Copper solvation

Use of Centered Period. A centered period is used to denote water of hydration, other solvates, and addition compounds for example, CUSO4 SHjO, copper(II) sulfate 5-water (or pen-tahydrate). 

Organolithium compounds can add to a, (3-unsaturated ketones by either 1,2- or 1,4-addition. The most synthetically important version of the 1,4-addition involves organocopper intermediates, and is discussed in Chap 8. However, 1,4-addition is observed under some conditions even in the absence of copper catalysts. Highly reactive organolithium reagents usually react by 1,2-addition, but the addition of small amounts of HMPA has been found to favor 1,4-addition. This is attributed to solvation of the lithium ion, which attenuates its Lewis acid character toward the carbonyl oxygen.111... 

Solvation of the divalent copper ion requires some special remarks. In solid state hexa-coordinate Cu2+ shows Jahn-Teller distortion the metal-ligand bonds of four ligands in the equatorial plane are shorter... 

Solutions of metals in liquid ammonia conduct electricity better than any salt in any liquid and the main current carrier is the solvated electron. This implies that the electron gets free from the parent metal atom sodium and occupy cavities in the liquid. At higher alkali metal concentrations the solutions are copper coloured and have a metallic lustre and all electrical conductivity studies indicate that they are very similar to liquid metals. 

The behavior of metal ions in reversed micelles may be more interesting, since the reversed micelle provides less solvated metal ions in its core (Sunamoto and Hamada, 1978). Through kinetic studies on the hydrolysis of the p-nitrophenyl ester of norleucine in reversed micelles of Aerosol OT and CC14 which solubilize aqueous cupric nitrate, Sunamoto et al. (1978) observed the formation of naked copper(II) ion this easily formed a complex with the substrate ester (formation constant kc = 108—109). The complexed substrate was rapidly hydrolyzed by free water molecules acting as effective nucleophiles. 

Association constants for salts of copper, silver, and thallium appear to reflect solvation in a fairly simple way. For example, of the perchlorate salts, only those of the poorly solvated thallium ion show association. 

After a period of time, a steep concentration gradient forms around the electrode since the solution immediately adjacent to the HMDE is entirely depleted of Cu. In response, (solvated) Cu analyte ions from the bulk of the solution will diffuse toward the HMDE and themselves be reduced. After a further period of time, all of the copper ions will have been removed from solution and accumulate on the surface of the drop (Figure 5.6(b)). Here, we say that we have exhausted the solution. ... 

Other aspects of solvation have included the use of surfactants (SDS, CTAB, Triton X-100), sometimes in pyridine-containing solution, to solubilize and de-aggregate hemes, i.e., to dissolve them in water (see porphyrin complexes, Section 5.4.3.7.2). An example is provided by the solubilization of an iron-copper diporphyrin to permit a study of its reactions with dioxygen and with carbon monoxide in an aqueous environment. Iron complexes have provided the lipophilic and hydrophilic components in the bifunctional phase transfer catalysts [Fe(diimine)2Cl2]Cl and [EtsBzNJpeCU], respectively. 

Alkylcadmium alkoxides, 11 399-400 alkylperoxides, 11 399-400 anions, 11 370-371 halides, 11 377 solvated, 11 392-394 Alkylcalcium halides, solvated, 11 390 Alkyl complexes, osmium, 37 239-242 Alkyl copper compounds, 17 140, 142, 143 Alkyl derivatives, phosphoniuilic halides and, 1 363... 

Tab. 1 Potential values for solvated copper ion in various solvents (all values in V versus aqueous SHE)...

Although the values of T igp are relatively large in water and in methanol, a finite amount of Cu(I) exists in any Cu(II) solution that is in contact with metallic copper. In fact, the molecularity associated with dictates that the fraction of copper in solution in the form of Cu(I) increases as the total concentration of solvated copper ion decreases. Thus, at micromolar levels in water, for example, the two oxidation states can be maintained in essentially equal amounts. In acetonitrile, the equilibrium for reaction 5 lies far to the left so that solvated Cu(I) is readily generated by placing copper metal in contact with a Cu(II) solution (conproportionation). As a consequence, the Cu(I) salt, [Cu(CH3CN)4]C104, is easily prepared [18] and is temporally stable. 

The standard potential values for solvated copper, as cited in Table 1, represent thermodynamic values in terms of activities. In practice, relatively high ionic strengths (>0.01 M) are used in most electrochemical measurements so that the... 

In the presence of complexing agents, the potential values are usually reported in terms of the concentrations of the complexed species rather than the concentrations of the solvated copper ions ... 

If the fraction of uncomplexed copper ion is relatively small in both oxidation states, the relationship between the concentration potential, 21, for any Cu(II/I) complex system and that for the solvated Cu(II/I) couple, can be represented as ... 

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