Copper electronic effects

Reaction 31 appears to be little affected by substituent electronic effects or by steric effects of either sulfonyl chloride or styrenes. Treatment of /5-chlorosulfones with triethylamine in benzene affords the corresponding a, /5-unsaturated sulfones in excellent yield. The copper-catalyzed addition of sulfonyl iodides to simple and cyclic alkenes has also been exploited76. 

Theoretical calculations have been carried out on a number of zinc-containing enzymatic systems. For example, calculations on the mechanism of the Cu/Zn enzyme show the importance of the full protein environment to get an accurate description of the copper redox process, i.e., including the electronic effects of the zinc ion.989 Transition structures at the active site of carbonic anhydrase have been the subject of ab initio calculations, in particular [ZnOHC02]+, [ZnHC03H20]+, and [Zn(NH3)3HC03]+.990... 

A comparison of the rate constants for the [Cun(FLA)(IDPA)]+-cata-lyzed autoxidation of 4/-substituted derivatives of flavonol revealed a linear free energy relationship (Hammett) between the rate constants and the electronic effects of the para-substituents of the substrate (128). The logarithm of the rate constants linearly decreased with increasing Hammett o values, i.e. a higher electron density on the copper center yields a faster oxidation rate. 

Tanner et al. (58) investigated the asymmetric aziridination of styrene using bis(aziridines) such as 85. Low induction is observed with these ligands, Eq. 64. A significant electronic effect was noted with the p-fluoro-phenyl substituted bis(az-iridine) 85c (59). A binaphthyl-derived diamine was used as a ligand for the copper-catalyzed aziridination of dihydronaphthalene (81). The product was formed in 21% ee and 40% yield, Eq. 65. Other structurally related ligands proved to be less selective in this reaction. 

Mulliken also studied other band spectra of diatomic molecules. Only one such study will be mentioned here and that is his study of copper iodide (Mulliken 1925c), where he examined the copper isotope effect. Mulliken s pioneering work was followed by more papers on isotope effects on electronic spectra (visible and UV) which will not be detailed here. Many of these papers deal with diatomics since the theory of such spectra is much better understood than that for general polyatomic systems. Further discussion of isotope effects on spectra will be mainly restricted to their use in the discovery of less abundant isotopes. 

There is still doubt over the mechanism of this reaction, although polarization of the C—Br bond and chelation of the metal play important roles. It is clear that Cu(I) is the effective catalyst and a tetrahedrally coordinated copper complex (489) can be envisaged to account for the steric and electronic effects observed in these reactions. 

The interesting observation, unexpected on the basis of limited published data of a tetradentate derivative of L8 249 250 but in full agreement with the MM analysis is that the stabilities do not follow the usual Irving-Williams behavior (Co2+ < Ni2+ < Cu2+ > Zn2+)251 252 but that L4 is zinc(II)-selective. This was interpreted as a combination of the steric effects discussed above, electronic effects (distorted coordination geometries, misdirected valences), which are unimportant for the d10 ion zinc(II), in contrast to copper(II), especially nickel(II) and smaller metal ions such as cobalt(III).78... 

These and other observations (51-55) suggest that the tendency towards hydroxylation in these kinds of chemical systems is very sensitive to electronic effects, as well as copper chelation and peroxide proximity and orientation toward xylyl substrate. This view is supported by observations involving an unsymmetrical system, [Cu2(UN)]2+ (56), an analogue of [Cu2(XYL)]2+ (6)... 

A large positive shift (0.21 V) in the Ered value of the Cu —Zn complex is observed as compared to the corresponding Cu(ll) mononuclear complexes (Fig. 56) (154). Such a positive shift of the E ed value of the Cu —Zn complex can be ascribed to the electronic effect of the imidazolate bound Zn(ll) ion, which leads to a decrease in the electron density on the copper ion. This result indicates... 

Thus, it is clear that the surrounding protein and solvent have an important influence on the structure and spectra of the copper sites. For reduction potentials and outer-sphere reorganisadon energies, these effects are of the same magnitude as the electronic effects and therefore essendal. We have used three different levels of approximadons for these effects an array of point charges, condnuum models, and combined quantum chemical and classical simuladons. We andcipate that this will be an area of intensive development in the future. 

For styrene-based random copolymers, functional groups can be introduced into the polymer chains via copolymerization with functional styrene derivatives, because the electronic effects of the substituents are small in the metal-catalyzed polymerizations in comparison to the ionic counterparts. Random copolymer R-6 is of this category, synthesized from styrene and />acetoxystyrene.372 It can be transformed into styrene// -vinylphenol copolymers by hydrolysis.380 The benzyl acetate and the benzyl ether groups randomly distributed in R-7 and R-8 were transformed into benzyl bromide, which can initiate the controlled radical polymerizations of styrene in the presence of copper catalysts to give graft copolymers.209 Epoxy groups can be introduced, as in R-9, by the copper-catalyzed copolymerizations without loss of epoxy functions, while the nitroxide-mediated systems suffer from side reactions due to the high-temperature reaction.317... 

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