METAL CHELATE SYSTEMS AS CATALYSTS FOR OLEFIN AND CARBON-MONOXIDE CONVERSION REACTIONS

The application of non-phosphine-based chelating ligands in homogeneous catalyst systems is a surprisingly recent and relatively unexplored area of research. Chelating ligands can concurrently stabilize intermediates, control catalyst activity and direct the product distribution far more effectively than monodentate ligands. In this review our studies with catalyst systems containing chelate ligands primarily of the beta-diketonate type [dithio-beta-diketonate (sacsac); monothio-beta-diketonate (sacac); and imino beta-diketonate (nacac) ligands] is discussed. Examples of the catalyst systems show enzyme-like superactivity. Studies modelling these catalyst systems have provided valuable information relating the effects of ligand modifications to reaction pathways and to activities. Our most recent investigations of simple chelating ligands based on picolinic acid are also discussed. Studies modelling CO/ethene insertion/elimination with extremely labile alkylplatinum picolinate complexes led to the development of new single-component nickel oligomerization catalysts.