Copper complex compounds, anions

C1CuC4H6CuC1, 6 217 Copper (II) complex compounds, anions, oxalato, K2[Cu(C204)2], 6 1... 

Fonnation of a complex with a copper cation only further stimulates this behaviour. As a result, S.lg is almost completely bound to the micelles, even at low concentrations of Cu(DS)2. By contrast, the reaction of 5.1 f still benefits from an increasing surfactant concentration at 10 mM of Cu(DS)2. In fact, it is surprising that the reaction of this anionic compound is catalysed at all by an anionic surfactant. Probably it is the copper complex of 5.If, being overall cationic, that binds to the micelle. Not surprisingly, the neutral substrate S.lc shows intermediate behaviour. 

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. 

Lippard, S.J., Ucko, D.A. 1968. Transition metal borohydride complexes. II. Th reaction of copper(I) compounds with boron hydride anions. Inorg Chem 7 1051-1058. 

A side-on p,-Tq2 Tq2-peroxo dicopper(II) complex. A very important development in copper-dioxygen chemistry occurred in 1989 with the report by Kitajima et al. [10,108] that another Cu202 species could be prepared and structurally characterized by using copper complexes with a substituted anionic tris(pyrazolyl)borate ligand. This intensely purple compound, Cu[HB(3,5-iPr2pz)3] 2(02) (5), was prepared either by reaction of Cu[HB(3,5-iPr2pz)3] (4) with 02 or by careful addition of aqueous hydrogen peroxide to the p-dihydroxo... 

The dimerization of the copper complex takes place to form the bis-Cu(II) compound 3, where the phenolate anion is the bridging ligand, just as proposed by Karlin [75], in the dinuclear complexes that act as the actual catalyst in the active state. 

Thus the rate of reduction is independent of the substrate concentration. It is very dependent on the environment surrounding the copper, such as solvent, anions, and complexing compounds. 

The redox reactions of carbon free radicals and copper(II) compounds have been portrayed as ligand-transfer and electron-transfer processes 178). The electron-transfer oxidation of alkyl radicals by copper(II) complexes, which are efficient radical interceptors, is considered to proceed via a metastable alkylcopper species which is consumed primarily by oxidative elimination [Eq. (129)] and oxidative solvolysis [Eq. (130)] 143b). The anionic counterion exerts a dominant effect in the selection... 

Many examples are given within the electron transfer (ET)-based series involving copper complexes (Table 3). In some cases (see for example entry 3 in Table 3), the supporting electrolyte consists of a mixture of a copper salt and of a salt containing the ligand concerned. In that case, the [Cu(L2)] anions only form within the solution and react with oxidized ET on the electrode. Moreover, note (see Table 3) that different modifications of the same compound may be obtained depending on the electrochemical conditions. 

Incorporation of metal ions into porphyrins is affected by other compounds in solution. Lowe and Phillips (25) found that copper(II) ions were chelated with dimethyl protoporphyrin ester 20,000 times faster in 2.5% sodium dodecylsulfate (SDS) than in 5% cetyl trimethyl ammonium bromide (CATB). The increased activity of SDS treated porphyrin was attributed to electrostatic attraction between anionic micelles formed around the tetrapyrrole nucleus and the metal cation. The authors also reported the influence of certain chelating agents on the rate of copper complex formation. Equimolar concentrations of copper and 8-hydroxyquinoline or sodium diethylthiocarbamate in 2.5% SDS increased the reaction rate 38 and 165 times, respectively, above the control. Secondary chelators may act by removing the hydration sphere on the metal ion increasing its attraction to pyrrole nitrogens (26). 

Complementary to the acylation of enolate anions is the acid-catalyzed acylation of the corresponding enols, where the regiochemistry of acylation can vary from that observed in base-catalyzed reactions. Although the reaction has been studied extensively in simple systems, it has not been widely used in the synthesis of complex molecules. The catalysts most frequently employed are boron trifluoride, aluminum chloride and some proton acids, and acid anhydrides are the most frequently used acylating agents. Reaction is thought to involve electrophilic attack on the enol of the ketone by a Lewis acid complex of the anhydride (Scheme 58). In the presence of a proton acid, the enol ester is probably the reactive nucleophile. In either case, the first formed 1,3-dicarbonyl compound is converted into its borofluoride complex, which may be decomposed to give the 3-d>ketone, sometimes isolated as its copper complex. 

Copper has the electronic structure s22s22p63s23p63di0Asl—it may lose one electron from the outer s orbital and become a Cu+ ion. Loss of two electrons will leave a copper ion Cu —with an outer structure 3d9. This cupric ion has a structure similar to other transition metal ions with a characteristic incompletely filled d orbital. Thus, besides combining ionically with bivalent anions, it may form complex compounds. 

Binary Copper(ll) Compounds. Black crystalline CuO is obtained by pyrolysis of the nitrate or other oxo salts above 800° it decomposes to CuzO. The hydroxide is obtained as a blue bulky precipitate on addition of alkali —hydroxidenxrcuprkrsolutions warming an aqueous slurry dehydrates this to the oxide. The hydroxide is readily soluble in strong acids and also in concentrated alkali hydroxides, to give deep blue anions, probably of the type [Cu (OH)2 2]2+. In ammoniacal solutions the deep blue tetraammine complex is formed. 

Many of the minerals in the Earth s crust are not simple ionic compounds consisting of one type of cation such as Cu and one type of anion such as carbonate, COs ". These more complex compounds can be classified as double (or triple or quadruple) salts. (These salts are also referred to as ternary or quaternary.) That is, they contain more than one type of cation and/or more than one type of anion. For example, one of the conunon ores of copper is malachite, which has the formula Cu2C03(0H)2. This is an ionic compound that contains the Cu " ion and both the carbonate and hydroxide anions. Double salts can be thought of as combinations (but not mixtmes) of two or more simple salts. Malachite can be visualized as CuCOs -1- Cu(OH)2. Malachite is frequently found with azurite, which has the formula Cu3(C03)2(0H)2. Azurite simply has a different ratio of the two simple salts 2 CuCOs + Cu(OH)2. 

Fluoride can be determined by means of an iron(iii) thiocyanato complex extracted into isobutylketone. Iron is extracted back into the aqueous phase with the fluoride sample solution. The atomic absorption signal of iron is directly proportional to the concentration of fluoride (0.5-6 ju,g F ml ). EDTA can be determined by a similar technique. Copper is first extracted as the hydroxyquinolinato complex into isobutylketone, and then extracted back into the aqueous solution with the EDTA sample solution. In these methods the analyte anion must form a more stable complex compound with the metal ion than the ligand used for the first solvent extraction. These kind of... 

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