A novel process for the polymerization of olefins is provided. The process involves contacting at least one olefin with a Ziegler-Natta type catalyst in the presence of a specified compound that results in the production of polymeric products having a narrower molecular weight distribution. Also provided is a process for narrowing the molecular weight distribution of a polyolefin comprising contacting an olefin, a Ziegler-Natta catalyst and a compound specified herein. Further provided are novel polyethylenes, and films and articles produced therefrom.