Isomeric complexes of ruthenium(II) with neutral heterocyclic schiff base ligands. High resolution proton resonance spectra of trans-cis isomeric pairs of RuX2L2 (L 2-arylpyridinecarboxaldimine, X Cl, Br) and comparison of their physical properties
摘要:
The reaction of 2-arylpyridinecarboxaldimine [RH4C6NC(H)Py, L (1)] with hydrated RuX3 (X = Cl, Br) in boiling C2H5OH affords dark crystals of RuX2L2. Two geometrical isomers of the compound have been isolated and characterized by analytical and spectroscopic data. The trans isomer of RuCl2L2 shows a single sharp band for nu(Ru-Cl), whereas two bands are observed for the corresponding cis isomer. The high-resolution H-1 NMR spectra of the isolated complexes are reported and completely assigned. All the complexes have multiple t2 --> pi*(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.