Charge-transfer and intraligand electronic spectra of bipyridyl complexes of iron, ruthenium, and osmium. II. Tervalent complexes

The electronic spectra of a series of six-coordinate octahedral tris-, bis-, and mono-bipyridyl complexes of tervalent iron, ruthenium, and osmium have been recorded and spectral bands assigned to intraligand and charge-transfer transitions. The tris-bipyridyl complexes and bis- and mono-bipyridyl complexes containing other ligands such as pyridine and cyanide show a metal reduction transition π(bipy) → t2(metal). Bipyridyl complexes of osmium containing halide ligands show a similar transition, but for the corresponding complexes of iron and ruthenium the metal reduction transition is now X(halogen) → t2(metal), the electron originating on the halide ligand. Bipyridyl-acetylacetonate complexes have more complicated spectra. Trends in the spectral bands, for all the complexes, indicate that of the three metal ions ruthenium probably forms the strongest M→L π-interaction.