VIBRATIONS OF CENTRAL OXYGEN IN A HIGH-SYMMETRY TETRANUCLEAR METAL CLUSTER - A DEFINITIVE ASSIGNMENT USING ISOTOPIC-SUBSTITUTION IN A BASIC ZINC CARBOXYLATE COMPLEX

The complex [Zn4O(OOCC(CH3)3)6] contains a tetrahedral oxo-centred metal cluster unit. Structures of this type have been characterised by X-ray diffraction, and in some cases exact tetrahedral symmetry has been found. However, crystal structures of high symmetry can conceal molecular structures of lower symmetry, averaged by static or dynamic disorder. The symmetry of this complex has therefore been checked over a short time-frame, in solution, by using vibrational spectroscopy with isotopic substitution. The antisymmetric vibration of the central oxide ion (t2 symmetry in the T(d) point group) has been located unambiguously and shown to be free of splitting by any symmetry lowering, and moreover to be essentially purely localised about the central oxygen.