Chemistry of ruthenium. Part 8. New tris complexes of ruthenium(III). Synthesis, spectra, and redox activity
Abstract
A group of new low-spin tris complexes of ruthenium(III) has been synthesized using triazene 1-oxides, RN(O)N–NH–C6H4X-p(HL; R = Et or Ph, X = Me, H, Cl, CO2Et, or NO2) as ligands. The green to yellow-green complexes [RuL3] are believed to have a meridional RuN3O3 co-ordination sphere. They display ligand → metal charge-transfer transitions in the region 550–750 nm. In acetonitrile solution the [RuL3] complexes exhibit a quasi-reversible RuIII–RuII couple (E2980, –0.6 to –1.2 V vs. s.c.e.) and a nearly reversible RuIV–RuIII couple (E2980, 0.2–0.7 V vs. s.c.e.) at a platinum working electrode. The E2980 values of both couples correlate linearly with the Hammett constant of substituent X. The reaction constants lie in the range 0.1–0.2 V. The electronic spectra of [RuL3]– and [RuL3]+ are briefly reported. The former complex is unstable.