Haloperoxidase activity of oxovanadium(V) thiobisphenolates

By employing the 2,2'-thiobis(2,4-di-tert-butylphenolate) ligand ((S)L(2-)) a novel oxovanadium(V) complex, (PPh(4))(2)[(S)LV(O)(μ(2)-O)(2)V(O)(S)L] (1), was synthesised that exhibits haloperoxidase activity: on addition of H(2)O(2) a sequence of successive peroxide formation and intramolecular thioether oxidation events (sulfoxide and sulfone) led to a mixture of five products, which were all identified unambiguously, partly through an independent synthesis and characterisation. It was shown that internal thioether oxidation proceeds through peroxide formation, but the sulfoxidation of external thioether functions requires further activation of the peroxide function by protons or alkyl cations. Consistently, the employment of tBuOOH instead of H(2)O(2) led to a very active system for the catalytic sulfoxidation of thioethers.     

Phosphide-borane complexes as key intermediates in the synthesis of optically active 1,3-oxaphospholanes

The syntheses, from the triphenylphosphine-borane complex, of chiral 1,3-oxaphospholanes and optically active bis-1,3-oxaphospholanes, obtained by cleavage of a carbon-phosphorus bond with lithium, are described. © 1997 John Wiley & Sons, Inc.     

Reductive Cross-Coupling of a Vinyl Thianthrenium Salt and Secondary Alkyl Iodides

We report the first reductive vinylation of alkyl iodides. The reaction uses a vinyl thianthrenium salt, a palladium catalyst, and an alkyl zinc intermediate formed in situ to trap the L_nPd^II(vinyl) complex formed after oxidative addition before it undergoes undesired homocoupling to form butadiene.     

Synthesis,Properties and Reactivity Studies of a Hetero-dicopper Complex Consisting of a Porphyrin and a Bispyridylamine Moiety Connected by a Xanthene Backbone

Synthesis, characterization and reactivity studies of a hetero-dicopper complex, particularly towards oxygen reduction are presented. A bischlorido copper(II) trishistidine-type coordination unit is positioned directly above a copper porphyrin unit. The close distance between the two coordination fragments is secured by a rigid xanthene backbone. Surprisingly, the dinuclear complex is not active towards oxygen reduction unlike the earlier published mononuclear analogues with a bispyridylamine copper center. However, the compound architecture of this multinuclear metal complex is interesting and can play an important role in the development of new catalysts for ORR.     

Indolyl Phosphine Nickel(II) Fluorido Complexes: Synthesis and Intermediates in Suzuki–Miyaura Cross-Coupling Reactions

The C−F bond activation of pentafluoropyridine and 2,3,5,6-tetrafluoropyridine at [Ni(cod)₂] (cod=1,5-cyclooctadiene) in the presence of the phosphine PPh₂(Ind) (Ind=3-methyl-2-indolyl) led to the formation of the nickel(II) fluorido bis(phosphine) complexes trans-[Ni(F)(2-C₅NF₄){PPh₂(Ind)}₂] and trans-[Ni(F)(2-C₅HNF₃){PPh₂(Ind)}₂]. The complexes are characterized by the presence of intramolecular hydrogen bonds between the NH group of the phosphine ligands and the fluorido ligand. Stochiometric model reactions of nickel(II) fluorido complexes with PhB(OH)₂ revealed that the former can be considered as intermediates in Suzuki–Miyaura cross coupling reactions. Catalytic experiments were attempted using 10 mol-% of trans-[Ni(F)(2-C₅NF₄){PPh₂(Ind)}₂] as catalyst and the activities of the PPh₂(Ind) complex were compared to the ones of an analogous nickel(II) fluorido complex, bearing PPh₃ instead of PPh₂(Ind) as ligands. The latter exhibited a somewhat lower catalytic activity suggesting a slight influence of the H-bonds in the outer coordination sphere.     

Indirect Raman identification of the proton insertion in the high‐temperature [Ba/Sr][Zr/Ti]O3‐modified perovskite protonic conductors

OH⁻ and H₃O⁺ species in hydrates and simple oxides are rather well characterised from their IR, Raman and inelastic neutron points of view. For the H⁺ (H₂O) species in solid state the variability is well established and assignment remains discussed. The question of the vibrational signature of isolated proton (e.g. the ionic proton, a proton sharing its interaction with more than two acceptors) and its dynamic nature (proton gas, polaron,…) is open. H⁺‐containing modified perovskites A(Ba,Sr,…) B(Zr,Ce,Ti,…) O₃ are potential ceramic membranes for fuel cell and medium temperature water electrolysis (300–800 °C). Comparison studies of the protonated and non‐protonated lanthanide/rare earth‐modified perovskites of type Ba(Sr)Zr(Ti)O₃ as well as Al‐modified BaTiO₃ show that a broad component centred at 2500 cm⁻¹ is observed after ‘proton insertion’. Its intensity is correlated to the protonic species content as well as to the conductivity of the materials. The mixed nature of this feature is discussed: fluorescence related to the dangling bonds, A, B, C bands or new phenomena related to the ionic protons and associated electronic defect. Copyright © 2008 John Wiley & Sons, Ltd.