Copper chloride with carboxylate ions

Oxidation of C—bonds by copper ion catalyzed reaction with an organic peroxy ester (the Kha-rasch-Sosnovsky reaction) was at one time very popular for allylic oxidation and has been thoroughly reviewed. The reaction is usually carried out by dropwise addition of peroxy ester (conunonly r-butyl peracetate or r-butyl perbenzoate) to a stirred mixture of substrate and copper salt (0.1 mol % commonly copper(I) chloride or bromide) in an inert solvent at mildly elevated temperature (60-120 C). The mechanism involves three steps (i) generation of an alkoxy radical (ii) hyttogen atom abstractitm and (iii) radical oxidation and reaction with carboxylate anion (Scheme 11). 

The third spectrum (c) was obtained from copper chloride dissolved in hydrated trioctylammonium 2-ethylhexanoate in toluene (the mixed extractant). It has a broad maximum absorbance at 725 nm, its symmetry is similar to that of copper carboxylate, and bonding of copper can be assumed to occur via the carboxylic oxygens in a manner similar to that of the dimer. Spectrum (c) bears an even greater similarity to that of the Cu-EDTA complex, the maximum absorption being at 734 nm, and which is known to have a distorted octahedral structure [12]. It is easy to convert the carboxyT ate dimer into a mixed complex. On adding trioctylamine to copper carboxylate, the maximum absorption shifts gradually from 680 to 725 nm. It is assumed that the addition of the amine converts the dimer into a monomer in which copper is bound to four monomeric carboxylic ligands and two amine molecules are located farther away in an axial position. It is of interest to note that the anion of the salt coextracted with the metal ion has no effect on the visible spectrum i.e., it is immaterial whether copper fluoride, chloride, or nitrate is extracted they all have the same spectrum. 

---