Copper quinoline complex, formation

The second order dependence In the benzene ME was ascribed to the equilibrium formation of a Cu(II) - quinoline complex, which is also in equilibrium with a "slttlng-atop complex" (SAT) with the porphyrin. The rate controlling step is then the loss of a proton from the SAT. It is also Implicitly assumed that the association constant of the copper-quinollne complex is sufficiently small so that the stoichiometric concentrations of both the metal ion and base may be employed in the rate equation. 

The formation of transient organocopper compounds has been inferred in many decarboxylations of copper(I) carboxylates or copper-carboxylic acid systems 20, 33, 47, 56, 211, 213, 215, 279). Only one copper compound has been isolated, so far. Tbe decarboxylation of copper(I) pentafluorobenzoate in quinoline proceeds smoothly at 60°C to give a pentafluorophenylcopper-quinoline complex 33, cf. 254). 

An organocopper intermediate was detected by Lewin and Cohen in the reaction of / -iodotoluene with copper in a good complexing solvent (184). Analysis of protonated aliquots from a reaction performed in quinoline indicated an accumulation of />-tolylcopper to a maximum of 43% after 95 hours, at which point the iodide was consumed, and then a slow decrease to by dimerization. Other experiments also indicate the formation of an arylcopper compound in Ullmann reactions (127,141, 210). The isolation of deuterated products, presumably from the decomposition of an intermediate organocopper species in deuterated benzene and cyclohexane, suggested decomposition to free radicals (127). Decompositions of certain o-haloarylcopper intermediates by a benzyne mechanism cannot be totally excluded. The formation of a dichlorobenzene and by-products such as dibenzofuran and triphenylene from only the ortho isomer of the chloroiodobenzenes in Ullmann coupling reactions (210)... 

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