From metal cyanides oxidative addition

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). 

Four oxidation states of palladium are encountered in organometallic chemistry see Palladium Inorganic Coordination Chemistry) In order of importance, they are Pd , Pd , Pd, and Pd . With the reduction of palladium from Pd to Pd , the metal changes its reactivity from electrophile to nucleophile. However, unlike main group nucleophiles such as thiolates or cyanide, Pd complexes react with both alkyl halides and aryl or vinyl halides. Reactions of Pd complexes with these latter sp halides generate new Pd aryl or vinyl bonds through the process of oxidative addition. 

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. 

Cytochrome c has 4 methionine residues, two of which are covalently linked to the haem moiety One of the other two methionine residues is coordinated to the iron in the axial position The major S 2 p band of the crystalline compound appears at 162.6 eV attributable to the methionine residues. Prolongued irradiation causes an increase of the RSOJ or the sulphate band from 28% to 40% (Table 2). When aqueous cytochrome c is recorded, the amount of oxidised sulphur rises to 63% of the methionine sulphur band. The possible extraneously bound redox active transition metals, probably, have created a metal driven Haber Weiss reaction which led to the marked amount of oxidised sulphur observed. Splitting of the iron-sulphur bonding by cyanide results in dramatic increase of the 167.7 band and the additional appearance of a S 2p signal at 164.3, probably due to RS=0 species. This oxidation is believed to be catalyzed by the haem iron. Hydrogen peroxide alone converts the methionine sulphur completly to sulphonic acid. 

Gravimetric Methods.—The main difficulty is to obtain the cobalt in the form of one of its compounds entirely free from nickel or other metal. This may be accomplished by the cyanide method described under Wet Tests above. The solution, after separation of the nickel, is evaporated with dilute sulphuric acid until white fumes are evolved. On addition of water a solution of cobalt sulphate results, and the cobalt may be precipitated in a variety of ways, for example as oxide with hypobromites or persulphates,2 as sulphide, as cobalti-nitroso p-naphthol, or as basic carbonate.3 In each case the precipitate is ignited and reduced to metallic cobalt in a current of pure hydrogen. 

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