Chemistry Reference
In-Depth Information
shown in Eq. (2.286):
O
O
Mo
2
(OEt)
6
(2.286)
CO
2
+
ROH
HOCOR
(ROCO)
2
Mo
2
(OR)
4
Nickel and cobalt methoxides, M(OMe)
2
(M D Ni, Co), are reported to be unreactive
towards carbon dioxide. However, it has been demonstrated that Cu
OMe
2
in the
presence of pyridine reacts with two moles of CO
2
to yield the corresponding carbonate
(Eq. 2.287):
934
O
py/25
°
C
Cu(OMe)
2
+
2CO
2
Cu(OCOMe)
2
(py)
(2.287)
Further the dimeric copper(
II
) acetylacetonate-methoxide was also found to take up
two moles of carbon dioxide in the presence of pyridine (Eq. 2.288):
934
Me
O
O
py/CO
2
(2.288)
(acac)Cu
Cu(acac)
2
(acac)Cu(OCOMe)(py)
O
Me
Tsuda
et al
.
935
also found that copper(
I
)
t
-butoxide in the presence of
t
-butyl
isocyanide or certain other ligands
PEt
3
,
PPh
3
reacted reversibly with carbon dioxide
to give the
t
-butyl carbonate complex (Eq. 2.289):
O
benzene/20°C
benzene/reflux
(Bu
t
O)Cu(CNBu
t
)
2CNBu
t
(Bu
t
OCO)Cu(CNBu
t
)
3
+
+
CO
2
2
.
289
Titanium and zirconium tetra-alkoxides undergo insertion reactions of both organic
isocyanates
936
,
937
and carbodiimides
938
into M - O bonds, as shown by Eqs (2.290) and
(2.291):
M
OR
4
C
x
R
0
NCO ! M
OR
4
x
fNR
0
C
O
ORg
x
2
.
290
M D Ti;
936
,
937
R D Et
,
Pr
i
,
Bu
t
;R
0
D Me
,
Et
,
Ph
,˛
-naphthyl
.
M D Zr;
938
R D Pr
i
;R
0
D Ph
R
′
Ti(OPr
i
)
4
(Pr
i
O
2
)Ti{N-C
(2.291)
+
2R
′
N
C
R
′
NR
′}
2
OPr
i
where R
0
D
p
-tolyl.
938
Both types of reaction are reversible in the case of Ti
OR
4
.
937
With niobium
939
and tantalum
940
penta-alkoxides, the degree of insertion of phenyl
isocyanate may be controlled, resulting in the formation of mono-, di-, tri-, tetra-, and
