Paul Kiprof Chemistry
Rhodium-phosphine catalyzed hydroformylation was first developed by Wilkinson in the late 1960’s. Because of its effectiveness over other catalytic systems, rhodium-based systems have become considerably important for hydroformylation on an industrial scale.
This study used computational methods in order to expand on experimental results and develop a plausible model for dealing specifically with the crucial step in the catalytic cycle that is widely believed to be responsible for the regioselectivity of the products.
It was found that the bite angle of rhodium
coordinated chelating phosphines has a considerable effect on the
regioselectivity of products produced by the catalyst.
This investigation studied a series of phosphines and determined, by computational methods, the effect the bite angle of chelating phosphines had on the transition states thought to control the regioselectivity of the rhodium catalyst.
Three transition states were found, which lead to the formation of two isomers of the catalytic species. It was found that when the bite angle of the chelating phosphine is changed, there is a definite change in the relative activation energy of the transition states.
Experimental results are interpreted in light of these transition states and we have a probable explanation as to why the bite angle affects the regioselectivity of hydroformylation.
Examples for transition states