Isomeric complexes of ruthenium(II) with neutral heterocyclic schiff base ligands. High resolution proton resonance spectra of trans- cis isomeric pairs of RuX 2L 2 (L  2-arylpyridinecarboxaldimine, X  Cl, Br) and comparison of their physical properties

Abstract

The reaction of 2-arylpyridinecarboxaldimine [RH 4C 6NC(H)Py, L ( 1)] with hydrated RuX 3 (X  Cl, Br) in boiling C 2H 5OH affords dark crystals of RuX 2L 2. Two geometrical isomers of the compound have been isolated and characterized by analytical and spectroscopic data. The trans isomer of RuCl 2L 2 shows a single sharp band for ν(RuCl), whereas two bands are observed for the corresponding cis isomer. The highresolution 1H NMR spectra of the isolated complexes are reported and completely assigned. All the complexes have multiple t 2→π *(L) transitions in the visible region. Each of the complexes display a quasi-reversible oxidative response due to an Ru III/Ru II couple in the range 0.25–0.40 V vs S.C.E. at a platinum working electrode. The formal potentials of this couple obey the Hammett relationship. The ligand-based irreversible oxidations are also briefly noted.