 between 00 and 00; X represents a halogen, selected from among chlorine, fluorine, bromine and iodine; wherein in formula Axe0x00x0, two ligand molecules Cp0 and Cp0, which may be identical or different, selected from a substituted or unsubstituted cyclopentadienyl and fluorenyl group are bonded to metal Ln; and in formula Bxe0x00x0, a ligand comprising Cp0 and Cp0 bonded to each other by a bridge P