Ruthenium-functionalized nickel hydroxide catalyst for highly efficient alcohol oxidations in the presence of molecular oxygen

Article abstract of DOI:10.1039/b900636b

Ru/Ni(OH)₂ composite, prepared by simple wetness impregnation method, has demonstrated highly efficient alcohol oxidation reaction in the presence of molecular oxygen at T = 363 K with good selectivity (>99%) and excellent reaction yield (TOF ～ 132 h^-1).

Full text of DOI:10.1039/b900636b

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Ruthenium-functionalized nickel hydroxide catalyst for highly efficient
alcohol oxidations in the presence of molecular oxygenw
a
b
c
c
a
S. Venkatesan, A. Senthil Kumar, Jyh-Fu Lee, Ting-Shan Chan and Jyh-Myng Zen*
Received (in Cambridge, UK) 12th January 2009, Accepted 2nd February 2009
First published as an Advance Article on the web 24th February 2009
DOI: 10.1039/b900636b
2
Ru/Ni(OH) composite, prepared by simple wetness impregnation
method, has demonstrated highly efficient alcohol oxidation
reaction in the presence of molecular oxygen at T = 363 K
with good selectivity (499%) and excellent reaction yield
ꢀ
1
(
TOF B 132 h ).
Oxidative functional transformation of alcohols to the
corresponding aldehydes and ketones represents an important
class of organic reaction for both academic research and the fine
chemical industry, especially in the preparation of food
1
additives, fragrances and many organic intermediates.
Traditional methods, performed with a variety of stoichiometric
inorganic oxidants (such as dichromate and permanganate) to
accomplish this transformation, tend to produce harmful
2
by-products. For this reason, the use of molecular oxygen or
Fig. 1 Radial distribution function with Ru as the central atom
air as a sole oxidant has received much attention for both
economic and environmental benefits. Many heterogeneous
catalysts have been developed for liquid-phase aerobic alcohol
oxidation reaction (AOR) using platinum group metals, such as
obtained by taking Fourier transformation (FT) (with Ru–O phase
3
correction) of the k weighted EXAFS data.
3
Au, Pd, Pt and Ru. Among these, Ru-based bimetallic or
2
Initially, a bbc-Ni(OH) powder sample was prepared as
4
a
8c,d
trimetallic systems including Ru–Al–Mg–hydrotalcite (HT),
4c
reported previously z and characterized by XRD, IR and
4b
Ru–Co–Al–HT,
(
Ru–Co–oxide,
Ru–Co–hydroxyapatite
4e
HAP), Ru/CeO /CoO(OH) and Ru/MnMn/HT are of
TGA (Fig. S1, S2A, S3A and S4A, respectivelyw). The dark
4d
4f
grey Ru/Ni(OH)
containing 1 g bbc-Ni(OH)
RuCl
at room temperature (RT). zThe Ru/Ni(OH)
the bbc-crystal structure and functional groups of Ni(OH)
composite was precipitated from a suspension
in 20 mL H O and 60 mL, 8.3 mM
retained
, as
(Fig. S2B, S3B
and S4Bw). The absence of chlorine in Ru/Ni(OH) was also
confirmed by EDX and XPS analysis (Fig. S5 and S6w). The
2
2
significant interest with better activity than those of classical
5e
/FAU systems under
2
2
5a
3
,
5c
Ru/alumina and RuO
2
Ru/Fe O
2
3
2
ambient temperatures (B110 1C). Nevertheless, an easy
approach to construct a selective, efficient and cleaner catalytic
system for AOR remains a challenge in organic synthesis.
2
8c,d
confirmed by XRD, IR and TGA studies
2
2
We report here a novel Ru/Ni(OH) composite as a highly
efficient and selective heterogeneous catalyst for liquid-phase
2
ꢀ1
BET surface area was measured as 189.6 m
g
and Ru
by ICP-MS.
X-Ray absorption spectroscopy (XAS) was further used to
characterize the local structure of the Ru/Ni(OH) . The Ni K
edge X-ray absorption near-edge structure (XANES) of
RuNi(OH) revealed an unchanged Ni(OH) structure even
after Ru was introduced (Fig. S9Aw) and Ru K edge XANES
feature resembled that of RuO (Fig. S9Bw). However, in view
6
a
ꢀ1
AOR. In recent years, Ni-based materials, notably Ni–Al–HT,
6c
content was estimated to be 0.38 mmol g
6b
9
nano-NiO2 and Ni(OH)2 have been reported for molecular
oxygen activation in AOR. However, low turn-over frequency
2
ꢀ1 ꢀ1 ꢀ1
(
TOF) values of 0.326 h , 0.412 h and 3.3 h were reported
7
for the benzyl alcohol oxidation reaction. Note that
Ni(OH) possesses the isomorph of layered double hydroxides
is isostructural with HT-like compounds.
Ru–Ohydroxo (Ru–OH) bond and the Ru–Ru bonded (Fig. 1)
Ru/Ni(OH) composite catalyst were found useful for a wide
2
2
2
8a,b
In this study, the
2
of either chemical shift of the edge position or intensity of
the white line (Fig. S9Bw), the oxidation state of Ru was
concluded to be lower than +4. Extended X-ray absorption
fine structure (EXAFS) analysis was used to depict the
2
ꢀ
1
.
range of AORs with TOF up to 132 h
2
arrangement of Ru in Ni(OH) . Table 1 summarises the
a
Department of Chemistry, National Chung Hsing University,
Taichung, 402, Taiwan. E-mail: jmzen@dragon.nchu.edu.tw;
Fax: +886 (0)4 22854007; Tel: +886 (0)4 22850864
Department of Chemistry, Vellore Institute of Technology
University, Vellore, 632014, India
calculated structural parameter values. Since the radial atomic
distribution around Ru is completely different from that
around Ni, Ru atoms were not incorporated inside the
Ni(OH)2 framework (Fig. S9Cw). It is expected that a
one-dimensional chain like Ru(OH)x is linked within the
b
c
National Synchrotron Radiation Research Center,
101 Hsin-Ann Road, Hsinchu Science Park, Hsinchu, 300, Taiwan
2 2
surface layer of bbc-Ni(OH) in the Ru/Ni(OH) composite
catalyst and further supported by a specific Ru–Ru bonding
w Electronic supplementary information (ESI) available: Further
experimental details. See DOI: 10.1039/b900636b
1
912 | Chem. Commun., 2009, 1912–1914
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a
a
Table 1 Structural parameters obtained from EXAFS data analysis
Table 2 Oxidation of benzyl alcohol with molecular oxygen
Absorber–backscatterer
Ru–O
Ru–Ru
Yield Selectivity
b c
Entry Catalyst
Solvent
T/K t/h (%) (%)
˚
Interatomic distance, R/A
Coordination number, N
2.043(3)
4.69(2)
0.007(4)
4.05–11.7
1.8–3.5
0.007
3.091(7)
1.20(7)
0.010(4)
d
e
f
1
2
3
4
5
6
7
8
9
0
1
2
Ru/Ni(OH)
Ru/Ni(OH)2
Ru/Ni(OH)2
Ru/Ni(OH)2
Ru/Ni(OH)
Ru/Ni(OH)
Ru/Ni(OH)
Ru/Ni(OH)
Ru/Ni(OH)
2
Toluene
Toluene
Toluene
Toluene
Xylene
363 0.5 99
363 0.5 93
363 0.5 64
363 0.5 40
363 0.5 99
499
499
499
499
499
499
499
499
499
499
499
499
499
41
2
2
˚
Debye–Waller factor, s /A
ꢀ1
˚
k space range/A
g
˚
r space range/A
R-factor fitting
2
2
2
2
2
Ethyl acetate 353 0.5 40
Acetonitrile 353 0.5 30
a
2
Curve fitting results for EXAFS data at Ru K edge of RuNi(OH) .
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
356 0.5 80
333 0.5 50
313 0.5 20
1
1
1
RuNi(OH)
2
Ru/Ni(OH)
Ni(OH)
˚
with a bond distance of 3.091 A, which is between the values
273 20
98
30
20
5e
2
˚
of 3.05 A in RuO
˚
/FAU and 3.24 A in the Ru
˚
and very close to the value of 3.10 A
h
2
2
(m-OH)
363
363
1
1
2
1
0a,b
h
cored complex
for Ru(OH) /TiO
13
14
NiO
i
1
0c
RuCl ꢂxH O
363 0.5 45
(Table 1).
bond length was found to be 2.04 A, which is higher
Besides, the Ru–Ohydroxo
˚
3
2
x
2
i
O
1
1
5
6
Ru(OH)
3
ꢂxH
2
363 0.5
363 0.5
5
5
499
499
i
RuO
2
ꢂxH
2
O
1
0d
5e
/FAU and
˚
than that of 1.97 A in RuO
˚
2
,
1.91 A in RuO
1
2
a
b
flow. Determined by GC.
0a,b
Benzyl alcohol (1 mmol) under O
1
2
˚
.95 A in Ru
1
2
(m-OH) cored complex.
These results again
c
d
Selectivity determined by
3 mol% Ru) and the same amount was used for other optimization
H NMR and GC. Ru/Ni(OH)
2
suggest the oxidation number of Ru should be lower than +4
and hence longer ionic radius and Ru–Ohydroxo bond length.
From the EXAFS data fitting results, each Ru atom has
approximately 4 nearest oxygen atoms (as the first shell) and
(
e
experiments (Entries 5ꢀ12). Ru/Ni(OH)
2
(2.6 mol% Ru).
Ru/Ni(OH)2 (1.5 mol% Ru). Ru/Ni(OH)2 (0.08 mol% Ru).
i
Ni catalyst (0.1 g). Ru catalyst (3 mol% of Ru).
f
g
h
1
next nearest Ru atom (as the second shell). It is most
likely that one dimensional polymeric array of Ru(OH)
species present in Ru/Ni(OH) . Moreover, there is no direct
x
x
interaction between Ru and Ni observed even at the third
coordination shell.
Note that, unlike the previous case with a Ru/Ni(OH)
precipitate (Fig. S10w), the addition of 1 g NiO (without the
OH functional group) as suspension in 20 mL H O with
2
–
Scheme 1
2
RuCl ꢂxH O (60 mL, 8.3 mM) solution resulted in no reaction
3
2
and retained their original colours of NiO powder (light gray)
and RuCl (brown) in the reaction mixture (Fig. S10Bw). The
IR spectrum of NiO before/after RuCl treatment also failed
RuNi(OH)2 during the course of the catalytic reaction
(Fig. S8w). These results confirmed that the observed catalysis
is truly heterogeneous in nature.
3
5a,d
3
to show any variation and further supported the above
structural information. Most importantly these studies clearly
illustrated the significant contribution of Ru–Ru and Ru–OH
To evaluate the scope of this catalyst, oxidation of a wide
range of alcohols was further studied (Table 3, entries 1–21).
Both substituted benzyl alcohols (p-OMe, p-Me, p-Cl, o-Br)
(entries 2–6) and secondary benzylic alcohols (benzhydrol and
cyclopropyl(phenyl)methanol) were found to oxidize to their
corresponding carbonyl compounds in good yields with high
bondings in the new Ru/Ni(OH)
Catalytic activity of the Ru/Ni(OH)
2
catalyst.
composite was tested
2
for benzyl alcohol oxidation reaction in presence of molecular
oxygen under different reaction conditions (including Ru
concentration, solvent and temperature). The results are
compared to other catalytic systems as listed in Table 2.
Among these, Ru (3 mol% Ru)/Ni(OH)2, toluene at
T = 363 K was found to be an optimal condition for highly
efficient (499% conversion) and selective (499%) oxidation
of benzyl alcohol (1a) to benzaldehyde (1b) (Scheme 1). The
ꢀ
1
TOFs in the range of 33 to 100 h (entries 8 and 9). These
TOF values were higher than the monomeric Ru species
containing Ru/Al O , RuCo/HAP and RuMnMn/HT for
2
3
respective AORs (Table S1w). Similarly, sterically hindered
alcohols such as borneol (TOF = 33 h ) and adamantanol
ꢀ
1
ꢀ
1
(TOF = 33 h ) were oxidized in a highly efficient manner
5
c
(entries 15 and 16) over those of the Ru/Al
2
O
3
catalyst
ꢀ
1
ꢀ1
ꢀ1
TOF was found to be 66 h (Table 2, entry 1), which is
significantly higher than the heterogeneous catalysts such
(TOF = 9 h and 6 h , respectively). The present catalyst
containing Ru–Ru bonding was also effective for heterocyclic
alcohols having sulfur and nitrogen atoms with high TOFs of
ꢀ
1 4a
as Ru–Al–Mg–HT (TOF = 1.1 h ),
(
Ru–Co–Al–HT
ꢀ1 4e
ꢀ
1
4b
TOF = 9.3 h ), Ru/CeO
ꢀ1
2
1
/CoO(OH) (TOF = 20 h ),
132 and 33 h , respectively (entries 20 and 21). Note that
ꢀ
4f
RuMnMn/HT, (TOF = 50 h ), Ru/Fe O (TOF = 26 h ),
ꢀ1 5a
ꢀ1 5c
2
3
monomeric Ru/TEMPO complex catalyst failed to oxidize the
heterocyclic alcohols due to strong coordination of Ru centre
ꢀ
1
5b
Ru/HAP (TOF = 2 h ), Ru/alumina (TOF = 40 h ),
ꢀ
1 5e
11a
RuO /FAU (TOF
1 6a
=
8.5
h
)
and Ni–Al–HT
TOF = 0.33 h ). ICP-MS analyis of the filtrate of benzyl
with TEMPO support.
as 2-pentanol and 2-octanol showed higher reactivity than
Noncyclic, aliphatic alcohols such
2
ꢀ
(
ꢀ
1
cyclobutanol (TOF = 2.5 h ) (entry 12). This trend is in
alcohol oxidation reaction was further done to test the
stability and leachability of the catalyst and no Ru traces
were observed (Fig. S7w). In addition, the oxidation of
benzyl alcohol was completely ceased after the removal of
5
e
2
agreement with that of Ru–Ru dimeric RuO /FAU catalyst,
5c,d
but unlike the monomeric Ru/alumina. Oxidation of
primary aliphatic alcohols (entries 18 and 19) was moderate
This journal is ꢁc The Royal Society of Chemistry 2009
Chem. Commun., 2009, 1912–1914 | 1913

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Table 3 Oxidation of primary alcohols and secondary alcohols to
carbonyl compounds using a Ru/Ni(OH) composite
in part by the Ministry of Education, Taiwan under the
ATU plan.
a
2
Conversion Selectivity
(%)
Entry Substrate
Benzyl alcohol
t/h (%)
Notes and references
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
8
9
0
1
0.5 499
0.33 499
0.40 499
0.6 499
2.30 499
499
1.5 499
0.5 499
499
499
499
499
499
499
499
499
499
499
498
499
499
499
499
499
498
498
499
499
z The detailed procedures of the preparation of bbc-Ni(OH)
Ru/Ni(OH) composite catalyst and typical procedure for alcohol
oxidation reactions are given in the ESI (Experimental section 1.3).w
2
powder,
4-Methylbenzyl alcohol
4-Methoxybenzyl alcohol
4-Chlorobenzyl alcohol
4-Nitrobenzyl alcohol
2-Bromobenzyl alcohol
1-Phenylethanol
2
1
(a) R. C. Larock, Comprehensive Organic Transformations, VCH,
New York, 1999; (b) D. H. Pybus and C. S. Sell, The Chemistry of
Fragrances, RSC paperbacks, Cambridge, 1999.
1
Benzhydrol
2
(a) R. A. Sheldon and J. K. Kochi, Metal-Catalyzed Oxidations of
Organic Compounds, Academic Press, New York, 1981;
(b) G. Cainelli and G. Cardillo, Chromium Oxidations in Organic
Chemistry, Springer Verlag, Berlin, 1984.
Cyclopropyl(phenyl)methanol 0.33 499
1
1
1
1
1
1
1
1
1
2
2
Cinnamyl alcohol
Geraniol
1.5 499
b
2.5
2
1
2
1
1
2
2
80
60
80
70
499
499
80
c
Cyclobutanol
2-Pentanol
2-Octanol
(ꢀ)-Borneol
3
(a) G. J. Hutchings, Chem. Commun., 2008, 10, 1148;
(b) R. A. Sheldon, I. W. C. E. Arends, G. J. ten Brink and
A. Dijksman, Acc. Chem. Res., 2002, 35, 774; (c) T. Mallat and
A. Baiker, Chem. Rev., 2004, 104, 3037; (d) T. Matsumoto,
M. Ueno, N. Wang and S. Kobayashi, Chem. Asian J., 2008, 3,
196; (e) M. Pagliaro, S. Campestrinian and R. Ciriminna, Chem.
Soc. Rev., 2005, 34, 837.
b
2-Adamantanol
1-Heptanol
cd
cd
1-Octanol
2-Thiophenemethanol
3-Pyridine methanol
75
0.25 499
0.5 499
b
4 (a) K. Kaneda, T. Yamashita, T. Matsushita and K. Ebitani,
J. Org. Chem., 1998, 63, 1750; (b) T. Matsushita, K. Ebitani and
K. Kaneda, Chem. Commun., 1999, 265; (c) M. Musawir,
P. N. Davy, G. Kelly and I. Kozhevikov, Chem. Commun., 2003,
1414; (d) Z. Opre, J.-D. Grunwaldt, M. Maciejewski, D. Ferri,
T. Mallet and A. Baiker, J. Catal., 2005, 230, 406; (e) H. B. Ji,
T. Mizugaki, K. Ebitani and T. Kaneda, Tetrahedron Lett., 2002,
a
Substrate (1 mmol), Ru/Ni(OH)
2
(3 mol% Ru), toluene (2 mL),
3
63 K, O
2
flow. Conversion and selectivity were determined by GC or
c
(6 mol% Ru). Substrate (0.5 mmol),
d
(6 mol% Ru). Hydroquinone (1 equivalent with respect
1
b
H NMR. Ru/Ni(OH)
2
Ru/Ni(OH)
2
to Ru) was added.
4
3, 7179; (f) K. Ebitani, K. Motokura, T. Mizugaki and
T. Kaneda, Angew. Chem. Int. Ed., 2005, 44, 3423; (g) Z. Opre,
J.-D. Grunwaldt, T. Mallet and A. Baiker, J. Mol. Catal., 2005,
in conversion (B80%). A further increase in the reaction time
led to overoxidation of the reaction product to carboxylic acid.
2
42, 224.
5
(a) M. Kotani, T. Koike, K. Yamaguchi and N. Mizuno, Green
Chem., 2006, 8, 735; (b) K. Yamaguchi, K. Mori, T. Mizugaki,
K. Ebitani and K. Kaneda, J. Am. Chem. Soc., 2000, 122, 7144;
5
b
Like Ru/alumina, small amount of hydroquinone was used
to get aldehydes in good yields. The RuNi(OH) also shows
2
(
4
c) K. Yamaguchi and N. Mizuno, Angew. Chem. Int. Ed., 2002,
1, 4538; (d) K. Yamaguchi and N. Mizuno, Chem. Eur. J., 2003, 9,
high chemoselectivity. Catalytic oxidation of equimolar
concentration of benzyl alcohol and 1-phenyl ethanol mixture
resulted in corresponding benzaldehyde and acetophenone of
4353; (e) B.-Z. Zhan, M. A. White, T.-K. Sham, J. A. Pincock,
R. J. Doucet, K. V. R. Rao, K. N. Robertson and T. S. Cameron,
J. Am. Chem. Soc., 2003, 125, 2195.
(a) B. M. Choudry, M. L. Kantam, A. Rahman, C. V. Reddy and
K. Rao, Angew. Chem. Int. Ed., 2001, 40, 763; (b) H.-B. Ji,
T.-T. Wang, M.-Y. Zhang, Y. She and L. Wang, Appl. Catal. A.,
9
2% and 18% respectively. Similarly, equimolar mixture
6
concentration of 2-octanol and 1-octanol resulted in
corresponding 2-octanone and n-octanal of 20% and 80%,
respectively.
2005, 282, 25; (c) H.-B. Ji, T.-T. Wang, M.-Y. Zhang, Q.-L. Chen
and X.-N. Gao, React. Kinet. Catal. Lett., 2007, 90, 251.
The mechanism for the Ru/Ni(OH)
2
catalyzed AOR is
7
8
Turnover frequency was calculated based on the molar ratio of
converted substrate to the active component of the catalyst, per
4
g,5c,11b
expected to follow the hydridometal pathways.
It
ꢀ1
involves the formation of ruthenium alcoholate species
followed by b-hydride elimination to give the aldehydes and
ruthenium hydride species. Later the ruthenium hydride
unit time (h ) and it refers to the average rate at high conversion.
(a) B.-H. Liu, S.-H. Yu, S.-F. Chen and C.-Y. Wu, J. Phys. Chem.
B., 2006, 110, 4039; (b) T. N. Ramesh, R. S. Jayashree and
P. Jayashree, Clays Clay Miner., 2003, 51, 570; (c) T. N. Ramesh
and P. Vishnu Kamath, J. Power Sources, 2006, 156, 655;
(d) Q. Song, Z. Tang, H. Guo and S. L. I. Chan, J. Power Sour.,
species get reoxidized with O to complete the catalytic cycle
2
(
Scheme S1w). The recyclability of the catalyst is also tested in
2
002, 112, 428.
the benzyl alcohol oxidation. It shows B20% loss in the
conversion yield after 5th cycle, but the selectivity still remains
9
X-ray Absorption: Principles, Applications, Techniques of EXAFS
SEXAFS, and XANES, ed. D. C. Koningsberger and R. Prins,
Wiley, New York, 1988.
9
9% (Fig. S11w).
In conclusion, a new and stable Ru/Ni(OH)
2
composite with
10 (a) Tanase, N. Takeshita, S. Yano, I. Kinoshita and A. Ichimura,
New J. Chem., 1998, 22, 927; (b) T. Tanase, N. Takeshita, C. Inoue,
M. Kato, S. Yano and K. Sato, J. Chem. Soc. Dalton Trans., 2001,
a specific Ru–Ru and Ru–OH bonds has been prepared
successfully using a simple procedure and utilized as a green
catalyst for a wide range of AOR in the presence of molecular
oxygen with high TOF values and selectivity. Since the catalyst
is easy to prepare, it is also suitable for other organic
functional group transformations.
2
293; (c) K. Yamaguchi, T. Koiki, J. W. Kim, Y. Ogasawara and
N. Mizuno, Chem. Eur. J., 2008, 14, 11480; (d) D. A. McKeown,
P. L. Hagans, L. P. L. Carette, A. E. Russell, K. E. Swider and
D. R. Rolision, J. Phys. Chem. B., 1999, 103, 482511.
1
1 (a) A. Dijksman, A. M. Gonzalez, A. M. Payeras, I. W. C.
E. Arends and R. A. Sheldon, J. Am. Chem. Soc., 2001, 123,
6826; (b) I. W. C. E. Arends, T. Kodama and R. A. Sheldon, Top.
Organometal. Chem., 2004, 11, 277.
The authors gratefully acknowledge financial support from
National Science Council of Taiwan. This work was supported
1
914 | Chem. Commun., 2009, 1912–1914
This journal is ꢁc The Royal Society of Chemistry 2009