Chemistry Reference
In-Depth Information
Mo
2
OPr
i
6
and similar alkoxides, on the other hand, provide a good source of
electrons to ligands that are capable of being reduced upon coordination. For example,
Ph
2
CN
2
reacts with Mo
2
OPr
i
6
in the presence of pyridine to afford the product
Mo
2
OPr
i
6
N
2
CPh
2
py
2
,
1028
in which, considering the diphenyldiazomethane as a
two electron (2e) ligand, Mo
D
N—N
D
CPh
2
, the molybdenums may be viewed as
Mo - Mo
10C
bonded.
4.17.1.2 Reactions with carbon monoxide
The reactions with hydrocarbon solutions of M
2
OR
6
(M D Mo, W) compounds with
CO are complex, and exhibit some remarkable differences depending on the nature of
M and R as well as on the reactions conditions. Novel products have been isolated
in the carbonylation of triply bonded dimolybdenum and ditungsten hexa-alkoxides
and their adducts as is shown by the reactions described below (Eqs 2.354 - 2.360).
For example, the reactions of
tert
-butoxides M
2
OBu
t
6
with one equivalent of CO in
hydrocarbon solvent proceed smoothly at room temperature and atmospheric pressure
in two stages
1029 - 1031
as shown by Eqs (2.354) and (2.355):
O
C
Bu
t
O
OBu
t
M
2
(OBu
t
)
6
+
CO
M
M
Bu
t
O
OBu
(2.354)
O
Bu
t
O
Bu
t
2Mo
2
OBu
t
6
-CO
C 4CO ! Mo
CO
6
C 3Mo
OBu
t
4
(2.355)
The overall reaction is given by Eq. (2.356).
2Mo
2
OBu
t
6
C 6CO ! Mo
CO
6
C 3Mo
OBu
t
4
2
.
356
By contrast, the room temperature reaction of Mo
2
OBu
t
6
with CO (1 atm pressure)
in hexane - pyridine solvent mixtures yields Mo
OBu
t
2
py
2
CO
2
, the structure of
which has been resolved by single-crystal X-ray study:
1032
Bu
t
O
OC
py
pyridine
−
hexane
(2.357)
Mo
2
(OBu
t
)
6
+
4CO
+
4py
2
Mo
OC
py
O
Bu
t
Reactions of isopropoxides, M
2
OPr
i
6
, with excess CO afford, in addition to
M
CO
6
,
(Eqs 2.358
1030
carbonyl
adducts
of
higher
valent
metal
alkoxides
and
2.359
1033
).
