Abstract: Bis(2,4-dimethylpentadienyl)vanadium, an open vanadocene, and its adducts of various Lewis bases bave been analyzed in detail by EHMOprocedure, and the obtained results could reasonably explain their magnetism, stability, the effect of substitutive methyl on pentadienyl and Lewis bases, and configuration as well. Moreover the formation and properties of similar compounds have been predicted.