Provided are catalyst systems, processes for polymerizing one or more olefins, polymers resulting therefrom, and articles prepared from such polymers. The processes comprise contacting under polymerization conditions one or more olefin monomers, preferably propylene, with a catalyst system comprising a transition metal compound and an activator of the formula (1) or (2) as described herein. The polymer compositions described herein exhibit advantageously narrow composition distributions and high melting points in comparison to conventional polymers having the same comonomer content. The polymers described herein exhibit improved properties, e.g., pellet stability, impact properties, heat seal properties, and structural integrity in film and fabricated parts applications.