Amino acid complexes of ruthenium: synthesis, characterization and cyclic voltammetric studies

Reaction of alpha-amino acids (HL) with [Ru(PPh3)(3)Cl-2] in the presence of a base afforded a family of complexes of type [Ru(PPh3)(2)(L)(2)]. These complexes are diamagnetic (low-spin d(6), S=0) and show ligand-field transitions in the visible region. H-1 and P-31 NMR spectra of the complexes indicate the presence of C-2 symmetry. Cyclic voltammetry on the [Ru(PPh3)(2)(L)(2)] complexes show a reversible ruthenium(II)-ruthenium(III) oxidation in the range 0.30-0.42 V vs. SCE. An irreversible ruthenium(III)-ruthenium(N) oxidation is also displayed by two complexes near 1.5 V vs. SCE. (C) 1999 Elsevier Science Ltd. All rights reserved.