0000000000181503
AUTHOR
Alain Vallat
Thermodynamic and kinetic control over the oxidation mechanism of the natural vanadyl porphyrin series (DPEP)VO in methylene chloride: electrogeneration of an unusual dicationic species [(DPEP)VO]22+
The electrochemical behavior of the natural (DPEP)VO series (where DPEP is the dianion deoxophylloerythroetioporphyrinate) is studied in methylene chloride. The investigated compounds, which were extracted from oil shales of Tarfaya (Morocco), exhibit a typical electrochemical behavior as compared to that of related synthetic vanadyl porphyrins. The electro-oxidation of (DPEP)VO is characterized by a splitting of the peaks when carried out at a glassy carbon electrode. This can be explained by two possible paths (CE and EC mechanisms) which are characterized by a “square diagram” where the chemical step, C, corresponds to a dimerization (radical–radical or substrate–substrate reaction). The…
Generation, Characterization, and Electrochemical Behavior of the Palladium-Hydride Cluster [Pd3(dppm)3(3-CO)(3-H)]+ (dppm=Bis(diphenylphosphinomethane)
Addition of formate on the dicationic cluster [Pd(3)(dppm)(3)(mu(3)-CO)](2+) (dppm=bis(diphenylphosphinomethane) affords quantitatively the hydride cluster [Pd(3)(dppm)(3)(mu(3)-CO)(mu(3)-H)](+). This new palladium-hydride cluster has been characterised by (1)H NMR, (31)P NMR and UV/Vis spectroscopy and MALDI-TOF mass spectrometry. The unambiguous identification of the capping hydride was made from (2)H NMR spectroscopy by using DCO(2) (-) as starting material. The mechanism of the hydride complex formation was investigated by UV/Vis stopped-flow methods. The kinetic data are consistent with a two-step process involving: 1) host-guest interactions between HCO(2) (-) and [Pd(3)(dppm)(3)(mu(3…
Electrochemically reduced titanocene dichloride as a catalyst of reductive dehalogenation of organic halides
Abstract We have studied a reaction between the reduced form of titanocene dichloride (Cp 2 TiCl 2 ) and a group of organic halides: benzyl derivatives (4-X C 6 H 4 CH 2 Cl, X = H, NO 2 , CH 3 ; 4-X C 6 H 4 CH 2 Br, X = H, NO 2 , PhC(O); 4-X C 6 H 4 CH 2 SCN, X = H, NO 2 ) as well as three aryl halides (4-NO 2 C 6 H 4 Hal, Hal = Cl, Br; 4-CH 3 O-C 6 H 4 Cl). It has been shown that the electrochemical reduction of Cp 2 TiCl 2 in the presence of these benzyl halides leads to a catalytic cycle resulting in the reductive dehalogenation of these organic substrates to yield mostly corresponding toluene derivatives as the main product. No dehalogenation has been observed for aryl derivatives. Base…
Evidence of intramolecular electron transfer between two metallic atoms in a bimetallic complex by electrochemical methods
The electrochemical properties of the monomeric complex [(η5-C5H5)(μ-η5:η1-C5H4(CH2)2P(C6H5)2TiCl2] 1 and the heterobimetallic complex [(η5-C5H5)(μ-η5:η1-C5H4(CH2)2P(C6H5)2TiCl2][RuCl2(C6H4(CH3)(C3H7))] 2 have been studied by cyclic voltammetry, controlled potential electrolysis and rotating disk electrode voltammetry. An unexpected electron transfer between the two heterobimetallic atoms has been observed. This transfer takes place via an intramolecular interaction, hence via a chloride bridge. Electrochemical simulation has been carried out to verify experimental results and to obtain the kinetic constant of the proposed square scheme.
Optical, Electrochemical, and Catalytic Properties of the Unsaturated Host Pd3(dppm)3(CO)2+and Pd4(dppm)4(H)2+2Clusters: An Overview
This paper presents an overview of the optical, photophysical, and photochemical properties including UV-visible and luminescence spectra in solution at 298 and 77 K, along with electrochemical, and catalytic behavior under reduction conditions (for both thermally and electrochemically assisted systems) of the tri- and tetranuclear Pd3(dppm)3(CO)2+ and Pd4(dppm)4(H)2+ 2 clusters (dppm=bis(diphenylphosphino)methane). This review is also complemented with relevant information about their syntheses, molecular and electronic structures supported from computer modeling, EHMO and DFT calculations, and their host-guest behavior with anions and neutral molecules, in relation with their observed rea…