Chemistry Reference
In-Depth Information
Figure 4.5
M
3
(
3
-OC)
2
(
-OC)
3
(OC)
6
core
structure
of
[M
3
(
3
-OR)
2
(
-
OR)
3
(OR)
4
(ROH)
2
].
Figure 4.6
M
4
(
3
-OC)
4
core
structure of [M
4
(
3
-OR)
4
].
Figure 4.7
M
4
O
12
core struc-
ture of [M
4
(
-OR)
6
(OR)
6
].
The cubane structure [M
4
3
-OR
4
] (Fig. 4.6) is favoured by the alkali metal tertiary
butoxides (M D K, Rb, Cs)
17
and thallium(
I
) alkoxides,
18
and also related species such
as [Me
4
Zn
4
(
-OMe
4
]
.
19
Another common tetranuclear structure [M
4
-OR
6
(OR)
6
]
(Fig. 4.7) involves one central octahedral metal bridged to three tetrahedral metals in
a chiral configuration (D
3
). Crystalline aluminium isopropoxide was the first example
established to have this structural type.
20
Interestingly in the heterometallic complex
[ErAl
3
OPr
i
12
] the central position is occupied by the erbium ion in a distorted trigonal
prismatic configuration.
21
Finally we draw attention to the unique dimeric alkoxides of molybdenum and
tungsten M
2
(OR)
6
which are held together by metal - metal triple bonds without the
