Copper complexes carbonates

A substantial fraction of the named enzymes are oxido-reductases, responsible for shuttling electrons along metabolic pathways that reduce carbon dioxide to sugar (in the case of plants), or reduce oxygen to water (in the case of mammals). The oxido-reductases that drive these processes involve a small set of redox active cofactors , that is, small chemical groups that gain or lose electrons. These cofactors include iron porjDhyrins, iron-sulfur clusters and copper complexes as well as organic species that are ET active. 

The name xanthate, derived from the Greek "xanthos (meaning blond), was coined by Zeiss in 1815, because the copper complexes that he isolated had a characteristic yellow color (22). Xanthates are formed by nucleophilic addition of an alkoxide ion to carbon disulfide. 

Copper complexes of sparteine have also been used for the catalysis of asymmetric carbon-carbon bond formation. The copper-catalyzed reaction... 

For the spectrophotometric method, the evolved carbon disulfide is reacted with copper acetate and diethylamine to form a yellow copper complex which can be measured at 435 nm." The recoveries range between 70 and 90%. Reproducibility of this method was improved by reducing the time and the mode of sample pretreatment. Since all alkylenebis(dithiocarbamates) decompose to carbon disulfide by acid degradation, the above analytical methods are not selective. The result is the measured total residues of all alkylenebis(dithiocarbamates) related products. However, this method is recommended as standard method S15 for alkylenebis(dithiocarbamates) by the German Research Association. ... 

Many examples of asymmetric reactions catalyzed by copper complexes with chiral ligand systems have been reported. In particular, various copper-bis(oxazoline) catalysts (e.g., complexes (H) to (L), Scheme 48) are effective for carbon-carbon bond-forming reactions such as aldol,204 Mukaiyama-Michael, Diels-Alder,206 hetero Diels-Alder,207,208 dipolar cycloaddition,209,210... 

The reaction is believed to proceed via a c-allyl copper complex, in which the carbon-copper bond is formed at the "/-position, anti to the acetate leaving group. Reductive elimination of copper led to pure "/-substitution. With cyclic aliphatic allylic acetates, the selectivity is generally lower because the o-allyl copper complex can isomerize to the ir-allyl complex with loss of regioselectivity. 

The same workers have been able to isolate another similarly reversible copper(I) carbon dioxide carrier, Cu(02CO-r-Bu)(CN-<-Bu)3 (153). This complex forms in benzene solution at 10°C according to (70). 

A number of attempts have been made to understand the mechanism of the adsorption of chelates on oxide minerals. For instance, IR spectroscopic studies10 have indicated the presence of a basic monosalicylaldoximate copper complex as well as the bis-salicylaldoximate complex on the surface of malachite (basic copper carbonate) treated with salicylaldoxime. However, other workers4 have shown that the copper chelate is partitioned between the surface and dispersed within the solution, and that a dissolution-precipitation process is responsible for the formation of the chelate. Research into the chemistry of the interaction of chelating collectors with mineral surfaces is still in its infancy, and it can be expected that future developments will depend on a better understanding of the surface coordination chemistry involved. 

Heterocyclic thiones have been extensively studied because of their facility to yield coordination complexes. All the ligands contain thione and occasionally thiol (mer-capto) groups directly attached to the carbon atoms of heterocyclic molecules. They have been previously reviewed by Raper in 1985576, and very recently the same author has reviewed28 the copper complexes of heterocyclic thioamides and related ligands. 

Copper complex formation. Add a few drops of aqueous copper(n) sulphate solution to an aqueous solution of the amino acid. A deep blue coloration is obtained. The deep blue copper derivative may be isolated by boiling a solution of the amino acid with precipitated copper(n) hydroxide or with copper(n) carbonate, filtering and concentrating the solution. These blue complexes are coordination compounds of the structure ... 

Thus, the historical development of the chemistry of metallocorrolates until 1980 includes complexes with Cu2+, Ni2+, Pd2+, Fe3+, Co3+, Rh+, Mo5+ and Cr5+. The palladium complex has been isolated as its pyridinium salt since the neutral species was too unstable to be isolated or spectroscopically characterized [19]. The nickel complex was non-aromatic, with one of the potentially tautomeric hydrogens displaced from nitrogen to carbon in such a way as to interrupt the chromophore. In contrast the electronic spectrum of the paramagnetic copper complex is similar to those of the fully conjugated lV(21)-methyl derivatives [11],... 

An unusual reaction of a diazolium salt was reported during an attempt to form copper complexes of the NHC.100 The isolated products showed ring expansion of the carbene to form six-membered lactams. The authors verified the product by X-ray crystallography and independent synthesis. It is not clear where the extra carbon comes from. The authors consider a possible mechanism involving a carbene dimer formation, but point out that the carbenes are very hindered. Possible reaction with atmospheric carbon dioxide was not considered. Direct oxidation of the carbene to give a urea is also noted. 

Matyjaszewski [83] and Sawamoto [84] have found that a-halo ester chain ends can be used to generate radical ends reversibly by treatment with copper complexes or RuCl2/MeAl(ODBP)2 (ODBP=ortho-di-terf-butylphenoxy) (Scheme 33a,b). In his early work Sawamoto used carbon tetrachloride as initiator and Matyjaszewski, a-halo esters. Percec [85, 86] discovered that sulfonyl chlorides provided advantages over the other initiators and has used these initiators extensively in his research (Scheme 33c). ATRP has been fine-tuned by the three groups. The reader is directed to reviews by Matyjaszewski [87] and by Sawamoto [88]. 

Munakata and coworkers (1991) have recently characterised copper complexes with ethylene, acetylene, carbon monoxide and cod and studied the structures by X-ray analysis to investigate the bonding involved. Ethylene and acetylene are sideways bonded to copper (Fig. 5-18). Sigma donation from ethylene to copper predominates and ti-back donation is very weak. 

Copper complex-catalysed carboxylation polycondensation of dibromoalkanes with arenediyls in the presence of carbon dioxide [scheme (17)], although producing low molecular weight polyesters in moderate yields, also represents pioneering efforts in the use of carbon dioxide as a non-petroleum-based carbon source [5],... 

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