Structure-activity relationship for chelating phosphite ligands used in rhodium-catalyzed hydroformylations

A simplified kinetic model was developed for the rhodium-catalyzed low-pres sure hydroformylation using chelating phosphite ligands. This allowed the d etermination of the relative rate constants for linear and branched aldehyd e formation starting with terminal olefins using data from complex product mixtures. Structural data were obtained using X-ray crystallography and ser ved as the basis for molecular modeling of rhodium complexes with such chel ating ligands. The interaction of linear and branched alkyl groups with the ligand environment in such complexes was quantified using molecular modeli ng. The energy differences obtained with molecular modeling were plotted ag ainst the energy differences obtained from kinetic experiments and a linear correlation was found. This type of approach, i.e., development of a struc ture-activity relationship, can be used to quickly and efficiently investig ate such catalytic systems. (C) 1999 Elsevier Science B.V. All rights reser ved.