Chemistry Reference
In-Depth Information
Ph
O
Ph
Cat.
O
O
O
+
O
H
N
Cat.
Yield (%)
Ru
3
(CO)
12
/
CNC
Ru
3
(CO)
12
CNC
Ru CNC
98
-
-
98
Scheme 9.11
A TEM image (Figure 9.3) reveals the cluster-in-cluster structure, with mean sizes of 5
and 18 nm for ruthenium and cobalt, respectively.
Under the optimized reaction conditions (1.5 equiv 2-pyridylmethyl formate, THF, 12 h,
and 130
◦
C), the
RuCNC
was a highly effective catalyst for intra- and intermolecular
Pauson-Khand-type reactions (Table 9.6). The catalyst system could be re-used five times
without loss of activity. Elemental analysis (by ICP-AES) of the reaction mixture after
completion of the reaction showed that less than 0.1 ppm of the ruthenium and cobalt
species had bled. The reusability of the catalyst and the environmentally friendly nature of
the process are especially attractive.
9.4.2 Heterobimetallic Co/RhNanoparticles
13
Enhancement of the catalytic activity of heterobimetallic (Co/Rh) nanoparticles in the PKR
compared to that of mono-metallic ones (Co or Rh) was reported by Chung's group.
13
The
choice of cobalt and rhodium metals as ingredients for the heterobimetallic nanoparticles
was made given the established performance of each constituent in the PKR.
34, 35
Figure 9.3
HR-REM of
RuCNC
. Reprinted with permission from [27]. Copyright 2002 Ameri-
can Chemical Society.
