Metal-aryl compounds, oxygenation

Despite its synthetic importance, the mechanism of the copper-quinoline method has been studied very little, but it has been shown that the actual catalyst is cuprous ion. In fact, the reaction proceeds much faster if the acid is heated in quinohne with cuprous oxide instead of copper, provided that atmospheric oxygen is rigorously excluded. A mechanism has been suggested in which it is the cuprous salt of the acid that actually undergoes the decarboxylation. It has been shown that cuprous salts of aromatic acids are easily decarboxylated by heating in quinohne and that aryl-copper compounds are intermediates that can be isolated in some cases. Metallic silver has been used in place of copper, with higher yields. ... 

K-Sites on Carbon Surface as Anchors for Metal Nanoparticles Noble metals, both in zerovalent and in ionic states (in particular in the low-oxidation state), are prone to form stable 7r-complexes with multiple C-C bonds of organic compounds [53]. The stability of the 7r-complexes increases if the ligand contains electron acceptor groups (for example, oxygen-containing or aryl) in close proximity of the >C—C< bond. 

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