Chemistry Reference
In-Depth Information
Figure 4.47
Structure of [W
2
-
OPr
i
2
OPr
i
4
OCMeDCMeO
2
]
(H atoms omitted).
the one in the axial position (2.42
˚
A)owingtothe
trans
influence of the carbyne
(W
C, 1.77 A).
312
See also [W
2
-OBu
t
2
OBu
t
4
CMe
2
] (Table 4.11).
323
The unsymmetrical chloride methoxide [Cl
2
MeO
2
W
-OMe
2
W
OMe
3
Cl] also
has the edge-shared bi-octahedral structure.
313
The remarkable compound [W
2
-
OCH
2
Bu
t
-H
-I
OCH
2
Bu
t
5
Me
2
NH
](W
D
W, 2.456 A) has the confacial bi-
octahedral structure with three different bridging groups.
314
A similar hydrido-bridged
confacial bi-octahedral structure was also found in [W
2
-OC
5
H
9
-
c
2
-H
OC
5
H
9
-
c
5
Me
2
NH
](W
D
W, 2.438 A).
315
Reaction of the latter compound gave rise to the novel
alkyl, alkene complex [Et
C
2
H
4
c
-C
5
H
9
O
W
-OC
5
H
9
-
c
3
W
OC
5
H
9
-
c
3
](W-W,
2.668 A) in which the confacial bridging is sustained by three alkoxo ligands. Other
related molecules are [W
2
-OC
5
H
9
-
c
2
-CH
2
CCH
2
OC
5
H
9
-
c
6
], [W
2
-OC
5
H
9
-
c
3
OC
5
H
9
-
c
5
f
2
-OC(CH
2
)
3
CH
2
g], [W
2
-OPr
i
3
OPr
i
4
H
2
-OCPh
2
], and [W
2
-
OPr
i
2
-
2
-HNCPh
D
CPhN] in which the nitrogen-containing ligand is both chelating
and bridging.
316
Reaction of xylylisonitrile
2,6-Me
2
C
6
H
3
NC
with W
2
OBu
t
6
gave the dinuclear
[W
2
-OBu
t
2
-CNC
6
H
3
Me
2
OBu
t
4
](W-W, 2.525 A) in which the five-
coordinated metals are in a face-sharing bi-square pyramidal configuration with
the carbon atom of the bridging isonitrile occupying the apical position.
316
See
also [W
2
tftb
6
CNC
6
H
3
Me
2
2
] (Table 4.11).
322
With W
2
OPr
i
6
the unsymmetrical
[W
2
-OPr
i
2
-CNC
6
H
3
Me
2
OPr
i
4
py
] species was formed. One metal is in
distorted octahedral and the other is in square pyramidal coordination in a confacial
bridged structure.
316
Reaction of the tetranuclear W
4
OBu
i
12
with nitric oxide gave the centrosym-
metrical dinuclear [W
2
-OBu
i
2
OBu
i
4
NO
2
py
2
] with the edge-shared isobutoxo-
bridged bi-octahedral structure.
317
The isobutoxo bridges are unsymmetrical with the
W-O bond
trans
to the linear NO ligand being longer (2.204 A) than the one
trans
to
the terminal isobutoxo ligand (2.054 A).
A number of binuclear organoimido alkoxo complexes have been studied. The
edge-shared bi-octahedral structure was found for [W
2
-OMe
2
OMe
6
NPh
2
].
The practically linear (WNC, 174
Ž
) imido group is
trans
to a bridging methoxo
