Intercalation of a multiply bonded dimolybdenum core into layered metal phosphates

Abstract

The spectroscopic and magnetic properties of a quadruply bonded dimolybdenum core intercalated into the layered metal phosphates (LMPs) of vanadium and niobium have been examined. Layer modification of the LMPs was achieved by redox intercalation of the Mo{sub 2}{sup 4+} core solvated by acetonitrile and by its ion-exchange reaction following reduction of the phosphate host layers with NaBH{sub 4}. Regardless of the reaction pathway, a similiar product is obtained. The reacted layers display a contraction of the d-spacing with concomitant insertion of up to 0.2 molybdenum atoms per layer unit cell. Structural characterization and absorption spectroscopy of these materials reveal that the bimetallic core residing in the gallery interlayer region is the mixed-valence Mo{sub 2}{sup 5+} center in a transverse orientation. In this arrangement the ubiquitous D{sub 4h} coordination environment of multiply bonded {open_quotes}Mo{sub 2}O{sub 8}{close_quotes} complexes is achieved with the dimolybdenum core keyed into tetragonal oxygen cavities of the layer. Magnetic susceptibility and EPRR studies reveal that electrons in the layers are antiferromagnetically coupled and that the exchange interaction is in a weak coupling regime. This exchange interaction is enhanced by the presence of the paramagnetic Mo{sub 2}{sup 5+} center within the interlayer region of the LMP. 95 refs.,more » 8 fig.« less