Ruthenium complexes of chiral diphosphinite ligands with cyclohexane or chiro-inositol backbones as catalysts for asymmetric hydrogenation reactions

Article abstract of DOI:10.1080/00958970903502744

Treatment of [RuCl₂(COD)]_n with the chiral diphosphinite ligand (1S,2S)-1,2-trans-bis-(O-diphenylphosphino)cyclohexane [(1S,2S)-14] and triethylamine gives the bis(diphosphinite) complex RuHCl[(1S,2S)-14]₂ (15) in good yield. If (rac)-1,2-trans-bis-(O-diphenylphosphino)-cyclohexane [(rac)-14] is used in place of (1S,2S)-14 in this reaction, a racemic mixture of RuHCl[(1S,2S)-14]₂ and RuHCl[(1R,2R)-14]₂ [(rac)-16] is formed. The X-ray crystal structure of (rac)-16 (2.5CH₂Cl₂) has been determined. Treatment of (rac)-16 with hydrogen in iso-propanol leads to the formation of a racemic mixture of RuH₂[(1S,2S)-14]₂ and RuH₂[(1R,2R)-14]₂ [(rac)-17]. The structure of (rac)-17 was confirmed by the X-ray analysis of a racemic crystal. Ruthenium mono(diphosphinite), diamine complexes of the general formula RuCl₂(NN)(PP) are formed by the treatment of RuCl₂(PPh₃)₃ with the appropriate diphosphinite (PP) and diamine (NN) ligands. In this way, the following complexes have been synthesized: RuCl₂[(+)-DPEN][(1S,2S)-14] (18), RuCl₂(-)-DPEN][(1S,2S)-14] (19), RuCl₂[(+)-DPEN][(1R,2R)-14] (20), RuCl₂[(-)-DPEN][(1R,2R)-14] (21), RuCl₂[(+)-DPEN][(rac)-14] (22), RuCl₂[(-)-DPEN][(rac)-14] (23), RuCl₂(D-NN2)[(1S,2S)-14] (24), RuCl₂(EDA)[(1S,2S)-14] (25), RuCl₂(D-NN2)(D-10) (26), RuCl₂(EDA)(D-10) (27), RuCl₂[(+)-DPEN](D-10Et) (28), RuCl₂(D-NN2)(D-10Et) (29), [where DPEN=1,2-diphenylethylenediamine, D-NN2=1D-1,2-dideoxy-1,2-diamino-3,4,5,6-tetra-O-benzyl-myo-inositol, EDA=1,2-diaminoethane, D-10=1D-3,4-bis(O-diphenylphosphino)-1,2,5, 6-tetra-O-methyl-chiro-inositol, D-10Et=1D-3,4-bis(O-diphenylphosphino)-1,2,5,6-tetra-O-ethyl-chiro-inositol]. These ruthenium complexes catalyze the hydrogenation of the ketones acetophenone and 3-quinuclidinone to give the corresponding alcohols in high yields, but with moderate to low enantiomeric excesses.

Full text of DOI:10.1080/00958970903502744

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Ruthenium complexes of chiral
diphosphinite ligands with cyclohexane
or chiro -inositol backbones as
catalysts for asymmetric hydrogenation
reactions
George R. Clark a , Andrew Falshaw b , Graeme J. Gainsford b
Cornelis Lensink b , Angela T. Slade a & L. James Wright a a
,
a Department of Chemistry , The University of Auckland , Private
Bag 92019, Auckland, New Zealand
b Industrial Research Limited , PO Box 31-310, Lower Hutt, New
Zealand
Published online: 04 Jan 2010.
To cite this article: George R. Clark , Andrew Falshaw , Graeme J. Gainsford , Cornelis Lensink ,
Angela T. Slade & L. James Wright (2010) Ruthenium complexes of chiral diphosphinite ligands
with cyclohexane or chiro -inositol backbones as catalysts for asymmetric hydrogenation reactions,
Journal of Coordination Chemistry, 63:3, 373-393, DOI: 10.1080/00958970903502744
To link to this article: http://dx.doi.org/10.1080/00958970903502744
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Journal of Coordination Chemistry
Vol. 63, No. 3, 10 February 2010, 373–393
Ruthenium complexes of chiral diphosphinite ligands with
cyclohexane or chiro-inositol backbones as catalysts for
asymmetric hydrogenation reactions
GEORGE R. CLARKy, ANDREW FALSHAWz, GRAEME J. GAINSFORDz,
CORNELIS LENSINKz, ANGELA T. SLADEy and L. JAMES WRIGHT*y
yDepartment of Chemistry, The University of Auckland, Private Bag 92019,
Auckland, New Zealand
zIndustrial Research Limited, PO Box 31-310, Lower Hutt, New Zealand
(Received 9 July 2009; in final form 25 August 2009)
Treatment of [RuCl2(COD)]n with the chiral diphosphinite ligand (1S,2S)-1,2-trans-bis-(O-
diphenylphosphino)cyclohexane [(1S,2S)-14] and triethylamine gives the bis(diphosphinite)
complex RuHCl[(1S,2S)-14]2 (15) in good yield. If (rac)-1,2-trans-bis-(O-diphenylphosphino)-
cyclohexane [(rac)-14] is used in place of (1S,2S)-14 in this reaction, a racemic mixture of
RuHCl[(1S,2S)-14]2 and RuHCl[(1R,2R)-14]2 [(rac)-16] is formed. The X-ray crystal structure
of (rac)-16ꢀ(2.5CH2Cl2) has been determined. Treatment of (rac)-16 with hydrogen
in iso-propanol leads to the formation of a racemic mixture of RuH2[(1S,2S)-14]2 and
RuH2[(1R,2R)-14]2 [(rac)-17]. The structure of (rac)-17 was confirmed by the X-ray analysis of
a racemic crystal. Ruthenium mono(diphosphinite), diamine complexes of the general formula
RuCl2(NN)(PP) are formed by the treatment of RuCl2(PPh3)3 with the appropriate
diphosphinite (PP) and diamine (NN) ligands. In this way, the following complexes have
been synthesized: RuCl2[(þ)-DPEN][(1S,2S)-14] (18), RuCl2[(ꢁ)-DPEN][(1S,2S)-14] (19),
RuCl2[(þ)-DPEN][(1R,2R)-14] (20), RuCl2[(ꢁ)-DPEN][(1R,2R)-14] (21), RuCl2[(þ)-
DPEN][(rac)-14] (22), RuCl2[(ꢁ)-DPEN][(rac)-14] (23), RuCl2(D-NN2)[(1S,2S)-14] (24),
RuCl2(EDA)[(1S,2S)-14] (25), RuCl2(D-NN2)(D-10) (26), RuCl2(EDA)(D-10) (27),
RuCl2[(þ)-DPEN](D-10Et)
(28),
RuCl2(D-NN2)(D-10Et)
(29),
[where
DPEN ¼
1,2-diphenylethylenediamine,
myo-inositol,
D-NN2 ¼ 1D-1,2-dideoxy-1,2-diamino-3,4,5,6-tetra-O-benzyl-
EDA ¼ 1,2-diaminoethane, D-10 ¼ 1D-3,4-bis(O-diphenylphosphino)-1,2,5,
6-tetra-O-methyl-chiro-inositol, D-10Et ¼ 1D-3,4-bis(O-diphenylphosphino)-1,2,5,6-tetra-O-
ethyl-chiro-inositol]. These ruthenium complexes catalyze the hydrogenation of the ketones
acetophenone and 3-quinuclidinone to give the corresponding alcohols in high yields, but with
moderate to low enantiomeric excesses.
Keywords: Ruthenium; Catalytic asymmetric hydrogenation of ketones; Chiro-inositol; Chiral
diphosphinite ligand; X-ray crystal structure
1. Introduction
A large number of studies have focused on the development of chiral ligands
for transition metal catalyzed asymmetric transformations of prochiral substrates [1].
*Corresponding author. Email: lj.wright@auckland.ac.nz
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ß 2010 Taylor & Francis
DOI: 10.1080/00958970903502744

374
G.R. Clark et al.
A general observation is that catalysts incorporating a given chiral ligand do not form
products of high enantiomeric purity with all prochiral substrates, and this has provided
a major impetus for the development of new chiral ligands [2]. Phosphorus donors have
been most commonly employed in the design of new chiral ligands [2, 3], and we
recently reported our preliminary results of the synthesis and study of new chiral
diphosphinite ligands that incorporate a chiro-inositol backbone [4]. Attractive features
of chiro-inositol (figure 1) that are not shared with many other carbohydrates are the
chemically robust cyclohexane backbone, the ready availability of both the D- and
Figure 1. Chiral alcohols and the chiral diphosphinite ligands synthesized from these.

Chiral diphosphinite ligands
375
L-enantiomers from natural products, and the presence of six hydroxyl groups that
provide extensive scope for selective functionalization. Although a number of chiral,
phosphorus-donor ligands based on other carbohydrates have been synthesized for
transition-metal-catalyzed asymmetric transformations [5–11], chiral inositols have
been rarely studied in this context [12]. In our recent study, we found that ruthenium
derivatives of chiro-inositol-based diphosphinite ligand, D-10 (figure 1), catalyze the
asymmetric hydrogenation of some ketones to give products with low to moderate
enantiomeric excesses. In an extension of this work, we have investigated the catalytic
activities of a series of ruthenium complexes that contain related diphosphinite ligands
in which the four remote carbon centers in the cyclohexane rings bear different
substituents. Chiral diamine ligands have also been incorporated into some of these
complexes as these ligands have been shown, in some cases, to enhance the
enantioselectivity of asymmetric hydrogenation reactions [13]. We now report (1) the
synthesis of the chiral ruthenium diphosphinite complexes 15–29 (schemes 2 and 3);
(2) the crystal structures of a racemic mixture of RuHCl[(1S,2S)-14]2 and
RuHCl[(1R,2R)-14]2 [(rac)-16] and a racemic mixture of RuH2[(1S,2S)-14]2 and
RuH2[(1R,2R)-14]2 [(rac)-17] [(1S,2S)-14] ¼ (1S,2S)-1,2-trans-bis-(O-diphenylphosphi-
no)cyclohexane; and (3) the results of catalytic asymmetric hydrogenation studies of the
prochiral ketones acetophenone and 3-quinuclidinone in the presence of 15–29.
2. Results and discussion
2.1. The chiral diphosphinite ligands, 1D-3,4-bis(O-diphenylphosphino)-1,2,5,
6-tetra-O-methyl-chiro-inositol (D-10), 1D-3,4-bis(O-diphenylphosphino)-1,2,5,
6-tetra-O-ethyl-chiro-inositol (D-10Et), (1R,2R)-1,2-trans-bis-(O-diphenyl-
phosphino)cyclohexane [(1R,2R)-14], (1S,2S)-14, and (rac)-14
We have previously reported the synthesis of the chiro-inositol-derived diphosphinite
ligand 1D-3,4-bis(O-diphenylphosphino)-1,2,5,6-tetra-O-methyl-chiro-inositol (D-10)
[4]. The more sterically encumbered analogue, 1D-3,4-bis(O-diphenylphosphino)-
1,2,5,6-tetra-O-ethyl-chiro-inositol (D-10Et) (see figure 1), can be prepared in a parallel
manner, but with the alkylating agent EtBr replacing the MeI used in the original
synthetic sequence, as indicated in scheme 1. For the clarity and ease of comparison, the
same compound numbering scheme that was used in our previous report [4] is also used
in this article, and the numbering of new compounds in this article continues on from
this original numbering scheme. Spectroscopic data for D-10Et and all other new
compounds reported in this article are collected in section 3. The NMR spectral data for
1
D-10Et are consistent with the C2 symmetry of the molecule. Thus, in the H NMR
spectrum, two apparent triplet signals at 0.64 and 1.18 ppm are observed for the CH3
groups of the two sets of symmetry-related ethyl groups. Complex sets of overlapping
signals are observed for the CH and CH2 resonances in the region 2.72–4.93 ppm. In
the 13C NMR spectrum, resonances for the methyl groups are observed at 14.7 and
15.4 ppm, and resonances at 66.9 and 67.2 ppm are observed for the methylene groups.
The three pairs of CH signals are observed at 76.1, 77.9, and 78.9 ppm. In the 31P NMR
spectrum of D-10Et, a singlet at 109.47 ppm is observed for the two equivalent
phosphorus atoms.

376
G.R. Clark et al.
Scheme 1. Syntheses of the chiral ligands D-10Et and (1R,2R)-14.
The previously reported chiral diphosphinite ligands (1R,2R)-1,2-trans-bis-
(O-diphenylphosphino)cyclohexane [(1R,2R)-14] [14] and (1S,2S)-1,2-trans-bis-
(O-diphenylphosphino)cyclohexane [(1S,2S)-14] [15], as well as the racemic mixture
of these two chiral ligands, [(rac)-14] (see figure 1), were prepared from the
corresponding alcohols by treating with Ph2PCl, using a slightly modified version of
the literature procedure (see scheme 1 and section 3).
2.2. Synthesis of the bis(diphosphinite) complexes RuHCl[(1S,2S)-14]2 (15),
a racemic mixture of 15 and RuHCl[(1R,2R)-14]2 [(rac)-16], and a
racemic mixture of RuH2[(1S,2S)-14]2 and RuH2[(1R,2R)-14]2 [(rac)-17]
Complexes containing chiral diphosphinite ligands that have the general formula
R2PO-X-OPR2 (where X is a chiral bridging group) are well known for a number of
metals, including rhodium [16]. However, ruthenium derivatives of ligands of this type
are relatively rare [17, 18]. In an extension of our previous study, in which we reported
that treatment of [RuCl2(COD)]n with D-10 in the presence of triethylamine [19] gives
RuHCl(D-10)2 (11), we now report that the treatment of [RuCl2(COD)]n with (1S,2S)-
14 and triethylamine gives the closely related orange/yellow bis(diphosphinite) complex,
RuHCl((1S,2S)-14)2 (15) (scheme 2). The hydride ligand in 15 probably originates from
the ꢀ-hydride elimination of coordinated triethylamine in an intermediate complex
[19d]. The NMR spectroscopic data for 15 are consistent with the idealized geometry

Chiral diphosphinite ligands
377
Scheme 2. Syntheses of 11, 15, (rac)-16, and (rac)-17.
drawn in scheme 2 and a single crystal X-ray structure determination of (rac)-16 reveals
that this overall geometry is retained in the solid state. Although the C2 axis of the free
diphosphinite ligand, (1S,2S)-14 is no longer present in 15. In the idealized structure
drawn in scheme 2 there is a C2 axis that passes through H, Ru, and Cl. Thus, the two
phosphorus atoms and the six cyclohexane ring carbons within one diphosphinite
ligand are all inequivalent, but each of these atoms is related by the C2 axis to a
corresponding atom in the other ligand. Consequently, six signals are observed for the
cyclohexane ring carbons in the 13C NMR spectrum of 15 (at 24.4, 24.5, 32.3, 33.0, 75.7,
and 78.9 ppm). In the 31P NMR spectrum two apparent triplets are observed for each
symmetry-related pair of phosphorus atoms (at 118.13 and 147.26 ppm), consistent with
coupling in the AA0XX0 spin system [20]. In the 1H NMR spectrum of 15 two multiplets
that each integrate for two protons at 3.76 and 5.10 ppm are observed for the two pairs
of cyclohexane CH protons, and a complex set of overlapping multiplets in the region
0.80–2.35 ppm is observed for the CH2 groups. The hydride resonance is observed as a
multiplet at ꢁ16.38 ppm. In the solid state, 15 survives unchanged on exposure to air for
months, although in solution compound 15 is slowly degraded by atmospheric oxygen
over a period of hours.
If (1S,2S)-14, that is used in the synthesis of 15, is replaced with [(rac)-14], the
product formed is a racemic mixture of the two complexes RuHCl[(1S,2S)-14]2 and
RuHCl[(1R,2R)-14]2 [(rac)-16]. The spectral data for (rac)-16 is identical to that
observed for 15. A crystal of (rac)-16 suitable for X-ray structure determination was

378
G.R. Clark et al.
Scheme 3. Syntheses of 12, 13, and 18–29.
grown from dichloromethane/hexane and the structure obtained. The unit cell contains
one inversion related pair of the enantiomers RuHCl[(1S,2S)-14]2 and RuHCl[(1R,2R)-
14]2. The ORTEP diagram of RuHCl[(1R,2R)-14]2 is shown in figure 2. The geometry
about ruthenium is close to octahedral with the hydride and chloride ligands mutually
trans. The two diphosphinite ligands occupy the four other coordination sites, but
as can be seen from the ORTEP diagram, the four phosphorus atoms and ruthenium
are not coplanar. The relevant angles are P1–Ru–P-4 ¼ 176.40(3)ꢂ and P2–Ru–
ꢂ
˚
P3 ¼ 158.28(3) . The Ru–P2 and Ru–P3 distances [2.3285(7) and 2.3251(7) A,
respectively] are slightly shorter than the Ru–P1 and Ru–P4 distances [2.3729(7) and
˚
2.3563(7) A, respectively]. The Ru–Cl distance of 2.5520(7) A is longer than the average
˚
˚
Ru–Cl distance of 2.407 A recorded in the Cambridge Crystallographic Database (4879
˚
obs, SD 0.047 A), most likely as a result of the trans-influence of the hydride ligand.
On the treatment of (rac)-16 with hydrogen in iso-propanol using conditions similar
to those used for the hydrogenation studies (section 2.4), a racemic mixture of the
dihydride complexes RuH2[(1S,2S)-14]2 and RuH2[(1R,2R)-14]2 [(rac)-17] is formed in
very good yield (scheme 2). The structure of (rac)-17 shown in scheme 2 was confirmed
by X-ray structure determination. Although the two hydrides are mutually cis, the
complex retains a C2 axis which relates the two hydrides and the two diphosphinite
ligands. Again the six cyclohexane ring carbons within one diphosphinite ligand are all
inequivalent and the corresponding six signals are observed in the 13C NMR spectrum
at 23.1, 24.0, 32.8, 32.9, 76.4, and 78.3 ppm. In the 31P NMR spectrum two apparent
triplet signals are observed for each symmetry-related pair of phosphorus atoms (at
151.07 and 153.05 ppm), consistent with coupling in the AA0XX0 spin system. In the

Chiral diphosphinite ligands
379
Figure 2. The inner coordination sphere of RuHCl[(1R,2R)-14]2 {which co-crystallizes with the other
enantiomer RuHCl[(1S,2S)-14]2 in crystals of (rac)-16}.
1H NMR spectrum of (rac)-17 two multiplet signals that each integrate for two protons
at 2.35 and 2.93 ppm are observed for the four cyclohexane CH groups, and a complex
set of overlapping multiplets in the region 0.59–1.81 ppm is observed for the CH2
groups. The hydride ligands are observed as a multiplet at ꢁ8.00 ppm, which collapses
1
to a broad singlet in the 31P decoupled H NMR spectrum.
A crystal of (rac)-17 suitable for X-ray structure determination was obtained from
iso-propanol solution and the crystal structure determined. There is one independent
molecule in centrosymmetric space group P21/c, so the unit cell contains two molecules
of each enantiomer RuH2[(1S,2S)-14]2 and RuH2[(1R,2R)-14]2. The ORTEP diagram
of RuH2[(1S,2S)-14]2 is shown in figure 3. The geometry about ruthenium is
approximately octahedral with the two hydride ligands mutually cis and the
configuration at the metal center is à for the RuH2[(1S,2S)-14]2 enantiomer. The
two phosphorus atoms P1 and P4 are nearly trans [P1–Ru–P4 ¼ 158.34(2)ꢂ] and the
˚
˚
two distances Ru–P1 [2.2776(6) A] and Ru–P4 [2.2858(7) A] are very similar. The other
phosphorus atoms, P2 and P3, are mutually cis [P2–Ru–P3 ¼ 97.17(2)ꢂ] and have
˚
essentially identical distances to ruthenium [Ru–P2 ¼ 2.3010(7)
A
and Ru–
˚
P3 ¼ 2.3010(6) A]. These distances are both longer than the distances Ru–P1 and
Ru–P4, and the differences can be ascribed to the large trans-influence of the hydride
ligands.
2.3. Syntheses of the ruthenium diphosphinite diamine complexes 18–29 that are
of general formula RuCl2(diphosphinite)(diamine)
Treatment of RuCl2(PPh3)3 with two equivalents of (1S,2S)-14 and one equivalent of
(1R,2R)-(þ)-1,2-diphenylethylenediamine [(þ)-DPEN] (see figure 4 for the structures of

380
G.R. Clark et al.
Figure 3. The inner coordination sphere of RuH2[(1S,2S)-14]2 {which co-crystallizes with the other
enantiomer RuH2[(1R,2R)-14]2 in crystals of (rac)-17}.
For clarity only the ipso carbon atoms of the phenyl rings are shown. The thermal ellipsoids are scaled to 50%
˚
probability. Selected bond lengths (A): Ru1–P1 2.2776(6), Ru1–P2 2.3010(7), Ru1–P3 2.3010(6), Ru1–P4
2.2858(7), Ru1–H1A 1.72(3), Ru1–H1B 1.87(3). Selected bond angles (ꢂ): P1–Ru1-P2 91.19(2), P1–Ru1–P3
101.92(2), P1–Ru1–P4 158.34(2), P2–Ru1–P3 97.17(2), P2–Ru1–P4 104.22(2), P3–Ru1–P4 91.33(2), and
H1A–Ru1–H1B 60.5(12).
Figure 4. The diamine ligands used to synthesize compounds 18–29.

Chiral diphosphinite ligands
381
the diamine ligands used to prepare the new ruthenium compounds, 18–29) in toluene
at ambient temperature produces the yellow complex RuCl2[(1S,2S)-14][(þ)-DPEN]
(18) (scheme 3). Although the stoichiometry of complex 18 indicates that only one
equivalent of the diphosphinite ligand is needed, experimentally it was found that the
best yields of 18 were obtained if two equivalents were used. The other new complexes
listed in scheme 3 (19–29) were synthesized in an analogous manner using the
appropriate diphosphinite and diamine ligands. Complexes 12 and 13, which we have
reported previously [4], are also listed in scheme 3 for comparative purposes. In the 31P
NMR spectrum of 18, the two phosphorus atoms of (1S,2S)-14 appear as a sharp
singlet at 148.83 ppm. This confirms that the ligands are arranged about the ruthenium,
1
as depicted in scheme 3, with the two chloride ligands mutually trans. The H and 13C
NMR spectra of 18 are also consistent with the geometry depicted in scheme 3, which
1
has a C2 axis bisecting the two bidentate ligands. In the H NMR spectrum the two
CH protons of the diamine ligand are a broad-structured signal at 4.42 ppm and the two
CH protons of the diphosphinite ligand are similarly shaped at 4.21 ppm. The four
amine protons are two broad multiplets at 3.37 and 3.50 ppm that each integrate
for two protons. Cyclohexane methylene protons are observed as overlapping
multiplets in the region 1.03–1.61 ppm. In the 13C NMR spectrum of 18, the three
pairs of symmetry-related cyclohexane carbons appear at 23.9, 32.4, and 77.4 ppm and
the two saturated carbons of (þ)-DPEN appear at 63.1 ppm. RuCl2[(1R,2R)-14][(ꢁ)-
DPEN] (21) (see scheme 3), which can be prepared by the same method, is the
enantiomer of 18 and has identical spectral properties.
RuCl2[(1S,2S)-14][(ꢁ)-DPEN] (19) (scheme 3), which is a diasteriomer of 18, has
similar NMR spectral properties to 18, but the chemical shifts are slightly different. In
the 31P NMR spectrum of 19, the two phosphorus atoms appear as a sharp singlet at
1
147.34 ppm. In the H NMR spectrum, the CH protons of the diamine ligand and the
diphosphinite ligands are at 4.25 and 4.41 ppm, respectively. The amine protons are
multiplets at 3.08 and 3.62 ppm. In the 13C NMR spectrum of 19 the cyclohexane
carbons appear at 23.8, 32.3, and 77.2 ppm and the two saturated carbons of (ꢁ)-DPEN
appear at 62.8 ppm. As expected, an identical set of NMR spectra are observed for
RuCl2[(1R,2R)-14][(þ)-DPEN] (20), which is the enantiomer of 19.
If RuCl2(PPh3)3 is treated with (rac)-14 and (þ)-DPEN, the product isolated is a
mixture of equal amounts of 18 and 20 and this is denoted as compound 22 (scheme 3).
As expected, the 1H, 13C, and 31P NMR spectra of 22 show signals due to both 18 and
20. In a similar way, the treatment of RuCl2(PPh3)3 with (rac)-14 and (ꢁ)-DPEN gives
23, which is a mixture of equal amounts of 19 and 21 (scheme 3). The NMR spectra
of 23 are identical to those for 22 because 18 and 21, as well as 19 and 20, form
enantiomeric pairs.
RuCl2[(1S,2S)-14](D-NN2) (24) contains the chiral diamine D-NN2 (figure 4), which
is a derivative of myo-inositol [21]. There is no C2 axis in D-NN2, and as a result there
is no C2 axis in 24 either. Therefore, in the 13C NMR spectrum of 24, individual
resonances are observed for each carbon of the two cyclohexane rings and for the four
CH2Ph methylene carbons in (1S,2S)-14 and D-NN2. The two phosphorus atoms are
2
also inequivalent as two doublets at 147.2 (d, JPP ¼ 59.5 Hz) and 151.4 (d,
2JPP ¼ 59.3 Hz) ppm. In contrast, in the related complex RuCl2[(1S,2S)-14](EDA)
(25), which contains the bidentate ethylenediamine ligand, the C2 axis in the complex is
restored and only a singlet is observed (at 147.63 ppm) for the two phosphorus atoms in

382
G.R. Clark et al.
the 31P NMR spectrum and three signals are observed for the cyclohexane ring atoms
at 23.8, 32.0, and 77.4 ppm in the 13C NMR spectrum.
We have already reported the synthesis of the related diphosphinite complexes
RuCl2(D-10)[(þ)-DPEN] (12) and RuCl2(D-10)[(ꢁ)-DPEN] (13) (scheme 3) [4]. The
diphosphinite ligand in these complexes, D-10 (see figure 1), is based on a chiro-inositol
scaffold. In the extension of this work, we now report the syntheses of
RuCl2(D-10)(D-NN2) (26) and RuCl2(D-10)(EDA) (27). As 24, 26 also does not
have a C2 axis. Therefore, in the 31P NMR spectrum of 26, two resonances are observed
for the inequivalent phosphorus atoms and in the 13C NMR spectrum 20 separate
resonances are observed for the inequivalent nonaromatic carbon atoms of the
diphosphinite and diamine ligands. Less complicated NMR spectra are observed for 27
which contains ethylenediamine. In the 31P NMR spectrum of 27 a single signal is
1
observed for the two phosphorus atoms at 150.50 ppm and in the H NMR spectrum
only two methyl resonances and three CH resonances are observed for D-10, consistent
with the presence of a C2 axis that bisects the bidentate D-10 and EDA ligands.
Two complexes that contain the D-10Et ligand (figure 1), RuCl2(D-10Et)[(þ)-DPEN]
(28) and RuCl2(D-10Et)(D-NN2) (29), have also been prepared. As expected, the 31P
NMR spectrum of 28 contains a singlet for the two equivalent phosphorus atoms that
1
are related by a C2 axis. The H and 13C NMR spectra are also consistent with the
presence of a C2 axis that bisects the two bidentate ligands. Thus, in the 13C NMR
spectrum of 28 only one resonance is observed for the CH carbons of (þ)-DPEN and
three CH resonances are observed for D-10Et. Similarly, only two methyl and two
methylene resonances are observed for the four ethyl substituents of this ligand. A more
complex set of signals is observed in the NMR spectra for RuCl2(D-10Et)(D-NN2) (29)
reflecting the lower symmetry of this molecule. As with the other compounds that
contain D-NN2 (24 and 26), there is no C2 axis present in 29. The four ethyl
substituents and the four benzyl substituents are therefore all inequivalent, as are the
cyclohexane ring carbons of both bidentate ligands. This is clearly seen in the 13C NMR
spectrum where separate resonances are observed for CH3, CH2O, and cyclohexane ring
carbons. In the 31P NMR spectrum, the two inequivalent phosphorus atoms have very
similar chemical shifts giving a second order spectrum with two nearly coincident
intense signals at 148.92 and 148.97 ppm.
2.4. Investigation of the catalytic activity of the new ruthenium diphosphinite
complexes in asymmetric hydrogenation reactions of the prochiral substrates
acetophenone and 3-quinuclidinone
In a previous study, we reported the results of our investigations into the catalytic
activity of 11, 12, and 13 towards the asymmetric hydrogenation of the ketones
acetophenone (to give sec-phenylethyl alcohol) and 3-quinuclidinone (to give
3-quinuclidinol) [4]. We now present catalytic asymmetric hydrogenation reactions of
the same substrates in the presence of the new ruthenium complexes described in
sections 2.2 and 2.3. Identical conditions to those in the previous study were used for
the hydrogenation reactions so that direct comparisons could be made with the earlier
results. The reactions were carried out in toluene/iso-propanol solution (1 : 1) with a
substrate to catalyst ratio of 200: 1, hydrogen pressure of 1000 psi, temperature of 60ꢂC,
and a time period of 3 h. As before, KOtBu (2 M equivalent vs. the ruthenium complex)

Chiral diphosphinite ligands
383
Table 1. Conversion (%), %ee, and configuration of the major enantiomer formed during the catalytic
hydrogenation of acetophenone and 3-quinuclidinone.
O
N
C
Acetophenone
3-Quinuclidinone
Conversion
(%)
O
CH3
Conversion
(%)
%ee
(configuration)
%ee
(configuration)
Precatalyst
RuHCl(D-10)2 (11)
RuHCl[(1S,2S)-14]2 (15)
20
0
2 (R)
NA
97
99
100
100
99
99
99
100
100
2 (S)
10 (R)
8 (S)
54 (R)
38 (S)
6 (R)
5 (S)
39 (R)
23 (S)
RuCl2(D-10)[(þ)-DPEN] (12)
RuCl2(D-10)[(ꢁ)-DPEN] (13)
RuCl2[(1S,2S)-14][(þ)-DPEN] (18)
RuCl2(1S,2S)-14)[(ꢁ)-DPEN] (19)
RuCl2[(1R,2R)-14][(þ)-DPEN] (20)
RuCl2[(1R,2R)-14][(ꢁ)-DPEN] (21)
RuCl2[(1S,2S)-14][(þ)-DPEN] and
RuCl2[(1R,2R)-14][(þ)-DPEN] (22)
RuCl2[(1S,2S)-14][(ꢁ)-DPEN] and
RuCl2[(1R,2R)-14][(ꢁ)-DPEN] (23)
RuCl2[(1S,2S)-14](D-NN2) (24)
RuCl2[(1S,2S)-14](EDA) (25)
RuCl2(D-10)(D-NN2) (26)
100
100
100
100
100
100
100
25 (S)
24 (R)
49 (S)
31 (R)
25 (S)
53 (R)
26 (S)
100
32 (R)
100
26 (R)
100
100
100
100
100
100
61 (S)
17 (S)
32 (S)
18 (R)
19 (S)
32 (S)
99
99
100
99
99
97
41 (S)
13 (S)
3 (R)
30 (R)
4 (S)
27 (R)
RuCl2(D-10)(EDA) (27)
RuCl2(D-10Et)[(þ)-DPEN] (28)
RuCl2(D-10Et)(D-NN2) (29)
Conditions: substrate: precatalyst ratio, 200: 1; hydrogen pressure, 1000 psi; KOtBu (2M vs. ruthenium complex);
temperature, 60ꢂC; time, 3 h; solvent, toluene/iso-propanol (1 : 1).
was added to each reaction because it has been shown that the presence of this base can
significantly improve the yield of product formed in catalytic hydrogenation reactions,
especially with complexes that incorporate a diamine ligand [22].
The hydrogenation results are presented in table 1 and the data previously obtained
for 11, 12, or 13 [4] are also included for comparative purposes. The ruthenium
complexes studied were selected to examine how changes to the diphosphinite and
diamine ligands influence the %ee values of the products formed. The results presented
in table 1 are discussed further in this context.
Compounds 11 and 15 are bis(diphosphinite) complexes of Ru(II). Whereas D-10 in
11 is based on the chiro-inositol backbone, (1S,2S)-14 in 15 is based on the related, less
sterically encumbered cyclohexanediol backbone (figure 1). Complex 11 does not
effectively catalyze the hydrogenation of acetophenone under the conditions used and
15 showed no detectible activity at all. In contrast, both complexes catalyzed the
complete hydrogenation of 3-quinuclidinone, although in both cases very little, if any
enantiomeric excess was observed in the products. A potentially complicating factor in
the hydrogenation reactions involving 15 or (rac)-16 was that the corresponding
ruthenium dihydride complexes RuH2[(1S,2S)-14]2 or (rac)-17 crystallized from
solution in significant amounts as the reactions proceeded. Exploratory experiments
in which acetophenone was subjected to the standard hydrogenation conditions in the
presence of (rac)-17 resulted in no hydrogenated products, and with 3-quinuclidinone
only ca 50% conversion to hydrogenated products was observed. These results
indicated that under these conditions the dihydride complexes have lower catalytic
activity than the precursor chloro hydride complexes, and were therefore not

384
G.R. Clark et al.
studied further. The formation of crystalline ruthenium derivatives was not observed
during the hydrogenation reactions involving any of the other ruthenium complexes
studied.
The remaining complexes listed in table 1 each contain one chelating diphosphinite,
one chelating diamine, and two chlorides. All these complexes catalyzed the
hydrogenation of both acetophenone and 3-quinuclidinone with essentially complete
conversion under the conditions used. Complexes 12, 18, 20, and 28 all have the same
diamine ligand [(þ)-DPEN] but different diphosphinite ligands. Comparison of the
hydrogenation results obtained with these different catalysts indicates that replacing
D-10 (which has methoxy substituents) in complex 12 with D-10Et (which has ethoxy
substituents) to give complex 28 has a slightly detrimental effect on the %ee values of
the products, while 20 with the less encumbered diphosphinite ligand (1R,2R)-14 shows
almost identical behavior to that observed for 12. Compound 18 (a diastereomer of 20)
gives products with much higher %ee values (49% for acetophenone and 38% for
quinuclidinone) than any of the other complexes in this set, even though the actual
values are still modest. Presumably, the (1S,2S)-14 and (þ)-DPEN ligands in 18 work
in concert as a ‘‘matched pair’’ to effect asymmetric hydrogenation of these substrates.
Complexes 13, 19, and 21 contain (ꢁ)-DPEN. Complex 13, which is a diastereomer of
12, catalyzes the hydrogenation of acetophenone to give products with essentially the
same %ee (but opposite stereochemistry), as obtained with 12. However, in the
hydrogenation of 3-quinuclidinone, 13 gives products with a much higher %ee (54%)
compared with 12 (8%), again showing that the combination of chiral ligands is very
important in determining %ee. Complexes 19 and 20 are enantiomers and, as expected,
the reactions catalyzed by 19 give, within experimental error, products with the same
%ee as those catalyzed by 20, but with the dominant enantiomer having the opposite
chirality. A similar situation is observed for enantiomers 18 and 21.
The material designated 22 is an equal mixture of the diastereomers 18 and 20, and
similarly 23 is an equal mixture of the diastereomers 19 and 21. As might be expected,
the %ee values of the products obtained from 22 lie between the corresponding values
obtained for reactions catalyzed by the individual complexes 18 and 20. The relative
rates at which each product enantiomer is formed by the two components 18 and 20 will
be important factors in determining the %ee of the products produced by 22. A similar
situation is observed for 23 where again the %ee values of the products lie between the
corresponding values obtained for reactions catalyzed by the individual complexes 19
and 21. Each of the components of 22 form an enantiomeric pair with one of the
components of 23, that is, 18 and 21 form an enantiomeric pair, as do 19 and 20.
Accordingly, the %ee values obtained for the hydrogenation reactions of 22 and 23 are
the same within experimental error, but the dominant enantiomer obtained from the
hydrogenation of each substrate has the opposite chirality.
The remaining data in table 1 provides some information about the influence that the
diamine ligand in the complex has on the %ee values of the products. The set of
complexes 12, 13, 26, and 27 all contain the same diphosphinite ligand, D-10, but have
different chelating diamine ligands. For the hydrogenation of acetophenone, similar
%ee’s (ca 25%) are observed for 12 [with (þ)-DPEN] and 13 [with (ꢁ)-DPEN], while
the higher value of 32% ee is observed for 26 (with D-NN2) and the lower value of 18%
ee is observed for 27 (with EDA). The same trend is not observed for the hydrogenation
of 3-quinuclidinone, where the complexes and corresponding %ee values of the
products are 12 (8%), 13 (54%), 26 (3%), and 27 (30%). In this case 13 gives the highest

Chiral diphosphinite ligands
385
value, and there is a big difference between 12 and 13, and 26 giving the lowest value.
Once again these results reinforce the importance of ligands working in concert as
‘‘matched pairs’’ to effect asymmetric hydrogenation of a particular substrate.
Comparisons of the products formed during reactions catalyzed by 18, 19, 24, and 25,
which contain the (1S,2S)-14 diphosphinite ligand but have different diamine ligands,
reveal that for the hydrogenation of acetophenone the complex that contains the
D-NN2 diamine ligand (24) again gives the highest %ee value (61%). This same
complex also gives the highest %ee value (41%) of this set for the hydrogenation of
3-quinuclidinone. Unlike the situation discussed above for 12, 13, 26, and 27, for the set
of complexes 18, 19, 24, and 25, the trend in increasing %ee values observed for
acetophenone is essentially the same as the trend observed for 3-quinuclidinone. Of the
two complexes prepared with D-10Et (28 and 29), the complex with the D-NN2 diamine
(29) gave the higher %ee values for the catalytic hydrogenation of both ketone
substrates.
The following general remarks can be made about the ability of the complexes that
are listed in table 1 to catalyze the asymmetric hydrogenation of acetophenone and
3-quinuclidinone. Under the conditions used, bis(diphosphinite) complexes 11 and 15
performed very poorly as asymmetric hydrogenation catalysts. Much better results were
obtained with some of the mixed diphosphinite, diamine complexes. Of the complexes
studied, 24 gave the highest %ee value for the hydrogenation of acetophenone (61%),
while 13 (which has different diphosphinite and diamine ligands) gave the highest %ee
value for the hydrogenation of 3-quinuclidinone (54%). Compared with other catalytic
systems, however, both these %ee values are modest [17, 23]. There was no evidence
obtained from these studies that there is an advantage in using one particular
diphosphinite or diamine ligand for the production of effective catalysts. Rather, the
results serve to confirm the general observation that a particular combination of ligands
that works well for one substrate will not necessarily be ideal for others. This further
highlights the need to extend the pool of chiral ligands that are available for the
construction of asymmetric hydrogenation catalysts.
3. Experimental
3.1. General synthetic procedures and instruments
Manipulations of air sensitive materials were conducted using either Schlenk techniques
(nitrogen atmosphere) or an Innovative Technology inert atmosphere glove box (argon
atmosphere). Tetrahydrofuran, ether and toluene were distilled from sodium
˚
benzophenone ketyl under nitrogen and stored over activated 4 A molecular sieves.
Dichloromethane was distilled from calcium hydride. n-Hexane was purified by passage
through a column of activated alumina. Triethylamine was distilled from calcium
hydride and stored over potassium hydroxide. Flash column chromatography was
1
carried out on 230–400 silica (Scharlau). H, 13C, and 31P NMR spectra were obtained
on a Bruker Avance 300 at 25ꢂC operating at 300.13 (1H), 75.48 (13C), and 121.5 (31P)
MHz, respectively. Resonances are quoted in parts per million and the 1H NMR
is referenced to the protio-impurity in the solvent (7.25 ppm for CDCl3) or
TMS (0.00 ppm). 13C NMR spectra were referenced to CDCl3 (77.00 ppm) and
31P NMR spectra to 85% orthophosphoric acid (0.00 ppm) as an external standard.

386
G.R. Clark et al.
Elemental analyses were obtained from the Microanalytical Laboratory, University
of Otago. FABþ mass spectra were obtained from a VG-70SE machine. Chloro-
diphenylphosphine, (rac)-trans-1,2-cyclohexanediol, (1S,2S)-trans-1,2-cyclohexanediol,
(1R,2R)-trans-1,2-cyclohexanediol, (þ)-DPEN, (ꢁ)-DPEN, and EDA were obtained
commercially. D-7, D-10, D-NN2 [21], [RuCl2(COD)]n [24, 25], and RuCl2(PPh3)3 [26]
were all prepared according to literature methods.
3.2. General procedures and instruments employed for the hydrogenation reactions
Hydrogenations were carried out in 12 mL glass vials equipped with a magnetic stirrer
bar. The vials were filled with catalyst (0.005 mmol), substrate (1.0 mmol), KOtBu
(0.01 mmol), and 1 : 1 toluene/iso-propanol (3 mL) for both the acetophenone and
3-quinuclidinone substrates inside an inert atmosphere glove box and then placed inside
a 300 mL Parr autoclave made from Hastelloy C. In this way, several hydrogenation
experiments could be carried out at the same time. The autoclave was sealed, taken
outside the glovebox, and heated to 60ꢂC using a thermostatic heating mantle. The
autoclave was then flushed with hydrogen three times before being filled with hydrogen
(1000 psi). After 3 h the autoclave was cooled and the pressure reduced to atmospheric
pressure. The autoclave was then opened and samples of the crude reaction mixture
were analyzed by GC. The GC analysis to obtain conversion and enantiomeric excess
values were performed on a HP 6890 Series gas chromatography apparatus with an FID
detector using a capillary Supelco GAMMA-DEX 225 (30 m ꢃ 0.25 mm ꢃ 0.25 mm)
column or a SGE CYDEX-B (2 m ꢃ 0.32 mm ꢃ 0.25 mm) column. The estimated error
in each %ee value is ꢄ 5%. The GC methods that were established for the two prochiral
substrates were (1) acetophenone (80ꢂC isothermal): starting material tR (min) 29.4;
products tR (min) R 33.3, S 34.2; (2) 3-quinuclidinone (140ꢂC for 10 min then ramped
up to 220ꢂC at 10ꢂC minꢁ1): starting material tR (min) 10.8; products tR (min) R 12.5,
S 12.9.
3.3. Preparation of a racemic mixture of (1R,2R)-1,2-trans-bis-
(O-diphenylphosphino)cyclohexane [(1R,2R)-14] and (1S,2S)-1,2-trans-bis-
(O-diphenylphosphino)cyclohexane [(1S,2S)-14)], [(rac)-14]
To a solution of (rac)-trans-1,2-cyclohexanediol (1.0 g, 8.6 mmol) and pyridine (1.4 mL,
17.2 mmol) in tetrahydrofuran (15 mL), ClPPh2 (3.1 mL, 17.2 mmol) was added
dropwise and the solution was stirred at RT for 16 h. The solution was then transferred
via a cannula fitted with a filter to another flask under nitrogen and tetrahydrofuran
was removed under reduced pressure to yield (rac)-14 as a white solid (3.75 g, 90%).
1H NMR (CDCl3, ꢁ): 1.22–1.28 (m, 2H, CH2), 1.44–1.48 (m, 2H, CH2), 1.59–1.63 (m,
2H, CH2), 2.02–2.06 (m, 2H, CH2), 3.99–4.04 (m, 2H, CH), and 7.17–7.51 (m, 20H, Ph).
13C{1H} NMR (CDCl3, ꢁ): 22.6 (CH2), 31.2 (CH2), 81.2 (CH), and 128.0–130.5
(multiple signals, Ph). 31P{1H} NMR (CDCl3, ꢁ): 107.30.
3.4. Preparation of (1S,2S)-1,2-trans-bis-(O-diphenylphosphino)cyclohexane
[(1S,2S)-14]
The same procedure that was used for synthesis of (rac)-14 was followed except that
(1S,2S)-trans-1,2-cyclohexanediol was used instead of rac-trans-1,2-cyclohexanediol.
1
The H, 13C, and 31P NMR spectra were identical to those obtained for (rac)-14.

Chiral diphosphinite ligands
387
3.5. Preparation of (1R,2R)-1,2-trans-bis-(O-diphenylphosphino)cyclohexane
[(1R,2R)-14]
The same procedure that was used for the synthesis of (rac)-14 was followed except that
(1R,2R)-trans-1,2-cyclohexanediol was used instead of rac-trans-1,2-cyclohexanediol.
1
The H, 13C, and 31P NMR spectra were identical to those obtained for (rac)-14.
3.6. Preparation of 1D-3,4-bis(O-diphenylphosphino)-1,2,5,6-tetra-O-ethyl-chiro-
inositol (D-10Et)
The ligand D-10Et was synthesized from D-7 following the same procedure that was
used for the synthesis of the corresponding tetramethyl ligand D-10 [4] except that ethyl
bromide was substituted for methyl iodide in the first step (scheme 1). Pure D-10Et was
obtained as a white solid in 60% overall yield. Anal. Calcd for C38H46O6P2: C, 69.08; H,
1
7.02. Found: C, 68.86; H, 6.88. H NMR (CDCl3, ꢁ): 0.64 (apparent t, 6H, CH3), 1.18
(apparent t, 6H, CH3), 2.72–4.93 (m, 14H, CH, CH2), 6.94–7.83 (m, 20H, Ph). 13C{1H}
NMR (CDCl3, ꢁ): 14.7 (CH3), 15.4 (CH3), 66.9 (CH2CH3), 67.2 (CH2CH3), 76.1 (CH),
77.9 (CH), 78.9 (CH), 127.3–133.0 (multiple signals, Ph). 31P{1H} NMR (CDCl3, ꢁ):
109.47 (s).
3.7. Preparation of RuHCl[(1S,2S)-14]2 (15)
Compound (1S,2S)-14 (0.090 g, 0.19 mmol), triethylamine (0.06 mL, 0.4 mmol), and
[RuCl2(COD)]n (0.030 g, 0.10 mmol) in toluene (30 mL) were heated under reflux for
6 h. The toluene was removed under reduced pressure and the resulting residue was
dissolved in a minimum of dichloromethane and purified by column chromatography
on basic alumina using dichloromethane as the eluent. The orange/yellow band was
collected and the dichloromethane was removed under reduced pressure. The resulting
residue was recrystallized from dichloromethane/n-hexane to give pure 15 as an orange/
yellow solid (0.036 g, 34%). MS (m/z): Calcd for C60H6135ClO4P4102Ru (Mþ) 1106.2252
1
(m/z). Found: 1106.2269. H NMR (CDCl3, ꢁ): ꢁ16.38 (m, 1H, RuH), 0.80–2.35 (m,
16H, CH2), 3.76 (m, 2H, CH), 5.10 (m, 2H, CH), and 6.55–7.72 (m, 40H, Ph). 13C
NMR{1H} (CDCl3, ꢁ): 24.4 (CH2), 24.5 (CH2), 32.3 (CH2), 33.0 (CH2), 75.7 (CH), 78.9
(CH), and 125.6–147.3 (multiple signals, Ph). 31P{1H} NMR (CDCl3, ꢁ): 118.13
(apparent t, lower intensity signals at 117.76 and 118.50), 147.26 (apparent t, lower
intensity signals at 146.89 and 147.63).
3.8. Preparation of a racemic mixture of RuHCl[(1S,2S)-14]2 and
RuHCl[(1R,2R)-14]2 [(rac)-16]
Compound (rac)-14 (7.507 g, 15.50 mmol), triethylamine (20 mL, 144 mmol), and
[RuCl2(COD)]n (1.61 g, 5.70 mmol) in toluene (50 mL) were heated under reflux for
12 h giving a yellow/orange solid suspended in solution. The solid was filtered and
washed with hexane (3 mL ꢃ 5 mL) to give pure (rac)-16 as a yellow/orange solid
(5.658 g, 90%). Anal. Calcd for C60H61ClO4P4Ru: C, 65.13; H, 5.56. Found: C, 65.12;
1
H, 5.79. The H, 13C and 31P NMR spectra were identical to those obtained for 15.

388
G.R. Clark et al.
3.9. Preparation of a racemic mixture of RuH2[(1S,2S)-14]2 and
RuH2[(1R,2R)-14]2 [(rac)-17]
Compound (rac)-16 (0.500 g, 0.452 mmol) and KOtBu (0.067 g, 0.60 mmol) were added
to degassed iso-propanol (32 mL) and placed in an autoclave inside a drybox (argon
atmosphere). The autoclave was then sealed, removed from the drybox and heated at
60ꢂC under 1000 psi of hydrogen for 16 h. On cooling and release of the pressure, pure
(rac)-17 was obtained from the solution by filtration as a cream/yellow microcrystalline
solid (0.45 g, 93%). Anal. Calcd for C60H62O4P4Ru: C, 67.22; H, 5.83. Found: C, 67.00;
H, 5.84. MS (m/z): Calcd for C60H61O4P4102Ru (M ꢁ H)þ 1071.25639 m/z. Found:
1071.25820. 1H NMR (CDCl3, ꢁ): ꢁ8.00 (m, 2H, RuH), 0.59–1.81 (m, 16H, CH2), 2.35
(m, 2H, CH), 2.93 (m, 2H, CH), and 6.88–7.97 (m, 40H, Ph). 13C NMR{1H} (CDCl3,
ꢁ): 23.1 (CH2), 24.0 (CH2), 32.8 (CH2), 32.9 (CH2), 76.4 (CH), 78.3 (CH), and 126.5–
131.6 (multiple signals, Ph). 31P{1H} NMR (CDCl3, ꢁ): 151.07 (apparent t, lower
intensity signals at 150.84 and 151.31), 153.05 (apparent t, lower intensity signals at
152.82 and 153.30).
3.10. Preparation of RuCl2[(Y)-DPEN][(1S,2S)-14] (18)
Compound (1S,2S)-14 (0.17 g, 0.34 mmol) and RuCl2(PPh3)3 (0.16 g, 0.17 mmol) were
added to toluene (20 mL) under nitrogen and stirred at 18ꢂC for 1 h. (þ)-DPEN
(0.037 g, 0.17 mmol) was then added and the mixture was stirred for an additional hour
at the same temperature. The toluene was removed under reduced pressure and the
crude solid dissolved in a minimum of dichloromethane and purified using column
chromatography. A bright yellow band was removed from the column using
dichloromethane as the eluent. The dichloromethane was removed under reduced
pressure and the residue was recrystallized from dichloromethane/n-hexane to give pure
18 as
a
yellow crystalline solid (0.045 g, 46%). MS (m/z): Calcd for
C44H4635Cl2N2O2P2102Ru (Mþ) 868.14551 m/z. Found: 868.14396. H NMR (CDCl3,
ꢁ): 1.03–1.61 (m, 8H, CH2), 3.37 (m, 2H, NH2), 3.50 (m, 2H, NH2), 4.21 (m, 2H, CH
diphosphinite), 4.42 (m, 2H, CH diamine), 6.99–7.80 (m, 30H, Ph). 13C{1H} NMR
(CDCl3, ꢁ): 23.9 (CH2), 32.4 (CH2), 63.1 (CH diamine), 77.4 (CH diphosphinite), and
127.0–133.9 (multiple signals, Ph). 31P{1H} NMR (CDCl3, ꢁ): 148.83 (s).
1
3.11. Preparation of RuCl2[(Z)-DPEN][(1S,2S)-14] (19)
The same procedure that was used for the synthesis of 18 was followed except that
(ꢁ)-DPEN was used instead of (þ)-DPEN. After recrystallization from diethylether/
n-hexane, pure 19 was obtained as yellow crystals in 20% yield. MS (m/z): Calcd
for C44H4635Cl2N2O2P2102Ru (Mþ) 868.14551 m/z. Found: 868.14618. 1H NMR
(CDCl3, ꢁ): 0.88–1.64 (m, 8H, CH2), 3.08 (m, 2H, NH2), 3.62 (m, 2H, NH2), 4.25 (m,
2H, CH diphosphinite), 4.41 (m, 2H, CH diamine), 6.98–7.77 (m, 30H, Ph). 13C{1H}
NMR (CDCl3, ꢁ): 23.8 (CH2), 32.3 (CH2), 62.8 (CH diamine), 77.2 (CH diphosphinite),
and 127.0–133.6 (multiple signals, Ph). 31P{1H} NMR (CDCl3, ꢁ): 147.34 (s).
3.12. Preparation of RuCl2[(Y)-DPEN][(1R,2R)-14] (20)
The same procedure used for the synthesis of 18 was followed except that (1R,2R)-14
was used instead of (1S,2S)-14. After recrystallization from diethylether/n-hexane, pure

Chiral diphosphinite ligands
389
20 was obtained as yellow crystals in 70% yield. MS (m/z): Calcd for
1
C44H4635Cl2N2O2P2102Ru (Mþ) 868.14551 m/z. Found: 868.14365. The H, 13C, and
31P NMR spectra were identical to those obtained for 19.
3.13. Preparation of RuCl2[(Z)-DPEN][(1R,2R)-14] (21)
The same procedure used for the synthesis of 18 was followed except that (1R,2R)-14
was used instead of (1S,2S)-14 and (ꢁ)-DPEN was used instead of (þ)-DPEN. After
recrystallization from diethylether/n-hexane, pure 21 was obtained as yellow crystals
in 60% yield. Anal. Calcd for C44H46Cl2N2O2P2Ru: C, 60.83; H, 5.34; N, 3.22. Found:
C, 61.12; H, 5.47; N, 3.21. MS (m/z): Calcd for C44H4635Cl2N2O2P2102Ru (Mþ)
868.14551 m/z. Found: 868.14485. The 1H, 13C, and 31P NMR spectra were identical to
those obtained for 18.
3.14. Preparation of RuCl2[(Y)-DPEN][(rac)-14] (22)
The same procedure used for the synthesis of 18 was followed except that (rac)-14 was
used instead of (1S,2S)-14. After recrystallization from diethylether/n-hexane, 22
was obtained as yellow crystals in 41% yield. Anal. Calcd for C44H46Cl2N2O2P2Ru:
C, 60.83; H, 5.34; N, 3.22. Found: C, 60.74; H, 5.60; N, 3.11%. MS (m/z): Calcd for
C44H4635Cl2N2O2P2102Ru (Mþ) 868.14551 m/z. Found: 868.14491. The 1H, 13C, and 31
NMR spectra appeared as a 1 : 1 overlap of the spectra obtained for 18 and 20.
P
3.15. Preparation of RuCl2[(Z)-DPEN][(rac)-14] (23)
The same procedure used for the synthesis of 18 was followed except that (rac)-14 was
used instead of (1S,2S)-14 and (ꢁ)-DPEN was used instead of (þ)-DPEN. After
recrystallization from diethylether/n-hexane, pure 23 was obtained as yellow crystals in
60% yield. Anal. Calcd for C44H46Cl2N2O2P2Ru: C, 60.83; H, 5.34; N, 3.22. Found:
C, 60.74; H, 5.73; N, 3.19%. MS (m/z): Calcd for C44H4635Cl2N2O2P2102Ru (Mþ)
868.14551 m/z. Found: 868.14402. The 1H, 13C, and 31P NMR spectra were identical to
those obtained for 22.
3.16. Preparation of RuCl2(D-NN2)[(1S,2S)-14] (24)
The same procedure used for the synthesis of 18 was followed except that D-NN2 was
used instead of (þ)-DPEN. After recrystallization from diethylether/n-hexane, pure 24
was obtained as yellow crystals in 85% yield. Anal. Calcd for C64H68Cl2N2O6P2Ru:
C, 64.32; H, 5.73; N, 2.34. Found: C, 65.00; H, 6.09; N, 2.32%. MS (m/z): Calcd for
C64H6835Cl2N2O6P2102Ru (Mþ) 1194.29732 m/z. Found: 1194.29933. 1H NMR (CDCl3,
ꢁ): 0.88–1.88 (m, 8H, CH2), 2.75–4.52 (m, 12H, CH diphosphinite, CH diamine, NH2),
4.69–4.92 (m, 8H, CH2Ph), and 7.06–8.00 (m, 40H, Ph). 13C{1H} NMR (CDCl3, ꢁ): 23.7
(CH2), 23.8 (CH2), 32.3 (CH2), 32.4 (CH2), 54.4 (CH diamine), 54.9 (CH diamine), 72.8
(CH2), 74.4 (CH2), 75.5 (CH2), 76.0 (CH2), 76.2 (CH), 76.4 (CH), 77.9 (CH), 78.3 (CH),
81.5 (CH), 85.0 (CH), and 127.4–137.3 (multiple signals, Ph). 31P{1H} NMR (CDCl3,
2
2
ꢁ): 147.2 (d, JPP ¼ 59.5 Hz), 151.4 (d, JPP ¼ 59.3 Hz).

390
G.R. Clark et al.
3.17. Preparation of RuCl2(EDA)[(1S,2S)-14] (25)
The same procedure used for the synthesis of 18 was followed except that EDA was used
instead of (þ)-DPEN. After recrystallization from diethylether/n-hexane, pure 25
was obtained as yellow crystals in 24% yield. Anal. Calcd for
C32H38Cl2N2O2P2Ru ꢀ 0.5CH2Cl2: C, 51.43; H, 5.18; N, 3.69. Found: C, 51.03; H,
1
5.12; N, 2.99. H NMR (CDCl3, ꢁ): 0.85–1.70 (m, 8H, CH2), 2.73 (broad s, 2H, NH2),
2.93 (broad s, 6H, CH2 diamine and NH2), 4.20 (s, 2H, CH diphosphinite), and 7.18–
7.73 (m, 20H, Ph). 13C{1H} NMR (CDCl3, ꢁ): 23.8 (CH2), 32.0 (CH2), 42.5 (CH2
diamine), 77.4 (CH, diphosphinite), and 127.2–135.7 (multiple signals, Ph). 31P{1H}
NMR (CDCl3, ꢁ): 147.63 (s).
3.18. Preparation of RuCl2(D-NN2)(D-10) (26)
The same procedure used for the synthesis of 18 was followed except that D-10 was used
instead of (1S,2S)-14 and D-NN2 was used instead of (þ)-DPEN. After recrystalliza-
tion from diethylether/n-hexane, pure 26 was obtained as yellow crystals in 77% yield.
Anal. Calcd for C68H76Cl2N2O10P2Ru: C, 62.10; H, 5.82; N, 2.13. Found: C, 61.87;
H, 5.91; N, 2.18%. MS (m/z): Calcd for C68H7635Cl2N2O10P2102Ru (Mþ) 1314.33958 m/
z. Found: 1314.34018. 1H NMR (CDCl3, ꢁ): 2.60–3.00 (m, 4H, NH2), 3.09 (s, 3H, CH3),
3.27 (s, 3H, CH3), 3.38 (s, 3H, CH3), 3.41 (s, 3H, CH3), 3.20–3.75 (m, 8H), 4.40–5.10
(m, 12H), and 7.17–7.81 (m, 40H, Ph). 13C{1H} NMR (CDCl3, ꢁ): 53.3 (CH diamine),
55.3 (CH diamine), 58.9 (CH3), 59.0 (CH3), 59.7 (CH3), 59.8 (CH3), 71.9 (CH2), 74.6
(CH2), 75.3 (CH2), 75.8 (CH2), 76.2 (CH), 76.3 (CH), 76.9 (CH), 77.2 (CH, 2
overlapping signals), 78.2 (CH), 80.7 (CH, 2 overlapping signals), 81.2 (CH), 84.8 (CH),
and 127.1–138.6 (multiple signals, Ph). 31P{1H} NMR (CDCl3, ꢁ): 149.73 (s, weak),
150.23 (s, strong), 150.31 (s, strong), and 150.82 (s, weak) (second-order spectrum).
3.19. Preparation of RuCl2(EDA)(D-10) (27)
The same procedure used for the synthesis of 18 was followed except that D-10 was used
instead of (1S,2S)-14 and EDA was used instead of (þ)-DPEN. After recrystallization
from diethylether/n-hexane, pure 27 was obtained as yellow crystals in 24% yield. Anal.
Calcd for C36H46Cl2N2O6P2Ru: C, 51.68; H, 5.54; N, 3.35. Found: C, 51.82; H, 5.52;
N, 3.25%. MS (m/z): Calcd for C36H4635Cl2N2O6P2102Ru (Mþ) 836.12517 m/z. Found:
1
836.12438. H NMR (CDCl3, ꢁ): 2.64 (m, 2H, NH2), 2.76 (m, 2H, NH2), 2.90 (s, 4H,
CH2), 3.13 (s, 6H, OCH3), 3.37 (s, 6H, OCH3), 3.41 (m, 2H, CH), 3.61 (m, 2H, CH),
4.73 (m, 2H, CH), and 7.16–7.77 (m, 20H, Ph). 13C{1H} NMR (CDCl3, ꢁ): 42.8 (CH2),
59.0 (CH3), 59.8 (CH3), 76.3 (CH), 77.2 (CH), 80.7 (CH), and 127.4–133.8 (multiple
signals, Ph). 31P{1H} NMR (CDCl3, ꢁ): 150.50 (s).
3.20. Preparation of RuCl2((Y)-DPEN)(D-10Et) (28)
The same procedure used for the synthesis of 18 was followed except that D-10Et was
used instead of (1S,2S)-14. After recrystallization from diethylether/n-hexane, pure 28
was obtained as yellow crystals in 39% yield. Anal. Calcd for C52H62Cl2N2O6P2Ru:
C, 59.77; H, 5.98; N, 2.68. Found: C, 59.64; H, 5.98; N, 2.67%. MS (m/z): Calcd for

Chiral diphosphinite ligands
391
C52H6235Cl2N2O6P2102Ru (Mþ) 1044.25037 m/z. Found: 1044.24924. 1H NMR (CDCl3,
ꢁ): 0.83 (apparent t, 6H, CH3), 1.18 (apparent t, 6H, CH3), 2.94 (m, 2H, NH2), 3.30–
3.80 (m, 8H, CH2), 3.50 (m, 2H, CH diphosphinite), 3.55 (m, 2H, NH2), 3.63 (m, 2H,
CH diphosphinite), 4.39 (m, 2H, CH, diamine), 4.82 (m, 2H, CH, diphosphinite), and
6.93–7.80 (m, 30H, Ph). 13C{1H} NMR (CDCl3, ꢁ): 15.4 (CH3), 15.8 (CH3), 62.9 (CH
diamine), 66.7 (CH2), 66.9 (CH2), 76.1 (CH diphosphinite), 77.2 (CH diphosphinite),
79.1 (CH diphosphinite), and 126.9–133.6 (multiple signals, Ph). 31P{1H} NMR
(CDCl3, ꢁ): 149.08 (s).
3.21. Preparation of RuCl2(D-NN2)(D-10Et) (29)
The same procedure used for the synthesis of 18 was followed except that D-10Et was
used instead of (1S,2S)-14 and D-NN2 was used instead of (þ)-DPEN. After
recrystallization from diethylether/n-hexane, pure 29 was obtained as yellow crystals in
42% yield. Anal. Calcd for C72H84Cl2N2O10P2Ru ꢀ C4H10O: C, 63.15; H, 6.55; N, 1.94.
Found: C, 63.84; H, 6.34; N, 1.79%. MS (m/z): Calcd for C72H8435Cl2N2O10P2102Ru
1
(Mþ) 1370.40218 m/z. Found: 1370.40210. H NMR (CDCl3, ꢁ): 0.71 (apparent t, 3H,
CH3), 0.96 (apparent t, 3H, CH3), 1.11 (apparent t, 3H, CH3), 1.18 (apparent t, 3H,
CH3), 2.57–3.80 (m, 20H), 4.15–5.20 (m, 12H), 7.03–7.75 (m, 40H, Ph). 13C{1H} NMR
(CDCl3, ꢁ): 15.2 (CH3), 15.6 (CH3), 15.7 (CH3), 15.8 (CH3), 53.2 (CH diamine), 55.5
(CH diamine), 66.8 (2 overlapping signals, CH2CH3), 67.0 (two overlapping signals,
CH2CH3), 71.9 (CH2Ph), 74.7 (CH2Ph), 75.3 (CH2Ph), 75.8 (CH2Ph), 76.1 (CH), 76.6
(CH), 77.0 (CH), 77.2 (CH), 77.8 (CH), 78.3 (CH), 79.2 (CH, 2 overlapping signals),
81.9 (CH), 84.8 (CH), and 127.1–133.9 (multiple signals, Ph). 31P{1H} NMR (CDCl3,
ꢁ): 148.92 and 148.97 (part of a second-order spectrum).
3.22. X-ray crystal structure determination of (rac)-16 (a racemic mixture of
RuHCl[(1S,2S)-14]2 and RuHCl[(1R,2R)-14]2)
A suitable crystal of (rac)-16 was isolated from dichloromethane/hexane. X-ray data
were collected on a Siemens SMART CCD diffractometer using monochrꢂomated
˚
graphite Mo-Kꢂ (ꢃ ¼ 0.71073 A). Data collection method: !-scan, range 0.8 . Data
reduction and cell determination were carried out with SAINT and XPREP(SMART)
programs [27]. Absorption corrections were applied using SADABS [28]. The structures
were determined and refined using SHELXS-97 and SHELXL-97 program packages
[29]. All non-H atoms were refined with anisotropic thermal parameters. The crystal
contains 2.5 molecules of dichloromethane per molecule of complex. The dichloro-
methane molecules are disordered and their hydrogens have not been included. All
˚
other hydrogens were constrained to their expected geometries (C–H 0.95, and 0.99 A)
and refined with Uiso 1.2 or 1.5 times the Ueq of their parent atom. The unit cell contains
one pair of enantiomers, but only RuHCl[(1R,2R)-14]2 is depicted in figure 2.
Crystal data for C60H61ClO4P4Ru ꢀ 2.5(CH2Cl2) [(rac)-16). M ¼ 1318.8, triclinic, P1,
ꢂ
ꢂ
˚
˚
˚
a ¼ 12.8472(1) A, b ¼ 15.4271(2) A, c ¼ 17.7810(2) A, ꢂ ¼ 98.442(1) , ꢀ ¼ 110.008(1) ,
ꢄ ¼ 106.490(1)ꢂ, V ¼ 3056.63(6) A , Z ¼ 2, Dx ¼ 1.433 mg mꢁ3
,
ꢅ ¼ 0.670 mmꢁ1
,
3
˚
T ¼ 83(2) K, measured 29,558 reflections (12,290 unique) in ꢆ range 1.8–26.3ꢂ.
Rint ¼ 0.018. Final R indices [for 10,674 reflections with I 4 2ꢇ(I)] R1 ¼ 0.043,
wR2 ¼ 0.115.

392
G.R. Clark et al.
3.23. X-ray crystal structure determination of (rac)-17 (a racemic mixture of
RuH2[(1S,2S)-14]2 and RuH2[(1R,2R)-14]2)
A suitable crystal of (rac)-17 was isolated from iso-propanol and analyzed as for
(rac)-16. The unit cell contains two molecules of each enantiomer, with only one,
RuH2[(1S,2S)-14]2, depicted in figure 3. Crystal data for C60H62O4P4Ru [(rac)-17].
˚
˚
˚
M ¼ 1072.05, monoclinic, P21/c, a ¼ 12.3274(15) A, b ¼ 14.7526(18) A, c ¼ 29.393(3) A,
b ¼ 95.409(2)ꢂ, V ¼ 5321.6(11) A , Z ¼ 4, Dx ¼ 1.338 mg mꢁ3
,
ꢅ ¼ 0.461 mmꢁ1
,
3
˚
T ¼ 113(2) K, measured 37174 reflections (10986 unique) in ꢆ range 2.1–26.5ꢂ.
Rint ¼ 0.050. Final R indices [for 8368 reflections with I 4 2ꢇ(I)] R1 ¼ 0.034,
wR2 ¼ 0.074.
Supplementary material
Crystallographic data (excluding structure factors) for (rac)-16 and (rac)-17 have been
deposited with the Cambridge Crystallographic Data Centre as supplementary
publication numbers CCDC 730333 and CCDC 730334, respectively. Copies of this
information can be obtained free of charge from the Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (Fax: þ44-1223-336-033; Email: deposit@ccdc.cam.ac.uk
or www: http://www.ccdc.cam.ac.uk).
Acknowledgements
We thank the Tertiary Education Commission, administered by Auckland UniServices
Limited, for granting an Enterprise Scholarship to ATS and Industrial Research
Limited New Zealand for the partial support of this work. We also thank The
University of Auckland for partial support of this work through grants-in-aid.
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