Metal cyanides reduction

Dehalogenation of monochlorotoluenes can be readily effected with hydrogen and noble metal catalysts (34). Conversion of -chlorotoluene to Ncyanotoluene is accompHshed by reaction with tetraethyl ammonium cyanide and zero-valent Group (VIII) metal complexes, such as those of nickel or palladium (35). The reaction proceeds by initial oxidative addition of the aryl haHde to the zerovalent metal complex, followed by attack of cyanide ion on the metal and reductive elimination of the aryl cyanide. Methylstyrene is prepared from -chlorotoluene by a vinylation reaction using ethylene as the reagent and a catalyst derived from zinc, a triarylphosphine, and a nickel salt (36). 

The complex cyanides of transition metals, especially the iron group, are very stable in aqueous solution. Their high co-ordination numbers mean the metal core of the complex is effectively shielded, and the metal-cyanide bonds, which share electrons with unfilled inner orbitals of the metal, may have a much more covalent character. Single electron transfer to the ferri-cyanide ion as a whole is easy (reducing it to ferrocyanide, with no alteration of co-ordination), but further reduction does not occur. 

Heating with the following solids, their fusions, or vapours (a) oxides, peroxides, hydroxides, nitrates, nitrites, sulphides, cyanides, hexacyano-ferrate(III), and hexacyanoferrate(II) of the alkali and alkaline-earth metals (except oxides and hydroxides of calcium and strontium) (b) molten lead, silver, copper, zinc, bismuth, tin, or gold, or mixtures which form these metals upon reduction (c) phosphorus, arsenic, antimony, or silicon, or mixtures which form these elements upon reduction, particularly phosphates, arsenates,... 

Polynuclear transition metal cyanides such as the well-known Prussian blue and its analogues with osmium and ruthenium have been intensely studied Prussian blue films on electrodes are formed as microcrystalline materials by the electrochemical reduction of FeFe(CN)g in aqueous solutionThey show two reversible redox reactions, and due to the intense color of the single oxidation states, they appear to be candidates for electrochromic displays Ion exchange properties in the reduced state are limited to certain ions having similar ionic radii. Thus, the reversible... 

FIGURE 9.5 Cyanide reduction via alkaline chlorination. (Adapted from U.S. EPA, Meeting Hazardous Waste Requirements for Metal Finishers, Report EPA/625/4-87/018, U.S. Environmental Protection Agency, Cincinnati, OH, 1987.)... 

Alkali metal boratabenzenes may be liberated from bis (boratabenzene) cobalt complexes 7 and 13 by reductive degradation with elemental Li, sodium amalgam, or Na/K alloy (60), or alternatively by degradation with cyanides (61). The latter method has been developed in detail (Scheme 4). It produces spectroscopically pure ( H-NMR control) solutions of the products 26 the excess alkali metal cyanide and the undefined cyanocobalt compounds produced are essentially insoluble in acetonitrile. 

The complications which result from the hydrolysis of alkali metal cyanides in aqueous media may be avoided by the use of non-aqueous solvents. The one most often employed is liquid ammonia, in which derivatives of some of the lanthanides and of titanium(III) may be obtained from the metal halides and cyanide.13 By addition of potassium as reductant, complexes of cobalt(O), nickel(O), titanium(II) and titanium(III) may be prepared and a complex of zirconium(0) has been obtained in a remarkable disproportion of zirconium(III) into zirconium(IV) and zirconium(0).14 Other solvents which have been shown to be suitable for halide-cyanide exchange reactions include ethanol, methanol, tetrahydrofuran, dimethyl sulfoxide and dimethylformamide. With their aid, species of different stoichiometry from those isolated from aqueous media can sometimes be made [Hg(CN)3], for example, is obtained as its cesium salt form CsF, KCN and Hg(CN)2 in ethanol.15... 

The preparation of cyanomethylbenzo[6]thiophenes by reaction of halomethylbenzo[6]thiophenes with alkali metal cyanides is discussed in Section VI,D, 4. Reduction of cyanomethylbenzo[6]thiophenes affords (2-aminoethyl)benzo[6]thiophenes (Section VI, H, 2), and they give the corresponding benzo[6]thienylacetic acid on alkaline hydrolysis (Section VI,M, 3). 

The dicyanophosphide(l-) ion was first prepared by reduction of P(CN)3. It is more conveniently obtained from white phosphorus in a nucleophilic disproportionation by an ammonium, phosphonium, or crown ether alkali metal cyanide. ... 

Accelerants are used to increase coating weight and shorten coating time. Many different accelerants can be used including a variety of organic and transition metal compounds [60, 91], The predominant accelerant in commercial formulations is ferricyanide, Fe(CN)6 , which is added to acid chromate-fluoride formulations in concentrations ranging from 2 to 5 mM [92, 93]. The two primary theories for the action of Fe(CN)6 are (1) formation of mixed metal cyanide compounds [91, 94, 95] and (2) acceleration of the film-forming Cr(VI) to Cr(III) reduction reaction by Fe(CN)6 /" redox mediation [96]. These types of CCCs are discussed in more detail below. 

Metal-catalyzed reduction of iron cyanide metal clusters internal or external location of metal duster in zeolite [Fe(CN) ] " does not enter the anionic teunework of zeolites L and Y and can be reduced only by metal outside the zeolite cages. 

The reductive pyrolysis of organic compounds in the presence of metals leads to the formation of the metal cyanide, which can be detected as Prussian blue (Fe4[Fe(CN)g]3) or by the copper(ii) acetate-benzidine test . Several metals and salts have been recommended for the fusion of the organic compound, e.g. potassium , sodium , magnesium mixed with potassium carbonate , zinc mixed with potassium carbonate , and a mixture of dextrose with sodium carbonate . When the compound contains sulphur the metal thiocyanate is also produced, which can be detected by ferric chloride . ... 

Preparative Methods prepared by lithium metal mediated reductive silylation of trimethylsilyl cyanide. ... 

If the metal cyanide complex 71 formed via oxidative addition of a C-CN bond can undergo the addition across unsaturated molecules and subsequent reductive elimination, a new nitrile 72 is produced (Scheme 6.14) This process is best described as carbocyanation since the transformation enables the simultaneous introduction of an R group and a cyano group in the it-system. The reaction shown in Scheme 6.12 [37] formally falls into this class of transformation, although it proceeds through a completely different mechanism from that depicted in Scheme 6.14, and thus has a limited reaction scope. 

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