Structure of the Trinuclear Titanium (IV) Alkoxides

Abstract

THE association of n-alkoxy derivatives of orthotitanic acid was first established as recently as December 1951 by Caughlan et al. ¹. Cryoscopic determinations of molecular weight in freezing benzene revealed that Ti(OC₂H₅)₄, Ti(OC₃H₇)₄ and Ti(OC₄H₉)₄ were all trimeric except at very high dilutions when dissociation to the monomer was observed. The association was ascribed to the strong tendency of quadrivalent titanium to attain a six-covalent oxygen environment, as, for example, in rutile or anatase. Caughlan et al. suggested that this could be achieved if each pair of titanium atoms was supported by three bridging alkoxy-groups giving two alternative structures I and II, which were based on the stacking of three TiO₆-octahedra face to face. Structure II necessitates a four-co-ordinated square planar oxygen atom attached to three titanium atoms and one alkyl group, and for this reason is considered by us to be untenable.