Quantum chemical investigation of the reaction of phosphine with alcohol in the coordination sphere of platinum(IV) and platinum(II)

Abstract

The CNDO method has been used to investigate a new autocatalytic reaction of reduction of alcohol solutions of platinum(IV) halides by phosphine, leading to the formation of products of O-phosphorylation — trialkyl phosphites — at low temperature (20–50°C) and products of C-phosphorylation — trihydroxyalkylphosphines — at high temperature (60–90°C). It was shown by comparing the metalligand and ligand-ligand bond energies in haloalcohol phosphine complexes of platinum(IV) and platinum(II) that alkoxylation proceeds through a step of deprotonation of the alcohol with nucleophilic assistance and introduction of phosphine at the metal-oxygen bond, whereas hydroxyalkylation includes a step of β-elimination of alkoxide hydrogen and insertion of phosphine at the metalcarbon bond. Autocatalysis is due to the fact that the indicated key steps on platinum(II) are significantly more profitable with respect to the energy difference of the bonds broken (metal-ligand) and formed (ligand-ligand).