Chemistry Reference
In-Depth Information
R
R
Co
2
(CO)
8
(2.5-3 mol%)
Z
O
Z
P
CO
2
(110-120 atm at 36-39 °C)
P
CO
(30 atm), ca. 90 °C
Z = C(CO
2
Et)
2
, R = H: 82%
Z = C(CO
2
Et)
2
, R = Me: 91%
Z = O, R = Ph: 70%
O
Ph
Co
2
(CO)
8
(3 mol%)
Ph
+
P
CO
2
(119 atm at 38 °C)
P
CO
(30 atm), 88 °C
87%
Scheme 3.30
Jeong further reported an intermolecular reaction in supercritical ethylene, which
was
reactant.
34
used
as
both
reaction
media
and
The
tetranuclear
complex
[Co
4
(CO)
11
{
] worked well, and various mono-substituted alkynes were submitted
to the reaction with ethylene (Scheme 3.31).
P(OPh)
3
}
O
R
R
[Co
4
(CO)
11
{P(OPh)
3
}] (3-5 mol%
)
+
CO (5 atm, at 34 °C)
85 °C
P
ethylene
R = Ph: 80%
R = n-C
5
H
11
: 70%
R = (CH
2
)
3
OTMS: 82%
R = (CH
2
)
2
CO
2
Me: 75%
(110 atm at 34 °C)
Scheme 3.31
The above mentioned colloidal cobalt nanoparticles
27
could operate as a catalyst even in
water, though a higher pressure of CO (20 atm) and a high reaction temperature (130
◦
C)
were required for a high yield.
35
In the same reaction conditions, Co
2
(CO)
8
had little
catalytic activity.
In contrast, Co
4
(CO)
12
was an efficient catalyst in water under much milder reaction
conditions.
36
The addition of surfactant (triton X) was the key to success, and the in-
tramolecular reaction of various enynes proceeded even under the ambient pressure of CO
at 70
◦
C (Scheme 3.32).
Co
2
(CO)
8
acted as a catalyst even in an ionic liquid, such as 1-butyl-2,3-
dimethylimidazolium salt, which is known to be a non-volatile and recyclable solvent.
37
