2 Homometallic Alkoxides

410 Alkoxo and Aryloxo Derivatives of Metals
Figure 5.11 Structure of [Ti11⊲ 3-
O⊳13⊲ -OPr i ⊳7⊲OPr i ⊳6⊲OEt⊳5] (ž D
3-oxo, D Ti; H atoms omitted).
Figure 5.12 Structure of [Ti12⊲ 3-
O⊳14⊲ -O⊳2⊲ -OPr i ⊳4⊲OPr i ⊳12] (ž D
3-oxo, D Ti; H atoms omitted).
structure is capped by five TiO moieties which lie above five of the six square faces
of the Td-distorted cuboctahedron. As shown in Fig. 5.13 all seventeen of the terminal
positions are occupied by tert-butoxo ligands and the single hydrogen atom is present
in the -OH group and is hydrogen bonded to the lattice Bu t OH molecule.
At the centre of the Ti18O45 framework is a tetrahedral Ti atom which is linked
by four 4-oxo ligands to four groups of three TiO6 octahedra (Keggin structure).