Perspectives of rhodium organometallic catalysis. Fundamental and applied aspects of hydroformylation

Today's hydroformylation process almost exclusively use rhodium homogeneous catalysts. Some domination of octacarbonyl dicobalt as the catalyst precur sor was followed with broad application of rhodium based organometallic cat alysts modified with mainly phosphorus ligands. of different donor-acceptor properties and/or different cone/bite angles. Although there are many pape rs dealing with the comparative studies on structure-reactivity correlation , the effects of electronic and steric parameters of P-ligands on the catal ytic activity of rhodium catalysts are not always predictable. Phosphines a nd phosphites as ligands, simple and structurally developed, bulky, mono an d bidentate are still of great interest in the modification procedures of r hodium catalysts, especially when high regioselectivity in the hydroformyla tion is expected. Further development of the synthesis of phosphorus ligand s led to the preparation of water soluble ligands and the creation of a new class of two-phase homogeneous catalysts, in this way solving problems of separation and/or catalysts reuse. Some new water soluble phosphines (PNS, PNa, PC) as well as N-pyrrolyl phosphines (PPhx(NC4H4)(3-x)) of required el ectronic parameters applied for synthesis of new rhodium catalyst precursor s will be discussed and the results of structural studies will be used in t he explanation of the observed catalytic activity in the model hydroformyla tion reaction of olefins (l-hexene, unsaturated alcohols) as well as relate d reactions, i.e. isomerization and hydrogenation. (C) 1999 Elsevier Scienc e S.A. All rights reserved.