Copper complexes dioxide

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. 

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. 

Van den Berg, C.M.G. and Kramer, 3.R., 1979. Determination of complexing capacities of ligands in natural waters and conditional stability constants of the copper complexes by means of manganese dioxide. Anal. Chim. Acta, 106 113-120. 

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],... 

Details of the preparation of methyl (-)-cis-chrysanthemate from (+)-car-3-ene have appeared (Vol. 5, p. 15 is misleading).159 Both ( )-cis- and (+)-trans-chrysanthemic acids are again reported from (+)-car-3-ene via ozonolysis 160 this work is very similar to that reported (Vol. 5, p. 15) by Sukh Dev and illustrates the lamentable delay from receipt to publication in some journals. The decomposition of ethyl diazoacetate in 2,5-dimethylhexa-2,4-diene in the presence of the chiral copper complex (72) leads to cis- and frvms-chrysanthemic acids in 60—70% optical yield the degree of asymmetric induction is dependent upon the steric bulk of R1 and R2 in (72).161 cis-Chrysanthemic acid has also been prepared from 3,3-dimethylcyclopropene, isoprene, and 2-methylpropenylmagnesium bromide followed by treatment with carbon dioxide.162... 

Similarly, adenosine, inosine and 2 -deoxyinosine have been converted into their 8-trifluoromethyl derivatives by reaction with the copper complex formed from trifluoromethyl iodide and copper in hexamethylphosphorotriamide (80JCS(P1)2755). iV -Trifluoromethyl-purine riboside was also produced from 6-chloropurine riboside. Recently, guanosine has been shown to give the C (8)-substituted derivative (148) by reaction with a benz[a]anthracene 5,6-dioxide at pH 9.5 over 4 days at 37 °C (80CC82). 

Carbon, 37 dioxide, 45 monoxide, 44 Complex compound, 51 Coordination number, 51 Copper complexes, 51, 53 Covalent bond, 6,25-31 Cyano complex, 52-54... 

As many carbonate complexes are synthesized usually in aqueous solution under fairly alkaline conditions, the possibility of contamination by hydroxy species is often a problem. To circumvent this, the use of bicarbonate ion (via saturation of sodium carbonate solution with COj) rather than the carbonate ion can often avoid the precipitation of these contaminants. Many other synthetic methods use carbon dioxide as their starting point. Transition metal hydroxo complexes are, in general, capable of reacting with CO2 to produce the corresponding carbonate complex. The rate of CO2 uptake, which depends upon the nucleophilicity of the OH entity, proceeds by a mechanism that can be regarded as hydroxide addition across the unsaturated C02. There are few non-aqueous routes to carbonate complexes but one reaction (3), illustrative of a synthetic pathway of great potential, is that used to prepare platinum and copper complexes. Ruthenium and osmium carbonate complexes result from the oxidation of coordinated carbon monoxide by dioxygen insertion (4). ... 

Carbonic anhydrase (CA) is a zinc metalloenzyme involved in mammalian respiration, which catalyzes the hydration of carbon dioxide. Copper-complexed TPPC, competitively inhibits CA enzymatic activity as does copper-complexed TPPSj [32]. Experiments comparing the spectrophotometric characteristics of the two porphyrins in the presence of CA and apo-CA indicate that the zinc atoms in the active site of the enzyme are indeed involved in the interaction between the porphyrins and the enzyme. The metal-free porphyrins TPPSj and TPPC, do not inhibit the enzymatic activity of CA. Further, the spectrophotometric characteristics of these porphyrins in the presence of apo-CA were identical to those in the presence of wild-type CA, indicating the lack of involvement of the active site-coordinated zinc in the porphyrin-enzyme interaction for metal-free porphyrins. 

What the Beckmann rearrangement is to azepine, so is the Baeyer-Villiger oxidation to oxepine chemistry. A recent aerobic catalytic study has shown that yields of up to 95 % can be achieved with benzaldehyde and ruthenium dioxide or manganese dioxide <94SL1037>. The rate of reaction is greatly increased in the presence of lithium perchlorate without any significant loss in yield. Chiral nickel and copper complexes have been demonstrated to oxidise 2-phenylcyclohexanone... 

Copper complexes catalyse the reduction of carhon dioxide to formate employing hydrosilane as a reducing agent (Scheme 15.70). In the reaction. 

Haines RJ, Wittrig RE, Kubiak CP (1994) Electrocatalytic reduction of carbon dioxide by the binuclear copper complex [Cu2(6-(diphenylphosphino-2,2 -bipyridyl)2(MeCN)2][PF6]2. Inorg Chem 33 4723 728... 

Increasing attention has been devoted in recent years to systems based on titanium dioxide (the most important photocatalytic oxide) containing surface copper species or well defined copper complexes. " This system can be used for the photocatalytic decomposition of chlorine-containing organic molecules or reduction of bis-dithiolene complexes. The role of EPR is important for following the one-electron photoinduced redox processes that occur in these reactions. " " ... 

---