Oxidation of cyclobutanol by aqueous Fe(IV) generates cyclobutanone in ∼70% yield. In addition to this two-electron process, a smaller fraction of the reaction takes place by a one-electron process, believed to yield ring-opened products. A series of aliphatic alcohols, aldehydes, and ethers also react in parallel hydrogen atom and hydride transfer reactions, but acetone and acetonitrile react by hydrogen atom transfer only. Precise rate constants for each pathway for a number of substrates were obtained from a combination of detailed kinetics and product studies and kinetic simulations. Solvent kinetic isotope effect for the self-decay of Fe(IV), kH2O/kD2O = 2.8, is consistent with hydrogen atom abstraction from water.

Reactivity of aqueous Fe(IV) in hydride and hydrogen atom transfer reactions.

The coordination compounds of the tridentate oligopyridine ligand 2,2′:6′,2′′-terpyridine (tpy) are utilized in very different fields of research, such as materials science (e.g. photovoltaics), biomedicinal chemistry (e.g. DNA intercalation), and organometallic catalysis. Applications in the latter area have arisen from initial reports on electro- or photochemical processes and, today, a broad range of reactions—from artificial photosynthesis (water splitting) to biochemical and organic transformations as well as polymerization reactions—have been catalyzed by terpyridines and their transition metal complexes. In this review, the scope and the limitations of these applications, which emerged particularly in organic and macromolecular chemistry, will be evaluated.

Catalytic Applications of Terpyridines and their Transition Metal Complexes

The phosphonated ruthenium complex, [Ru(tpy-PO3H2)(OH2)3]2+ (1) (tpy-PO3H2 = 4‘-phosphonato-2,2‘:6‘,2‘ ‘-terpyridine), was synthesized and attached to glass|ITO or glass|ITO|TiO2 electrodes. After ...

Reactivity of an adsorbed Ru(VI)-oxo complex: oxidation of benzyl alcohol.

Heterogeneously catalyzed oxidation of butanediols in base free aqueous media

The kinetics of the hexacyanoferrate (III) oxidation of dihydroxyfumaric acid to hexacyanoferrate (II) and diketosuccinic acid was looked into within the 0.04 to 5.3 M HCl acidity range under different temperatures, ionic strengths, and solvent permittivity conditions. The kinetic effect of alkali metal ions, transition metal impurities, and substrate concentrations have also been analyzed. The observed inhibition effect brought about by addition of the reaction product, hexacyanoferrate (II), is a sign of a complex mechanism. The rate constants remained essentially unchanged up to 1 M HCl, diminished between 1.0 and 3.0 M HCl, and rose above 3.0 M HCl. Depending on the medium acidity, three mechanisms can be put forward, which involve different kinetically active forms. At low acidity, the rate-determining step involves a radical cation and both the neutral and the anion substrate forms are equally reactive ( k 1 = k 2 = 2.18 +/- 0.05 M (-1) s (-1), k -1 = 0.2 +/- 0.03). When the medium acidity is boosted, the rate-determining step involves the neutral dihydroxyfumaric acid and two hexacyanoferrate (III) forms. In the intermediate region the rate constant diminished with rising [H (+)] ( k' 1 = 0.141 +/- 0.01 and k' 2 = 6.80 +/- 0.05). Specific catalytic effect by binding of alkali metal ions to oxidant has not been observed. In all instances it was assessed that the substrate decomposition is slow compared to the redox reaction.

S. Villarreal

Papers

Comparative study of the catalytic behaviour of Ru(III) and Ru(VI) on the oxidation of alcohols by hexacyanoferrate(III)

Oxidation of 2,3-butanediol by alkaline hexacyanoferrate(III) using Ru(III) or Ru(VI) as catalyst†