Photoinduced arene deligation of a dicationic bis(arene)—iron (II) complex

Continuous photolysis, flash photolysis and photosensitization studies are reported for Fe(η6-mes)22+, where mes = 1,3,5-trimethylbenzene (mesitylene). The complex absorbs in the visible and ultraviolet spectral regions owing to the presence of ligand field, mes → Fe charge transfer, and intraligand π-π∗ absorption bands. Selective irradiation of the various bands causes substitution of both mesitylene ligands by solvent. The quantum efficiency of arene deligation ranges from 0.6 to 1.0 depending upon the excitation wavelength, but is independent of complex concentration, solvent, oxygen content and excess PF6− counterion. Reaction occurs from both ligand field and mes → Fe charge transfer excited states, with no evidence of communication between the states.