Chemistry Reference
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2
2
OPr
i
6
py
2
] also containing the bridging
2
-ketenyl ligands but the analo-
gous reaction with [W
OPr
i
3
CNMe
2
py
2
] gave the unsymmetrical molecule [W
2
-
OPr
i
3
OPr
i
3
f
2
-C
2
NMe
2
2
g
CO
2
]. The latter has a confacial bi-octahedral structure
with one W atom terminally bonded to one Pr
i
O and two CO ligands whilst the other
is bonded terminally to two Pr
i
O ligands and
2
-bonding alkyne.
335
Carbonylation of
[W
2
hftb
4
NMe
2
2
] gave rise to the unsymmetrical dinuclear complex [W
2
-CO
2
-
NMe
2
hftb
4
CO
NMe
2
](hftbD OCMe
CF
3
2
) which has a confacial bi-octahedral
structure with one bridging NMe
2
ligand and two semi-bridging carbonyls. One tung-
sten is bonded terminally to two Pr
i
O and one CO ligand and the other tungsten is
terminally bonded to two Pr
i
O and one NMe
2
ligand.
304
Reactions of W
2
OR
6
with alkynes have led to the isolation of several interesting
complexes. From W
2
OBu
t
6
and PhC
2
Ph two compounds were obtained: [W
2
-
CPh
2
OBu
t
4
](W-W, 2.665 A) involving two tetrahedra sharing a common edge and
[W
2
-C
2
Ph
2
2
OBu
t
4
](W-W, 2.677 A).
336
With other tungsten alkoxides and other
alkynes the following binuclear complexes were characterized: [W
2
-OPr
i
2
-
C
2
H
2
OPr
i
4
py
2
](W-W, 2.567 A), [W
2
-OCH
2
Bu
t
-C
2
Me
2
OCH
2
Bu
t
5
py
2
]
(W-W, 2.602 A), and [W
2
-OPr
i
-C
4
Me
4
OPr
i
5
C
2
Me
2
](W-W, 2.852 A);
337 - 339
[W
2
-OPr
i
-C
4
H
4
OPr
i
5
C
2
H
2
],
339
[W
2
-OBu
t
-C
2
H
2
OBu
t
5
py
].
338
The binuclear complex [W
2
-CSiMe
3
2
OPr
i
4
]
340
reacted with acetylene giving
[W
2
-CSiMe
3
-CHCHCSiMe
3
OPr
i
4
]
340
and
with
2,6-Me
2
C
6
H
3
NC
giving
[W
2
-CSiMe
3
-CCSiMe
3
OPr
i
4
NC
6
H
3
Me
2
].
341
Other organo-tungsten isopropoxo compounds characterized are [W
2
-
OPr
i
2
OPr
i
2
CH
2
Ph
2
2
-C
2
Me
2
2
]and[W
2
-C
4
Me
4
-CH
2
Ph
OPr
i
4
].
342
Interesting alkyne [W
2
-OBu
t
-C
2
Me
2
OBu
t
5
CO
]
343
and allene complexes
[W
2
-C
3
H
4
OBu
t
6
], [W
2
-OBu
t
2
-C
3
H
4
OBu
t
4
2
-C
3
H
4
], and [W
2
-
OBu
t
2
-C
3
H
4
OBu
t
4
CO
2
] have been prepared.
344
Alkyne adducts have also
been prepared from reactions involving the neopentoxide [W
2
OCH
2
Bu
t
6
py
2
],
e.g.
[W
2
-OCH
2
Bu
t
-C
2
H
2
OCH
2
Bu
t
5
py
2
] d[W
2
-OCH
2
Bu
t
-
C
2
Et
2
OCH
2
Bu
t
5
py
].
345
Addition of ethylene gave the interesting binuclear
bis-adduct [W
2
-OCH
2
Bu
t
4
OCH
2
Bu
t
2
2
-C
2
H
4
](W-W, 2.533 A) with four
unsymmetrical neopentoxo bridges between the two tungsten atoms. The longer bridge
bonds (av. 2.31 A,
cf.
2.00 A) are
trans
to the terminal alkoxo or ethylene ligands.
346
This type of complex appears to be a precursor to other species formed in the reaction
of ethylene with W
2
OR
6
,
e.g.
[W
2
-OPr
i
3
OPr
i
3
2
-CH
2
CH
2
CH
2
CH
2
2
-C
2
H
4
]
(W-W, 2.643 A) in which the
CH
2
4
ligand is chelating one tungsten atom to
form a tungstacyclopentane ring.
347
In [W
2
-OPr
i
OPr
i
5
,
2
-CCH
2
CH
2
CH
2
py
]
(W-W, 2.674 A) the hydrocarbyl ligand bridges two tungstens, chelating one of
them.
347
The 1,2-R
2
W
2
OR
4
compounds also react with alkynes producing a variety of prod-
ucts,
e.g.
[W
2
-OPr
i
2
OPr
i
2
C
3
H
7
-
n
2
2
-C
2
Me
2
2
](W-W, 2.681 A),
348
[W
2
-
OPr
i
2
OPr
i
2
CH
2
Ph
2
2
-C
2
Me
2
2
](W-W, 2.668 A),
349
[W
2
-OPr
i
2
OPr
i
2
Ph
2
2
-
C
2
Me
2
2
](W-W, 2.658 A),
349
[W
2
-OPr
i
2
OPr
i
2
CH
2
Bu
t
2
CEt
2
],
349
and
[Me
2
Bu
t
O
W
-OBu
t
-C
2
Me
2
W
OBu
t
2
py
](W-W, 2.622 A).
349
Related mole-
cules are [W
2
-CPh
,
2
-C
4
Me
4
H
OPr
i
4
](W-W, 2.755 A) ,
350
[W
2
-CSiMe
3
,
2
-
C
4
Me
4
OPr
i
4
CH
2
SiMe
3
](W-W,
2.780 A),
350
[W
2
-C
2
Me
2
2
OPr
i
4
](W-W,
2.611 A),
351
[W
2
-OCH
2
Bu
t
2
f
,
2
-CH
2
CH
2
CH
2
g
OCH
2
Bu
t
4
py
]
(W-W,
2.471 A),
352
and [W
2
-OCH
2
Bu
t
4
OCH
2
Bu
t
2
2
-C
2
H
4
2
](W-W, 2.533 A).
353
In
