Hexametalates as Catalysts for Photochemical Oxidation Reactions
The reaction of TiCl$\sb4$ with WO$\sb4$((n-C$\sb4$H$\sb9$)$\sb4$N) $\sb2$ in acetonitrile yields ClTiW$\sb5$O$\sb $ ((n-C$\sb4$H$\sb9$)$\sb4$N) $\sb3$. The complexes ROTiW$\sb5$O$\sb $ (n-C$\sb4$H$\sb9$)$\sb4$N) $\sb3$ (R = CH$\sb3$, C$\sb2$H$\sb5$, and (CH$\sb3$)$\sb2$CH) are prepared in an analogous fashion by acidification of Ti(OR)$\sb4$ and WO$\sb4$ ((n-C$\sb4$H$\sb9$)$\sb4$N) $\sb2$. Spectroscropic data (IR, $\sp $O, and $\sp{183}$W NMR) indicate that these anions all have structures related to the C$\sb5$H$\sb5$TiW$\sb5$O$\sb \sp{3-}$ structure by replacement of the C$\sb5$H$\sb5$ ligand by a chloride or alkoxide ligand. Hydrolysis of ROTiW$\sb5$O$\sb \sp{3-}$ results in formation of O(TiW$\sb5$O$\sb $)$\sb2$ ((n-C$\sb4$H$\sb9$)$\sb4$N) $\sb6$. This salt can also be prepared by the reaction of ClTiW$\sb5$O$\sb \sp{3-}$ with hydroxide ion. Spectroscopic data indicates that the structure of this anion is based on two TiW$\sb5$O$\sb \sp{2-}$ units linked through an oxide bridging two titanium atoms.
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