Analysis of Multiple Redox Sites in Complexes [M(C5Me5)(Q)(NO)]n, M=Ru or Os, Q=o-Quinones

Neutral complexes [M-II(C5Me5)(Q(2-))(NO+)] with M=Ru or Os and the catecholates Q(2-) with 3,5-di-tert-butyl (dtbc) or 3,4,5,6-tetrachloro substituents (tcc) were identified with the oxidation and charge states indicated. Reversible electron transfer was analyzed spectroelectrochemically (EPR, UV-vis-NIR, IR), supported by DFT calculations. Reversible reduction was observed for [Ru(C5Me5)(tcc)(NO)] to occur on the nitrosyl ligand to yield the NO radical complex [Ru-II(C5Me5)(tcc(2-))(NO.)](-), whereas the stepwise oxidation yielded o-semiquinone cations, [M-II(C5Me5)(Q(.-))(NO+)](+), and dications. The metals remained in the stable low-spin d(6) states, Ru-II and Os-II, respectively. Redox potentials were found to depend strongly on the donor or acceptor substitution pattern at Q(n).

Automated summary

Neutral complexes [M-II(C5Me5)(Q(2-))(NO+)] with M=Ru or Os and the catecholates Q(2-) with 3,5-di-tert-butyl (dtbc) or 3,4,5,6-tetrachloro substituents (tcc) were identified with determined oxidation and charge states. Reversible electron transfer process was analyzed through spectroelectrochemical methods, supported by DFT calculations, revealing the dependence of redox potentials on the donor or acceptor substitution pattern at Q(n).