Chemistry Reference
In-Depth Information
The compound [Ti
16
4
-O
4
3
-O
8
-O
4
-OEt
16
OEt
16
] was obtained in two
forms, I (stable in air, monoclinic) and II (sensitive to moisture, tetragonal) due to
different packings of the hexadecanuclear molecules in the crystals. The Ti
16
O
48
core in
each form is built up of two orthogonal blocks of eight TiO
6
octahedra. In each block six
octahedra form a layer structure (NiAs-type) with the seventh and eighth being on either
side (Fig. 5.8). The coordination around the
4
-oxo atoms is unsymmetrical (Ti
2
O
angles, 94.4 - 150.3
Ž
) whilst some
3
-O are pyramidal and others trigonal planar.
118
In the decanuclear molecule [Ti
10
4
-O
4
3
-O
2
-O
2
-OEt
10
OEt
14
] (Fig. 5.9)
it can be seen how three more octahedra have been attached to the Ti
7
O
4
OEt
20
structure.
9
The hydrolysis of Ti
OCH
2
Ph
4
PhCH
2
OH
gave rise to the crystalline octanuclear
compound [Ti
8
3
-O
4
-O
2
-OCH
2
Ph
8
OCH
2
Ph
12
] (Fig. 5.10)
9
which contains
4 octahedral and 4 five-coordinated titanium atoms presumably due to the greater steric
effect of the benzyloxo ligand compared to the ethoxide. In solution there was
17
O
Figure 5.8
Ti
16
O
48
core struc-
ture of [Ti
16
4
-O
4
3
-O
8
-
O
4
-OEt
16
OEt
16
].
Figure 5.9
Ti
10
O
32
core structure
of [Ti
10
4
-O
4
3
-O
2
-O
2
-
OEt
10
OEt
14
](
ž
D Ti; Et groups
omitted).
