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

Using tridentate, neutral PyBox ligands, several new osmium and ruthenium complexes [M(PYBox)Cl-2(C2H4), 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(C2H4) 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 (Delta G(dagger) =32.0 kcal/mol) is more reactive for benzene C-H activation than Ru/PyBox in basic conditions (Delta G(dagger) =34.8 kcal/mol at pH =13). The stability of hydroxide- and chloride-bridged dinuclear resting states determines calculated barriers. (C) 2011 Elsevier B.V. All rights reserved.