Oxo complexes of ruthenium(VI) and (VII) as organic oxidants

Abstract

Oxidation of a variety of saturated and unsaturated primary and secondary alcohols by tetraoxoruthen-ate(VI), [RuO₄]^2–, tetraoxoruthenate(VII), [RuO₄]^–, barium trans-trioxodihydroxoruthenium(VI), trans-Ba[Ru(OH)₂O₃], dioxotrichlororuthenate(VI), [RuO₂Cl₃]^–, and dioxodichlorobipyridylruthenate(VI), [RuO₂(bipy)Cl₂], has been studied; [RuO₄]^2–may be used catalytically in conjunction with [S₂O₈]^2– under basic aqueous conditions. For some of these systems, the oxidation of several aldehydes and amines were also examined. Both [RuO₄]^2–and [RuO₄]^– oxidise primary alcohols to carboxylic acids and secondary alcohols to ketones; the reactivity of these reagents towards unsaturated alcohols was studied in particular. The new species [PPh₄][RuO₂Cl₃] and also [RuO₂(bipy)Cl₂] cleanly oxidise a wide range of alcohols to aldehydes and ketones without attack of double bonds. Ba[Ru(OH)₂O₃] functions as a heterogeneous oxidant in dichloromethane, oxidising only the most reactive alcohols to aldehydes.