Metal hydride hydroxide

In anionic polymerization the reaction is initiated by a strong base, eg, a metal hydride, alkah metal alkoxide, organometaHic compounds, or hydroxides, to form a lactamate ... 

Industrially, chlorine is obtained as a by-product in the electrolytic conversion of salt to sodium hydroxide. Hazardous reactions have occuned between chlorine and a variety of chemicals including acetylene, alcohols, aluminium, ammonia, benzene, carbon disulphide, diethyl ether, diethyl zinc, fluorine, hydrocarbons, hydrogen, ferric chloride, metal hydrides, non-metals such as boron and phosphorus, rubber, and steel. 

Hydrogen can be prepared by the reaction of water or dilute acids on electropositive metals such as the alkali metals, alkaline earth metals, the metals of Groups 3, 4 and the lanthanoids. The reaction can be explosively violent. Convenient laboratory methods employ sodium amalgam or calcium with water, or zinc with hydrochloric acid. The reaction of aluminium or ferrosilicon with aqueous sodium hydroxide has also been used. For small-scale preparations the hydrolysis of metal hydrides is convenient, and this generates twice the amount of hydrogen as contained in the hydride, e.g. ... 

Heterocyclic structures analogous to the intermediate complex result from azinium derivatives and amines, hydroxide or alkoxides, or Grignard reagents from quinazoline and orgahometallics, cyanide, bisulfite, etc. from various heterocycles with amide ion, metal hydrides,or lithium alkyls from A-acylazinium compounds and cyanide ion (Reissert compounds) many other examples are known. Factors favorable to nucleophilic addition rather than substitution reactions have been discussed by Albert, who has studied examples of easy covalent hydration of heterocycles. 

Nickel hydroxides have been used as the active material in the positive electrodes of several alkaline batteries for over century [1], These materials continue to attract much attention because of the commercial importance of nickel-cadmium and nickel-metal hydride batteries. In addition to being the cathode active material in nickel-metal hydride batteries, Ni(OH)2 is an important corrosion product of the anode during cycling. There are several reviews of work in the field [2-10],... 

In normal battery operation several electrochemical reactions occur on the nickel hydroxide electrode. These are the redox reactions of the active material, oxygen evolution, and in the case of nickel-hydrogen and nickel-metal hydride batteries, hydrogen oxidation. In addition there are parasitic reactions such as the corrosion of nickel current collector materials and the oxidation of organic materials from separators. The initial reaction in the corrosion process is the conversion of Ni to Ni(OH)2. 

Electrode corrosion is the critical problem associated with the use of metal hydride anodes in batteries. The extent of corrosion is essentially determined by two factors alloy expansion and contraction in the charge-discharge cycle, and chemical surface passivation by the formation of corrosion—resistant oxides or hydroxides. 

There are few systematic guidelines which can be used to predict the properties of AB2 metal hydride electrodes. Alloy formulation is primarily an empirical process where the composition is designed to provide a bulk hydride-forming phase (or phases) which form, in situ, a corrosion— resistance surface of semipassivating oxide (hydroxide) layers. Lattice expansion is usually reduced relative to the ABS hydrides because of a lower VH. Pressure-composition isotherms of complex AB2 electrode materials indicate nonideal behaviour. 

In acidic electrolytes only lead, because it forms passive layers on the active surfaces, has proven sufficiently chemically stable to produce durable storage batteries. In contrast, in alkaline medium there are several substances basically suitable as electrode materials nickel hydroxide, silver oxide, and manganese dioxide as positive active materials may be combined with zinc, cadmium, iron, or metal hydrides. In each case potassium hydroxide is the electrolyte, at a concentration — depending on battery systems and application — in the range of 1.15 - 1,45 gem"3. Several elec-... 

In this context we postulated that the shift reaction might proceed catalytically according to a hypothetical cycle such as Scheme I. There are four key steps in Scheme I a) nucleophilic attack of hydroxide or water on coordinated CO to give a hydroxycarbonyl complex, b) decarboxylation to give the metal hydride, c) reductive elimination of H2 from the hydride and d) coordination of new CO. In addition, there are several potentially crucial protonation/deprotonation equilibria involving metal hydrides or the hydroxycarbonyl. The mechanistic details have been worked out (but only incompletely) for a couple of the alkaline solution WGSR homogeneous catalysts. In these cases,... 

The use of amines allows much higher nucleophile concentrations than those achievable with Bronsted bases. We have used solutions as concentrated as 6 M Me N. This vast difference in available nucleophile concentration partially explains the huge increase in rate afforded by NMe3 over the rate with Bronsted bases. Very large concentrations of hydroxide may promote the base attack step but can decrease the rate of the WGSR due to inhibition of the protonation of the metal hydride species. 

A mechanism similar to Scheme 10 was proposed, involving CO addition, followed by H20 addition (in lieu of hydroxide anion) to form a metallocarboxylic acid complex. Then, decomposition to C02 and a metal hydride was proposed, followed by hydride elimination. Table 15 provides data from reaction testing in the temperature range 140 to 180 °C. In later testing, they compared Rh and Ir complexes for the reduction of benzalacetone under water-gas shift conditions. 

Alkali-immobile dye-releasing quinone compounds, 19 293-294 Alkali lignins, 15 19-20 Alkali manganate(VI) salts, 15 596 Alkali manganates(V), 15 592 Alkali-metal alkoxide catalysts, 10 491 Alkali-metal alkoxides, effects of, 14 252 Alkali-metal alkylstannonates, 24 824 Alkali-metal fluoroxenates, 17 329-330 Alkali-metal hydrides, 13 608 Alkali-metal hydroxides, carbonyl sulfide reaction with, 23 622 Alkali-metal metatungstates, 25 383 Alkali-metal perchlorates, 18 211 Alkali-metal peroxides, 16 393... 

Nickel hydroxides, 17 111 Nickel—iron alloys, 17 101 Nickel—iron—aluminum catalyst, 17 121 Nickel—iron cells, 3 491—493 Nickel—iron—chromium alloy 825 in galvanic series, 7 805t Nickel—iron—chromium alloys, 17 102—103 Nickel—iron plating, 9 821 Nickel itch, 12 691, 701 Nickel—matrix composites, 17 104 Nickel metal, forms of, 17 95—99 Nickel metal hydride cells, 3 431, 471, 509-512... 

Atkah metal hydrides too abstract protons from boranes. While water is produced with basic hydroxides, hydrogen is liberated with hydrides. Except diborane, all other boron hydrides undergo similar reactions, liberating hydrogen ... 

Lithium hydride and sodium hydride are the only alkali metal hydrides of much practical importance. They are useful when it is desirable for proton (or hydrogen atom) transfers to accompany electron-transfer events. Because these hydrides react quickly with water to form alkali metal hydroxides and hydrogen gas, they are frequently used as drying agents, particularly for hydrocarbons and ethers. Care should be exercised in using them to dry solvents that are not predried, and they should not be used to dry alcohols or halogenated solvents. 

The classic Hieber-base reaction 16 is that of a hydroxide with metal carbonyls, which proceeds by nucleophilic attack of the hydroxide at a carbon atom of a carbonyl ligand to give a carboxy group or consequently carbon dioxide and a metal hydride.17 Metal carbonyls are catalysts for the water-gas shift reaction.18 Pentacarbonyl(tetrafluoroborato)rhenium reacts with alkali hydroxide in a similar way however, due to the coordinatively unsaturated nature of the [Re(CO)5]+ group polynuclear compounds are formed.15... 

The key intermediate in the reduction of metal ions by carbon monoxide and water is the hydroxycarbonyl (18). Initially (18) was proposed to form by a migratory insertion of CO into a M—OH bond, but more recent studies have favored a direct attack of water or hydroxide on a coordinated carbonyl (4,62). This latter view is in accord with the expected reactivity of coordinated CO toward nucleophiles. Intermediate (18) may then decarboxylate to give C02 and either a reduced metal ion or a metal hydride, as in (29) and (30), respectively. 

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