A THEORETICAL-STUDY OF DINITROGEN ACTIVATION BY VANADIUM(II) AND VANADIUM(III) - AB-INITIO CALCULATIONS ON VARIOUS MODEL COMPOUNDS

Ab initio RHF and CI calculations have been carried out on the [H3VN2V H3(mu-Na)](-), [H3VN2VH3](-), [H3VN2VH3], and [H3VN2VH3](2-) complexes and related fragments in order to study the energetics and the mechan ism of dinuclear dinitrogen activation by vanadium(II) and anadium(III ). Analogous calculations have been performed also on the [H3VN2], [H3 VN2](-), and [H3VN2Na] complexes to compare mononuclear and dinuclear activation. Various energy gradient optimizations have been performed on the complexes and the various fragments, followed by MRCI calculati ons on the stationary structures. The results indicate that in the din uclear complexes dinitrogen is poorly to strongly activated through me chanisms which depend on the presence of the alkali atom, the net char ge, and the spin multiplicity of the considered state, while in the mo nonuclear complexes dinitrogen is always poorly activated.