Homolytic cleavage of the O-Cu(ii) bond: XAFS and EPR spectroscopy evidence for one electron reduction of Cu(ii) to Cu(i).

The investigation into the active copper(i) catalysts from copper(ii) precursors has become a fundamental and important task in copper catalysis. In this work, we demonstrate that the (t)BuO(-) anion serves not only as a base but also as a mediator to promote the reduction of Cu(ii) to Cu(i) in copper catalysis. XAFS and EPR spectroscopy evidence the [Cu(O(t)Bu)3](-) ate complex as the key intermediate which undergoes homolytic-cleavage of the O-Cu(ii) bond generating [Cu(O(t)Bu)2](-) ate complex.

Direct observation of reduction of Cu(II) to Cu(I) by terminal alkynes.

X-ray absorption spectroscopy and in situ electron paramagnetic resonance evidence were provided for the reduction of Cu(II) to Cu(I) species by alkynes in the presence of tetramethylethylenediamine (TMEDA), in which TMEDA plays dual roles as both ligand and base. The structures of the starting Cu(II) species and the obtained Cu(I) species were determined as (TMEDA)CuCl2 and [(TMEDA)CuCl]2 dimer, respectively.

A carbon-nanotube-supported graphene-rich non-precious metal oxygen reduction catalyst with enhanced performance durability.

A non-precious metal catalyst for oxygen reduction in acid media, enriched in graphene sheets/bubbles during a high-temperature synthesis step, has been developed from an Fe precursor and in situ polymerized polyaniline, supported on multi-walled carbon nanotubes. The catalyst showed no performance loss for 500 hours in a hydrogen/air fuel cell. The improved durability is correlated with the graphene formation, apparently enhanced in the presence of carbon nanotubes.

Labile Cu(I) catalyst/spectator Cu(II) species in copper-catalyzed C-C coupling reaction: operando IR, in situ XANES/EXAFS evidence and kinetic investigations.

Insights toward the Cu-catalyzed C-C coupling reaction were investigated through operando IR and in situ X-ray absorption near-edge structure/extended X-ray absorption fine structure. It was found that the Cu(I) complex formed from the reaction of CuI with ß-diketone nucleophile was liable under the cross-coupling conditions, which is usually considered as active catalytic species. This labile Cu(I) complex could rapidly disproportionate to the spectator Cu(II) and Cu(0) species under the reaction conditions, which was an off-cycle process. In this copper-catalyzed C-C coupling reaction, ß-diketone might act both as the substrate and the ligand.