Oxygenation and carbonylation studies of some ruthenium(III) Schiff base complexes containing nitrogen and oxygen as donor atoms. II

Abstract

Synthesis and characterization of a series of ruthenium(III) Schiff base complexes of the type [Ru IIILXY] where L=Schiff base viz. bis(naphthaldehyde)- o-phenylenediimine (naphoph), bis(naphthaldehyde)ethylenediimine (naphen), bis(naphthaldehyde)propylenediimine (naphprop) and bis(naphthaldehyde)diethylenetriimine (naphdien); XCl and YCl imidazole (Im) or 2-methylimidazole (2-MeIm) are reported. Elemental analysis, conductivity and IR studies of the complexes suggest an octahedral geometry around ruthenium. Magnetic moments of the complexes indicate a single unpaired electron in a low spin d 5 configuration. Oxygenation studies in DMF or THF solutions suggest the reversible binding of molecular oxygen to the ruthenium(III) complexes. EPR studies at liquid nitrogen temperature and UVVis measurements at room temperature support the formation of a Ru(IV) superoxo species [Ru IVL(O 2 ·.) −Y]. The EPR spectrum of the Ru(IV) superoxo complex at 77 K ( g 1 = 2.063, g 2 = 2.047, g 3 = 2.023) is consistent with the odd electron occupying a highly localized antibonding π * orbital of molecular oxygen. The reversible binding of O 2 and CO has been carried out in DMF at 10, 25 and 40 °C. The complexes show discrimination against the binding of CO over O 2 as evinced by values of K O 2 and K CO in the complexes. The thermodynamic paramegers Δ H°, Δ G° and Δ S° for oxygenation and carbonylation reactions are evaluated.