Distant protonated pyridine groups in water-soluble iron porphyrin electrocatalysts promote selective oxygen reduction to water.

Fe(III)-meso-tetra(pyridyl)porphyrins are electrocatalysts for the reduction of dioxygen in aqueous acidic solution. The 2-pyridyl derivatives, both the triflate and chloride salts, are more selective for the desired 4e(-) reduction than the isomeric 4-pyridyl complexes. The inward-pointing pyridinium groups influence proton delivery despite their distance from the iron centre.

Electrocatalytic oxygen reduction by iron tetra-arylporphyrins bearing pendant proton relays.

Iron(III) meso-tetra(2-carboxyphenyl)porphine chloride (1) was investigated as a soluble electrocatalyst for the oxygen reduction reaction (ORR) in acetonitrile with [H(DMF)(+)]OTf(-). Rotating ring-disk voltammetry, spectroelectrochemistry, and independent reactions with hydrogen peroxide indicate that 1 has very high selectivity for reduction of O(2) to H(2)O, without forming significant amounts of H(2)O(2). Cyclic voltammetric measurements at high substrate/catalyst ratios (high oxygen pressure) allowed the estimation of a turnover frequency (TOF) of 200 s(-1) at -0.

Transmetalation reactions of a scandium complex supported by a ferrocene diamide ligand.

Efforts to transfer to aluminum the heterocyclic ligand of a ring-opened imidazole scandium complex, which was previously reported, are presented. A ring-opened imidazole aluminum compound was formed at 50 °C and characterized as a trialuminum complex. At high temperature (85 °C), the formation of an unusual scandium/aluminum methylidene was observed.

Dearomatization reactions of N-heterocycles mediated by group 3 complexes.

Group 3 (Sc, Y, Lu, La) benzyl complexes supported by a ferrocene diamide ligand are reactive toward aromatic N-heterocycles by mediating their coupling and, in a few cases, the cleavage of their C-N bonds. When these complexes reacted with 2,2'-bipyridine or isoquinoline, they facilitated the alkyl migration of the benzyl ligand onto the pyridine ring, a process accompanied by the dearomatization of the N-heterocycle. The products of the alkyl-transfer reactions act as hydrogen donors in the presence of aromatic N-heterocycles, ketones, and azobenzene.

Reactions of group III biheterocyclic complexes.

Group III alkyl complexes supported by a ferrocene diamide ligand (1,1'-fc(NSi(t)BuMe(2))(2)) have been found to be reactive toward aromatic N-heterocycles such as 1-methylimidazole and pyridines. These reactions were investigated experimentally and computationally. An initial C-H activation event is followed by a coupling reaction to form biheterocyclic complexes, in which one of the rings is dearomatized.

Ring-opening reactions of aromatic N-heterocycles by scandium and yttrium alkyl complexes.

The C-N bond in aromatic N-heterocycles is a strong bond, its cleaving involving mostly examples of metal-element multiple bonds. We report on the C-C coupling of two molecules of an aromatic N-heterocycle mediated by scandium and yttrium benzyl complexes supported by a ferrocene 1,1'-diamide ligand. The reaction with 1-methylimidazole leads, ultimately, to the formation of a ring-opened imidazole coupled to a 1-methylimidazole fragment, a structure showing extended conjugation of double bonds.

Redox processes in a uranium bis(1,1'-diamidoferrocene) complex.

Oxidation of a uranium(IV) bis(1,1'-diamidoferrocene) gives a compound which is best described as a mixed-valence bisferrocene complex in which uranium mediates the electronic communication.