Rutheniumtetraoxide oxidation of alkenes—a density functional theory study

Abstract

The general interest in the dihydroxylation of olefins by means of transition metal catalysts prompted us to study the oxidation of ethene by rutheniumtetraoxide, a well-known active catalyst. Different mechanistic pathways on the singlet and triplet potential energy surface were investigated by density functional theory calculations (B3LYP) using different combinations of ECPs (Hay–Wadt, Stuttgart/Dresden 1997) and basis sets (6-31G(d), 6-311+G(d,p)). We find that the reaction follows a (3+2) addition pathway on the singlet surface, favored by 22 kcal/mol in activation energy over a (2+2) cycloaddition pathway. Complexes of RuO 4 with donor substituents like amines are significantly less stabilized compared to the osmiumtetraoxide case, which is in good agreement with experimental results. The RuO 4·NH 3 complex also reacts via a (3+2) singlet pathway and shows a 5 kcal/mol lower barrier, while stabilizing the ruthenate intermediate by 13 kcal/mol.