Synthesis of osmium and ruthenium complexes bearing dimethyl (S,S)-2,2′-(pyridine-2,6-diyl)-bis-(4,5-dihydrooxazol-4-carboxylate) ligand and application to catalytic H/D exchange

Abstract

Using tridentate, neutral PyBox ligands, several new osmium and ruthenium complexes [M(PyBox)Cl_(2)(C_(2)H_(4)), where M = Ru, Os] have been prepared, all thermally stable. Some of these PyBox compounds are active for C–H activation of benzene. The Os(PyBox)Cl_(2)(C_(2)H_(4) complex was characterized by X-ray diffraction. DFT calculations (B3LYP and M06 including Poisson–Boltzmann solvation) corroborate that the Os/PyBox complex in acetic acid (ΔG‡ = 32.0 kcal/mol) is more reactive for benzene C–H activation than Ru/PyBox in basic conditions (ΔG‡ = 34.8 kcal/mol at pH = 13). The stability of hydroxide- and chloride-bridged dinuclear resting states determines calculated barriers.