Electronic and steric effects of phosphine ligands in the formation of ethylene glycolfrom synthesis gas catalyzed by rhodium

Abstract

The catalytic activity of the rhodium/phosphine system in the formation of ethylene glycol from synthesis gas is determined by the electronic and steric effects of the phosphine ligands, including alkyl-substituted phosphorinane and alkyl diisopropylphosphine. Taft's substitution constant of the alkyl substituent and the 31P NMR chemical shifts for the coordinated phosphine are used as the electronic and steric parameters, respectively. For both types of phosphine, the rate of ethylene glycol formation increases with an increase in the electron-donating effect of the alkyl substituent. The steric hindrance of the substituents in alkyl diisopropylphosphine inhibits the electronic effect for glycol formation.