Ruthenate ester

The mechanism of the Ley oxidation is complex and the exact nature of the species involved in the catalytic cycle is unknown. The difficulty in establishing an exact mechanism arises from the fact that the complexes of Ru ", Ru ", Ru , Ru and Ru are all capable of stoichiometrically oxidizing alcohols to carbonyl compounds. The TRAP reagent can oxidize alcohols stoichiometrically as a three-electron oxidant and can also be used as a catalyst when a co-oxidant is present (e.g., NMO, TMAO, or hydroperoxides). Data suggests that the oxidation proceeds via the formation of a complex between the alcohol and TRAP (ruthenate ester). It was also found that the stoichiometric oxidation of isopropyl alcohol with TRAP is autocatalytic and the catalyst is suspected to be colloidal RUO2. Small amounts of water decrease the degree of autocatalysis. This observation is supported by the finding that the addition of molecular sieves improves the efficiency of the reaction. 

Kinetic studies were made on the cleavage of franx-cinnamate to benzoic acid by stoich. [Ru0 p7aq. 1.7M NaOH/85°C isotope effects and activation parameters were determined. Formation of an alkene-[RuO ] cyclic Ru(lV) ester (1), oxidation of this with more ruthenate to the cyclic Ru(Vl) ester (2) and oxidative decomposition of this via (3) to aldehydes R CHO and R CHO was suggested. The aldehydes are subsequently oxidised to R COOH and R COOH by more [RuO ] (not shown in the Scheme) (Fig. 1.16) [349, 350],... 

Two out of the three products of base hydrolysis of the [Co(NH3)5(p-nitrophenylphosphate)] cation arise from attack of hydroxide at the coordinated ligand. These products are p-nitrophenolate and hydroxophosphor-amidotetraamminecobalt(Ill). These result from intramolecular attack at the phosphorus by a deprotonated coordinated ammine ligand, which generates a five-coordinate aminophosphorane. Ester hydrolysis is about 10 times faster in this complex than in the free / -nitrophenylphosphate—one of the most dramatic examples of the kinetic consequences of coordination to a metal center, comparable with the activation of acetonitrile on coordination to ruthen-... 

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