Silver and Copper

An examination of the wavelength dependence of the photorearrcungements of CuCl complexes of cyclododeca-1,5,9-trienes has revealed no reason to assume that the two types of reaction, cis-trans-photoisomer iaation and rearrangement, occur on separate energy surfaces The photolysis of 

The effect of Ag(I) on alkene E/Z photoisomerisation has been described together with further observations on the Ag(I) phoboinduced 1,3-hydrogen shift. 

Luminescence spectra of a series of Ce(III) compounds containing halide, alkyl, aryl, ether, nitrile, and cyclic aromatic hydrocarbon ligands have been recorded under a range of conditions auid a matrix isolation UV study of the direct synthesis of (C2H4 f Eu using europium atoms has been reported.  

Roloff, K. Meier, and M. Rlediker, Pure Appl. Chem.. 1986, iS. 1267. 

Szymanska-Buzar, M. Gyor, A. Rockenbauer, and L. Sumegi, React. KInet. Catal. Lett.. 1986, Hr 407. 

A review of the photochemical properties of copper complexes includes a survey of the photocatalysed reactions of copper-olefin complexes. The addition of acetonitrile to norbornene may be induced by irradiation in the presence of silver ions. The reaction appears to involve excitation of a LMCT excited state of the norbomene-silver complexes and the formation of norbornene radical cations. 

The detection of CuH and CuMe in methane matrices at 12K following the 320 nm photolysis of copper atoms has led to the proposal that optically excited copper atoms insert into the C—H bond of methane. The HCuMe species thus produced undergoes secondary photolysis to give CuH and methyl radicals and also CuMe and hydrogen atoms. The photoproperties of silver atoms in matrices have been studied in detail. 

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Finally, other tests to control jet fuel corrosivity towards certain metals (copper and silver) are used in aviation. The corrosion test known as the copper strip (NF M 07-015) is conducted by immersion in a thermostatic bath at 100°C, under 7 bar pressure for two hours. The coloration should not exceed level 1 (light yellow) on a scale of reference. There is also the silver strip corrosion test (IP 227) required by British specifications (e.g., Rolls Royce) in conjunction with the use of special materials. The value obtained should be less than 1 after immersion at 50°C for four hours. 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

The preparation of a series of transition metal complexes (Co. Ni. Pd. Pt, Ir. Au. Cu. Ag) with ambident anion (70) and phosphines as ligands has been reported recently (885). According to the infrared and NMR spectra the thiazoline-2-thione anion is bounded through the exocyclic sulfur atom to the metal. The copper and silver complexes have been found to be dimeric. 

For the most part, the chemistry of gold is more closely related to that of its horizontal neighbors ia the Periodic Table, platinum and mercury, than to the other members of its subgroup, copper and silver. Comprehensive treatments of gold chemistry can be found ia the Hterature (see General References). 

Copper and silver combined with refractory metals, such as tungsten, tungsten carbide, and molybdenum, are the principal materials for electrical contacts. A mixture of the powders is pressed and sintered, or a previously pressed and sintered refractory matrix is infiltrated with molten copper or silver in a separate heating operation. The composition is controlled by the porosity of the refractory matrix. Copper—tungsten contacts are used primarily in power-circuit breakers and transformer-tap charges. They are confined to an oil bath because of the rapid oxidation of copper in air. Copper—tungsten carbide compositions are used where greater mechanical wear resistance is necessary. 

Group 11 (IB) Perchlorates. Copper and silver perchlorates have been studied quite extensively. Copper(I) perchlorate [17031-33-3] ... 

Spectroscopic. The electronic configuration of Pu vapor is [Xe] The earliest studies of copper- and silver-spark spectra... 

Attack on metals can be a function of fuel components as well as of water and oxygen. Organic acids react with cadmium plating and 2inc coatings. Traces of H2S and free sulfur react with silver used in older piston pumps and with copper used in bearings and brass fittings. Specification limits by copper and silver strip corrosion tests are requited for fuels to forestall these reactions. 

Many investigations are reported on azides of barium, calcium, strontium, lead, copper, and silver in the range 100 to 200°C (212 to 392°F). Time exponents were 6 to 8 and activation energies of 30 to 50 kcal/g mol (54,000 to 90,000 Btu/lb mol) or so. Some difficulties with reproducibility were encountered with these hazardous materials. 

The principal effects of air pollutants on metals are corrosion of the surface, with eventual loss of material from the surface, and alteration in the electrical properties of the metals. Metals are divided into two categories—ferrous and nonferrous. Ferrous metals contain iron and include various types of steel. Nonferrous metals, such as zinc, aluminum, copper, and silver, do not contain iron. 

Copper and silver are used extensively in the electronics industry because of their excellent electrical conductivity. These metals tend to form a protective surface coating which inhibits further corrosion. When exposed to HjS, a sulfide coating forms, increasing the resistance across contacts on electrical switches (6). 

Metallic copper and silver both have antibacterial properties and Au thiol complexes have found increasing use in the treatment of rheumatoid arthritis, but only copper of this group has a biological role in sustaining life. It is widely distributed in the plant and animal worlds, and its redox chemistry is involved in a variety of... 

Making of Inorganic Materials by Electrochemical Methods Aluminium alloys with iron, cobalt, nickel, copper, and silver... 

The tarnishing of copper and silver in dry air containing traces of hydrogen sulphide (Table 2.6) is another example of film growth by lattice diffusion at ambient temperatures. In these cases defects in the sulphide lattice enable the films to grow to visible thicknesses with the consequent formation of tarnish films which are aesthetically objectionable and may have a significant effect on the behaviour of the metals in particular applications, e.g. electrical contacts. 

Hydrogen sulphide This is produced by the putrefaction of organic sulphur compounds or by the action of sulphate-reducing bacteria in anaerobic conditions (e.g. in polluted river estuaries). It is fairly rapidly oxidised to SOj and concentrations are considerably lower than those of (Table 2.6). Nevertheless it is responsible for the tarnishing of copper and silver at normal atmospheric concentrations. 

Copper and silver tarnish readily in sulphide atmospheres, and copper in contact with sulphur-vulcanised rubber will sometimes react with the sulphur, devulcanising it in the process. The growth of conducting sulphide whiskers on silver is noteworthy as these whiskers may give rise to short circuits across silver-plated contacts. Ammonia has little effect on most metals, but traces will tarnish many copper alloys and cause stress-corrosion cracking of certain stressed brasses. 

A copper strip with a mass of 2.00 g is dipped into a solution of AgN03. After some time has elapsed, the copper strip is coated with silver. The strip is removed from the solution, dried, and weighed. The coated strip has a mass of 4.18 g. What are the masses of copper and silver metals in tile strip (Hint Remember that the copper metal is being used up as silver metal forms.)... 

Now let s be more quantitative. Let s repeat the experiment, weighing the metal rods before and after the test. The weighing shows that during the test the copper rod has become 0.63S gram lighter and the silver rod has become 2.16 grams heavier. Chemical reaction has occurred and, as any good chemist will do, we immediately ask, How many moles of copper and silver are involved ... 

It follows from the Second Law that when a given current is passed in series through solutions containing copper)II) sulphate and silver nitrate respectively, then the weights of copper and silver deposited in a given time will be in the ratio of 63.55/2 to 107.87. 

All three M+ ions are known to form compounds with the unusual digonal linear coordination (see also section 4.9.7), though this is most common for gold. As a result, complexes R3PMX of copper and silver are normally di-and tetranuclear species with 3- or 4-coordinate metals, while the gold analogues are 2-coordinate monomers. This is the reverse of what would be expected on steric grounds [13, 14],... 

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