Copper complexes oxides

Some of these activated species like HO Cu -hydroperoxo, or Cu -hydroxo have been also proposed in the case of the oxidations of the DNA nucleobases (55). Various mechanisms like HO addition on a double-bound, hydrogen abstraction on the methyl groups or electron transfer induce nucleobases oxidations and copper complexes are oxidant enough to perform them, but, in the presence of excess of reductants, such as in the conditions often used during DNA oxidation by copper complexes, oxidized nucleobases (base radicals and radical cations) may be reduced back to undamaged species. Thus the ability of copper complexes to oxidize nucleobases could be underestimated. 

Copper III) is known in complex oxides and fluorides and in amino-acid complexes. 

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). 

Copper. Some 15 copper compounds (qv) have been used as micronutrient fertilizers. These include copper sulfates, oxides, chlorides, and cupric ammonium phosphate [15928-74-2] and several copper complexes and chelates. Recommended rates of Cu appHcation range from a low of 0.2 to as much as 14 kg/hm. Both soil and foHar appHcations are used. 

Hydrogenation. Gas-phase catalytic hydrogenation of succinic anhydride yields y-butyrolactone [96-48-0] (GBL), tetrahydrofiiran [109-99-9] (THF), 1,4-butanediol (BDO), or a mixture of these products, depending on the experimental conditions. Catalysts mentioned in the Hterature include copper chromites with various additives (72), copper—zinc oxides with promoters (73—75), and mthenium (76). The same products are obtained by hquid-phase hydrogenation catalysts used include Pd with various modifiers on various carriers (77—80), Ru on C (81) or Ru complexes (82,83), Rh on C (79), Cu—Co—Mn oxides (84), Co—Ni—Re oxides (85), Cu—Ti oxides (86), Ca—Mo—Ni on diatomaceous earth (87), and Mo—Ba—Re oxides (88). Chemical reduction of succinic anhydride to GBL or THF can be performed with 2-propanol in the presence of Zr02 catalyst (89,90). 

In acidic solution, the degradation results in the formation of furfural, furfuryl alcohol, 2-furoic acid, 3-hydroxyfurfural, furoin, 2-methyl-3,8-dihydroxychroman, ethylglyoxal, and several condensation products (36). Many metals, especially copper, cataly2e the oxidation of L-ascorbic acid. Oxalic acid and copper form a chelate complex which prevents the ascorbic acid-copper-complex formation and therefore oxalic acid inhibits effectively the oxidation of L-ascorbic acid. L-Ascorbic acid can also be stabilized with metaphosphoric acid, amino acids, 8-hydroxyquinoline, glycols, sugars, and trichloracetic acid (38). Another catalytic reaction which accounts for loss of L-ascorbic acid occurs with enzymes, eg, L-ascorbic acid oxidase, a copper protein-containing enzyme. 

Copper(I) chloride is insoluble to slightly soluble in water. SolubiUty values between 0.001 and 0.1 g/L have been reported. Hot water hydrolyzes the material to copper(I) oxide. CuCl is insoluble in dilute sulfuric and nitric acids, but forms solutions of complex compounds with hydrochloric acid, ammonia, and alkaU haUde. Copper(I) chloride is fairly stable in air at relative humidities of less than 50%, but quickly decomposes in the presence of air and moisture. 

Pyridazines form complexes with iodine, iodine monochloride, bromine, nickel(II) ethyl xanthate, iron carbonyls, iron carbonyl and triphenylphosphine, boron trihalides, silver salts, mercury(I) salts, iridium and ruthenium salts, chromium carbonyl and transition metals, and pentammine complexes of osmium(II) and osmium(III) (79ACS(A)125). Pyridazine N- oxide and its methyl and phenyl substituted derivatives form copper complexes (78TL1979). 

Asymmetric ring-opening of saturated epoxides by organoctiprates has been studied, hut only low enantioselectivities f -c 1596 ee) have so far been obtained [49, 50]. Muller et al., for example, have reported that tlie reaction between cyclohexene oxide and MeMgBr, catalyzed by 1096 of a chiral Schiffhase copper complex, gave froiis-2-metliylcyclohexanol in 5096 yield and with 1096 ee [50]. 

The bromo substituent in l-bromo-19-meLhyl-l,l9-dideoxybiladienes- c is not essential for porphyrin formation. When 1-methylbiladiene-ac dihydrobromide or the 1,19-dimethyl-biladienc-ac are heated in refluxing methanol or dimethylformamide in the presence of cop-per(II) salts, the porphyrin copper complexes 13 are formed by oxidative cyclization. The free porphyrins can then be obtained by removal of the copper with acid. A wide range of porphyrins 13 can be prepared by this method. However, a restriction is the accessibility of the starting material with special substitution patterns. 

Copper and brasses in the systems are more resistant to corrosion because of a stable oxide film however, if ammonia is present together with oxygen, corrosion of copper and copper oxide rapidly occurs. The corrosion is an oxidation process and results in the formation of the ammonia-copper complex [Cu(NH3)42+], Corrosion of nickel and zinc components also may occur in like fashion. 

A number of investigations of the copper-group oxides and dioxygen complexes have been reported. The electronic spectra of CuO, AgO, and AuO were recorded in rare-gas matrices (9), and it was found that the three oxides could be formed effectively by cocondensation of the metal atoms with a dilute, oxygen matrix, followed by near-ultraviolet excitation. The effective wavelengths for CuO or AgO formation were X > 300 nm and for AuO was X > 200 nm. In addition, the laser fluorescence spectrum of CuO in solid Ar has been recorded (97). 

CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Chrysene, 58,15, 16 fzans-Cinnamaldehyde, 57, 85 Cinnamaldehyde dimethylacetal, 57, 84 Cinnamyl alcohol, 56,105 58, 9 2-Cinnamylthio-2-thiazoline, 56, 82 Citric acid, 58,43 Citronellal, 58, 107, 112 Cleavage of methyl ethers with iodotri-methylsilane, 59, 35 Cobalt(II) acetylacetonate, 57, 13 Conjugate addition of aryl aldehydes, 59, 53 Copper (I) bromide, 58, 52, 54, 56 59,123 COPPER CATALYZED ARYLATION OF /3-DlCARBONYL COMPOUNDS, 58, 52 Copper (I) chloride, 57, 34 Copper (II) chloride, 56, 10 Copper(I) iodide, 55, 105, 123, 124 Copper(I) oxide, 59, 206 Copper(ll) oxide, 56, 10 Copper salts of carboxylic acids, 59, 127 Copper(l) thiophenoxide, 55, 123 59, 210 Copper(l) trifluoromethanesulfonate, 59, 202... 

Various a-addition reactions are observed to be metal- or acid-catalyzed, or to be uncatalyzed. In this review only the metal-catalyzed reactions will be discussed, since it is generally assumed that metal isocyanide complexes are involved in these systems. A number of metal-catalyzed a-addition reactions have been mentioned recently. Copper(I) oxide seems to be the most commonly used catalyst, although other metal complexes sometimes are satisfactory. Table III presents a partial survey of this work. 

This group showed that isolable silver(I) diaminocarbene complexes can be use in situ instead of free carbenes, to generate the copper carbene complex. The silver salts that precipitates during the formation of the copper complex have not any negative effect on the conversion. This method is advantageous since most of the silver complexes are isolable, air-stable and easily obtained by treatment of the corresponding imidazohnium salt by 0.5 equiv of silver oxide (Scheme 53). The solid structure of 78 was analyzed by X-ray diffraction. 

SELECTIVE OXIDATION WITH COPPER COMPLEXES INCORPORATED IN MOLECULAR SIEVES... 

There is virtually no knowledge of the setting and stmcture of copper phosphate cements. Mostly, they are complex materials. The simplest was based on a powder containing 91-5% CuO and 8-4% CO3O4. Others contained respectively 62-2 % CuO and 29-8 % ZnO, and 23-9 % Cu O and 66 7% ZnO, with other metal oxides. The strength of these cements is about the same as the zinc phosphate cement (Ware, 1971). There are also pseudo-copper cements, which are zinc phosphate cements coloured by minor amounts of copper(II) oxide. 

The selectivity of the aldol addition can be rationalized in terms of a Zimmer -man-Traxler transition-state model with TS-2-50 having the lowest energy and leading to dr-values of >95 5 for 2-51 and 2-52 [18]. The chiral copper complex, responsible for the enantioselective 1,4-addition of the dialkyl zinc derivative in the first anionic transformation, seems to have no influence on the aldol addition. To facilitate the ee-determination of the domino Michael/aldol products and to show that 2-51 and 2-52 are l -epimers, the mixture of the two compounds was oxidized to the corresponding diketones 2-53. 

Iron or copper complexes will catalyse Fenton chemistry only if two conditions are met simultaneously, namely that the ferric complex can be reduced and that the ferrous complex has an oxidation potential such that it can transfer an electron to H2O2. However, we must also add that this reasoning supposes that we are under standard conditions and at equilibrium, which is rarely the case for biological systems. A simple example will illustrate the problem whereas under standard conditions reaction (2) has a redox potential of —330 mV (at an O2 concentration of 1 atmosphere), in vivo with [O2] = 3.5 x 10 5 M and [O2 ] = 10 11 M the redox potential is +230 mV (Pierre and Fontecave, 1999). 

A still more complicated reaction is the chemiluminescent oxidation of sodium hydrogen sulfide, cysteine, and gluthathione by oxygen in the presence of heavy metal catalysts, especially copper ions 60>. When copper is used in the form of the tetrammin complex Cu(NH3) +, the chemiluminescence is due to excited-singlet oxygen when the catalyst is copper flavin mononucleotide (Cu—FMN), additional emission occurs from excited flavin mononucleotide. From absorption spectroscopic measurements J. Stauff and F. Nimmerfall60> concluded that the first reaction step consists in the addition of oxygen to the copper complex ... 

---