There have been great advances in the field of organometallic catalysts for polymerization and organic synthesis. One of the main driving forces for this challenging area of research has been the search for more environmentally friendly processes and materials. Metallocenes were the main players for many processes a few years ago, however new catalysts are now being developed with better reactivities and stereoselectivities. A basic understanding of these new complexes is essential in trapping the active species and the key to designing new materials. 

This Dalton Transactions Perspective by Elena Smolensky and Moris Eisen from the Technion-Israel Institute of Technology, Haifa, Isreal presents the synthesis and design features of allylic, benzamidinate and aminopyridine group IV complexes. The second part of the review is dedicated to the catalytic properties of these complexes for polymerization of olefins and other olefin metathesis-centered organic transformations.