Chemistry of ruthenium. Part 10. Triazene 1-oxide complexes of bis(2,2′-bipyridine)ruthenium-(II) and -(III). Synthesis, spectra, and electrochemistry

Abstract

Mixed ruthenium complexes of type [Ru(bipy)₂L]ClO₄·H₂O derived from 2,2′-bipyridine (bipy) and triazene 1-oxides, RN(O)N–NH–C₆H₄X-p(HL: R = Et or Ph; X = Me, H, Cl, CO₂Et, or NO₂) are described. In solution they display two quasi-reversible reductions due to electron transfer to co-ordinated bipy units. The Ru^III–Ru^II couple occurs in the range 0.16–0.44 V versus s.c.e. The formal potential of this couple is linearly related to the Hammett constant of substituent X. The low-spin ruthenium(III) analogue, [Ru(bipy)₂L]²⁺, is furnished by both coulometric and chemical oxidations. The energy of the ligand-to-metal charge-transfer band of [Ru(bipy)₂L]²⁺ correlates linearly with the Ru^III–Ru^II formal potential.