Herein, we present a detailed kinetic and thermodynamic analysis of the anodic allylic esterification of alkenes as well as the bulk application of the anodic amination and esterification of nonactivated alkenes catalyzed by diselenides. The electrochemical study led to a comprehensive picture of the coupled electrochemical and chemical reaction steps. Cyclic voltammetry measurements are consistent with a bimolecular step after initial electrochemical 1e − oxidation of the diphenyl diselenide catalyst, 1a, and therefore we postulate a dimerization of the cation, which reacts very rapidly with the alkene, forming the addition product, i.e. the selenolactone 2a. Subsequent electrochemical oxidation of 2a occurs at a slightly higher potential than initial oxidation of 1a. The second oxidation is also followed by a bimolecular process and we hypothesize a dimerization of the cation, which finally eliminates 1a and protons in the rate-determining step, forming the product. Electrochemical analysis of various catalysts, i.e. nonsterically demanding diaryl diselenides with electron withdrawing and donating substituents, revealed that the oxidation potential of the catalyst and the intermediate can be readily tuned by the substituents, thus, prospectively allowing for a wide application of olefinic and nucleophilic substrates. The substituent pattern at the alkene has a smaller influence on the redox potential of the adduct. Controlled potential electrolysis experiments employing different nucleophiles proved that the reaction can be run electrochemically. The functionalization of unactivated alkenes with N-and O-nucleophiles was successfully demonstrated in several bulk electrolysis experiments, and the products were isolated in good yields.
We have used a combination of electrospray ionization mass spectrometry and electrical conductivity measurements to analyze solutions of the Gilman cuprates LiCuR2·LiX, with R=Ph, Bu and X=Cl, Br, I, in tetrahydrofuran and have compared our findings with previous results on cyanocuprates LiCuR2·LiCN. Among the various polynuclear organocuprate ions observed, Li2Cu3Ph6(-), LiCu4Ph6(-), and Cu5Ph6(-) are of particular interest because aggregates of the same composition are known from X-ray crystal structures. Control experiments have indicated that the polynuclear organocuprate anions detected in solution are indeed identical to those formed in the solid state. As abundant ions of the type Li2Cu3R6(-) are found in solutions of Gilman cuprates and cyanocuprates alike, their possible involvement in organocuprate reactions should be considered. For comparison, we have also included solutions of LiCu(R)I, LiCuX2·LiX, LiCuX2, and CuCN·2LiX in the present study.
Herein, we present the application of a copper(II) complex, [CuL 1 ](ClO 4 ) 2 (L 1 : 1,3-bis{[(1-methyl-1H-imidazol-2yl)methyl]amino}propan-2-ol) (1), as a catalyst in the electrochemically driven hydrogen evolution reaction (HER) in buffered water and standardised artificial seawater. Potentiometric titrations revealed that a [Cu II HL 1 ] 3+ species is the main species in aqueous solutions at pH 4 to 8. Complex solutions of 1 are active in the electrochemical HER at solutions at pH 4 to 8, yet, the active species is different depending on the reaction [a]
Herein, we present the thermodynamic analysis of a cobalt complex with a new pentadentate N-donor ligand bearing four ionisable pyrazole protons in aqueous solution. A detailed analysis of the Co II complex [Co(L)(X)] +/2+ in the solid state revealed that the 6 th ligand X at the metal centre depends on the cobalt source employed. Small anions such as Cland NO 3 coordinate to the metal ion, while larger anions that are weaker hydrogen-bond acceptors are found in the second coordination sphere of the complex and instead a solvent molecule coordinates. However, in aqueous KCl solution, the sixth ligand [a]
Herein, we present the synthesis of a cobalt complex with a pentadentate ligand platform and its application in the electrochemical hydrogen evolution reaction (LCF3=2,6‐bis(methoxybis(4‐trifluormethyl‐1H‐imidazol‐2‐yl)methyl)pyridine). The complex is active in neutral to acidic solvent mixtures containing 50 % water. Electronic tuning in the ligand backbone, that is introduction of electron‐withdrawing CF3‐groups, shifts the onset potential of the catalytic wave to less negative potentials. NMR and UV/Vis studies indicate that the CoIII complex is deprotonated twice in the ligand backbone under neutral conditions. Reduction is accompanied by protonation, as indicated by pH‐dependent CV measurements, and the CoI state initiates catalysis. The result suggests that the pentadentate ligand is an ideal platform for cobalt catalysts in the oxidative and reductive water splitting reaction.
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