Copper hydroxo

Andrew et o . ( 2) studied the effects of carbonate, orthophosphate, and pyrophosphate on the toxicity of copper(II) to Vapknia magna at constant pH and total hardness. They reported mortality rates and reciprocal survival times to be directly correlated with cupric and copper-hydroxo ion activities as de-tennined by equilibrium calculations. They also found toxicity to be negatively related to activities of soluble copper carbonate (CuC0°), and independent of total or dissolved copper concentration. Data for their set of experiments involving addition of orthophosphate are included in Table I but were not used in some... 

Different properties have to be associated with different substances. Comparing the green substance of the copper roof with various copper carbonates, copper sulfates and copper chlorides, one realizes that there are different green or blue copper compounds, but no green copper exists The discussion should result in the statement that copper is covered with a green copper compound, called copper hydroxo carbonate. 

In the case of copper complexes, the chemistry is less well understood. High valent copper-oxo species are not likely to be formed, consequently copper-hydroperoxo or copper-hydroxo species are usually proposed as active species in DNA oxidation. These species are thus more susceptible to homo-lytic cleavage of the peroxide or the metal-hydroxo bond and consequently, to 1-electron oxidation mechanism. However, the labeling of the product of deoxyribose oxidation at Cl by Cu(l,10-phenanthroline)2 clearly demonstrated that these complexes can mediate a 2-electron oxidation mechanism of DNA damage since the oxygen atom incorporated in DNA originates from H2O. 

In 1996 Stack and co-workers reported an unusual 3 1 (copper 02 stoichiometry) reaction between a mononuclear copper(I) complex of a A-permethylated (lR,2R)-cyclohexanediamine ligand with dioxygen. The end product of this reaction, stable at only low temperatures (X-ray structure at —40 °C) is a discrete, mixed-valence trinuclear copper cluster (1), with two Cu11 and a Cu111 center (Cu-Cu 2.641 and 2.704 A).27 Its spectroscopic and magnetic behavior were also investigated in detail. The relevance of this synthetic complex to the reduction of 02 at the trinuclear active sites of multicopper oxidases4-8 was discussed. Once formed, it exhibits moderate thermal stability, decomposed by a non-first-order process in about 3h at —10 °C. In the presence of trace water, the major isolated product was the bis(/i-hydroxo)dicopper(II) dimer (2). 

Chemical Reviews paper. We can only discuss a small number of these here, but some important categories are (1) synthetic Fe(II)-Cu(I) complexes and their reactions with O2, (2) oxidized heme-copper models (Fe(III)-X-Cu(II) complexes, where X equals 0x0- and hydroxo-bridged complexes, cyanide-bridged complexes, or other X-bridged complexes), (3) crosslinked histidine-tyrosine residues at the heme-copper center, and (4) Cua site synthetic models. 

A related explanation has to do with the stability of the peroxo dicopper(II) intermediate, since it will either attack the substrate or decompose the kinetics of formation of the intermediate relative to those of the ensuing decomposition reactions will thus be important. Nelson (53) and Sorrell (90) have both described systems that undergo a Cu 02 = 4 1 reaction stoichiometry for dicopper(I) complexes where they propose that degradation of the peroxo dicopperfll) intermediate proceeds by the fast bimolecular two-electron transfer fiom a second dicopper(I) molecule to the putative peroxo-dicopper(II) intermediate to give an aggregated oxo-copper(II) product. [The latter may form hydroxo-Cu(II) species in the presence of protic solvents]. 

Oxo- and Hydroxo-Bridged Heme-Copper Assemblies Formed from Acid-Base or Metal-Dioxygen Chemistry (Kopf et al., 1999)... 

The hydroxo-compound, [Pd(NH3)2(OH)2], is obtained on treating the ehloro-derivative with moist silver oxide, or by precipitation from a solution of the sulphato-compound with the calculated quantity of barium hydroxide. The solution is filtered and evaporated in vacuo or in air free from carbon dioxide, when a yellow residue of microscopic octahedra is obtained. The aqueous solution is strongly alkaline, rapidly absorbs carbon dioxide from the air, and combines with evolution of heat with acids, forming the corresponding aeido-derivatives. In the dry state it may be heated to 105° C. without decomposition. Prolonged boiling with water causes it to lose ammonia, as in the case of the dibromo-derivative, leaving a brown residue. It precipitates the hydroxides of the metals copper and silver from solutions of their salts, and liberates ammonia from ammonium salts.2... 

Copper(I) pyrazolates react with neutral ligands (L), such as 1,10-phenan-throline and cyclohexyl isocyanide, giving binuclear complexes of general formula [Cu(pzXL)]2.9,10 Solutions of [Cu(dmpz)]3 in pyridine rapidly absorb oxygen in the presence of water, giving the blue octanuclear hydroxo-... 

Under different reaction conditions, phenols can be oxidized to p-quinones (equations 272600-602 and 273603), but in the case of phenol itself, insufficient selectivity has prevented, as yet, the commercial application of this potentially important synthesis of p-benzoquinone and hydroquin-one. The selectivity of p-benzoquinone, or p-quinol formation can be increased at the expense of oxidative coupling products by using a large excess of the copper reagent [Cu4Cl402(MeCN)3 or CuCl + 02 in MeCN] with respect to the phenolic substrate.604 The suggested mechanism involves the oxidation of the phenoxide radical (189) by a copper(II)-hydroxo species to p-quinol (190) which can rearrange (for R2 = H) to hydroquinone (191 Scheme 14), which is readily oxidizable to p-quinone.6... 

Both intramolecular and intermolecular attack by M—OHn+ species are well established for cobalt(III) and other kinetically inert metal centres (Section 61.4.2.2.3). However, reactions of this type are not as well defined with labile metal ions. In copper(II) complexes, the pKa values for coordinated water ligands usually fall within the range pKa 6-8. If coordinated hydroxide ion is an important nucleophile in copper(II)-promoted reactions, the reactions would be expected to become independent of [OH-] at pH 8 when the bulk of the complex was converted to the active hydroxo species. Studies of the pH dependence of a number of copper(II)-promoted reactions to such pH levels have been carried out and no evidence obtained for the production of catalytically active hydroxo complexes however, some reactions do proceed by this pathway. 

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