Specific solvatochromism of the prototypical olefin complexes (η2-TCNE)M(CO)5(M = Cr, W) resulting from n and π donation of aprotic solvents toward the π-acceptor ligand

The solvatochromism of the well-separated long-wavelength charge-transfer bands of the title complexes was studied in 36 aprotic solvents and in dichloromethane solutions durene and hexamethylbenzene. The observed effects may be interpreted consistently in terms of strong n- and π-donor contributions from the solvents