Zinc metal lead halides

Vinylic copper reagents react with CICN to give vinyl cyanides, though BrCN and ICN give the vinylic halide instead." Vinylic cyanides have also been prepared by the reaction between vinylic lithium compounds and phenyl cyanate PhOCN." Alkyl cyanides (RCN) have been prepared, in varying yields, by treatment of sodium trialkylcyanoborates with NaCN and lead tetraacetate." Vinyl bromides reacted with KCN, in the presence of a nickel complex and zinc metal to give the vinyl nitrile. Vinyl triflates react with LiCN, in the presence of a palladium catalyst, to give the vinyl nitrile." ... 

The pentavalent halides are the most stable, but even these can be prepared only in the dry way because of the readiness with which they undergo hydrolysis. The trichloride is obtained by reduction of the pentachloride with a powdered metal (lead, aluminium, zinc) the same process has also given a dichloride and perhaps a tetrachloride, but their formation awaits independent confirmation. The preparation of the chloroadi, HTasCl7.4H20, is of interest in that corresponding... 

Numerous modifications of the direct zinc insertion procedure can be found in the hterature. For example, simple diaUcylzincs can be used as reagents instead of metallic Zn, bnt in this case the reaction is accelerated by catalytic qnantities of zinc salts or transition metal see Transition Metals) salts. Whereas the Cu -catalyzed iodine-zinc exchange reaction provides diorganozincs, the Pd, Mn and nF catalyzed iodine- or bromine-zinc exchange leads to organozinc halides. 

Aryl halides containing less reactive halogen can also be converted into sulfides by thiols if heavy-metal (lead, zinc, mercury) thiols are used at 225-230° 1-naphthyl, 2-naphthyl sulfide,301 1- and 2-naphthyl phenyl sulfide,302 and 1-and 2-naphthyl o-, m-, and p-tolyl sulfide303 have been obtained in this way. When the heavy-metal thiolates are too stable and do not react with aryl bromides even at 240°, the aryl sulfides can nevertheless often be prepared by a generally applicable reaction of aryl iodides with sodium thiolates under the influence of copper as catalyst.304... 

The first attempts (5) to reduce metal salts with sodium at low temperatures were made by researchers working with solutions of sodium in liquid ammonia. In 1925 Kraus and Kurtz (7) showed that liquid ammonia solutions of sodium could be used to reduce halides of metals that form alloys with sodium. Operating at temperatures below the boiling point of the ammonia solutions they succeeded in reducing the halides of mercury, cadmium, zinc, tin, lead, antimony, bismuth, and thallium, and, by using an excess of sodium, concomitantly produced sodium alloys of these metals. Kraus and Kurtz postulated mechanisms for the reactions and showed that many of the alloys formed were unstable in liquid ammonia— i.e., they disproportionated into free sodium and lower sodium alloys. 

Interaction of long-chain n-alkylammonium halides with a halide of a divalent metal leads to the formation of salts of the general formula (RNH3)2MX4 with peculiar phase changes in the solid state [65]. Bis(n-alkylammonium)bromo zinc-ates with n = 10-16 display two reversible high entropy solid crystalline-solid crystalline phase transitions and a solid crystalline-liquid crystalline (smectic phase) transition up to at least 450 K. 

The formation of rare earth silicates can be accelerated by the addition of flux material to the reaction mixture. The accelerators may be halides, carbonates, sulfates or oxides of alkali metals, earth alkaline metals, lead, zinc, bismuth, etc. (Leskela and Niskavaara, 1981). The amount of the accelerator represents only a few percent of the total weight of the reaction mixture. For example, using alkah fluorides it is possible to reach a complete conversion to silicate in the temperature range 1000-1300°C (Watanabe and Nishimura, 1978 Leskela and Niskavaara, 1981). 

Rubidium metal alloys with the other alkali metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double halide salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and zinc. These complexes are generally water insoluble and not hygroscopic. The soluble rubidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide,... 

The synthesis of organozinc compounds by electrochemical processes from either low reactive halogenated substrates (alkyl chlorides) or pseudo-halogenated substrates (phenol derivatives, mesylates, triflates etc.) remains an important challenge. Indeed, as mentioned above, the use of electrolytic zinc prepared from the reduction of a metal halide or from zinc(II) ions does not appear to be a convenient method. However, recent work reported by Tokuda and coworkers would suggest that the electroreduction of a zinc(II) species in the presence of naphthalene leads to the formation of a very active zinc capable of reacting even with low reactive substrates (equation 23)11. 

One of the most interesting aspects of molten salt chemistry is the readiness with which metals dissolve. FOr example, the alkali halides dissolve large amounts of the corresponding alkali metal, and some systems (e.g., cesium in cesium halides] are completely miscible at all temperatures above the melting point. On the other hand, the halides of zinc, lead, and tin dissolve such small amounts of the corresponding free metal that special analytical techniques must be devised in order to estimate the concentration accurately. 

---