The Structural Conversion of Multinuclear Titanium(IV) μ-Oxo-complexes

For the first time we report the structural conversion processes of hexanuclear mu-oxo-Ti(IV) complexes into tetranuclear ones. Single-crystal X-ray diffraction studies reveal that metastable hexanuclear p-oxo complexes ([Ti6O6((OBu)-Bu-t)(O2CR')(6)]) are formed in the first stage of reactions between [Ti((OBu)-Bu-t)(4)] and branched carboxylic acids R'COOH (R' = C(Me)(2)Et, (CH2Bu)-Bu-t, Bu-t). In the next stage they convert into tetranuclear mu-oxo-Ti(IV) complexes of the formula [Ti4O4((OBu)-Bu-t)(4)(O2CR')(4)]. Spectroscopic investigations (C-13 NMR, IR, and MS) proved that the conversion of hexanuclear clusters relies on the attachment of smaller units (e.g., [Ti3O((OBu)-Bu-t)(8)(O2CR')(2)] or [Ti4O2((OBu)-Bu-t)(6)(O2CR')(6)]) and intermediate species formation (e.g., [Ti9O8((OBu)-Bu-t)(14)(O2CR')(6)]). The decomposition of intermediate systems in the next reaction stage leads to the formation of tetranuclear clusters. The type of solvent used in the synthesis of multinuclear oxo-Ti(IV) complexes is an important actor, which influences the kind of clusters formed.