Chemistry Reference
In-Depth Information
In the above reaction of Mo
2
OPr
i
6
NO
2
with two equivalents of Me
2
NH
in hydrocarbon solvent, the dimer did not split into a five-coordinate monomer
Mo
OPr
i
3
NO
NHMe
2
; instead, the dinuclear structure was retained and each metal
atom became six-coordinate.
1038
By contrast, an X-ray crystallographically characterized five-coordinate mononuclear
tungsten derivative has been obtained by the reaction between W
2
OBu
t
6
and NO in
hydrocarbon solutions in the presence of pyridine:
1039
NO
Bu
t
O
pyridine
22°C
W
2
(OBu
t
)
6
+
OBu
t
(2.362)
NO
W
Bu
t
O
py
4.17.1.4 Reactions with alkenes or alkynes
Reactions of alkenes
1040 - 1042
and alkynes with M
2
OR
6
compounds lead to a variety
of
interesting
reactions
and
products
depending
upon
the
system,
as
shown
by
Eqs. (2.361) - (2.363):
R
R
CH
2
O
O
RO
CH
2
22
°
C/hydrocarbon
W
2
(OR)
6
+
2C
2
H
4
(2.363)
W
W
H
2
C
H
2
C
OR
O
O
R
R
R
R
CH
2
CH
2
O
O
0
°
C/hydrocarbon
W
W
(2.364)
W
2
(OR)
6
+
3C
2
H
4
OR
OR
O
O
R
R
C
RO
22°C/hydrocarbon
CH
2
CH
2
W
W
W
2
(OR)
6
+
3C
2
H
4
(2.365)
OR
OR
RO
O
O
R
R
where R D
c
-hex,
c
-pent, Pr
i
,CH
2
Bu
t
.
By contrast, the sterically encumbered W
2
OBu
t
6
fails to react with H
2
C
D
CH
2
in
hydrocarbon solvents at room temperature.
Reactions between ditungsten hexa-alkoxides and alkynes have led to a remarkable
variety of products, depending on the nature of the alkoxide, the alkyne, and the
reaction conditions,
1043 - 1047
as illustrated by Eqs (2.366), (2.368) - (2.370).
The reactions between
RO
3
MM
OR
3
and R
0
CCR
00
or R
0
CN
1043
may be
viewed as complementary redox reactions. The dinuclear metal centre as well as
the alkyne and nitrile are potential six-electron (6e) reducing agents. It has been
possible to prepare
Bu
t
O
3
WCR
0
(R
0
D Me, Et, Ph) or (Bu
t
O
3
WN by the reaction
of W
2
OBu
t
6
with R
0
CCR
0
or R
0
CN, respectively (Eqs 2.366 - 2.368) in which
