Platinum group metals halides

The hydrogen reduction of the metal halides, described in Sec. 1.2, is generally the favored reaction for metal deposition but is not suitable for the platinum-group metals since the volatilization and decomposition temperatures of their halides are too close to provide efficient vapor transport. 1 1 For that reason, the decomposition of the carbonyl halide is preferred. The exception is palladium which is much more readily deposited by hydrogen reduction than by the carbonyl-halide decomposition. 

CVD Reactions. The rhodium halides, like those of the other platinum group metal s, are volatile with a decomposition pointtoo close to the vaporization point to make them usable for CVD transport. The metal is commonly produced by the decomposition of metallo-organic precur-... 

Hydrosilylations of fluorine-containing alkenes are free radical reactions initiated by UV light or organic peroxides The direction of addition is the same as with fluonnated alkyl halides However, the reaction between hydrosilanes and fluorine-containing olefins catalyzed by platinum group metal complexes may result in bidirectional addition and/or formation of a vinylic silane, the latter by de hydrogenative silylation[/] The natures of both the silane and the catalyst affect the outcome of the reaction[7] A random selection of some typical new reactions of silanes are shown in Table 1 [1, 2, 3 4]... 

The most usual synthetic routes to the derivatives of platinum group metals are the exchange reactions of the complexes containing halide ligands with alkali metal alkoxides (method 5), alcoholysis of the same kind derivatives (usually by phenols, method 4), alcoholysis of hydroxide complexes (method 3), and redox reactions — reduction of chlorides or 0s04 in alcohol media (method 7) (Table 12.25). 

The reaction is carried out by thermal decomposition of fluoroformates at temperatures in the range of 300-500 C in the presence of a catalyst. Suitable catalysts are platinum gauze. " V dluminum oxide, or platinum group metal impregnated alumina, where platinum shows the best results. Moreover iron, sled or oxides and halides of chromium. 

Numerous elements form multicharged anionic complexes which are able to associate with hydrophobic basic dyes. They include anions of the heteropoly acids of Si, Ge, P(V), and As(V), the bromide complexes of Bi and Te(IV), and the thiocyanate complexes of Mo and W. Flotation of sparingly soluble ion-associates formed between the multicharged anionic complexes (with halides, SnC, and thiocyanate) of the platinum-group metals and... 

Carbonyl halides of the platinum group metals, however, are often prepared by reacting the metal halide with carbon monoxide. [Ru(CO)3Cl,], and [Rh(CO),Cl], are mentioned above (p. 167). Platinum forms Pt(CO),X, and [Pt(CO)X,],. The latter were the first carbonyl complexes of any element to be described. They were reported by the French chemist, P. Schutzenberger, in 1870. 

Palladium complexes exhibit even higher catalytic activity and produce branched acids preferentially.132 133 The selectivity, however, can be shifted to the formation of linear acids by increasing the phosphine concentration.134 Temperature, catalyst concentration, and solvent may also affect the isomer ratio.135 Marked increase in selectivity was achieved by the addition of Group IVB metal halides to palladium136 and platinum complexes.137 Linear acids may be prepared with selectivities up to 99% in this way. The formic acid-Pd(OAc)2-l,4-bis(diphe-nylphosphino)butane system has been found to exhibit similar regioselectivities.138 Significant enhancements of catalytic activity of palladium complexes in car-bomethoxylation by use of perfluoroalkanesulfonic acid resin cocatalysts was reported.139,140... 

The halides of the palladium and platinum groups of metals closely resemble in character those of gold, which have already been described. The dihalides of the palladium group are all soluble, save Pdl2, which is prepared by precipitation with potassium iodide. Nitro-hydro-chloric acid yields the higher chloride it remains on evapo-... 

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