Two pseudo-N3 ligands and the catalytic activity of their ruthenium(II) complexes in transfer hydrogenation and hydrogenation of ketones

Article abstract of DOI:10.1016/j.jorganchem.2007.01.058

Complex RuCl₂(PPh₃)(iBu-BTP) (5) was synthesized by the reaction of 2,6-bis(5,6-bis(iso-butyl)-1,2,4-triazin-3-yl)pyridine (iBu-BTP) and RuCl₂(PPh₃)₃ in refluxing toluene, and its molecular structure was confirmed by X-ray crystallographic determination. Complex 5 was applied as a catalyst for transfer hydrogenation of ketones and exhibited catalytic activity comparable to RuCl₂(PPh₃)(Me₄BPPy) (1) (Me₄BPPy = bis(3,5-dimethylpyrazol-1-yl)pyridine) in some cases. The difference between the catalytic activity of 5 and 1 is attributed to the significantly different arrangement and positions of the PPh₃ and chlorides and also to the different electron density on the N-heterocycles. Complex 1 exhibited good to excellent catalytic activity in hydrogenation of ketones under mild conditions. These results have suggested new applications of iBu-BTP and Me₄BPPy as promising planar tridentate pseudo-N₃ ligands to construct highly active transition-metal catalysts.

Full text of DOI:10.1016/j.jorganchem.2007.01.058

Journal of Organometallic Chemistry 692 (2007) 2306–2313
www.elsevier.com/locate/jorganchem
Two pseudo-N3 ligands and the catalytic activity
of their ruthenium(II) complexes in transfer hydrogenation
and hydrogenation of ketones
a,
a
a
b
Z.K. Yu *, F.L. Zeng , X.J. Sun , H.X. Deng a,b, J.H. Dong ,
a
c
c
J.Z. Chen , H.M. Wang , C.X. Pei
a
Dalian Institute of Chemical Physics, Chinese Academy of Sciences (CAS), 457 Zhongshan Road, Dalian, Liaoning 116023, PR China
School of Pharmaceutical Engineering, Shenyang Pharmaceutical University, 103 Wenhua Road, Shenyang, Liaoning 110016, PR China
b
c
Beijing Institute of Pharmaceutical Chemistry, Beijing 102205, PR China
Received 8 November 2006; received in revised form 20 January 2007; accepted 30 January 2007
Available online 8 February 2007
Abstract
Complex RuCl2(PPh3)(iBu-BTP) (5) was synthesized by the reaction of 2,6-bis(5,6-bis(iso-butyl)-1,2,4-triazin-3-yl)pyridine (iBu-BTP)
and RuCl2(PPh3)3 in refluxing toluene, and its molecular structure was confirmed by X-ray crystallographic determination. Complex 5
was applied as a catalyst for transfer hydrogenation of ketones and exhibited catalytic activity comparable to RuCl2(PPh3)(Me4BPPy) (1)
(Me4BPPy = bis(3,5-dimethylpyrazol-1-yl)pyridine) in some cases. The difference between the catalytic activity of 5 and 1 is attributed to
the significantly different arrangement and positions of the PPh3 and chlorides and also to the different electron density on the N-het-
erocycles. Complex 1 exhibited good to excellent catalytic activity in hydrogenation of ketones under mild conditions. These results have
suggested new applications of iBu-BTP and Me4BPPy as promising planar tridentate pseudo-N3 ligands to construct highly active tran-
sition-metal catalysts.
ꢀ 2007 Elsevier B.V. All rights reserved.
Keywords: N3 Ligands; Ruthenium; Transfer hydrogenation; Hydrogenation; Ketones
1. Introduction
alysts [5]. Planar N3 ligand 2,6-bis(5-methyl-1,2,4-triazol-3-
yl)pyridine (E, BMTZP) was used to synthesize lanthanide
complexes [6]. Very recently, bis(pyrazol-1-yl)pyridines (F)
were reported to construct rare transition metal catalysts
from our laboratories [7a,7b] and Karam’s group [7c],
respectively. In our previous communication [7b], complex
RuCl2(PPh3)(Me4BPPy) (1) (Me4BPPy = a ligand of F type,
i.e., bis(3,5-dimethylpyrazol-1-yl)pyridine) was synthesized
and used as an efficient catalyst for transfer hydrogenation
of ketones. Fe(II) and Co(II) complexes of ligands of type
F, i.e., F Æ FeCl2 and F Æ CoCl2, were prepared and applied
for ethylene polymerization [7c]. However, other types of
N3 and pseudo-N3 ligands have been seldom reported to
construct late transition metal catalysts. Encouraged by
the excellent catalytic activity of complex 1 in transfer
hydrogenation of ketones [7b], we further investigated
Nitrogen-containing ligands have been extensively stud-
ied in coordination chemistry, and have been shown impor-
tant applications in the fields of homogeneous catalysis and
organic synthesis due to the easy manipulations and high
reactivities of their transition metal complexes [1].
Recently, planar tridentate nitrogen donor (N3) ligands
2,20:60,200-terpyridines (A, terpy) [2], 2,6-bis(imino)pyridines
(B) [3], and 2,6-bis(oxazolinyl)pyridines (C, Pybox) [4]
(Chart 1) have been paid much attention. Non-planar
pseudo-N3 ligands hydridotris(pyrazol-1-yl)borates (D,
Tp) have also been employed to build transition metal cat-
*
Corresponding author. Tel./fax: +86 411 8437 9227.
E-mail address: zkyu@dicp.ac.cn (Z.K. Yu).
0022-328X/$ - see front matter ꢀ 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.01.058

Z.K. Yu et al. / Journal of Organometallic Chemistry 692 (2007) 2306–2313
2307
shifted upfield by 0.2–0.3 ppm in the proton NMR spec-
trum as compared with those of the free ligand 4.
R1
R2
R1
R2
N
N
In the solid state, complex 5 exhibits a neutral molecular
structure in which 4 acts as a planar pseudo-N3 ligand, and
the metal center is six-coordinated with the tridentate
pseudo-N3 ligand, two chlorides, and one PPh3 ligand
(Fig. 1). The three Ru–N, two Ru–Cl and Ru–P bond dis-
tances are 1.982(3), 2.032(3), 2.058(3), 2.3919(13),
N
N
N
N
N
A [2]
B [3]
H
B
O
O
N
N
N
N
N
N
Rn
N
N
Rn
Rn
˚
2.4110(13), and 2.3631(11) A, respectively (Table 2). The
R
R
C
D [5]
[4]
Ru–N bond distances in 5 are very close to their analogues
in 1 [7b], but the Ru–Cl and Ru–P bonds in 5 are shorter
than those in 1. The significant structural difference
between complexes 5 and 1 is that the two chlorides in 5
are closely linear to each other (Cl(1)–Ru–Cl(2),
174.91(3)ꢁ) and positioned on the two sides of the pseudo-
N3 ligand plane, while the two chloride atoms in 1 are
nearly perpendicular to each other. The pyridyl nitrogen
atom is positioned trans to the PPh3 ligand in 5 (N(1)–
Ru–P, 175.80(8)ꢁ) (Fig. 1), while the PPh3 ligand in 1 is
arranged trans to one chloride and they are situated on
the two sides of the ligand plane, respectively [7b]. The
molecular structure of 5 demonstrates a rare example of
R1
R1
R3
N
N
N
N
N
N
N
N
R2
NH
HN
R2
N
N
R3
R
R
F
E [6]
[7]
Chart 1. N3 and pseudo-N3 ligands.
hydrogenation of ketones catalyzed by RuCl2(PPh3)
(Me4BPPy) (1). As a comparison study, ligand 2,6-
bis(5,6-bis(iso-butyl)-1,2,4-triazin-3-yl)pyridine (iBu-BTP)
(4) and complex RuCl2(PPh3)(iBu-BTP) (5) were synthe-
sized. Herein, we report synthesis and X-ray crystal struc-
ture of complex 5 and the catalytic activity of complexes
5 and 1 in transfer hydrogenation and hydrogenation of
ketones under mild conditions (see Chart 2).
transition metal complexes of
a new pyridyl-based
pseudo-N3 ligand which has been structurally
characterized.
O
OH
OH
O
0.2 mol% 5
NaOH, 82 oC
ð1Þ
+
+
2. Results and discussion
R
R'
R
R'
2.1. Synthesis and X-ray crystal structure of complex 5
2.2. Transfer hydrogenation of ketones catalyzed by complex
5
Ligand 4 was prepared by means of a modified literature
procedure (Chart 3) [6,8]. Condensation of pyridine-2,6-
dicarbohydrazide imide (2) with 1,2-diketone (3) at heating
Ruthenium(II) complexes have been used as the most
potential catalysts for transfer hydrogenation of ketones
afforded
2,6-bis(5,6-bis(iso-butyl)-1,2,4-triazin-3-yl)pyri-
dine (iBu-BTP) (4). Compound 4 is usually hydrated with
one molecule of water after isolation from flash silica gel
column chromatography. Although 4 is a poly-heterocyclic
compound, it is bestowed with very good solubility in
organic solvents including petroleum ether due to introduc-
tion of four iso-butyl side chains to the two triazinyl rings.
Reaction of ligand 4 with 1.0 equiv of RuCl2(PPh3)3 [9] in
refluxing toluene afforded complex RuCl2(PPh3)(iBu-BTP)
(5) in 86% yield (Chart 3). Complex 5 is air- and moisture-
stable and its single crystals suitable for X-ray crystallo-
graphic study were obtained from recrystallization in
CH2Cl2/hexane (v/v, 1/4) at ꢀ20 ꢁC. The NMR spectra
of 5 reveals 4 to be a coordinating ligand in 5. The chemical
shifts of the pyridyl CH hydrogen atoms in complex 5 are
O
HN
NH
N
+
NH
HN
O
H2N
NH2
2
3
N
N
N
N
N
N
N
4
RuCl2(PPh3)3
- 2 PPh3
Me
Me
Me
N
N
N
N
N
N
N
N
N
N
N
N
N
Cl
Cl
N
Cl
N
N
N
Ru
N
Ru
Cl
Ru
N
Me
Cl
Ph3P
Cl
PPh3
PPh3
1 [7b]
5
5
Chart 2. Ru(II) complexes 1 and 5.
Chart 3. Synthesis of ligand 4 and complex 5.

2308
Z.K. Yu et al. / Journal of Organometallic Chemistry 692 (2007) 2306–2313
Fig. 1. Perspective view of complex 5.
[10] and are also becoming very promising catalysts for
hydrogenation of ketones [11,12]. Complex 1 has showed
excellent catalytic activity to transfer hydrogenation of
ketones in 2-propanol, achieving a final TOF value as high
as 6000 hꢀ1 [7b]. That is, 2 mmol of acetophenones were
completely transformed to the corresponding alcohols
within 5 min in refluxing 2-propanol using 0.2 mol% 1 as
the catalyst and KOiPr as the base. In a similar fashion
complex 5 was applied in the catalytic transfer hydrogena-
tion of ketones (Table 3). Using 0.2 mol% 5 as the catalyst
with a molar ratio of 500/25/1 for ketone/base/catalyst,
transfer hydrogenation of acetophenone was carried out
in 2-propanol at 82 ꢁC (Eq. 1). K2CO3, KOiPr, KOH,
and NaOH were tested as the bases to optimize the reaction
conditions. Over a period of 4 h, the corresponding alcohol
product from acetophenone reached 98%, 96%, 97%, and
46% yields by GC analysis in the reactions using NaOH,
KOH, KOiPr, and K2CO3 as the base, respectively. Thus,
NaOH was selected as the reaction promoter although
both KOH and KOiPr also worked well as a base in the
Table 2
Table 1
˚
Selected bond distances (A) and angles (ꢁ) for complexes 5 and 1
Crystal data and refinement details for complex 5
Complex 5
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system, space group
Unit cell dimensions
C45H54C12N7PRu
895.89
293(2)
0.71073
Ru–N(1)
Ru–N(5)
Ru–Cl(1)
N(5)–N(6)
1.982(3)
2.058(3)
2.3919(13)
1.341(4)
Ru–N(2)
Ru–P
Ru–Cl(2)
2.032(3)
2.3631(11)
2.4110(13)
˚
Monoclinic, P2(1)/c
Cl(1)–Ru–Cl(2)
N(1)–Ru–N(5)
N(1)–Ru–P
N(1)–Ru–Cl(2)
P–Ru–Cl(1)
P–Ru–Cl(2)
Complex 1 [7b]
174.91(3)
N(1)–Ru–N(2)
N(2)–Ru–N(5)
N(1)–Ru–Cl(1)
N(2)–Ru–Cl(2)
N(2)–Ru–P
78.85(12)
156.03(12)
90.05(8)
93.88(8)
99.77(9)
˚
a (A)
11.286(5)
11.148(5)
35.528(15)
90
97.230(8)
90
4435(3)
4, 1.342
78.67(12)
175.80(8)
84.96(8)
93.83(4)
91.20(4)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
N(5)–Ru–P
103.23(9)
3
˚
V (A )
Z, Dc (g cmꢀ3
)
Me
5
Me
Me
l (mmꢀ1
F(000)
)
0.550
1864
3
1
N
N
N
Cl
Ru 2
N
N
Crystal size (mm3)
0.503 · 0.458 · 0.367
1.82–27.00
25260/9612 [Rint = 0.0882]
99.2%
9612/2/508
6414
2
4
Me
h Limit (ꢁ)
Ph3P
Cl
1
Reflections collected/unique
Completeness to h = 27.00
Data/restraints/parameters
No. of data observed with I > 2r(I)
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
Ru–N(1)
Ru–N(4)
Ru–Cl(1)
N(1)–Ru–Cl(1)
Cl(1)–Ru–Cl(2)
P–Ru–Cl(2)
1.955(3)
Ru–N(2)
Ru–P
Ru–Cl(2)
P–Ru–N(1)
P–Ru–Cl(1)
N(2)–Ru–N(4)
2.078(4)
2.2927(14)
2.4771(13)
94.87(11)
88.09(5)
2.051(4)
2.4546(12)
176.97(12)
91.56(4)
0.933
R1 = 0.0486, wR2 = 0.1112
R1 = 0.0720, wR2 = 0.1182
0.822 and ꢀ0.472
ꢀ3
˚
Largest difference peak and hole (e A
)
176.06(5)
156.97(15)

Z.K. Yu et al. / Journal of Organometallic Chemistry 692 (2007) 2306–2313
2309
Table 3
Transfer hydrogenation of ketones catalyzed by 5a
Table 3 (continued)
Entry
13
Ketone
Time (h)
24
Yieldb (%) TOFc (hꢀ1
)
Entry
1
Ketone
Time (h)
4
Yieldb (%)
TOFc (hꢀ1
1080
)
O
O
78 (2)
60
98 (36)
O
O
N
Ph
Ph
Me
Me
Et
2d
3e
4
2.5
4
100 (45)
100 (9)
60 (35)
900
180
14
15
8
34 (<1)
<30
N
O
O
24
80 (8)
240
30
1050
O
Me
O
Cl
16
17
24
24
0
0
O
5
6
24
30
96 (35)
89 (32)
1050
960
Cl
Me
96 (16)
480
O
O
Me
Me
Cl
18
19
O
9
97 (19)h
570
7
O
7
100 (10)
300
Me
O
4.5
98 (39)
1170
8
9
10
8
99 (19)
570
600
O
Me
Me
20e
21e
2.5
4
100 (64)
100 (33)
1280
660
O
100 (20)
O
Me
OMe
O
O
10
11
8
6
85f
53g
MeO
Me
Me
22
26
3 (3)
90
O
O
98 (31)
930
a
Reaction conditions: ketone/base/5 = 500/25/1. Ketone, 2 mmol; cat-
alyst 5, 3.6 mg (0.2 mol%); NaOH, 0.1 mmol; 2-propanol, 20 mL;
0.1 MPa, 82 ꢁC.
b
MeO
GC yield of the alcohol product. Data in parentheses are the GC yields
after 10 min.
c
TOF after 10 min.
0.3 mol% 5.
0.3 mol% 5, and KOH as the base.
Isolated yield.
Final TOF.
HPLC yield.
d
12
24
63 (1)
30
O
e
N
f
Me
g
h

2310
Z.K. Yu et al. / Journal of Organometallic Chemistry 692 (2007) 2306–2313
Table 4
reactions. Increasing the catalyst loading, the reaction was
accelerated. For example, with 0.3 mol% 5, acetophenone
was reached a complete conversion to form the alcohol
product within 2.5 h (Entry 2, Table 3). Because a compar-
ison study was intended between complexes 5 and 1,
0.2 mol% catalyst loading was used in the typical reactions
(Table 3).
Hydrogenation of ketones catalyzed by 1a
Entry
1
Ketone
Time (h)
4
P(H2) (atm)
20
Yieldb (%)
96
O
Me
Et
For most of the acetophenone substrates, their initial
reaction rates were fast within the first 10 min within the
10 min and then became smooth, or even very slow (Entries
1–11, Table 3). For example, acetophenone, substituted
chloroacetophenones, and p-methylacetophenone reached
36–45%, 32–35%, and 31% conversions within the first
10 min (Entries 1, 2, 4–6, and 11, Table 3). For propiophe-
none, its initial reaction rate was not fast, but its reaction
proceeded at a very constant rate, achieving a complete
conversion within 4 h (Entry 3, Table 3). Pyridyl ketones
slowly underwent the reactions and could not reach a high
conversion within 24 h (Entries 12–14, Table 3), neither did
a-tetralone show a high reactivity (Entry 15, Table 3).
Internal ketones, i.e., b-tetralone and 3-heptanone hardly
reacted over a period of 24 h (Entries 16 and 22, Table
3). However, 1-indanone and 9-fluorenone reached >96%
conversions within 9–24 h (Entries 17 and 18, Table 3).
Catalyst 5 exhibited excellent catalytic activity to cyclohex-
anone, cyclopentanone, and 2-heptanone (Entries 19–21,
Table 3). It should be noted that the catalytic activity of
complex 5 is comparable to that of complex 1 in the reac-
tions of propiophenone, 4-methoxyacetophenone, 2-benzo-
pyridine, a-tetralone, 1-indanone, 9-fluorenone, and the
aliphatic ketones (Entries 3, 11, 13, 15, and 17–21) under
the stated conditions, and in other cases complex 1 showed
much higher catalytic activity than 5 [7b]. The difference
between the catalytic activity of complexes 1 and 5 in trans-
fer hydrogenation of ketones is presumably attributed to
the significantly different arrangements of the PPh3 ligand
and the two chloride atoms around the metal centers and
also to the various electronic properties of the pyridyl-sup-
ported N-heterocycles. That pyrazolyls in 1 are stronger r-
donor ligands than 1,2,4-triazin-3-yls in 5 may help to form
a relatively electron-rich ruthenium center, thus stabilizing
the active catalytic species. These results suggest that the
arrangement of the PPh3 and chloride moieties in 1 may
be more favorable to stabilize the active catalytic species.
2
3
4
4
20
20
94
O
O
>99
Me
O
Cl
4
5
4
4
20
20
43 (96)c
Cl
Me
97
O
Me
Cl
6
7
8
4
4
4
20
20
20
>99
Me
O
Me
O
O
98
Me
Me
Me
Me
96
9
8
50
99d
O
Me
O
OH
R'
OMe
0.2 mol% 1
t-BuOK, 25 oC
2-propanol
+
H2
ð2Þ
R
R'
R
10
11
4
4
20
20
98
96
O
MeO
MeO
Me
Me
2.3. Hydrogenation of ketones catalyzed by complex 1
Complex 1 exhibited excellent catalytic activity for
transfer hydrogenation of ketones [7b], which led us to
investigate its catalytic activity for hydrogenation of
ketones. It was found that complex 1 can also exhibit high
catalytic activity in hydrogenation of ketones under mild
conditions (Eq. 2, Table 4). With a molar ratio of 500/
O

Z.K. Yu et al. / Journal of Organometallic Chemistry 692 (2007) 2306–2313
2311
Table 4 (continued)
period of 4 h, acetophenones and aliphatic ketones were
reduced to the corresponding alcohols in excellent yields
(Entries 1–11, 15, and 18–20). For benzophenone and 9-flu-
orenone, their corresponding alcohol products were
formed in 83–92% yields (Entries 12 and 17, Table 4), while
pyridyl ketones and 1-indanone were stubborn to be
reduced under the stated conditions (Entries 13, 14, and
16, Table 4). It is noteworthy that by-products were not
detected in the reaction mixtures. This protocol has dem-
onstrated a promising catalyst system for hydrogenation
of ketones under mild conditions.
Ruthenium hydride species generated from complexes 1
and 5 were presumably considered as the catalytically
active species in transfer hydrogenation and hydrogenation
of ketones. Thus, reduction of complexes 1 and 5 was car-
ried out in methanol with NaBH4 or dihydrogen under
pressure and heating in order to isolate the ruthenium
hydride complexes. Unfortunately, no success has been
achieved. Ligands 4 and Me4BPPy did not react with
RuH(Cl)(PPh3)3 in CH2Cl2 or toluene at ambient tempera-
ture or heating to form the desired complexes
RuH(Cl)(L)(PPh3) which might be generated in situ to pro-
mote the catalytic transfer hydrogenation and hydrogena-
tion of ketones. For the present transfer hydrogenation
of ketones catalyzed by complex 5, no obvious reaction
undergo at ambient temperature in most cases, suggesting
that heating is necessary to promote formation of the cat-
alytically active species. In the hydrogenation of ketones
using complex 1 as the catalyst, the reaction was negligible
under a nitrogen atmosphere without dihydrogen, indicat-
ing that dihydrogen under pressure was involved in the
reaction to promote formation of the catalytically active
species at ambient temperature.
Entry
12
Ketone
Time (h)
4
P(H2) (atm)
20
Yieldb (%)
83e
O
Ph
13
14
O
O
8
8
50
50
1.8d
N
N
Ph
Ph
23
15
4
20
5
O
6
4
30
20
97c
22
O
16
17
8
4
50
20
27d
92f
O
O
18
19
4
20
99
3. Summary
4
4
20
20
79 (97c)
>99
In summary, complex RuCl2(PPh3)(iBu-BTP) (5) has
exhibited moderate to good and excellent catalytic effi-
ciency in the transfer hydrogenation of ketones, and its cat-
alytic activity is comparable to that of complex
RuCl2(PPh3)(Me4BPPy) (1) in some cases. In most cases,
complex 5 showed lower catalytic activity than 1, which
is presumably attributed to the significant structural differ-
ence between 5 and 1 and also to the various electronic
properties of the pyridyl-supported N-heterocyclic rings.
That the PPh3 ligand and one chloride are linearly
arranged and positioned on the two sides of the pseudo-
N3 ligand plane may lead to high catalytic activity for com-
plexes of type RuCl2(PPh3)L (L = a planar tridentate
ligand). The structural confirmation of complex 5 by
X-ray crystallography and its catalytic activity have
revealed promising applications of the new family of planar
tridentate pseudo-N3 ligands, i.e., 2,6-bis(1,2,4-triazin-3-
yl)pyridines, in transition metal-promoted catalysis. Com-
plex RuCl2(PPh3)(Me4BPPy) (1) exhibited good to excel-
lent catalytic activity in hydrogenation of ketones under
relatively mild conditions, suggesting that Me4BPPy is a
O
O
20
a
Reaction conditions: ketone/t-BuOK/catalyst = 500:10:1. Ketone,
1.5 mmol; catalyst 1, 2 mg (0.2 mol%); KOtBu, 3.4 mg (2 mol%); 2-pro-
panol, 3 mL; 25 ꢁC.
b
GC yield.
Catalyst, 0.5 mol%.
Catalyst, 2 mol%.
Isolated yield.
c
d
e
f
HPLC yield.
20/1 for ketone/base/catalyst, the catalyst system with a
combination of 2-propanol as the reaction medium and
KOtBu as the base promoter showed the best efficiency
for hydrogenation of ketones. With 0.2 mol% 1 as the cat-
alyst, hydrogenation of ketones was carried out in 2-propa-
nol at 25 ꢁC under a hydrogen atmosphere (20 atm). Over a

2312
Z.K. Yu et al. / Journal of Organometallic Chemistry 692 (2007) 2306–2313
promising planar tridentate pseudo-N3 ligand to construct
highly active transition-metal catalysts.
0.79 (d each, J = 4.95 Hz, 12:12H, 8 · CH3). 13C{1H}
NMR (CDCl3): d 164.72, 159.88, 158.13 and 155.76 (Cq
each, C–N), 136.26 (Cq, i-C of Ph), 135.87, 135.31,
135.22, 128.53, 127.10, 127.02, and 124.41 (pyridyl and
phenyl CH), 41.98 and 40.95 (2:2, 4 · CH2), 27.64 and
27.52 (2:2, 4 · CH), 22.88 (8 · CH3). Anal. Calc. for
C45H54Cl2N7PRu: C, 59.96; H, 6.10; N, 10.80. Found: C,
60.33; H, 6.08; N, 10.94%.
4. Experimental section
4.1. General considerations
All the reactions were carried out under a nitrogen
atmosphere with a drybox and standard Schlenk tech-
1
niques. H and 13C{1H} NMR spectra were recorded on
4.4. General procedure for transfer hydrogenation of ketones
catalyzed by 5
a 400 MHz spectrometer. Chemicals were used as received.
4.2. Preparation of the ligand iBu-BTP (4)
Under nitrogen atmosphere, a mixture of ketone
(2 mmol), catalyst 5 (3.6 mg, 0.004 mmol), and 2-propanol
(19 mL) was stirred at 82 ꢁC for 10 min. 1.0 mL of 0.1 M
NaOH solution in 2-propanol was then introduced. The
reaction mixture was stirred at the refluxing temperature
and samples were taken for GC analysis at 10 min, 1 h,
1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h, 24 h,
etc. After the reaction was finished, the mixture was con-
densed under reduced pressure and subject to flash silica
gel column chromatography to afford the alcohol product.
Acetone and the corresponding alcohols were detected as
the products in all the cases. The alcohol products were
identified by comparison with the authentic samples and/
or by proton NMR measurements.
Under nitrogen atmosphere, a mixture of pyridine-2,6-
dicarbohydrazide imide 2 (9.66 g, 50 mmol) and 1,2-dike-
tone 3 (17.02 g, 100 mmol) was stirred at 160 ꢁC for 7 h.
After cooled to ambient temperature, the resultant residue
was purified by flash silica gel column chromatography
with petroleum ether (30–60 ꢁC) as the eluent. Further
recrystallization from petroleum ether (30–60 ꢁC) at
ꢀ20 ꢁC afforded yellow crystalline solid
4 (11.00 g,
1
45.9%). M.p.: 61–63 ꢁC. H NMR (CDCl3, 400 MHz): d
8.73 (d, J = 5.82 Hz, 2H) and 8.10 (t, 1H) (pyridyl CH),
3.55 (br, 2H, H2O), 2.96 (d, 4H, J = 5.37 Hz, 2 · CH2),
2.83 (d, 4H, J = 5.31 Hz, 2 · CH2), 2.43 and 2.29 (m each,
2:2H, 4 · CH), 1.03 (d, J = 4.89 Hz, 4 · CH3), 1.01 (d,
J = 4.92 Hz, 4 · CH3). 13C{1H} NMR (CDCl3): d 161.75,
161.09, 159.63, and 154.07 (Cq each, C–N), 138.16 and
125.16 (1:2, aromatic CH), 42.49 and 41.25 (2:2,
4 · CH2), 28.53 and 28.04 (2:2, 4 · CH), 22.77 and 22.63
(4:4, 8 · CH3). Anal. Calc. for C27H39N7 Æ H2O: C, 67.61;
H, 8.62; N, 20.44. Found: C, 67.64; H, 8.51; N, 20.95%.
4.5. Typical procedure for hydrogenation of ketones
catalyzed by 1
Under nitrogen atmosphere, complex
1 (2.0 mg,
0.003 mmol), KOtBu (3.4 mg, 0.03 mmol) and 1 mL of 2-
propanol were successively added to a 10-mL vial, and
the mixture was stirred at ambient temperature for 5 min.
A ketone (1.5 mmol) in 2 mL 2-propanol were added,
and the vial was placed in a 200-mL autoclave, and then
the autoclave atmosphere was replaced with hydrogen for
three times, pressured H2 to the stated pressure to start
the reaction with stirring. After the reaction was finished,
the reaction mixture was analyzed or condensed for isola-
tion of the product in the above mentioned procedures.
4.3. Preparation of complex RuCl2(PPh3) (iBu-BTP) (5)
A mixture of ligand iBu-BTP 4 (0.498 g, 1.0 mmol),
RuCl2(PPh3)3 (0.995 g, 1.0 mmol) in 60 mL of refluxing tol-
uene was stirred until all the ligand was consumed over a
period of ca 3 h. The reaction mixture was cooled to ambi-
ent temperature, and all the volatiles were removed under
reduced pressure, affording a purple residue. The resultant
residue was washed with hexane (10 · 2 mL) until no free
ligand was detected from the filtrate by TLC analysis.
The resultant material was dissolved in 40 mL toluene at
50 ꢁC and then cooled to ambient temperature. Recrystal-
lization at ꢀ20 ꢁC overnight afforded purple crystals. The
mother liquor was concentrated under reduced pressure
and then subject to flash silica gel column chromatography
(diethyl ether/petroleum (30–60 ꢁC), 10/1). Combined the
purple solid, a total of 0.80 g (86.0%) 5 was obtained.
The single crystals suitable for X-ray crystallographic study
were grown in CH2Cl2/hexane (v/v, 1/4) at ꢀ20 ꢁC. M.p.:
4.6. X-ray crystallographic studies
Single crystal X-ray diffraction studies for complex 5
was carried out on a SMART APEX diffractometer with
graphite-monochromated Mo Ka radiation (k = 0.71073
˚
A). Cell parameters were obtained by global refinement
of the positions of all collected reflections. Intensities were
corrected for Lorentz and polarization effects and empirical
absorption. The structures were solved by direct methods
and refined by full-matrix least squares on F2. All non-
hydrogen atoms were refined anisotropically. All hydrogen
atoms were placed in calculated positions. Structure solu-
tion and refinement were performed by using the SHELXL-
97 package. Crystal data and refinement details for these
complex 5 are summarized in Table 1.
1
232 ꢁC. H NMR (CDCl3, 400 MHz): d 8.42 (d, 2H), 7.90
(m, 7H) and 7.27 (m, 9H) (pyridyl and phenyl CH), 2.70
(d, J = 5.16 Hz, 4H, 2 · CH2), 2.41 (d, J = 5.37 Hz, 4H,
2 · CH2), 2.35 and 1.63 (m each, 2:2H, 4 · CH), 1.06 and

Z.K. Yu et al. / Journal of Organometallic Chemistry 692 (2007) 2306–2313
2313
[5] (a) Selected recent literatures on Tp-based transition metal catalysts,
see: J. Oxgaard, R.A. Periana, W.A. Goddard, J. Am. Chem. Soc.
126 (2004) 11658;
Acknowledgements
We are grateful to the ‘‘Hundred Talented Program’’
Funding of CAS and the National Natural Science Foun-
dation of China (Grant No. 20501018) for support of this
research.
(b) K.A. Pittard, J.P. Lee, T.R. Cundari, T.B. Gunnoe, J.L. Petersen,
Organometallics 23 (2004) 5514;
(c) P.M. Graham, D.A. Delafuente, W.J. Liu, W.H. Myers, M.
Sabat, W.D. Harman, J. Am. Chem. Soc. 127 (2005) 10568;
(d) Y.Q. Zhang, L.S. Liebeskind, J. Am. Chem. Soc. 127 (2005)
11258;
(e) Y.Q. Zhang, L.S. Liebeskind, J. Am. Chem. Soc. 128 (2006) 465;
(f) N.M. West, S. Reinartz, P.S. White, J.L. Templeton, J. Am.
Chem. Soc. 128 (2006) 2059.
Appendix A. Supplementary material
CCDC 626622 contains the supplementary crystallo-
[6] M.G.B. Drew, M.J. Hudson, P.B. Iveson, C. Madic, M.L. Russell, J.
Chem. Soc., Dalton Trans. (1999) 2433.
[7] (a) X.J. Sun, Z.K. Yu, S.Z. Wu, W.-J. Xiao, Organometallics 24
(2005) 2959;
graphic data for 5. These data can be obtained free of
charge
via
http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
(b) H.X. Deng, Z.K. Yu, J.H. Dong, S.Z. Wu, Organometallics 24
(2005) 4110, and references therein;
(c) A.R. Karam, E.L. Catar´ı, F. Lo´pez-Linares, G. Agrifoglio, C.L.
´
Albano, A. Dıaz-Barrios, T.E. Lehmann, S.V. Pekerar, L.A. Albor-
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