Catalysts for the polymerization of olefins are provided. The catalysts comprise: (a) a first active polymerization catalyst which is a Fe or Co complex of a ligand of the formula: wherein: R1, R2 and R3 are each independently hydrogen, hydrocarbyl, substituted hydrocarbyl, or an inert functional group; R4 and R5 are each independently hydrogen, hydrocarbyl, an inert functional group or substituted hydrocarbyl; and R6 and R7 are aryl or substituted aryl; and (b) a second active polymerization catalyst which contains one or more transition metals; and (c) a catalyst support.