Tuning the reactivities of ruthenium–oxo complexes with robust ligands. A ruthenium(IV)–oxo complex of 6,6′-dichloro-2,2′-bipyridine as an active oxidant for stoichiometric and catalytic organic oxidation

Abstract

The synthesis and characterization of [Ru^II(terpy)(dcbipy)(H₂O)]²⁺(terpy = 2,2′:6′,2″-terpyridine; dcbipy = 6,6′-dichloro-2,2′-bipyridine) are described. Oxidation of this complex with Ce^IV gave [Ru^IV(terpy)(dcbipy)O]²⁺, isolated as a greenish yellow perchlorate salt. The Ru^IVO complex is paramagnetic (µ_eff= 2.83) and exhibits a RuO stretch at 780 cm^–1. It is a powerful oxidant with E°(Ru^IV–Ru^III)= 1.13 V vs. saturated calomel electrode at pH 1.0 and can selectively oxidize the tertiary C–H bond of adamantane. The mechanism of alkene oxidation by Ru^IVO has been investigated and discussed. The complex [Ru^II(terpy)(dcbipy)(H₂O)]²⁺ is a robust catalyst for the oxidation of saturated alkanes by tert-butyl hydroperoxide.