Copper carboxylates

Reaction of ot-diazoester 413 with several copper carboxylate catalysts afforded azocyclooctene 414 along with perhydropyrido[2,l-r ][l,4]oxazin-l-one 415 (Equation 77) <1996TL2165>. 

The molecular structures of these benzoates (4, 13, 16,18) are analogous to those of the copper carboxylates, including copper acetate, and our discussion makes use of the coordinate frames shown in Fig. 2. A full description of our approach (8, 7) to the magnetism of these systems is outside the scope of this review, but the following sketch illustrates some of the more important features. We consider a Hamiltonian acting upon the binuclear entity,... 

Structures of this type are especially abundant among copper carboxylate complexes ([537] and references cited therein). 

Later, in a collaborative work between Roland and Alexakis, it was found that the use of copper carboxylates as the copper source and Et20 as the solvent was critical to achieving high ee values (Eq. 30) [65]. In this study, several Ag/carbene complexes (20-24) were tested and found to produce significantly higher ee values than those in previous studies. Other Michael acceptors such... 

Cu(OTf)2 (2mol%) is required (Equation (110)).183 The nature of the copper salt strongly influences the enantio-selectivity, and copper carboxylates proved to be especially efficient (Equation (lll)).184b It has been applied for an enantioselective synthesis of prostaglandin E methyl ester (Equation (112)),185 and can be used for the performance of a highly regiodivergent and catalytic parallel kinetic resolution.186... 

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). 

Addition of alcohols to dimeric copper carboxylates can also produce hexanuclear complexes. Dissolving copper(II) acetate in 2-diethylaminoethanol, followed by addition of ether, produces... 

Bold and Balu escu (13) found the monomeric copper(II) a-bromostearate CuA2(HA)2 in the extraction of Cu(II) with a-bromostearic acid in benzene. The bromine in the a-position was said to prevent sterically the formation of dimeric copper(II) species, a-Bromocarboxylic acid, being stronger than the nonsubstituted hom-ologues, is anticipated to form a less stable copper carboxylate dimer. 

The synergistic effect of pyridine is larger for zinc than for copper. This will stem from the high stability of dimeric copper carboxylate in the organic phase. 

The influence of solvent on the extraction of copper(II) with decanoic acid in some alcohols (151) and ketones (153) was studied by Yamada and associates who found that in these solvents both the monomeric and dimeric Cu(II) decanoates were responsible for the extraction. In this case the dimerization of copper carboxylate was formulated as in Eq. (22) ... 

Mohamed and Galwey [71], in contrast, obtained evidence that copper underwent stepwise reduction when a was less than 0.5, from titration measurements of the copper(II) content (Cu " + KI — y in samples of partially decomposed salt. This is consistent with the behaviour foimd for other copper carboxylates [72]. Moreover, it was shown that the reactivities of both (Cu " and Cu" ) oxalates were similar and reactions overlapped. In agreement with the previous study [69], ur-time curves for the overall decomposition of copper(II) oxalate were sigmoidal and, in this slightly higher temperature interval (515 to 550 K), was increased to 180 7 kJ mol". ... 

Figure 81 Schematic of the arrangement of copper carboxylates bridged by heterocyclic ligands.

Dimeric cyclopentadienyl vanadium(iii) carboxylates, Cp2V2(C02R)4, (R = Me, Ph, or furanyl) are exchange-coupled with large coupling constants (J 200 cm similar to those for the bridged copper carboxylates (see Vol. 5 p. 41). A... 

TV/Tetal surfaces often have adverse catalytic effects on the rates of oxidative degradation (by molecular oxygen) of polymers, particularly polyolefins. Previous papers in this series have shown for the specific case of the 02/polyethylene/copper system between 40 °C and 90 °C that copper carboxylate salts, initially formed at the interface, are re-... 

Solubilities. Extrapolation from Liquid Phase. Solubilities of various copper carboxylate salts in pure octane and hexadecane at 90 °C are shown in Figure 2. The solubility of the octanoate salt is quite high but cannot be measured accurately because of experimental difficulties (discussed above). If one applies regular solution theory (6) with the assumption that the excess free energies of mixing (or alternatively the solvent-solute interaction parameters) are equal for a particular salt in an alkane medium, then the following equation can be derived (7) ... 

Table I. Diffusion of Copper Carboxylates into Polyethylene0...

Mechanisms of Inhibition. A number of diffusion experiments were run in which various concentrations of N,N -diphenyloxamide (< 0.1 wt % or 3 X 10 3 mol/kg) were loaded in the polyethylene films. The great majority of runs showed essentially no effect of the additive on the diffusion rate, nor were any unusual surface phases reproducibly noted (see Tables I and III for typical results). Previous work (2,5) has indicated that the inhibition effect of a deactivator may be caused by both surface and homogeneous scavenging effects. On the basis of the present results we conclude that the major effect of the deactivator involves surface-interface reactions rather than bulk scavenging mechanisms. The former may consist of poisoning of active surface sites on the Cu20/Cu film (13) and/or conversion of an interfacial copper carboxylate layer to a relatively inert phase of insoluble copper complex (5). Work is in progress to separate these mechanisms further. 

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