Pure acetonitrile as solvent for the efficient electrochemical conversion of aryl bromides in organozinc species and their coupling reaction with acetyl chloride

Valve turning towards on-cycle in cobalt-catalyzed Negishi-type cross-coupling

Ligands and additives are often utilized to stabilize low-valent catalytic metal species experimentally, while their role in suppressing metal deposition has been less studied. Herein, an on-cycle mechanism is reported for CoCl2bpy2 catalyzed Negishi-type cross-coupling. A full catalytic cycle of this kind of reaction was elucidated by multiple spectroscopic studies. The solvent and ligand were found to be essential for the generation of catalytic active Co(I) species, among which acetonitrile and bipyridine ligand are resistant to the disproportionation events of Co(I). Investigations, based on Quick-X-Ray Absorption Fine Structure (Q-XAFS) spectroscopy, Electron Paramagnetic Resonance (EPR), IR allied with DFT calculations, allow comprehensive mechanistic insights that establish the structural information of the catalytic active cobalt species along with the whole catalytic Co(I)/Co(III) cycle. Moreover, the acetonitrile and bipyridine system can be further extended to the acylation, allylation, and benzylation of aryl zinc reagents, which present a broad substrate scope with a catalytic amount of Co salt. Overall, this work provides a basic mechanistic perspective for designing cobalt-catalyzed cross-coupling reactions.

Recent Advances in Metal-Catalyzed, Electrochemical Coupling Reactions of sp2 Halides/Boronic Acids and sp3 Centers

Traditionally, metal-catalyzed cross-coupling reactions rely on stable but expensive metals, such as palladium. However, the recent development of synthetic organic electrochemistry allows for in situ redox manipulations, expanding the use of cheaper, abundant and sustainable metals, such as nickel and copper as efficient cross-coupling catalysts. This short review covers the recent advances in metal-catalyzed electrochemical coupling reactions, with a focus on reactions of sp2 electrophiles and nucleophiles with sp3 coupling partners to form both C–C and C–heteroatom bonds.

1 Introduction

2 Nickel-Catalyzed C–C sp2–sp3 Coupling Reactions

3 Coupling of Aryl Groups with Heteroatomic Nuclei

4 Conclusion

The influence of inorganic anions on photocatalytic CO2 reduction

The influence of common inorganic anions on photocatalytic CO₂ reduction has been investigated in a semiconductor/complex (CdS/Co(bpy)₃Cl₂) system.

Synthesis by a Cost-Effective Method and Electroluminescence of a Novel Efficient Yellowish-Green Thermally Activated Delayed Fluorescent Molecule

A new thermally activated delayed fluorescent molecule, TRZ 3(Ph-PTZ), containing three phenothiazines as donor units and a 2,4,6-triphenyl-1,3,5-triazine as the acceptor unit was synthesized using a simple cost-effective method based on a cobalt catalyzed cross-coupling. This compound was tested in organic light-emitting diodes and was found to show superior yellowish-green electroluminescence performance with a maximum external quantum efficiency of 17.4% and a maximum luminance value of 7430 cd/m².

Improving the photocatalytic reduction of CO2 to CO for TiO2 hollow spheres through hybridization with a cobalt complex

A chemical system with enhanced efficiency for electron generation and transfer was constructed by the integration of TiO₂ hollow spheres with [Co(bipy)₃]²⁺. The introduction of [Co(bipy)₃]²⁺ remarkably enhances the photocatalytic activity of pristine semiconductor photocatalysts for heterogeneous CO₂ conversion, which is attributable to the acceleration of charge separation. Of particular interest is that the excellent photocatalytic activity of the heterogeneous catalysts can be utilised for a universal photocatalytic CO₂ reduction system. Yields of 16.8 μmol CO and 6.6 μmol H₂ can be obtained after 2 h of the photoredox reaction, and the apparent overall quantum yield was estimated to be 0.66% under irradiation at λ = 365 nm. The present findings clearly demonstrate that the integration of electron mediators with semiconductors is a feasible process for the design and development of efficient photochemical systems for CO₂ conversion.

A chemical system with enhanced efficiency for electron generation and transfer was constructed by the integration of TiO₂ hollow spheres with [Co(bipy)₃]²⁺.

A zinc porphyrin-based molecular probe for the determination of contamination in commercial acetonitrile

A zinc porphyrin-based receptor containing four triazole groups at the ortho-position of each phenyl group (1) was utilized as a useful probe for the determination of contaminants in acetonitrile (MeCN). Through the simple observation of the absorption spectrum of 1 in MeCN, the cyanide contamination concentration could be directly determined.

New chemical synthesis of functionalized arylzinc compounds from aromatic or thienyl bromides under mild conditions using a simple cobalt catalyst and zinc dust

A new chemical method for the preparation of arylzinc intermediates is described in acetonitrile, on the basis of the activation of aryl bromides by low-valent cobalt species arising from the reduction of cobalt halide by zinc dust. This procedure allows for the synthesis of a variety of functionalized aryl- and thienylzinc species in good to excellent yields. The versatility and the simplicity of that original method represent an alternative to most known procedures.