Simple and cheap steric and electronic characterization of the reactivity of Ru(II) complexes containing oxazoline ligands as epoxidation catalysts

The reactivity of a new family of complexes with general formula [RuIV(T)(R-D)(O)]2+ (T = trispyrazolylmethane (tpm); D = N-(1-hydroxy-3-methylbutan-(2S)-(−)-2-yl)-(4S)-(−)-4-isopropyl-4,5-dihydrooxazole-2-carbimidate, R = Bz (1); iPr (2)) has been analyzed. There is a significant difference in regioselectivity between the two catalysts in the epoxidation of 4-vinylcyclohexene; 1 leads to the regioselective oxidation at the ring alkene position, whereas 2 leads to the oxidation at the terminal position. Although computational calculations indicate small energy differences, both the geometry through steric maps and the electronic parameters of the reactants via conceptual DFT, or charges via NPA, explain the reactivity differences found for the catalysts depending on the substituents of the oxazoline ligands.