Charge-transfer and intraligand electronic spectra of bipyridyl complexes of iron, ruthenium, and osmium. I. Bivalent complexes

Abstract

A series of spin-paired bivalent bipyridyl complexes of iron, ruthenium, and osmium, of the type [M(bipy)3]2+, [M(bipy)2X2]n+, [M(bipy)2XY]n+, [M(bipy)X4]n+, [M(bipy)(X2)2]n+, and [M(bipy)X2Y2]n+ (X and Y include a range of monodentate ligands and X2 a range of bidentate ligands) have been prepared. Their electronic spectra within the range 41000-7000 cm-1 have been recorded. All the complexes show two intraligand transitions which are present in free bipyridyl. The iron and ruthenium complexes have two metal oxidation charge-transfer bands, while the osmium complexes have a more complex charge-transfer pattern. Trends in the positions of the bands have been related to the bonding of the ligands X and Y to the metal ions. It is suggested that the energy of the metal t2 type orbitals relative to the ligand π and π* orbitals is the main factor in determining the intense electronic spectra of these complexes.