Bismuth chloride-metal iodide

The redistribution reaction in lead compounds is straightforward and there are no appreciable side reactions. It is normally carried out commercially in the liquid phase at substantially room temperature. However, a catalyst is required to effect the reaction with lead compounds. A number of catalysts have been patented, but the exact procedure as practiced commercially has never been revealed. Among the effective catalysts are activated alumina and other activated metal oxides, triethyllead chloride, triethyllead iodide, phosphorus trichloride, arsenic trichloride, bismuth trichloride, iron(III)chloride, zirconium(IV)-chloride, tin(IV)chloride, zinc chloride, zinc fluoride, mercury(II)chloride, boron trifluoride, aluminum chloride, aluminum bromide, dimethyl-aluminum chloride, and platinum(IV)chloride 43,70-72,79,80,97,117, 131,31s) A separate catalyst compound is not required for the exchange between R.jPb and R3PbX compounds however, this type of uncatalyzed exchange is rather slow. Again, the products are practically a random mixture. 

Bismuth(III) iodide has been prepared in the absence of solvents by the reaction of iodine with elemental bismuth1,2 or with bismuth (III) sulfide.3 Alternative methods involve precipitation of bismuth(III) iodide from aqueous solutions of bismuth salts by adding alkali-metal iodides,4 and the addition of bismuth (III) oxide to a solution of iodine and tin(II) chloride in saturated hydrogen chloride.5 In either case the initial product is purified by sublimation, usually in an atmosphere of carbon dioxide. The product obtained by precipitation requires several resublimations for complete purification.6... 

The use of BiCl, as a Lewis acid catalyst of the Mukaiyama aldol reaction was introduced by Wada et al. [56]. The catalytic activity of BiCla is not so high however, Dubac et al. found that addition of metal iodides such as Nal, Znh, and Snh is very effective in the BiCls-catalyzed reaction (Scheme 10.18) [57]. Treatment of BiCl3 with these iodides forms Bilj, but iSii, alone and the ISilj-melal chloride system do not have high activity. In contrast, a mixture of Bilj and BiClj is very effective. Bi I, generated in situ from BiCl j would promote silylation of the intermediary bismuth aldolates 23 with TMSX to facilitate the catalytic cycle. 

Samarium selenides. Reductive cleavage of ArSeSeAr by samarium is catalyzed by a great number of metal halides bismuth(III) chloride, cadmium chloride, chromium(IIl) chloride, cobalt(II) chloride, potassium iodide, and titanium(lV) chloride. The resulting samarium arylselenides readily react with various organic halides. 

The first example bismuth-catalyzed aldol reaction was reported by Wada and Akiba and co-workers in 1988, in which 5 mol% of Bids mediated the Mukaiyama aldol reaction efficiently at room temperature (Scheme 48) (189). Subsequently, metallic iodide-activated bismuth(III) chloride, and Bi(OTf)3, were also examined for the Mukaiyama aldol reactions in organic solvents or ionic liquids (190-193). An extension of bismuth triflate catalyzed aldol or aldol-type reaction to the synthesis of substituted 3,4-dihydro-2if-l-benzopyrans has also been reported by Mohan and co-workers (Scheme 49) (194). 

Luberoff et al. [490] employed as initiators metal salts such as chloride, bromide, iodide, sulfate, and nitrate of mercury(II) the chloride, bromide, and iodide of bismuth and the chloride of antimony. The mechanism of polymerization with these initiator systems is still unknown, but the experimental results show that the systems are neither Friedel-Crafts nor free-radical catalysts. 

Previous works have shown that metallic iodide activated bismuth(lll) chloride efficiently catalyzes the Mukaiyama aldol and Michael reactions. Moreover, it has been shown that ultrasound activates significantly the catalytic power of these metallic halide systems [32a]. Interestingly, the use of these catalytic systems proved to be particularly remarkable in the case of the synthesis of functional furan derivatives [24c, 32b]. The use of Bi(OTf)3 xH20 has also been reported for these reactions [32c-e]. The Mukaiyama aldol reaction in an ionic liquid such as [Bmim][BF4] proceeds smoothly with silyl enolates and a catalytic amount of Bi(0Tf)3 %H20 [32d,e]. Various silyl enolates and aldehydes were tested. Moderate to very good yields of P-hydroxy ketones were obtained. 

Rubidium metal alloys with the other alkaU metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double haUde salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and 2iac. These complexes are generally water iasoluble and not hygroscopic. The soluble mbidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide. 

The reaction is a sensitive one, but is subject to a number of interferences. The solution must be free from large amounts of lead, thallium (I), copper, tin, arsenic, antimony, gold, silver, platinum, and palladium, and from elements in sufficient quantity to colour the solution, e.g. nickel. Metals giving insoluble iodides must be absent, or present in amounts not yielding a precipitate. Substances which liberate iodine from potassium iodide interfere, for example iron(III) the latter should be reduced with sulphurous acid and the excess of gas boiled off, or by a 30 per cent solution of hypophosphorous acid. Chloride ion reduces the intensity of the bismuth colour. Separation of bismuth from copper can be effected by extraction of the bismuth as dithizonate by treatment in ammoniacal potassium cyanide solution with a 0.1 per cent solution of dithizone in chloroform if lead is present, shaking of the chloroform solution of lead and bismuth dithizonates with a buffer solution of pH 3.4 results in the lead alone passing into the aqueous phase. The bismuth complex is soluble in a pentan-l-ol-ethyl acetate mixture, and this fact can be utilised for the determination in the presence of coloured ions, such as nickel, cobalt, chromium, and uranium. 

Bismuth reacts with chlorine, bromine and iodine vapors forming chloride, bromide and iodide of the metal, respectively. Molten bismuth and sulfur combine to form bismuth sulfide, Bi2S3. 

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