Studies on transition-metal oxo and nitrido complexes. 13. Perruthenate and ruthenate anions as catalytic organic oxidants

Abstract

Oxo complexes of ruthenium are effective catalysts for the selective oxidation of various organic substrates. Thus the ruthenate ion trans-[Ru(OH)[sub 2]O[sub 3]][sup 2[minus]], which is stable above pH 12 in aqueous base, with persulfate as cooxidant will oxidize primary alcohols to carboxylic acids and secondary alcohols to ketones, the perruthenate ion [RuO[sub 4]][sup [minus]], which is stable from pH 8 to 12 in aqueous base, will also effect such oxidations stoichiometrically in solution. The organic-soluble TPAP' ((n-Pr[sub 4]N)[RuO[sub 4]]) with N-methylmorpholine N-oxide is an efficient selective catalyst for converting primary alcohols to aldehydes and secondary alcohols to ketones. The [RuO[sub 4]][sup [minus]] ion can be generated in aqueous base at pH 11 from aquated ruthenium trichloride with excess bromate, and this reagent will catalytically oxidize primary alcohols, activated alkyl halides, aldehydes, 1,2-diols, and nitroalkanes to carboxylic acids, while secondary alcohols and secondary halides are oxidized to ketones, bromate being the cooxidant. These oxidations are compared with those effected catalytically by trans-[Ru(OH)[sub 2]O[sub 3]][sup 2[minus]] in aqueous base at pH 14 with persulfate as cooxidant. A new preparation for organic-soluble salts of [RuO[sub 4]][sup [minus]] avoiding the use of RuO[sub 4] is described. 29 refs., 1 tab.