Chemistry of Square Planar Organometallic Complexes of the Nickel Group Relevant to Catalysis

Square planar dialkyl complexes of nickel, palladium and platinum exhibit intriguing difference in their reactivities. Thermolysis pathways of these dialkyls vary depending on the metal, ligands, alkyl groups, geometry as well as the presence or absence of added ligand. Kinetic studies on the thermolysis and trans-cis isomerizations of PdR,L2 (L = tertiary phosphine) complexes showed involvement of -, 4-, and 5-coordinate intermediates. Effects of constraint of these geometries on the reaction pathways to induce reductive elimination or s-hydrogen elimination are discussed. Reactions of these dialkyl complexes with carbon monoxide give different products depending on the metal, geometry and the alkyl groups. Reaction courses of PdR,L2 type complexes with carbon monoxide can be accounted fo consistently by assuming the alkyl migration to the coordinated CO ligand. Based on the information obtained in the basic studies novel catalytic systems promoted by palladium complexes converting organic halides, CO and amines into a—keto amides have been developed.