Synthesis and characterization of ruthenium complexes of 1,8-bis(diphenylphosphinomethyl)naphthalene (BDNA) and their catalytic hydrogenation reactions to α,β-unsaturated aldehydes

Article abstract of DOI:10.1016/S0022-328X(98)00889-4

A new ligand BDNA [1,8-bis(diphenylphosphinomethyl)naphthalene] and three ruthenium complexes containing the new ligand, Ru₂Cl₄(BDNA)₂ 1, RuHCl(CO)(PPh₃)(BDNA) 2, and RuH₂(CO)(PPh₃)(BDNA) 3, have been synthesized. Their compositions and structures were characterized by ³¹P{¹H}-NMR, ¹H-NMR, and elemental analysis. Molecular structure of 3 was also confirmed by single-crystal X-ray diffraction. The crystal belonged to the triclinic crystal system, P1 space group, a=10.7450(7), b=12.7100(7), c=18.1390(13) A, α=89.558(6), β=83.117(2), γ=80.859(5)°, V=2428.0(3) A³, and Z=2. The hydrogenation results of citral and cinnamaldehyde revealed that complex 2 had good catalytic activity and complex 3 had the high selectivity for the hydrogenation of C=O bond in α,β-unsaturated aldehydes to form the corresponding allylic alcohols. In the presence of complex 3, very high selectivities of 99.5 and 95.1% were obtained for the hydrogenation of the carbonyl group in citral and cinnamaldehyde, respectively.

Full text of DOI:10.1016/S0022-328X(98)00889-4

Journal of Organometallic Chemistry 571 (1998) 223–229
Synthesis and characterization of ruthenium complexes of
1,8-bis(diphenylphosphinomethyl)naphthalene (BDNA) and their
catalytic hydrogenation reactions to h,i-unsaturated aldehydes
Rui-Xiang Li a, Ning-Bew Wong a, Xian-Jun Li b, Thomas C.W. Mak c, Qing-Chuan Yang c,
Kam-Chung Tin a,*
a Department of Biology and Chemistry, City Uni6ersity of Hong Kong, Tatchee A6enue, Kowloon, Hong Kong, People’s Republic of China
b Department of Chemistry, Sichuan Uni6ersity, Chengdu 610064, People’s Republic of China
c Department of Chemistry, Chinese Uni6ersity of Hong Kong, Satin, Hong Kong, People’s Republic of China
Received 18 May 1998; received in revised form 25 July 1998
Abstract
A new ligand BDNA [1,8-bis(diphenylphosphinomethyl)naphthalene] and three ruthenium complexes containing the new
ligand, Ru2Cl4(BDNA)2 1, RuHCl(CO)(PPh3)(BDNA) 2, and RuH2(CO)(PPh3)(BDNA) 3, have been synthesized. Their compo-
1
sitions and structures were characterized by 31P{1H}-NMR, H-NMR, and elemental analysis. Molecular structure of 3 was also
(
confirmed by single-crystal X-ray diffraction. The crystal belonged to the triclinic crystal system, P1 space group, a=10.7450(7),
3
˚
˚
b=12.7100(7), c=18.1390(13) A, h=89.558(6), i=83.117(2), k=80.859(5)°, V=2428.0(3) A , and Z=2. The hydrogenation
results of citral and cinnamaldehyde revealed that complex 2 had good catalytic activity and complex 3 had the high selectivity
for the hydrogenation of CꢀO bond in h,i-unsaturated aldehydes to form the corresponding allylic alcohols. In the presence of
complex 3, very high selectivities of 99.5 and 95.1% were obtained for the hydrogenation of the carbonyl group in citral and
cinnamaldehyde, respectively. © 1998 Elsevier Science S.A. All rights reserved.
Keywords: Ruthenium complex; 1,8-Bis(diphenylphosphinomethyl)naphthalene; Hydrogenation; Citral; Cinnamaldehyde
the coordination number, stoichiometry and stereo-
chemistry of the resulting complex than the monoden-
tate phosphine ligand. Bidentate phosphine complexes
could enhance better catalytic activity and selectivity in
comparison to the monodentate phosphine complexes
[9,10], especially, in asymmetric catalysis [11–15]. h,i-
Unsaturated aldehydes are valuable intermediates in
the field of fragrance and flavor chemistry, and they are
also often involved in the tedious syntheses of novel
fine chemical products [16]. The selective reduction of
carbonyl group conjugated with the CꢀC bond is still a
challenging problem, and only a few reports have been
published on the selective formation of unsaturated
alcohols by using boron and aluminum hydride as
reducing agents [17,18] or catalyzed by transition metal
complexes with primary or secondary alcohols serving
1. Introduction
The syntheses and catalytic reaction of platinum
group metal complexes have been one of the most
active research areas because they generally exhibit
excellent hydrogenation properties for unsaturated or-
ganic compounds [1–5]. A number of neutral ruthe-
nium complexes of tertiary phosphine, hydride and
carbonyl ligands, such as, RuCl2(PPh3)3 [6], RuH-
Cl(CO)(PPh3)3 [7] and RuH2(CO)(PPh3)3 [8] are excel-
lent catalysts and their hydrogenation mechanisms have
also been extensively investigated. In general, bidentate
phosphine ligand will have better capability to control
* Corresponding author. Fax: +852 27887406; e-mail:
bhkctin@cityu.edu.hk
0022-328X/98/$ - see front matter © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00889-4

224
R.-X. Li et al. / Journal of Organometallic Chemistry 571 (1998) 223–229
Table 1
as hydrogen donors [19–22]. Catalytic hydrogenation
appears to be the most attractive way to carry out these
reductions, when economic and industrial processing
factors are taken into consideration, but results with
high activity and selectivity are still scarce [23,24]. In
the previous paper [9], we have reported that ruthenium
complexes bearing a BISBI [2,2%-bis(diphenylphosphi-
nomethyl)-1,1%-biphenyl] ligand had very good catalytic
hydrogenation activity for citral and cinnamaldehyde
and adequate hydrogenation selectivity to form the
corresponding allylic alcohols. In this paper, we would
like to report the synthesis of BDNA, a new bidentate
phosphine ligand, and three novel ruthenium complexes
bearing the new BDNA ligand, Ru2Cl4(BDNA)2, RuH-
Cl(CO)(PPh3)(BDNA) and RuH2(CO)(PPh3)(BDNA).
Initial results have shown that these complexes were
much better catalysts for the selective hydrogenation of
CꢀO bond in h,i-unsaturated aldehydes than the
analogous ruthenium complexes of PPh3 or BISBI.
Experimental data for the X-ray diffraction studies
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
C55H51O3P3Ru
953.94
293(2)
0.71073
Triclinic
˚
(
P1
Unit cell dimensions
˚
a (A)
10.7450(7)
12.7100(7)
18.1390(13)
89.558(6)
83.117(2)
80.859(5)
2428.0(3), 2
1.305
0.464
988
0.30×0.24×0.15
1.13–25.00
−135h512, −155k50,
−225l521
7286
˚
b (A)
˚
c (A)
h (°)
i (°)
k (°)
3
˚
Volume (A ), Z
Dcalc. (g cm−3
)
Absorption coefficient (mm−1
F (000)
)
Crystal size (mm)
q range for data collection (°)
Limiting indices
Reflections collected
Independent reflections
Absorption correction
Refinement method
7286 (Rint=0.0000)
Abscor
2. Experimental
Full-matrix least-squares on
F2
2.1. Materials
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I\2| (I)]
R indices (all data)
7236/0/560
0.704
R1=0.0787, wR2=0.2191
R1=0.0855, wR2=0.2564
0.0108 (8)
All synthetic reactions were performed with standard
Schlenk technique and under nitrogen atmosphere. Sol-
vents were dried over appropriate drying agents and
distilled under nitrogen prior to use. Reagent-grade
PPh3 and 1,8-di(bromomethyl)naphthalene were pur-
chased from Aldrich, citral (97%) and cinnamaldehyde
(98%) from Riedel-deHaen and they were distilled be-
fore use. RuCl3 ·xH2O (\42% Ru) was purchased
from Kunming Nobel Metals, China. Starting materials
RuCl2(PPh3)3 [25], RuHCl(CO)(PPh3)3 [26] and
RuH2(CO)(PPh3)3 [26] were prepared according to the
reported methods.
Extinction coefficient
Largest difference peak and hole 1.205 and −1.750
−3
˚
(e A
)
tor). The autoclave was evacuated and flushed with
high purity hydrogen five times, consecutively, and was
filled with hydrogen to the reaction pressure. After the
reaction solution was heated to the desired temperature,
the stirrer was started (400 rpm) and the reaction time
was noted. The reaction was quenched by immersing
2.2. Analytical methods
Table 2
Selected bond lengths and angles for RuH2(CO)(PPh3)(BDNA)
The 1H- and 31P{1H}-NMR spectra were recorded on
a Bruker DPX 400 spectrometer at room temperature
˚
Bond length (A)
1
(r.t.), 400.13 MHz for H and 160.97 MHz for 31P. The
Ru–P(1)
Ru–P(2)
Ru–P(3)
Ru–C(63)
2.3236(6)
2.3688(6)
2.3014(6)
1.8291(2)
chemical shifts of 31P{1H}-NMR were relative to 85%
1
H3PO4 as external standard, H-NMR relative to TMS
as internal standard, with downfield shifts as positive.
Elemental analyses were performed by the Shanghai
Institute of Organic Chemistry, Chinese Academy of
Sciences. FTIR was recorded on a Perkin Elmer 1600
spectrometer with a KBr plate.
Bond angle (°)
C(63)–Ru–P(3)
C(63)–Ru–P(1)
P(3)–Ru–P(1)
C(63)–Ru–P(2)
P(3)–Ru–P(2)
76.71(8)
100.25(7)
154.22(2)
97.24(7)
95.56(2)
101.36(2)
114.9(3)
126.0(2)
113.2(3)
126.5(2)
P(1)–Ru–P(2)
2.3. Catalytic hydrogenation
C(58)–C(59)–C(62)
C(60)–C(59)–C(62)
C(52)–C(51)–C(61)
C(60)–C(51)–C(61)
An appropriate amount of catalyst and substrate
solution were introduced into a stainless steel autoclave
(100 ml) equipped with a stirrer (Parr 4561 minireac-

R.-X. Li et al. / Journal of Organometallic Chemistry 571 (1998) 223–229
225
3.2. Ru2Cl4(BDNA)2 1
RuCl2(PPh3)3 0.48 g (0.5 mmol) and BDNA 0.26 g
(0.5 mmol) were suspended in 20 ml acetone. After the
mixture was heated to reflux for 1 h, the reaction
mixture changed to dark brown color with the forma-
tion of orange–red precipitates. Then, the mixture was
cooled to r.t. and the product was filtered, washed with
diethyl ether, and dried under vacuum to give 0.34 g
(80%) yield of 1 as orange–red powder. Anal. Calc. for
C72H60Cl4P4Ru2: C, 63.49; H, 4.44. Found: C, 63.14; H,
4.56%. 31P{1H}-NMR spectrum: l(ppm) PA 61.89 (d),
PB 55.75 (d) with JAB=47.1 Hz; Pc 43.03 (d), Pd 49.87
(d) with JCD=31.5 Hz.
Fig. 1. Proposed structure of complex 1.
the reactor in an ice bath at the end of the hydrogena-
tion. The products were analyzed on GC (Hewlett-
Packard (HP) 5890 series II) with an FID and a
capillary column (HP-FFAP, 25 m×0.2 mm×0.33
mm), and the GC graphs were obtained with a HP 3396
integrator. The components were identified by authen-
tic sample on GC and GC–MS (HP 5890 GC with a
series mass selective detector).
3.3. RuHCl(CO)(PPh3)(BDNA) 2
RuHCl(CO)(PPh3)3 0.190 g (0.2 mmol) and BDNA
0.105 g (0.2 mmol) were dissolved in 10 ml toluene. The
solution was refluxed for 3 h. During reflux, the color
of the solution was slowly changed to pale yellow. At
the end of reaction, 20 ml n-hexane was added, then the
solution was kept in refrigerator overnight to form
microcrystalline white needles. The product was
filtered, washed with diethyl ether and dried under
vacuum to give 0.14 g (85%) of 2 as white needles.
Anal. Calc. for C55H46ClOP3Ru: C, 69.36; H, 4.87.
Found: C, 69.29; H, 4.93%. FTIR: wCO=1934.0 cm−1
(vs). 1H-NMR and 31P{1H}-NMR had two sets of
peaks with the intensity ratio of ca. 3:1. 1H-NMR peaks
of the major complex was centered at l (ppm) −6.44
(ddd) with JH–P =17.4, 17.4 Hz and JH–P =112.5
3. Preparation of ligand and complexes
3.1. Preparation of
1,8-bis(diphenylphosphinomethyl)naphthalene (BDNA)
Triphenylphosphine 3.6 g (13.7 mmol) and lithium
0.3 g (43.2 mmol) in 25 ml THF were stirred for 3
hours at r.t., and the orange–red solution was filtered
to remove the unreacted lithium. t-Butylchloride 1.25 g
(13.5 mmol) in 10 ml THF was dropped slowly into the
filtrate which was cooled using an ice-bath. At the end
of addition, the solution was heated to reflux for 10
min. After the solution was cooled to 0°C, 1,8-di(bro-
momethyl)naphthalene 2.0 g (6.4 mmol) in 20 ml THF
was dropped slowly into the cooled solution over a
period of 30 min. During the addition of 1,8-dibro-
momethylnaphthalene, the reaction mixture changed to
a pale orange color with the formation of white micro-
crystalline precipitates. The reaction mixture was
heated to reflux for 30 min before the solvent was
evaporated under vacuum to give a yellowish orange
sticky solid. CH2Cl2 (50 ml) and water (20 ml) were
added to dissolve the solid mixture, and then the mix-
ture was separated in a separatory funnel. The organic
layer was collected and reduced to about 20 ml under
vacuum. Addition of 30 ml ethanol to the CH2Cl2
solution caused the formation of white needle crystals.
The product was filtered, washed with ethanol, and
dried under vacuum for 2 h to give 2.4 g (72%) of
BDNA as white needles. M.p.: 226–228°C (in air) with
decomposition. Anal. Calc. for C36H30P2: C, 82.27; H,
5.76. Found: C, 82.15; H, 5.64%. 31P{1H}-NMR: l
(ppm) −10.8 (s); 1H-NMR: l (ppm) 4.22 (4H, s),
6.64–7.66 (26 H, m).
cis
trans
Hz, and the minor complex was centered at l (ppm)
−6.78 (ddd) with JH–P =20.4, 20.6 Hz and JH–P
cis
trans
=111.0 Hz. 31P{1H}-NMR of the major complex had
peaks at l (ppm) 51.82 (dd), 37.98 (dd) and 27.03 (dd)
with JP–P =18.9, 18.8 Hz and JP–P =292.8 Hz, the
cis
trans
minor complex had peaks at l (ppm) 37.90 (dd), 31.78
(dd) and 6.12 (t) with JP–P =12.7 Hz and JP–P
=
cis
trans
297.6 Hz.
3.4. RuH2(CO)(PPh3)(BDNA) 3
RuH2(CO)(PPh3)3 0.183 g (0.2 mmol) and BDNA
0.105 g (0.2 mmol) dissolved in 10 ml toluene was
refluxed for 3 h. During reflux, the solution color
changed slowly to pale yellow. At the end of the
reaction, 20 ml n-hexane was added, then the solution
was kept in refrigerator overnight to form white micro-
crystals. The product was filtered, washed with diethyl
ether and dried under vacuum to give 0.12 g (72%) of 3
as
white
microcrystals.
Anal.
Calc.
for
C55H47OP3Ru·2H2O: C, 69.24; H, 5.39. Found: C,
69.21; H, 5.23%. IR: wCO=1953.3 cm−1
.
31P{1H}- and
1H-NMR were similar to those of the complex 2.
1H-NMR: trans-isomer, l (ppm) −7.35 (dddd) with

226
R.-X. Li et al. / Journal of Organometallic Chemistry 571 (1998) 223–229
Fig. 2. Proposed structures of complex 2.
JH –P =35.6 Hz, JH –P =61.1 Hz, and JH –H =
b
peared
during
the
addition
of
1,8-di(bro-
a
a
a
cis
trans
11.0 Hz; and −8.24 (dddd) with JH –P =36.3 Hz,
momethyl)naphthalene. BDNA has shown good
solubility in CH2Cl2 and CHCl3 but was only sparingly
soluble in alcohol. The ligand was very sensitive to air
oxidation in organic solution although the dry white
needle crystals appeared to be quite stable in air.
b
JH –P =125.4 Hz; cis-isomer, the peakscicsould not be
b
trans
clearly identified because of the overlapping with the
hydride peaks of the trans-isomer. 31P{1H}-NMR:
trans-isomer: l (ppm) 56.8 (ddd) and 49.8 (t) with
JP–P =17.5 Hz and JP–P =183.8 Hz; cis-isomer: l
cis
trans
(ppm) 61.4 (d) and 46.3 (t) with JP–P=17.0 Hz.
4.2. Complex 1
3.5. X-ray crystallographic analysis of
RuH2(CO)(PPh3)(BDNA) 3
The orange–red complex was not very stable either
in solution or in solid form. When the complex was
dissolved in organic solvent, such as toluene or
dichloromethane, the color of the solution was orange
under nitrogen atmosphere. If the solution was exposed
to air, the orange color would change to green color
within a few minutes. However, the orange–red powder
of complex 1 was more stable to air oxidation, the color
change could only be observed after exposing to air for
24 h. Our original plan was to synthesize
The crystal used for X-ray diffraction was prepared
from a 1:1 solvent mixture of dichloromethane and
n-hexane. The colorless prism crystal was mounted on a
MSC/Rigaku PAXIS IIC imagine-plate diffractometer.
Intensity data were collected at 294 K using graphite-
˚
monochromatized Mo–Kh (u=0.71073 A) radiation
from a rotating-anode generator operating at 50 kV
and 90 mA (taking 53 oscillation photos in the range
0–159°, exposure 8 min per frame). A self-consistent
semi-empirical absorption correction based on Fourier
coefficient fitting of symmetry-equivalent reflections
was applied using the ABSCOR program. All calcula-
tions were performed with Siemens SHELXTL PLUS
(PC Version) system. Structure refinement was based
on F2 for all 7236 reflections. A final R-factor was
0.0787, wR 0.2191, the largest and mean D/|, and the
largest difference peaks are presented in Table 1. Table
2 contains selected bond distances and angles.
RuCl2(PPh3)(BDNA)
by
ligand
exchange
of
RuCl2(PPh3)3 with BDNA. Unexpectedly, the 31P{1H}-
NMR spectrum showed two doublets of doublets with
equal intensities and elemental analyses also agreed
with the dinuclear structure of Ru2Cl4(BDNA)2. The
structural differences of the ligands have obviously
influenced the formation of the target complexes and
their properties. In our previous study [9], when BISBI
was used as ligand, only the desired product
RuCl2(PPh3)(BISBI) was isolated under similar prepa-
ration conditions. Although the PPh3 in the complex
RuCl2(PPh3)(BISBI) would completely dissociate in
benzene or chloroform to form the dimer complex
[RuCl2(BISBI)]2 in solution, only the original mononu-
clear complex RuCl2(PPh3)(BISBI) could be crystallized
from the organic solution when we attempted to isolate
the dimer complex. Basset et al. have also reported
similar observation for the reaction of RuCl2(PPh3)3
and TPPTS [trisodium salt of the tri(m-sul-
fophenyl)phosphine] to form the dimer complex
[RuCl2TPPTS2]2 owing to the large cone angle of
TPPTS (ca. 170 vs. 145° for PPh3) [30]. To the best of
our knowledge, it is very unusual to observe that a
4. Results and discussion
4.1. The BDNA ligand
There are several reported routes for the synthesis of
di-t-phosphines [27–29]. In the present study, reaction
of alkali metal diphosphide with dibromide in THF was
chosen because it was a convenient route with satisfac-
tory yield. The ligand BDNA was not very soluble in
THF, therefore, a lot of crystalline solid product ap-

R.-X. Li et al. / Journal of Organometallic Chemistry 571 (1998) 223–229
227
Fig. 3. Proposed structures of complex 3.
dinuclear complex could be generated in high yield with
4.4. Complex 3
equilmolar amounts of RuCl2(PPh3)3 and a bidentate
phosphine ligand. According to the 31P{1H}-NMR
spectrum, the structure of the dinuclear complex was
proposed as shown in Fig. 1. In order to ensure the
dinuclei structure of the complex, measurement of
molecular weight by vapor pressure osmometer would
be helpful in future studies.
The colorless microcrystalline product was prepared
by a similar method as complex 2 and it was stable in
air. If the organic solution of the complex was exposed
to air, it would slowly decompose to brownish color
after two days. The absorption peak of Ru–H in
complex 3 could not be clearly identified in the IR
spectrum because of the very strong carbonyl peak
1
4.3. Complex 2
overlapping with the weak Ru–H absorption. The H-
NMR spectra showed two sets of peaks, one had much
higher intensity than the other with the intensity ratio
of ca. 10:1. The strong peaks appeared as two doublets
of doublets of double doublets at −7.35 and −8.25
ppm, and the weak peaks were shown as two octets at
−7.95 and −8.70 ppm. The 31P{1H}-NMR spectra
also displayed two sets of peaks, and the intensity ratio
of the two sets were also ca. 10:1. The strong peaks
appeared as a doublet of double doublets at 56.7 ppm
and a triplet at 49.8 ppm, and the weak peaks appeared
as a doublet at 61.3 ppm and a triplet at 46.2 ppm.
These NMR spectra have strongly indicated that the
stronger peaks were from the the trans-isomer, and the
weaker peaks were from the cis-isomer. The proposed
structures of the two isomeric complexes are shown in
Fig. 3.
The results of single-crystal X-ray diffraction were
listed in Tables 1 and 2 and Fig. 4. They were in
agreement with the proposed trans-structure as shown
in Fig. 3. According to the X-ray diffraction results, a
crystal cell contained four water molecules. Ru–P(3)
and Ru–P(1) were in trans-positions to each other and
the steric barrier was less than Ru–P(2) in the middle
position, so the bond lengths were shorter than Ru–
P(2). The same phenomenon was also observed in the
analogous complex of BISBI [9]. The phosphorus
atoms of the bidentate phosphine ligand occupied the
trans-position because of the flexible backbone and
larger chelating ring of the bidentate phosphine ligand
in the BISBI complex. The rigid backbone of BDNA
restricted the bidentate phosphine ligand to coordinate
It was prepared by the ligands exchange of RuH-
Cl(CO)(PPh3)3 with BDNA in refluxing toluene. The
solid state complex as well as its organic solution were
quite stable to air oxidation. However, the yellow or-
ganic solution would gradually change to dark brown
color after it had been exposed to air for 2 days. The
carbonyl absorption peak was very strong and had
overlapped with the Ru–H bond absorption of com-
plex 2 in the IR spectrum. 1H-NMR spectra of the
hydride in the complex showed two sets of doublets of
double doublet peaks with similar splitting pattern. The
intensity ratio of the two sets of peaks was ca. 3:1.
31P{1H}-NMR also showed two sets of peaks. The
results have suggested that the product was a mixture
containing two kinds of structures. According to the
splitting pattern of peaks and the coupling constants,
all phosphorus atoms in the two isomers were arranged
in meridional forms and the hydrides in the two isomers
were in the trans-position to one of the phosphorus
atoms. Therefore, the hydride in the major isomer was
in trans position of a phosphorus atom of BDNA (Fig.
2 A), but the hydride in the minor isomer was in trans
position of triphenylphosphine (Fig. 2 B). The amount
of the former isomer was about three time higher than
the latter isomer. The two phosphorus atoms of BDNA
in the latter configuration were not equal because the
rigid backbone of BDNA had caused the complex to
form a distorted octahedron. The conclusion was also
supported by the doublets of double doublets of the
1
hydride in H-NMR spectrum.

228
R.-X. Li et al. / Journal of Organometallic Chemistry 571 (1998) 223–229
Fig. 4. ORTEP drawing of complex 3.
in cis-position, and created a large distorted force in the
chelating ring, and resulted in that the bond angles of
P(1)–Ru–P(2), C(60)–C(59)–C(62) and C(60)–C(51)–
C(61) were much larger than those of P(2)–Ru–P(3),
C(58)–C(59)–C(62) and C(52)–C(51)–C(61), respec-
tively. Although the hydrides were not located in the
structure, it was reasonable to believe that they occu-
pied the trans-positions of CO and P(2).
4.5. Hydrogenation of citral and cinnamaldehyde
catalyzed by ruthenium complexes 1–3
Hydrogenation results of citral and cinnamaldehyde
are summarized in Table 3. The substitution of PPh3 by
BDNA had significantly improved the selectivities of
ruthenium complexes 1–3 for the hydrogenation of
CꢀO bond in h,i-unsaturated aldehydes to form allylic
Table 3
Hydrogenation of h,i-unsaturated aldehydes
Catalyst
Citrala
Cinnamaldehydeb
Conversion (%)
Selectivityc (%)
Conversion (%)
Selectivityc (%)
RuCl2(PPh3)3
Ru2Cl4(BDNA)2
RuHCl(CO)(PPh3)3
RuHCl(CO)(PPh3)(BDNA)
RuH2(CO)(PPh3)3
35.4
15.5
11.4
92.7
4.3
35.8
92.3
65.6
95.5
89.7
99.5
39.7
13.6
10.8
86.4
8.8
61.5
86.8
67.6
93.9
70.7
95.1
RuH2(CO)(PPh3)(BDNA)
63.8
61.5
Reaction conditions: toluene: 8.0 ml, substrates: 2.0 ml, catalyst conc.: 1.0×10−3 M, H2 pressure: 50 kg cm−2, time: 3 h.
a Reaction temperature: 80°C.
b Reaction temperature: 70°C.
c Selectivity in allylic alcohol.

R.-X. Li et al. / Journal of Organometallic Chemistry 571 (1998) 223–229
229
[2] C. Masters, Homogeneous Transition-Metal Catalysis, Chapman
and Hall, London, 1981.
[3] H.A. Mayer, W.C. Kaska, Chem. Rev. 94 (1994) 1239.
[4] B.R. James, A. Pacheco, S.J. Rettig, J. Mol. Catal. 41 (1987)
147.
[5] R. Noyori, H. Takaya, Acc. Chem. Res. 23 (1990) 345.
[6] P.S. Hallman, D. Evans, J.A. Osborn, G. Wilkinson, J. Chem.
Comm. (1967) 305.
[7] R.A. Sanchez-Delgado, N. Valencia, R.L. Maruez-Silva, A. An-
driollo, M. Medina, Inorg. Chem. 25 (1986) 1106.
[8] W. Strohmeier, L. Wiegelt, J. Organomet. Chem. 145 (1978) 189.
[9] R.X. Li, N.B. Wong, C.K. Mak, Z.Y. Zhang, X.J. Li, K.C. Tin,
J. Organomet. Chem. 557 (1998) 207.
[10] A.M. Joshi, K.S. MacFarlane, B.R. James, J. Organomet. Chem.
488 (1995) 161.
[11] S.A. King, A.S. Thompson, A.O. King, T.R. Verhoeven, J. Org.
Chem. 57 (1992) 6689.
[12] K. Mashima, T. Hino, H. Takaya, J. Chem. Soc. Dalton Trans.
(1992) 2099.
[13] T. Ohta, Y. Tonomura, K. Nozaki, H. Takaya, K. Mashima,
Organometallics 15 (1996) 1521.
[14] A. Mezzetti, G. Consiglio, J. Chem. Soc. Chem. Commun.
(1991) 1675.
[15] P.J. Pye, K. Rossen, R.A. Reamer, N.N. Tsou, R.P. Volante,
P.J. Reider, J. Am. Chem. Soc. 119 (1997) 6207.
[16] K. Bauer, D. Garbe, Ullman Encyclopedia, vol. A11, 3rd ed.,
VCH, New York, 1988, p. 141.
[17] A.L. Gemal, J.L. Luche, J. Am. Chem. Soc. 103 (1981) 5454.
[18] S.L. Fukuzawa, T. Fujinami, S. Yamauchi, S. Sakai, J. Chem.
Soc. Perkin Trans. (1986) 1929.
[19] T. Mizoroki, K. Seki, S. Meguro, A. Ozaki, Bull. Chem. Soc.
Jpn. 50 (1977) 2148.
alcohols. Although the catalytic activity of 1 was lower
than the analogous PPh3 complex, complexes 2 and 3 have
shown much higher catalytic activities and selectivities for
theformationofallylicalcoholsthantheiranaloguesPPh3
complexes. For example, the selectivity of 2 for the
hydrogenation of CꢀO in citral was 95.5% (92.7% conver-
sion) and the selectivity of 3 was 99.5% (63.8% conver-
sion). Complex 2 had the highest catalytic activity and
complex 3 showed the highest selectivity among the three
complexes. These results have followed the same trend
as the analogous ruthenium complexes containing BISBI
described in our previous study [9]. The chemical environ-
ment of the phosphorus atoms in the BDNA ligand
appeared to be very similar to the phosphorus atoms in
the BISBI ligand. The immense difference of hydrogena-
tion activity and selectivity between BISBI and BDNA
complexes might originate from their different backbone
structures, i.e., theyweremainlycontrolledbystericfactor
and not electronic factor. The rigid structure of BDNA
backbone and the large chelating ring in these complexes
could play an important role for the significant improve-
ment of hydrogenation selectivity. The IR spectra results
have shown that the absorption of carbonyl group in
complex 3 appeared at a higher wavenumber (wCO
=
1953.3 cm−1) than complex 2 (wCO=1934.0 cm−1) after
the chloride in 2 was substituted by the hydride. This
means that the electronic density of ruthenium in 2 was
higher than in 3 which was in good agreement with the
observed higher catalytic activity of 2 than 3 for the
hydrogenation of h,i-unsaturated aldehydes.
[20] M. Visintin, R. Spogliarich, J. Kaspar, M. Graziani, J. Mol.
Catal. 32 (1985) 349.
[21] E. Farnetti, G. Nardin, M. Graziani, J. Chem. Soc. Chem.
Commun. (1989) 1264.
[22] B.R. James, R.H. Morris, J. Chem. Soc. Chem. Commun. (1978)
929.
[23] J.M. Grosselin, C. Mercier, G. Allmang, F. Grass, Organometal-
lics 10 (1991) 2126.
Acknowledgements
[24] M. Hernandez, P. Kalck, J. Mol. Catal. A Chem. 116 (1997) 131.
[25] P.S. Hallman, T.A. Stephenson, G. Wilkinson, Inorg. Synth. 12
(1970) 237.
[26] J.J. Levison, S.D. Robinson, J. Chem. Soc. A (1970) 2947.
[27] R. Uriarte, T.J. Mazanec, K.D. Tau, D.W. Meek, Inorg. Chem.
19 (1980) 79.
TheauthorsgratefullyacknowledgetheCityUniversity
of Hong Kong and the Hong Kong Research Grants
Council for financial support.
[28] T.A. Puckertte, T.J. Devon, G.W. Phillips, J.L. Stavinoha, US
Patent 4879416, Chem. Abstr. 112 (1989) (1989) 217269k.
[29] H.C.E. McFarlane, W. McFarlane, Polyhedron 2 (1983) 303.
[30] E. Fache, C. Santini, F. Senocq, J.M. Basset, J. Mol. Catal. 72
(1992) 331.
References
[1] B.R. James, Homogeneous Hydrogenation, Wiley, New York,
1973.
.