Current studies on novel metallocene-based catalysts for the polymerization of ethylene and α-olefins have far-reaching implications for the development of new materials as well as for the understanding of basic reaction mechanisms responsible for the growth of a polymer chain at a catalyst center and control of its stereoregularity. In contrast to heterogeneous Ziegler-Natta catalyst polymerization of a homogeneous, metallocene-based catalyst occurs principally at a single type of metal center with a defined coordination environment. This makes it possible to correlate metallocene structure with polymer properties such as molecular weight, stereochemical microstructure, crystallization behavior and mechanical properties. Of course, there are many factors that influence the performance of the catalyst, but the ligand is probably one of the most important elements. From this point of view, the development of new ligands is very critical and of great interest.