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 [RuII(terpy)(dcbipy)(H2O)]2+ (terpy = 2,2′:6′,2″-terpyridine; dcbipy = 6,6′-dichloro-2,2′-bipyridine) are described. Oxidation of this complex with CeIV gave [RuIV(terpy)(dcbipy)O]2+, isolated as a greenish yellow perchlorate salt. The RuIV=O complex is paramagnetic (μeff = 2.83) and exhibits a Ru=O stretch at 780 cm-1. It is a powerful oxidant with E°(RuIV-RuIII) = 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 RuIV=O has been investigated and discussed. The complex [RuII(terpy)(dcbipy)(H2O)]2+ is a robust catalyst for the oxidation of saturated alkanes by tert-butyl hydroperoxide.