Bismuth-methyl compounds

While the plots of enthalpies of formation indicate that the arsenic, antimony and bismuth data are problematic, they cannot be used to recommend alternative values since both the methyl and ethyl are thought to be affected by large errors. If one of these were known to be reliable, it could be used to predict the second one. The difference between the enthalpies of formation of methyl and ethyl derivatives relates to the electronegativity of the affixed atom or group, wherefore the more electronegative it is, the less relatively stable is the methyl compared to the ethyl derivative. This stability reasoning extends to the relative stability of methyl and ethyl cation, and antithetically to methyl and ethyl anion, hence we conclude that only for extremely electropositive elements such as lithium is it at all conceivable that the methyl compound has the more... 

A considerable number of organometallic species of arsenic, antimony and bismuth have been detected in the natural environment in different manners. A number of these are nonmethyl compounds which have entered the environment after manufacture and use [e.g. butyltin and phenyltin compounds for antifouling paints on boats, and arsanilic acid (Figure 2, 5) and phenylarsonic acids (Figure 2, 6-8) for animal husbandry]. Only a few methyl compounds are now manufactured and used (e.g. methyltin compounds for oxide film precursors on glass and methylarsenic compounds for desiccants or defoliants). 

Triethylbismuthine, ( 2115)361, has been obtained by the action of ethyl iodide on potassium-bismuth alloy, and from bismuth bromide and zinc diethyl. It is a fuming oil, distilling unchanged at 107° C. at 79 mm., and exploding when heated in air at ordinary pressures. Its density is 1 82. Its solubihty and behaviour towards halogens is similar to that of the methyl compound. Evaporation of its ether solution in the presence of air leads to the formation of bismuth hydroxide, and if the solution be saturated with hydrogen sulphide, bismuth sulphide separates. If to a warm dilute alcoholic solution of triethylbismuthine a sinular solution of mercuric chloride is added, a precipitate of mercurous chloride is thrown down but if the order of addition is reversed, ethylmercuric chloride and ethyldichlorobismuthine are produced ... 

Diethylbromobismuthine, ( 2H5)26iBr, is prepared in a similar manner to the methyl compound, and is a white powder, igniting in air, with the formation of bismuth oxide. 

Both alkyl and aryl metals have been studied, but not a very wide range of compounds. Several studies of triphenylarsene and triphenylstibine have been done. Methyl and ethyl compounds of arsenic, germanium, mercury, bismuth, and lead essentially complete the list. In virtually all cases the results have been clouded by difficulties in effecting chemical separation without altering the product distribution. The results do, nonetheless, lead to valid and important conclusions. 

Aryl chlorides can also be used as coupling partners for azabismocine reagents 2. In the coupling reaction with aryl chlorides, Pd(PPh3)4 was not an efficient catalyst, and Pd(OAc)2/l,l,-bis(diphenylphosphino)ferrocene (dppf) combination was found to be effective [54]. Not only the arylation, but also methylation, alkenylation and alkynylation reactions can be accomplished by using the corresponding bismuth compounds (Scheme 35). The addition of CsF improved the product yields. However, electron-rich aryl chlorides were unable to be coupled efficiently under these reaction conditions. 

Because organobismuth(V) compounds have found considerable use as oxidizing agents, the oxidizing ability of methyl di-l-naphthylbismuthinate [124066-66-6], C21H17Bi02, was investigated. Benzoin yields benzil, naphthalene, and metallic bismuth hydrazobenzene yields azobenzene, and 1,1,2,2-tetraphenylethanediol yields benzophenone. 1,2-Diphenyl-1,2-ethanedione dihydrazone gives diphenylacetylene in 50% yield. Cyclohexane-1,2-diol and 1-phenylethane-l,2-diol, however, were unaffected. 

The only known example is hexahydro-lH-arsolo[l,2-a]arsole (17) (63JCS725). This unusual compound is prepared when the arsonium bromide (18) is heated to 200 °C (equation 6). Cyclization is accompanied by loss of methyl bromide to give (17 b.p. 100-102 °C/17 mmHg) which was characterized as the red palladium dibromide adduct (m.p. 150 °C). No analogous derivatives of antimony or bismuth have been reported. 

Sodium bismuthate reacts with 1 (47, 52), as does BiON03 (46). Methyl exchange between Cr(II) and 1 follows second-order kinetics (55) the rate constant was 360 30M sec-1, and values for the activation parameters A H and A 5 were 15.9 0.9 kJ mol-1 and -144 J mol-1 K respectively. Ferric compounds are reported to demethylate 1 (30, 31, 37). Cupric nitrate gives no noticeable reaction by itself with 1 (46, 54), but de-methylation proceeds readily in the presence of high chloride or bromide concentrations (>2 M). Methyl chloride and methyl bromide formed as products. When ethanol was used as solvent, methyl ethyl ether also formed as product (54). An unstable intermediate CH3CuC1 may form as... 

Many studies on the direct reaction of methyl chloride with silicon-copper contact mass and other metal promoters added to the silicon-copper contact mass have focused on the reaction mechanisms.7,8 The reaction rate and the selectivity for dimethyldichlorosilane in this direct synthesis are influenced by metal additives, known as promoters, in low concentration. Aluminum, antimony, arsenic, bismuth, mercury, phosphorus, phosphine compounds34 and their metal complexes,35,36 Zinc,37 39 tin38-40 etc. are known to have beneficial effects as promoters for dimethyldichlorosilane formation.7,8 Promoters are not themselves good catalysts for the direct reaction at temperatures < 350 °C,6,8 but require the presence of copper to be effective. When zinc metal or zinc compounds (0.03-0.75 wt%) were added to silicon-copper contact mass, the reaction rate was potentiated and the selectivity of dimethyldichlorosilane was enhanced further.34 These materials are described as structural promoters because they alter the surface enrichment of silicon, increase the electron density of the surface of the catalyst modify the crystal structure of the copper-silicon solid phase, and affect the absorption of methyl chloride on the catalyst surface and the activation energy for the formation of dimethyldichlorosilane.38,39 Cadmium is also a structural promoter for this reaction, but cadmium presents serious toxicity problems in industrial use on a large scale.41,42 Other metals such as arsenic, mercury, etc. are also restricted because of such toxicity problems. In the direct reaction of methyl chloride, tin in... 

This derivative is obtained by condensing 3-amino-4-hydroxyphenyl-arsine with bismuth trichloride m methyl alcohol solution in the presence of hydrogen chloride. It is a black jjowder, decomposing in a similar manner to the preceding compound, and boiling its aqueous solution even leads to decomposition. 

Other metal compounds that are capable of decomposing at end gas temperatures to produce oxide smokes also can act as anti-knocks. These include iron and nickel carbonyls, trimethyl bismuth and methyl cyclopen-tadienyl manganese tricarbonyl [6]. The last has been used commercially for some years in Canada. Its anti-knock properties also can be amplified by organic co-anti-knocks (diketones in this case) [47]. Concerns over the possible toxicity of fine aerosols which are emitted in the exhaust will limit the acceptability of these metal containing materials in the future. 

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