“…In all these compounds, the Lewis acid E(C 6 F 5 ) 3 (E ¼ B, Al) abstracted the Me group, also in the presence of an oxygen atom bound to the niobium atom, in contrast with the behaviour observed in oxametallacyclic niobium compounds [54]. H 3 ) aryloxo ligand of compound 2c might be the reason for the higher stability of the active species, favoring the polymerization process [42].…”