N) coordination mode through the
process (Scheme 4). This rearrangement is certainly the
consequence of the increased soft character of the Ru
center due to the coordination of CO.
75.8(1)
91.3(1)
Ru(1)-O(1)-C(8)
C(2)-O(1)-C(8)
P(1)-C(1)-C(2)
P(1)-C(1)-C(7)
C(2)-C(1)-C(7)
O(1)-C(2)-C(1)
N(1)-C(7)-C(1)
C(21)-P(1)-C(31) 101.6(2)
Ru(1)-P(2)-C(41) 111.9(1)
Ru(1)-P(2)-C(51) 119.7(1)
phenomenon observed by NMR for 5b and 6b could
result from an easy reversible opening of the Ru-O
bond, which is not totally frozen at the lowest temper-
ature we have operated (193 K).
The solid state structure of 6b has allowed us to
deduce the relative arrangements of the ligands in 6a
(or 5a ) and 4, as shown in Scheme 3. Indeed, the selec-
1
tive H{31P} NMR experiments run at 193 K show that
the proton in the 6-position on the pyridyl in 6a , 5a ,
and 4 are coupled with the phosphorous atom of the
triphenylphosphine ligand. So, the triphenylphosphine
ligand is now in a trans position relative to the nitrogen
atom of the pyridine ring in 6a and its diastereoisomer
5a . Since 5a and 6a experience the same type of flux-
ional process in solution as 4, we propose the same type
of structure for the latter. Note that in these structures,
the triphenylphosphine is now in a cis position to the
ether group. This could explains why 5a and 6a are
less stable than 5b and 6b, where the bulky menthyl
ether group is far away from the triphenylphosphine.
Finally, the behavior in solution of complexes 4, 5,
and 6 show that the labile arm of the P,O,N ligands is
the arm in a trans position to the triphenylphosphine
ligand. This shows that the hemilabile character of this
type of ligand is governed by the trans effect of the
ancillary ligands bound to ruthenium.
The infrared spectrum of complex 8 shows two
absorptions at 310 and 272 cm-1, which is consistent
with the cis position of the Ru-Cl bonds.19 As the J pp
value indicates that the the two phosphorus atoms are
mutually trans, we propose the structure shown in
Scheme 4 for 8.
Ch a r a cter iza tion of th e Com p lex Ru Cl2(P P h 3)-
(3) (9). The complex RuCl2(PPh3)(3) (9) has been
isolated in 90% yield as a yellow powder. Its 31P{1H}
(16) J effrey, J . C.; Rauchfuss, T. B. Inorg. Chem. 1979, 18, 2658.
(17) Lindner, E.; Schober,U.; Fawzi, R.; Hiller, W.; Englert, U.;
Wegner, P. Chem. Ber. 1987, 120, 1621.
(18) Lindner, E.; Mo¨ckel, A.; Mayer, H. A.; Fawzi, R. Chem. Ber.
1992, 125, 1363.
(19) Lindner, E.; Mo¨ckel, A.; Mayer, H. A.; Ku¨hbauch, H.; Fawzi,
R.; Steimann, M. Inorg. Chem. 1993, 32, 1266.
(20) Barnard, C. F. J .; Daniels, J . A.; J effery, J .; Mawby, R. J . J .
Chem. Soc., Dalton Trans. 1976, 1861.

Ruthenium(II) Complexes
Organometallics, Vol. 16, No. 7, 1997 1405
Sch em e 4
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Ru Cl2(P P h 3)(3) (9), w ith Esd in
P a r en th eses
Ru(1)-Cl(1)
Ru(1)-Cl(2)
Ru(1)-P(1)
Ru(1)-P(2)
Ru(1)-O(1)
Ru(1)-N(1)
P(1)-C(1)
P(1)-C(11)
P(1)-C(21)
P(2)-C(41)
2.461(7)
2.405(7)
2.207(8)
2.248(8)
2.25(2)
2.10(2)
1.79(2)
1.82(2)
1.82(2)
1.83(1)
P(2)-C(51)
P(2)-C(66)
O(1)-C(2)
O(1)-C(26)
C(1)-C(31)
C(31)-N(1)
C(32)-C(33)
C(33)-C(34)
C(34)-C(35)
C(35)-N(1)
1.84(1)
1.86(1)
1.44(3)
1.39(2)
1.51(3)
1.37(3)
1.39(3)
1.34(3)
1.37(3)
1.38(3)
Cl(1)-Ru(1)-Cl(2)
89.6(2)
Cl(1)-Ru(1)-N(1)
Cl(2)-Ru(1)-N(1)
P(1)-Ru(1)-N(1)
P(2)-Ru(1)-N(1)
O(1)-Ru(1)-N(1)
Ru(1)-P(1)-C(1)
Ru(1)-P(1)-C(11)
C(1)-P(1)-C(11)
Ru(1)-P(1)-C(21)
C(1)-P(1)-C(21)
C(1)-C(31)-N(1)
Ru(1)-N(1)-C(31)
Ru(1)-N(1)-C(35)
93.3(5)
171.8(3)
78.8(5)
92.0(3)
86.5(5)
104.9(8)
135.2(6)
105.8(10)
103.3(6)
101.5(10)
118.0(20)
120.4(16)
121.1(15)
121.7(11)
118.0(10)
Cl(1)-Ru(1)-P(1) 166.6(3)
Cl(2)-Ru(1)-P(1)
Cl(1)-Ru(1)-P(2)
Cl(2)-Ru(1)-P(2)
P(1)-Ru(1)-P(2)
Cl(1)-Ru(1)-O(1)
Cl(2)-Ru(1)-O(1)
P(1)-Ru(1)-O(1)
P(2)-Ru(1)-O(1)
96.8(2)
90.6(2)
95.6(2)
100.4(3)
86.8(4)
86.0(4)
82.0(5)
176.9(4)
C(11)-P(1)-C(21) 101.8(6)
Ru(1)-P(2)-C(41) 111.1(4)
Ru(1)-P(2)-C(51) 122.2(7)
F igu r e 2. CAMERON drawing of compound 9 with 50%
thermal ellipsoids.
Ru(1)-O(1)-C(2)
125.6(15) P(1)-C(21)-C(22)
Ru(1)-O(1)-C(26) 116.6(12) P(1)-C(21)-C(26)
NMR spectrum has an AB pattern (δA ) 64.6, δB ) 62.9,
C(2)-O(1)-C(26)
P(1)-C(1)-C(31)
115.1(16) C(22)-C(21)-C(26) 120.3(7)
105.2(15) O(1)-C(26)-C(21) 118.0(14)
1
J PP ) 37.5 Hz), and its H NMR spectrum indicates that
3 is P,N,O-bound. Indeed, the hydrogen in the 6-posi-
tion on the pyridyl ring appears as a doublet at 9.61
ppm, while the methoxy group resonance is observed
at 4.61 ppm, at lower field than the corresponding
signals in the free ligand (8.44 and 3.66 ppm, respec-
tively). As the 1H{31P} NMR experiment shows that the
pyridyl ring is not in a trans position to any phosphorus
atom, we propose a structure for 9 similar to that of 6b
in terms of the relative arrangement of the ligands.
However, contrary to complexes 4-6, no fluxional
process has been evidenced in solution.
The solid state structure of complex 9 has been
determined by X-ray diffraction. A CAMERON per-
spective view of the complex is shown in Figure 2. Bond
distances and angles of interest are presented in Table
2. Though the crystals were of poor quality, this study
confirms our hypothesis that triphenylphosphine is
trans to the ether group.
C(1)-C(31)-C(32) 123.6(22)
transfer hydrogenation of ketones by ruthenium com-
plexes containing optically active ligands met only
moderate success.21 In the last three years, however,
considerable advancements have been reported, both in
terms of activity and enantioselectivity.22 Today, enan-
tiomeric excesses up to 97% have been obtained with
bi-22e or tetradentate ligands22f coordinating phosphorus
and nitrogen atoms in ruthenium complexes. In these
particularly efficient complexes, the ligands bear a
chiral carbon atom in an R-position relative to the
nitrogen binding site.
Our first experiments were performed under reaction
conditions similar to those described by Ba¨ckvall et al.,
using RuCl2(PPh3)3 as the catalyst precursor.23 We have
previously shown that in these conditions, the complex
4 is a very efficient catalyst, as a turnover frequency of
90 000 h-1 has been observed for the transfer hydroge-
nation of acetophenone.10
When the complex 9 in dichloromethane solution is
treated with carbon monoxide, the new complex RuCl2-
(CO)(PPh3)(3) (10) immediately forms. In the IR spec-
trum, there is a characteristic ν(CO) band at 1987 cm-1
.
(21) Zassinovich, G.; Mestroni, G.; Gladiali, S. Chem. Rev. 1992, 92,
1051.
The 31P{1H} NMR spectrum shows an AX spin system
(22) (a) Geneˆt, J -P.; Ratovelomanana-Vidal, V.; Pinel, C. Synlett
1993, 478. (b) Hashiguchi, S.; Fujii, A.; Takehara, J .; Ikariya, T.;
Noyori, R. J . Am. Chem. Soc. 1995, 117, 7562. (c) Takehara, J .;
Hashiguchi, S.; Fujii, A.; Inoue, S.; Ikariya, T.; Noyori, R. J . Chem.
Soc., Chem. Commun. 1996, 233. (d) J iang, Q.; Van Piew, D.; Murtuza,
S.; Zhang, X. Tetrahedron Lett. 1996, 37, 797. (e) Langer, T.; Helmchen,
G. Tetrahedron Lett. 1996, 37, 1381. (f) Gao, J . X.; Ikariya, T.; Noyori,
R. Organometallics 1996, 15, 1087.
1
(δA ) 44.9, δX ) 16.2, J PP ) 29.4 Hz), and the H NMR
spectrum indicates that the ligand 3 is not O bound.
Indeed, the methoxy resonance is observed at 3.24 ppm.
As expected, carbon monoxide has replaced the coordi-
nated ether arm of the ligand on ruthenium.
Ca ta lytic Tr a n sfer Hyd r ogen a tion of Acetop h e-
n on e. When this work was initiated, asymmetric
(23) Chowdhury, R. L.; Ba¨ckvall, J . E. J . Chem. Soc., Chem.
Commun. 1991, 1063.

1406 Organometallics, Vol. 16, No. 7, 1997
Ta ble 3. Ru th en iu m -Ca ta lyzed Asym m etr ic Tr a n sfer Hyd r ogen a tion of Acetop h en on e
Yang et al.
catalyst
Substrate/Catalyst ratio
time (min)
base/catalyst ratio
temp (°C)
yield (%)
ee (%)
config
5
6
9
9
9
5
5
9
9
1000
1000
1000
1000
500
200
200
200
200
20
20
1
90
90
60
5
240a
240a
240a
240a
240a
0.5b
1b
80
80
80
50
30
45
45
45
45
90
90
80
24
30
50
95
2
2
3
0
10
5
60
22
R
R
R
R
R
R
60
60
0.5b
1b
30
12
R
a
b
NaOH as base. (CH3)2CHOK as base.
ethyl)pyridine,9 1-(diphenylphosphino)-2-ethoxy-1-(2-pyridyl)-
ethane,9 and (2R,4S,5R)-3,4-dimethyl-1,3,2-oxazaphospholidine-
2-borane12 have been prepared according to published pro-
cedures.
The complexes 5 and 6 (used as mixtures of isomers
5a and 5b and 6a and 6b) are less active, and the
enantiomeric excesses are very poor (Table 3). In both
cases, the major enantiomer is R. Complex 9 is much
more active and a turnover frequency of 48 900 h-1 has
been obtained. To our disappointment, no enantiomeric
excess is, however, detected. We have tried to improve
the enantioselectivity of the system by lowering the
reaction temperature. At 55 °C, the activity of the
system notably decreases, but an enantiomeric excess
of 10% is noticed (Table 3). At 30 °C and with a
substrate/catalyst ratio of 1/500, a similar activity is
observed but the stereoselectivity lowers.
In the last attempts to optimize the performance of
our complexes, we have used the reaction conditions
described by Noyori et al., which allowed them to obtain
the most efficient system to date for this catalytic
reaction.22f The main differences between the later
system and Ba¨ckvall’s system, besides the temperature
of the runs (45 °C), reside in the use of a low concentra-
tion of potassium 2-propoxide as a base (1/2 equiv with
respect to Ru) and a higher concentration of the complex
(substrate/catalyst ) 200). Under these conditions,
complex 5 shows a lower activity, as the system deac-
tivates after 1 h with a conversion of 53%. Neverthe-
less, a considerable increase of the enantiomeric excess
of the reaction to 60% has been observed. For complex
9, the result was disappointing as no significant activity
could be noticed (Table 3). These results led us to
slightly increase the base concentration to 1 equiv of
potassium 2-propoxide per Ru. This induced a net
increase of the activity for 5 but concurrently a net
decrease in the enantioselectivity of the reaction. For
complex 9, some activity was then observed but the
enantiomeric excess remained modest.
Syn th esis of (R)-1-(Dip h en ylp h osp h in o)-2-((1R,2S,5R)-
m en th oxy)-1-(2-p yr id yl)eth a n e (2R) a n d (S)-1-(Dip h e-
n ylp h osp h in o)-2-((1R,2S,5R)-m en t h oxy)-1-(2-p yr id yl)-
et h a n e (2S). To 2.77 g of 2-((diphenylphosphino)methyl)-
pyridine (10 mmol) dissolved in 10 mL of diethyl ether cooled
at 0 °C was slowly added 6.8 mL of a 1.6 M solution of n-BuLi
in hexanes (10 mmol). The solution was stirred for 0.5 h at 0
°C. Then, 2.05 mL of chloromethyl (1R,2S,5R)-menthyl ether
(10 mmol) was slowly added, and the solution was stirred for
3 h at 0 °C and then for 2 h at room temperature. The solvents
were removed under vacuum, and the oily residue was
dissolved in 50 mL of diethyl ether. The solution was washed
with 2 × 50 mL of water, then dried over sodium sulfate.
Evaporation of the solvent under vacuum left 4 g of a crude
racemic mixture of 1-(diphenylphosphino)-2-((1R,2S,5R)-men-
thoxy)-1-(2-pyridyl)ethane (2) as a yellow oil (95% yield).
A crude racemic mixture of 1-(diphenylphosphino)-2-
((1R,2S,5R)-menthoxy)-1-(2-pyridyl)ethane (1 g, 2.25 mmol)
was dissolved in toluene (10 mL). To this was added 1.13 mL
of a 2 M solution of BH3‚SMe2 in toluene (2.25 mmol), and the
mixture was stirred for 4 h at room temperature. The toluene
was removed under vacuum to leave the complex 2‚BH3 as a
white powder. The two diastereoisomers thus formed have
been purified and separated by column chromatography on
silica gel 60 using a CH2Cl2/hexanes (5:1) mixture as the
eluant. Complexes 2R‚BH3 and 2S‚BH3 have been isolated
in 29% and 43% yields, respectively, as white solids.
Each of the borane complexes 2R‚BH3 and 2S‚BH3 was
dissolved in morpholine (5 mL) and the solution was heated
at 70 °C for 2 h. Excess morpholine was eliminated under
vacuum. The residue was treated by a mixture of diethyl ether
(20 mL) and water (20 mL). The water phase, which contains
most of the morpholine-borane complex, was discarded. The
diethyl ether phase was evaporated under vacuum, and the
residue was purified by filtration on a short column of silica
gel using diethyl ether as the eluant. The phosphines 2R and
2S have been isolated as white powders (2R: 0.25 g, 26% yield
(from 2‚BH3). 2S: 0.4 g, 41% yield (from 2‚BH3)).
From these results it appears that with our catalyst
precursors, an increase of the activity occurs with a
decrease in the stereoselectivity. This suggests that
contrary to the Noyori’s catalysts,22f the reversibility of
the transfer hydrogenation of acetophenone must be
important in our case.
2R‚BH3. 1H NMR (CDCl3, 200 MHz): δ 8.3 (m, 1H, C5H4N),
7.0-7.9 (m, 13H, 2 × C6H5 and C5H4N), 4.37 (m, 2H, CH2),
3.80 (m, 1H, PCHR), 2.95 (m, 1H, H1 (menthyl)), 0.9-2.0 (m,
11H, CH and CH2 (menthyl), BH3), 0.79 (d, 3H, CH3, J HH
)
Exp er im en ta l Section
6.6 Hz), 0.69 (d, 3H, CH3, J HH ) 7.0 Hz), 0.57 (d, 3H, CH3,
J HH ) 7.0 Hz). 31P{1H} NMR (CDCl3, 81.01 MHz): δ 20.0 (br).
All reactions were performed under a nitrogen atmosphere
with the use of standard Schlenk techniques. Tetrahydrofuran
and diethyl ether used for the syntheses were distilled under
nitrogen from sodium benzophenone ketyl just before use.
Other solvents were purified following the standard procedures
and stored under nitrogen. NMR spectra were recorded on
Bruker AC 200, WM 250, or AMX 400 instruments. Elemental
analyses were performed in our laboratory on a Perkin-Elmer
2400 CHN analyzer. Optical rotations were measured with a
Perkin Elmer 341 polarimeter using 10 cm cells. Chlorom-
ethyl-(1R,2S,5R)-menthyl ether,24 2-((diphenylphosphino)m-
2S‚BH3. 1H NMR (CDCl3, 200 MHz): δ 8.30 (m, 1H,
C5H4N), 6.9-7.9 (m, 13H, 2 × C6H5 and C5H4N), 4.28 (m, 1H,
CHaHb), 4.03 (m, 2H, CHaHb PCHR), 2.82 (m, 1H, H1 (men-
thyl)), 0.5-2.2 (m, 11H, CH and CH2 (menthyl), BH3), 0.77 (d,
3H, CH3, J HH ) 6.5 Hz), 0.53 (d, 3H, CH3, J HH ) 7.0 Hz), 0.18
(d, 3H, CH3, J HH ) 7.0 Hz). 31P{1H} NMR (CDCl3, 81.01
MHz): δ 20.0 (br).
(24) Shatzmiller, S.; Dolithzky, B. Z.; Bahar, E. Liebigs Ann. Chem.
1991, 375.

Ruthenium(II) Complexes
Organometallics, Vol. 16, No. 7, 1997 1407
2R. [R]D ) + 119.1° (c ) 0.96, C6H6). 1H NMR (CDCl3, 200
MHz): δ 8.49 (m, 1H, C5H4N), 6.94-7.68 (m, 13H, 2 × C6H5
eluant. Phosphine-borane 3‚BH3 was isolated as a yellow oil
(0.7 g, 70% yield).
and C5H4N), 4.17 (ddd, 1H, CHaHb, J H
) 9.2 Hz, J H
)
3c. 1H NMR (CDCl3, 200 MHz): δ 8.35 (m, 1H, C5H4N),
7.85-6.83 (m, 12H, C6H5, C6H4, and C5H4N), 4.01 (AB(X), 2H,
H
H
R
a
b
a
3.3 Hz, J H ) 9.2 Hz), 3.96 (ddd, 1H, PCHR, J H
) 3.3 Hz,
P
H
a
R
a
J H
) 4.6 Hz, J H ) 8.1 Hz), 3.64 (ddd, 1H, CHaHb, J H
)
PCH2, J H
) 13.5 Hz, J H ) 13.9 Hz, J H ) 12.6 Hz), 3.70
H
P
H
H
P
P
R
b
R
b
a
a
b
a
b
9.2 Hz, J H
) 4.6 Hz, J H ) 6.9 Hz), 2.89 (m, 1H, H1
(s, 3H, CH3), 2.1-0.2 (m, 3H, BH3). 31P{1H} NMR (CDCl3,
81.01 MHz): δ 17.0 (q, J PB ) 52 Hz).
H
P
b
b
R
(menthyl)), 0.85-2.01 (m, 8H, CH and CH2 (menthyl)), 0.78
(d, 3H, CH3, J HH ) 5.5 Hz), 0.75 (d, 3H, CH3, J HH ) 6.9 Hz),
0.58 (d, 3H, CH3, J HH ) 6.9 Hz). 31P{1H} NMR (CDCl3, 81.01
MHz): δ -7.6. Anal. Calcd for C29H36NOP: C, 78.16; H, 8.16;
N, 3.14. Found: C, 77.36; H, 8.41; N, 3.40.
2S. [R]D ) -145.1° (c ) 0.94, C6H6). 1H NMR (CDCl3, 200
MHz): δ 8.51 (m, 1H, C5H4N), 6.92-7.70 (m, 13H, 2 × C6H5
and C5H4N), 3.96 (m, 3H, PCHR and CHaHb), 2.83 (m, 1H, H1
(menthyl)), 0.87-1.97 (m, 8H, CH and CH2 (menthyl)), 0.81
(d, 3H, CH3, J HH ) 6.5 Hz), 0.60 (d, 3H, CH3, J HH ) 7.0 Hz),
0.24 (d, 3H, CH3, J HH ) 6.9 Hz). 31P{1H} NMR (CDCl3, 81.01
MHz): δ -8.4. Anal. Calcd for C29H36NOP: C, 78.16; H, 8.16;
N, 3.14. Found: C, 77.60; H, 8.61; N, 3.43.
(S)-(P h en yl(2-an isyl)ph osph in o)(2-pyr idyl)m eth an e (3).
The phosphine-borane complex 3‚BH3 (0.7 g, 2 mmol) was
dissolved in 10 mL of morpholine, and the solution was heated
at 70 °C for 2 h. Excess morpholine was eliminated under
vacuum. The residue was treated by a mixture of diethyl ether
(20 mL) and water (20 mL). The water phase, which contains
most of the morpholine-borane complex, was discarded. The
diethyl ether phase was evaporated under vacuum, and the
residue was purified by filtration on a short column of silica
gel using diethyl ether as the eluant. The phosphine 3 has
been isolated as a white solid (0.6 g, 95% yield).
3 [R]D ) +61.4° (c ) 0.7, C6H6). 1H NMR (CDCl3, 200
MHz): δ 8.44 (m, 1H, C5H4N), 6.78-7.49 (m, 12H, C6H5, C6H4,
Syn t h esis of (S)-(P h en yl(2-a n isyl)p h osp h in o)(2-p y-
r id yl)m eth a n e (3). Syn th esis of (S)-(Meth yl[(1R,2S)-(1-
h yd r oxy-2-m eth yl-1-p h en yl-2-p r op yl)]a m in o)(o-a n isyl)-
p h en ylp h osp h in e-bor a n e (3a ). To 5.54 mL of a 1.3 M
solution of s-BuLi in cyclohexane (7.2 mmol) cooled at 0 °C
was added 0.75 mL of 2-bromoanisole, and the reaction
mixture was stirred for 0.5 h. To the solution of 2-(methox-
yphenyl)lithium thus formed was added 2 mL of THF, and the
mixture was slowly added to a solution containing 1.71 g (6
mmol) of (2R,4S,5R)-3,4-dimethyl-1,3,2-oxazaphospholidine-
2-borane in THF (6 mL) cooled at -40 °C. Once the transfer
was completed, the reaction medium was allowed to reach
room temperature, stirred for an additional hour, and then
hydrolyzed by the addition of water (0.1 mL). After elimina-
tion of the solvents, the residue was dissolved in dichlo-
romethane and chromatographed on silica gel, using diethyl
ether as the eluant. The ether was eliminated under vacuum
to leave 3a as a white solid (2.2 g, 93% yield).
3a . 1H NMR (CDCl3, 200 MHz): δ 7.60-6.86 (m, 14H, 2 ×
C6H5 and C6H4), 4.88 (d, 1H, CH, J HH ) 6.9 Hz), 4.32 (m, 1H,
CH), 3.57 (s, 3H, OCH3), 2.54 (d, 3H, NCH3, J HP ) 8.1 Hz),
1.22 (d, 3H, CH3, J HH ) 6.9 Hz), 0.3-2.0 (m, 3H, BH3). 31P-
{1H} NMR (CDCl3, 81.01 MHz): δ 69.1 (bm).
Syn th esis of Meth yl (R)-(o-An isyl)p h en ylp h osp h in ite-
Bor a n e (3b). One molar equivalent of sulfuric acid (0.3 mL)
was added to a solution of 3a (2 g, 5.1 mmol) in anhydrous
methanol (20 mL). After the mixture was stirred overnight,
the solution was first filtered on a short column of silica gel to
eliminate the acid in excess and then the methanol was
evaporated under vacuum. The residue containing the phos-
phinite-borane complex 3b was extracted by dichloromethane
and purified by column chromatography on silica gel, using
dichloromethane as the eluant. 3b was isolated as a colorless
liquid (1 g, 80% yield).
and C5H4N), 3.60 (AB, 2H, PCH2, J H
) 13.2 Hz), 3.66 (s,
H
a
b
OCH3). 31P{1H} NMR (CDCl3, 81.01 MHz): δ -19.2 (s). Anal.
Calcd for C19H18NOP: C, 74.24; H, 5.92; N, 4.56. Found: C,
74.01; H, 5.97; N, 4.51.
Syn t h esis of t h e Com p lexes 4, 5, 6, a n d 9. Gen er a l
P r oced u r e. A dichloromethane solution (4 mL) of the ap-
propriate phosphine (0.5 mmol) was added to a solution of
0.5 g of RuCl2(PPh3)3 (0.5 mmol) in the same solvent (10 mL).
The reaction medium was stirred overnight. The solvent
was removed under vacuum, and the solid residue was
washed with a toluene/hexanes mixture (1:3, 2 × 4 mL) to
eliminate triphenylphosphine. The complexes have been
purified by recrystallization from dichloromethane/hexane
mixtures.
Ru Cl2(P P h 3)(1) (4): yellow (73% yield). 1H NMR (CD2Cl2,
303 K, 250 MHz): δ 8.48-6.20 (m, 29 H, C6H5, C5H4N), 4.30
(dt, J HH ) 1.6 Hz, J PH ) 10.4 Hz, 1H, CH-CH2-O-CH2-CH3),
3.56, 3.55 (ABMX spin system (M ) H, X ) P), J AB ) 7.8 Hz,
J AH ) J BH ) 1.6 Hz, J PA) 20 Hz, J PB ) 7.8 Hz, 2H, CH-CH2-
O-CH2-CH3), 4.19, 4.18 (J AB ) 5.1 Hz, J AH ) J BH ) 7 Hz,
2H, CH-CH2-O-CH2-CH3)), 1.07 (t, J HH ) 7 Hz, 3 H, CH-
CH2-O-CH2-CH3). 1H NMR (CD2Cl2, 183 K, 250 MHz): δ
9.70 (bt, 1H, C5H4N), 8.28-6.19 (m, 28H, C6H5, C5H4N),
4.35 (d, J PH ) 10.5 Hz, 1H, CH-CH2-O-CH2-CH3), 3.50
(m, 2H, CH-CH2-O-CH2CH3), 4.18, 4.01 (bm, 2H, CH-
CH2-O-CH2-CH3)), 1.10 (bm, 3H, CH-CH2-O-CH2CH3).
31P{1H} NMR (CD2Cl2, 303 K, 32 MHz): δ 62.2. 183 K, 31P{1H}
NMR (CD2Cl2, 183 K, 101 MHz): δ 66.7, 64.7 (J ) 39 Hz).
31P{1H} NMR (C6D6, 303 K, 32 MHz): δ 63.3, 61.2 (J ) 39
Hz). IR (ν(Ru-Cl, CsI): 300, 275 cm-1
39H37Cl2P2ONRu: C, 60.86; H, 4.85; N, 1,82. Found: C,
60.87; H, 5.17; N, 1.78.
Ru Cl2(P P h 3)(2R) (5): yellow (64% yield).
5a (only significant NMR data are reported). 1H NMR (CD2-
Cl2, 297 K, 400 MHz): δ 8.45 (b, 1H, C5H4N), 4.29 (d, J PH
. Anal. Calcd for
C
)
3b. 1H NMR (CDCl3, 200 MHz): δ 7.84-6.84 (m, 9H, C6H5
and C6H4), 3.73 (d, 3H, OCH3, J HP ) 12 Hz), 3.62 (s, 3H, CH3),
1.8-0.2 (m, 3H, BH3). 31P{1H} NMR (CDCl3, 81.01 MHz): δ
106.2 (q, J PB ) 81 Hz). Anal. Calcd for C14H18BO2P: C, 64.65;
H, 6.98. Found: C, 64.94; H, 7.08.
10.4 Hz, 1H, CH-CH2-O-menthyl), 3.51 (dd, J HH ) 8 Hz,
J PH ) 12.7 Hz), 3.38 (d, J HH ) 8 Hz, CH-CH2-O-menthyl),
4.41 (m, 1H, H1 (menthyl)). 1H NMR (CD2Cl2, 193 K): δ 9.73
(bt, 1H, C5H4N), 4.35 (d, J PH ) 10 Hz, 1H, CH-CH2-O-
menthyl), 3.46 (dd, J HH ) 7 Hz, J PH ) 12 Hz), 3.23 (d, J HH
)
Syn t h esis of (S)-(P h en yl(2-a n isyl)p h osp h in o)(2-p y-
r id yl)m eth a n e-Bor a n e (3‚BH3). To a solution containing
0.55 g of 2-picoline (5.94 mmol) in 3 mL of diethyl ether cooled
at 0 °C was slowly added 3.7 mL of a 1.6 M solution of n-BuLi
in hexane (5.94 mmol). The mixture was stirred at 0 °C for
1h and then added to a solution containing 0.8 g of 3b (2.97
mmol) in THF (3 mL) cooled at -20 °C. Once the addition
was completed, the reaction mixture was stirred for an
additional 15 min at -20 °C and then for 1 h at 0 °C. The
hydrolysis was performed at room temperature by adding a
minimum amount of water. After the removal of the solvents
under vacuum, the residue was purified by chromatography
on silica gel using a diethyl ether/hexanes mixture as the
7 Hz, CH-CH2-O-menthyl), 4.26 (m, 1H, H1 (menthyl)).
31P{1H} NMR (CD2Cl2, 297 K, 161.9 MHz): δ 62 (b), 66.4 (bd,
J ) 38 Hz). 31P{1H} NMR (CD2Cl2, 193 K, 161.9 MHz): δ 62
(d), 66.8 (d, J ) 39 Hz).
5b (only significant NMR data are reported). 1H NMR (CD2-
Cl2, 297 K, 400 MHz): δ 9.42 (d, J ) 5.2 Hz, 1H, C5H4N), 3.31
(dd, J HH ) 8 Hz, J PH ) 12.3 Hz, 1H, CH-CH2-O-menthyl),
3.59 (t, J HH ) 9 Hz), 3.23 (t, J HH ) J PH ) 9 Hz, CH-CH2-
O-menthyl), 2.79 (m, 1H, H1 (menthyl)). 1H NMR (CD2Cl2,
193 K, 400 MHz): δ 9.44 (d, J HH ) 4.9 Hz, 1H, C5H4N), 3.06
(b, 1H, CH-CH2-O-menthyl), 3.56, 2.78 (b, CH-CH2-O-
menthyl), 2.71 (b, 1H, H1 (menthyl)). 31P{1H} NMR (CD2Cl2,
297 K, 161.9 MHz): δ 52 (b), 75.3 (b). 31P{1H} NMR (CD2Cl2,

1408 Organometallics, Vol. 16, No. 7, 1997
Ta ble 4. Cr ysta l Da ta , Da ta Collection , a n d Refin em en t P a r a m eter s for 6b a n d 9
Yang et al.
6b
9‚CH2Cl2
Crystal Data
chem formula
mol wt
cryst syst
space group
a (Å)
C47H51Cl2NOP2Ru
C38H35Cl4NOP2Ru
879.85
orthorhombic
P212121
10.020(2)
16.746(2)
25.711(4)
4314(1)
4
1.28
25
12-14
5.77
826.53
orthorhombic
P212121
8.747(2)
16.347(4)
27.196(5)
3888(2)
4
1.41
25
12-14
7.82
b (Å)
c (Å)
V (Å3)
Z
Fcalcd (g‚cm-3
)
no. of reflns for cell params
range for cell params (deg)
µ (mm-1
F000
)
1820.31
1677.33
Data Collection
data collection method
no. of indep reflns
no. of obsd reflns
obs criterion
θ max (deg)
range of hkl
ω/2θ
5707
4933
ω/2θ
3218
1470
Fo > 3σFo2
Fo > 3σFo2
2
2
23
23
0 g h g 11, 0 g k g 18, -28 g l g 28
0.8 + 0.35 tan θ
0 g h g 8, 0 g k g 18, -26 g l g 26
0.8 + 0.35 tan θ
scan range θ (deg)
Refinement
0.0243
R
0.0765
Rw
0.0279
0.0844
abs corr
weighting scheme
coeff Ar
Ψ-scans
DIFABS
Chebyshev
Chebyshev
2.21, 0.110, 1.65
0.00(3)
0.909, 0.2081, 0.688,
Flack’s parameter
GOFa
0.978
1.063
no. of reflns used
no. of params refined
residual electron density (e‚Å-3
4933
488
1470
224
)
-0.76 (min), 0.70 (max)
-1.01 (min), 2.33 (max)
a
Goodness of Fit ) [∑w(|Fo| - |Fc|)2/(Nobs - Nparas)]1/2
.
193 K, 161.9 MHz): δ 53.2 (d), 74.5 (d, J ) 32.5 Hz). Anal.
Calcd for C47H51Cl2NOP2Ru: C, 64.15; H, 5.97; N, 1.59.
Found: C, 62.94; H, 5.98; N, 1.60.
isolated upon filtration as a pale yellow powder (0.15 g, 70%
yield). IR (ν(CO), CH2Cl2): 1980 cm-1 1H NMR (CD2Cl2, 200
.
MHz): δ 8.40-6.62 (29H, C6H5, C5H4N), 6.57 (dd, J HH ) 5.2
Hz, J PH ) 9.8 Hz, 1H, CH-CH2-O-CH2-CH3), 4.16, 3.63 (m,
2H, CH-CH2-O-CH2-CH3), 3.12 (m, 2H, CH-CH2-O-
CH2-CH3), 1.03 (t, J HH ) 7 Hz, 3H, CH-CH2-O-CH2-CH3).
Ru Cl2(P P h 3)(2S) (6): yellow (79% yield).
6a (only significant NMR data are reported). 1H NMR (CD2-
Cl2, 297 K, 400 MHz): δ 8.39 (b, 1H, C5H4N), 4.31 (d, J PH
10.7 Hz, 1H, CH-CH2-O-menthyl), 3.57 (dd, J HH ) J PH
)
)
31P{1H} NMR (CDCl3, 81.01 MHz): δ 40.4 (d), 25.5 (d, J PP
)
5.8 Hz), 3.39 (d, J HH ) 5.8 Hz, CH-CH2-O-menthyl), 4.50
(m, 1H, H1 (menthyl)). 1H NMR (CD2Cl2, 193 K): δ 9.74 (b,
1H, C5H4N), 4.35 (m, 1H, CH-CH2-O-menthyl), 3.48 (b), 3.23
(b, CH-CH2-O-menthyl), 4.35 (b, 1H, H1 (menthyl)). 31P{1H}
NMR (CD2Cl2, 297 K, 161.9 MHz): δ 63.7 (d), 66.4 (d, J ) 39
Hz). 31P{1H} NMR (CD2Cl2, 193K, 161.9 MHz): δ 64.3 (d),
66.5 (J ) 39 Hz).
27.6 Hz).
Syn th esis of 8. Complex 7 (0.15 g) was dissolved in 5 mL
of CH2Cl2, and the solution was stirred for 15 h at room
temperature. The addition of 5 mL of hexanes induced the
precipitation of 0.1 g (70% yield) of 8 as a pale yellow powder.
IR (ν(CO), CH2Cl2): 1962 cm-1; (ν(Ru-Cl), CsI) 310, 272 cm-1
.
1H NMR (CD2Cl2, 200 MHz): δ 8.41-6.63 (m, 29H, C6H5,
C5H4N), 5.91 (dd, J HH ) 7.8 Hz, J PH ) 14.3 Hz, 1H, CH-CH2-
O-CH2-CH3), 3.95 (m, 2H, CH-CH2-O-CH2-CH3), 3.49 (m,
2H, CH-CH2-O-CH2-CH3), 1.20 (t, J HH ) 7 Hz, 3H, CH-
CH2-O-CH2-CH3). 31P{1H} NMR (CDCl3, 81.01 MHz): 61.2
(d), 18.8 (d, J PP ) 354.5 Hz). Anal. Calcd for C40H37Cl2NO2P2-
Ru: C, 60.23; H, 4.68; N, 1.76. Found: C, 60.45; H, 5.01; N,
2.02.
6b (only significant data are reported). 1H NMR (CD2Cl2,
297 K, 400 MHz): δ 9.43 (d, J ) 5.6 Hz, 1H, C5H4N), 3.26 (dd,
J HH ) 9.1 Hz, J PH ) 7.7 Hz, 1H, CH-CH2-O-menthyl), 3.70
(t, J HH ) J PH ) 9 Hz), 3.13 (b, CH-CH2-O-menthyl), 2.91
(m, 1H, H1 (menthyl)). 1H NMR (CD2Cl2, 193 K): δ 9.38 (b,
1H, C5H4N), 2.90 (b, 1H, CH-CH2-O-menthyl), 3.70, 3.07
(b, CH-CH2-O-menthyl), 2.95 (b, 1H, H1 (menthyl). 31P{1H}
NMR (CD2Cl2, 297 K, 161.9 MHz): δ 53.2 (b), 74 (b). 31P{1H}
NMR (CD2Cl2, 193 K, 161.9 MHz): δ 53.2 (d), 73.9 (d, J )
32.6 Hz). Anal. Calcd for C47H51Cl2NOP2Ru: C, 64.15; H,
5.97; N, 1.59. Found: C, 63.84; H, 5.68; N, 1.48.
Rea ctivity of 9 tow a r d CO. Syn th esis of 10. Carbon
monoxide was bubbled through a solution of RuCl2(PPh3)(4)
(9, 0.1 g) in dichloromethane (10 mL) for 10 min. The addition
of hexanes (10 mL) induced the precipitation of 10, which was
isolated upon filtration as a pale yellow powder (0.09 g, 43%
yield). IR(ν(CO), CH2Cl2): 1987 cm-1
MHz): δ 8.40-6.20 (28H, C6H5, C5H4N), 4.92 (dd, J HH ) 16.8
Ru Cl2(P P h 3)(3) (9): yellow (91% yield). 1H NMR (CDCl3,
200 MHz): δ 9.61 (d, 1H, C5H4N, J HH ) 5.4 Hz), 7.64-6.51
(m, 24H, 4 × C6H5, C6H4), 4.61 (s, 3H, OCH3), 3.55 (AB(X),
.
1H NMR (CDCl3, 200
2H, PCH2, J H
) 15.9 Hz, J H )13.7 Hz, J H ) 8.4 Hz).
H
P
P
a
b
a
b
31P{1H} NMR (CDCl3, 81.01 MHz): δ 64.5 (d), 62.9 (d, J PP
)
Hz, J PH ) 10.9 Hz, 1H, CH2), 4.34 (dd, J HH ) 16.8 Hz, J PH
)
12.2 Hz, 1H, CH2), 3.25 (s, 3H, OCH3). 31P{1H} NMR (CDCl3,
81.01 MHz): 44.9 (d), 16.2 (d, J PP ) 29.4 Hz). Anal. Calcd
for C37H31Cl2NO2P2Ru: C, 58.82; H, 4.14; N, 1.85. Found: C,
58.56; H, 4.01; N, 1.92.
37.5 Hz). Anal. Calcd for C37H33Cl2NOP2Ru: C, 59.91; H,
4.49; N, 1.89. Found: C, 58.61; H, 4.51; N, 1.71.
Rea ctivity of 4 tow a r d CO. Syn th esis of 7. Carbon
monoxide was bubbled through a solution of RuCl2(PPh3)(1)
(4, 0.2 g) in dichloromethane (10 mL) for 10 min. The addition
of hexanes (10 mL) induced the precipitation of 7, which was
X-r a y Diffr a ction Stu d ies. Crystals of 6b and 9 suitable
for X-ray diffraction were obtained through recrystallization

Ruthenium(II) Complexes
Organometallics, Vol. 16, No. 7, 1997 1409
at -20 °C from dichloromethane/hexane. Data were collected
on an Enraf-Nonius CAD4 diffractometer at 22 °C. Cell
constants were obtained by the least-squares refinement of the
setting angles of 25 reflections in the range 24° < 2θ(Mo KR1)
< 28°. The space group was determined by careful examina-
tion of systematic extinctions in the listing of the measured
reflections.
All calculations were performed on a PC-compatible com-
puter. Data reductions were carried out using the RC93
program.25 Full crystallographic data are given in Table 4.
The structures were solved by using the SIR92 program,26
which revealed the positions of most of the non-hydrogen
atoms. All remaining non-hydrogen atoms were located by the
usual combination of full-matrix least-squares refinement and
difference electron density syntheses by using the CRYSTALS
program.27,28 Complex 9 was found to crystallize with 1
molecule of dichloromethane per unit cell. The least-square
refinements were carried out by minimizing the function
∑w(|Fo| - |Fc|)2, where Fo and Fc are the observed and the
calculated structure factors. The weighting scheme used in
the last refinement cycles was w ) w′[1 - (∆F/6σ(Fo)2]2, where
w′ ) 1/∑n)1nArTr(x) with a variable number of coefficients Ar
for the Chebyshev polynomial ArTr(x), where x was Fc/Fc-
(max).29 Models reached convergence with R ) ∑||Fo| - |Fc||/
2
∑|Fo| and Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| )]1/2 having the values
given in Table 4. Atomic scattering factors were taken from
the usual tabulations.30 Anomalous dispersion terms for the
Ru atoms were included in Fc.31 For the structure of 6b, all
non-hydrogen atoms were allowed to vibrate anisotropically.
For the structure of 9, owing to the poor quality of the
monocrystal used, only Ru, P, and Cl atoms have been refined
with anisotropic temperature factors. For both structures, all
of the hydrogen atoms were set in idealized positions (C-H )
0.99 Å). The absolute configuration of 6b was determined by
refining the Flack’s enantiopole parameter,32 which is defined
as: Fo2 ) (1 - x)F(h)2 + xF(-h)2. No attempts have been made
to determine the absolute configuration of 9.
Su p p or tin g In for m a tion Ava ila ble: Tables giving final
values of all refined atomic coordinates, calculated atomic
coordinates, anisotropic thermal parameters, and all bond
lengths and angles (14 pages). Ordering information is given
on any current masthead page.
OM960955J
(25) Watkin, D. J .; Prout, C. K.; de Q Lilley, P. M. RC93; Chemical
Crystallography Laboratory: Oxford, U.K., 1994.
(26) Altomare, A.; Cascarano, G.; Giacovazzo, G.; Gualiardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. SIR92-A program for automatic
solution of crystal structures by direct methods. J . Appl. Crystallogr.
1994, 27, 435.
(27) Watkin, D. J .; Prout, C. K.; Carruthers, R. J .; Betteridge, P.
CRYSTALS, Issue 10; Chemical Crystallography Laboratory: Oxford,
U.K., 1996.
(29) Carruthers, J . R.; Watkin, D. J . Acta Crystallogr. 1979, A35,
698.
(30) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, England, 1974; Vol. 4,
Table 2.2B.
(31) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, England, 1974; Vol. 4,
Table 2.3.1.
(28) Watkin, D. J .; Prout, C. K.; Pearce, L. J . CAMERON; Chemical
Crystallography Laboratory: Oxford, U.K., 1996.
(32) Flack, H. Acta Crystallogr. 1983, A39, 876.