Rhenium complexes kinetic studies

A detailed kinetic study of the water exchange of the dioxo complex of rhenium(V) (206), however, gave very valuable information about the relative reactivities of the aqua and hydroxo complexes toward substitution The ratio of the water exchange rate of the aqua and hydroxo complexes of rhenium(V) was determined to be about 50. The 0 NMR studies of these complexes demonstrate its effectiveness for the characterization of these type of complexes in aqueous solutions (207). 

The two seminal contributions of Mimoun and Sharpless laboratories led to a controversy on the reaction mechanism that was lasting longer than for two decades [82] and expanded to the olefin epoxidation with other metal peroxo complexes, in particular those of rhenium. Kinetic studies of Al-Ajlouni and Espenson [83,84] on the MTO-catalyzed olefin epoxidation with H2O2 revealed the importance of both mono- and diperoxo species in the catalytic process as well as substituent effects on reaction rates, but the molecular mechanism remained uncertain. 

Kinetic studies on the photogeneration of CO using [Re(bpy)(CO)3Cl] in a DMF/TEOA solution shows a linear relationship between formation of CO and time when excess chloride anions are present [19]. A 14 % quantum yield has been determined. The absence of excess Cl lowers the CO generation (8.7 % quantum yield), due to the formation in solution of a formato-rhenium (I) species as observed by NMR, FT-IR spectroscopies and also confirmed by X-ray crystal stracture determination [70]. This new complex could be formed by insertion of CO2 into a hydrido-rhenium (I) species (eq. 11) [71], formed as a by-product during the process. 

Technetium complexes with dtpa, dmsa, or mdp (methylene diphos-phonate) can be prepared by exchange reactions of the respective rhenium complexes with pertechnetate. Despite the complication that redox as well as substitution is involved here, rates correlate with metal-ligand bond strengths. A detailed kinetic study of these reactions would be welcome. Another type of ligand exchange reaction where kinetic studies are needed is the similar situation encountered in the preparation of technetium(III), (IV), or (V) complexes by reduction of pertechnetate with tin(II) complexes of the respective ligands. 

Kinetic studies on the reactions of primary aliphatic amines with manganese and rhenium complexes of the type trans- M CO)J-, (L = tertiary phosphine ligand) show that the reaction... 

In the case of technetum, this is the most practically used element among non-/ radioactive ones for medical and technical purposes [283], so the permanent interest in its coordination chemistry (in particular, the structural aspect of its compounds [547] and kinetics of substitution reactions [548]) is not surprising [549]. The theoretical interest in Tc is provoked, in particular, by the fact that this is a rhenium analogue. This element (Re) forms multiple metal-metal bond complexes and has been studied intensively in order to achieve a better understanding of the physical and chemical properties of multiple bonds between metal atoms [533],... 

The formation and growth of an electrodeposited phase is a complex process and many methods have been used to study it. The main feature of our laboratory scientific investigations is intensive study of the structure of poly- and monocrystalline refractory metal deposits, such as tungsten, molybdenum, rhenium, iridium, ruthenium and etc. We have shown that the structure of electrodeposited layers directly depends on the conditions of electrolysis [1]. Moreover this structures a most sensitive instrument to study the properties of our electrolyte, including purity of the melt, ion composition, dissipative ability, and kinetic parameters of electrodeposition. It was established that the reduction of oxygen in a chloride melt changed the direction of molybdenum growth texture from <111> to <001 > direction with a fine structure of epitaxial layers [2]. 

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