Reaction of Electrogenerated Ligand-Reduced Nickel Salen with Benzyl Bromide, 1-Bromomethylnaphthalene, and α-Bromodiphenylmethane: A Study of Steric Effects

Abstract

Cyclic voltammetry (CV) and controlled-potential electrolysis (CPE) were employed to examine the reactions of electrogenerated ligand-reduced nickel(II) salen with benzyl bromide, 1-bromomethylnaphthalene, and α-bromodiphenylmethane. Cyclic voltammograms for nickel(II) salen in the presence of benzyl bromide or 1-bromomethylnaphthalene exhibit characteristic features for the catalytic reduction of substrates involving radical intermediates. Bulk electrolyses of benzyl bromide and 1-bromomethylnaphthalene at carbon cathodes catalyzed by nickel(II) salen were also carried out at selected potentials to afford various products. These results were compared with similar reaction involving 1-bromooctane as the substrate. Further comparison of the CVs for nickel(II) salen before and after reactions with the four different organic halides reveals that the steric effect could play an important role in the corresponding nucleophilic attack of the substrates by ligand-reduced catalyst (a radical−anion), which follows the sequence of 1-bromooctane > benzyl bromide > 1-bromomethylnaphthalene > α-bromodiphenylmethane in terms of reaction efficiency. Moreover, theoretical calculations using density functional theory were carried out to establish a proposed mechanism for the electrochemical reactions on the basis of previous and current studies.

Analyzing mechanisms in Co(i) redox catalysis using a pattern recognition platform

“…Multiple reports harness this electrochemical strategy to reduce aliphatic halides with transition metal complexes owing to the importance of the alkyl radical generated for alkylation and cross-coupling reactions. 2,3 However, it remains challenging to identify the inner- or outer-sphere nature of the reduction of the carbon–halogen bond by the metal, 4 a differentiation that is key to understanding directions for optimization of the redox catalyst.…”

Benzylic C(sp3)–H Bonds Play the Dual Role of Starting Material and Oxidation Inhibitor for Hydrazides in the Electrochemical Synthesis of Hydrazones

“…As shown in Figure S4, the electrochemical oxidation peak of benzyl alcohol for conversion to benzaldehyde appears as previously reported. , Also, in the blank sample, we did not observe any oxidation peak near 2 volts; thus, the oxidation peak near 2 volts can be attributed to benzyl alcohol. Similarly, in CVs of aryl halides, an oxidation peak appears in the same voltage associated with the electrochemical generation of benzyl alcohol on the electrode surface. , Further, we identified the oxidation peak of benzyl alcohol in the CV of toluene. − The cyclic voltammogram of tosyl hydrazide was first recorded in water. However, due to its low solubility in water, the oxidation peak was not clearly observed.…”

“…Similarly, in CVs of aryl halides, an oxidation peak appears in the same voltage associated with the electrochemical generation of benzyl alcohol on the electrode surface. 50,51 Further, we identified the oxidation peak of benzyl alcohol in the CV of toluene. 52−55 The cyclic voltammogram of tosyl hydrazide was first recorded in water.…”

Synthesis and Characterization of Novel Non-conjugated hyperbranched polysiloxanes with AIE Effect

“…The specific scan results are shown in Figures 7(c),(d).With the increase of the wavelength of the excited light, the peak position of the emission spectrum has an obvious red-shifted, this characteristic is mainly caused by the inhomogeneity of molecular structure and the broad distribution of molecular weight. 18 And the fluorescence intensity has also changed obviously, P 1 reaches the maximum fluorescence intensity when the excitation wavelength is 300 nm, and the overall trend is to increase at first and then decrease. The fluorescence intensity of P 2 decreases monotonously in the test interval.…”

“…Because the -OH of o-diol can theoretically undergo transesterification condensation, the intramolecular structure becomes more crowded and the overall molecular configuration tends to be stable, with the progress of the reaction, it is more and more difficult for the molecule to further polycondensation. [15][16][17][18] Therefore, the polymer P 2 with higher steric hindrance is difficult to further combine with other polymer molecules. This effect will also affect the formation of other conjugated systems within or between molecules, for example, π-π conjugation, which also has a great influence on the luminescence effect.…”