Chemistry Reference
In-Depth Information
O
OH
4
x
y
z
d
n
4
r
4
n
g
|
0
O
x/y/z = 84/12/4
O
Figure 3.7
Structure of copolymer for encapsulating ruthenium species (PI).
H
H
Cl
N
P
Ru
H
2
O
O
Cl
Figure 3.8
Structure of polymer-anchored Ru(
III
) complex.
by FTIR, reflectance UV-VIS, ESR, ESCA, SEM and TGA techniques
(Figure 3.8).
70
Catalysis by polyoxometallates has attracted much attention because of
their strong acidity and redox properties. Another attractive aspect of poly-
oxometallates in catalysis is their inherent stability towards oxygen
donors.
71,72
RuCl
3
nH
2
O successfully reacts with the lacunary silicotung-
state [SiW
11
O
39
]
8
in an organic solvent to give an Ru
31
-substituted silico-
tungstate, which acts as a heterogeneous catalyst for the aerobic oxidation of
a wide range of alcohols and also alkanes.
73
An ionic compound,
[RuCl
4
(L)
2
]
3
PW
12
O
40
, containing the Ru(
III
)-complex cation and a-Keggin-
type phosphotungstate anion was synthesized (Equation 3.6) and was found
to be an ecient, reusable catalyst for aerobic oxidations of alcohols without
bases and/or a nitroxyl radical.
74
.
L
L
H
3
PW
12
O
40
acetone
MeOH
Cl
Cl
Cl
Cl
Cl
Cl
Ru
III
Ru
III
[
L
]PF
6
-
+ RuCl
3
.
3H
2
O
PF
6
PW
12
O
40
Cl
Cl
L
L
3
(3.6)
PPh
2
n
Bu
L
=
N
+
N
Compared with traditional catalyst supports, carbon nanotubes (CNTs)
with high external surface area and aspect ratio display unusual behaviors,
such as being able to increase significantly the contact surface between the
reactants and the active sites of catalysts and to minimize greatly the dif-
fusion limitations.
75
Herringbone CNT-supported RuO
2
hydrate nano-
particles can be readily prepared by a homogeneous oxidation-precipitation
Search WWH ::
Custom Search