. . "Ind represents an indenyl group, R??? represents a substituent, other than hydrogen, bound to the Ind group at the 2-position, Cp represents a cyclopentadienyl group, M represents a transition metal from group 3, 4, 5, or 6 of the Periodic System of Elements, Q represents a ligand to M, and k is an integer linked to the valence of M, and wherein compounds in which the Cp-group is an indenyl group" . .