XVL-Organo-Derivatives of Bismuth. Part V. the Stability of Halogen, Cyano-, and Thiocyano- Derivatives of Tertiary Aromatic Bismuthines
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View Article Online / Journal Homepage / Table of Contents for this issue ORGANO-DERIVATIVES OF BISMUTH. PART V. 91 XVL-Organo-derivatives of Bismuth. Part V. The Stability of Halogen, Cyano-, and Thiocyano- derivatives of Tertiary Aromatic Bismuthines. By FREDERICKCHALLENGER and JOHNFREDERICK WILKINSON. THE dihaloids of triphenylbismuthine show diminished stability with increase in the positive character of the halogen until, with iodine, the di-iodide, Ph,BiI,, has not been isolated but immediately decomposes, giving iodobenzene and diphenyliodobismuthine (Challenger and Allpress, T., 1915, 107, 21 ; Gillmeister, Ber., 1897, 30, 2843). As a result of work described in this and in previous communications, the relations existing between the dihaloids and similar derivatives may be summarised thus- 31. p. Temp. of Decomposition. Difluoride ........................ 159" 190-200" Dichloride ........................ 141" 150°, and slowly in boiling benzene. Dibromide ........................ 122" looo, and easily in boiling benzene. Di-iodide, not isolated, unstable, yielding Ph,BiI and PhI. Dicyanide, not isolated, unstable, yielding Ph,Bi.CN and Ph-CN. Dithiocyanate, not isolated, unstable, yielding Ph,Bi. SCN and Ph-SCN. The decomposition of the dihaloids may be represented by the equations- (i) Ph,BiX, = Ph,BiX + PhX or (ii) 2Ph,BiX, = Ph,Bi + PhBiX, + 2PhX and at a higher temperature, Published on 01 January 1922. Downloaded by University of Western Ontario 31/10/2014 11:40:05. (iii) 2Ph,Bi = 3Ph, + 2Bi. When triphenylbismuthine dichloride is treated with potassium fluoride in aqueous-alcoholic solution, triphenylbismuthine dijluoride, m. p. 159", is produced. This decomposes when heated, giving fluorobenzene, triphenylbismuthine ,diphenyl, and probably bismuth fluoride. Although no tetraphenylbismuthonium haloids have so far been obtained, the stability of the difluoride led us to hope that, by interaction with magnesium phenyl bromide, tetraphenyl- bismuthonium fluoride might possibly be formed, but only triphenyl- bismuthine was isolated. The action of potassium hydrogen fluoride on triphenylbismuthine dichloride differs from that of the normal fluoride, triphenylbismuth- ine being obtained. The production of this substance from potass- ium fluoride and diphenylbromobismuthine (p. 101) appears to View Article Online 92 CHALLENGER AND WILKMSON be analogous, and is possibly due to the production of potassium hydroxide by hydrolysis (see p. 94; and Challenger and Goddard, T., 1920, 117, 766). The course of the reaction between diphenylbromobismuthine and silver nitrate depends on the temperature and possibly on the time of interaction. In boiling alcohol, silver bromide, bismuth oxynitrate, and sometimes triphenylbismuthine are produced, whilst reaction in the cold yields the bismuthine, bismuth salts, diphenyl, silver bromide, and metallic silver. Probably the first product is diphenylbismuthine nitrate, Ph,BiNO,, which may react with water, forming benzene and bismuth oxynitrate. It may also be hydrolysed to nitric acid and diphenylhydroxybismuthine, Ph,Bi*OH, which would then yield triphenylbismuthine and bismuth hydroxide (Michaelis and Marquardt, Annalen, 1889, 251, 323). Challenger and Allpress (T., 1921, 119, 916) have shown that triphenylbismuthine and silver nitrate give a yellow, crystalline precipitate, probably having the composition AgN0,,2AgPh, a compound which has been described by Krause and Schmidt (Ber., 1919,52,2150). This compound would probably decompose, giving metallic silver and diphenyl *- AgNO,,ZAgPh = AgNO, + 2Ag + Ph,. This would be analogous to the behaviour of alkyl and aryl plumbanes, which also reduce silver nitrate to the metal, giving organo-silver compounds as intermediate products (Krause and Schmidt, Zoc. cit.). From lead thiocyanate and diphenylbromobismuthinein alcoholic solution, triphenylbismuthine and diphenylthiocyanobisrnuthine, Ph,Bi*SCN, were obtained. The production of triphenylbismuthine Published on 01 January 1922. Downloaded by University of Western Ontario 31/10/2014 11:40:05. is due to decomposition of the diphenylthiocyanobismuthine in alcoholic solution, a reaction which has been observed during the purification of this substance, and which is analogous to the behaviour of diphenylcyanobismuthine (T., 1915, 107, 20)- 3Ph,Bi*SCN = ZPh,Bi + Bi(SCN),. Diphenylcyanobismuthine was also obtained from diphenyl- bromobismuthine and potassium cyanide in aqueous-alcoholic solution. In an attempt to obtain the unknown dicyanide, Ph,Bi(CN),, from the dichloride and alcoholic potassium cyanide, diphenyl- * Mr. A. L. Smith has shown that diphenyIbromobismuthine and silver fluoride in the cold give silver bromide, bismuth fluoride, diphenyl, and metallic silver. View Article Online ORGANO-DERIVATIVES OF BISMUTH. PART V. 93 cyanobismuthine was isolated, which may be explained by the elimination of benzonitrile from the dicyanide. When the dry dichloride and silver cyanide are gently heated, the odour of benzo- nitrile is apparent at 75". It was hoped that the unknown triphenyl- bismuthine dithiocyanate, Ph,Bi(SCN),, might be obtained by treating the dichloride with silver thiocyanate in cold alcohol, but no reaction occurred. When lead thiocyanate and triphenylbismuthine dichloride were heated to about 85", phenyl thiocyanate was produced. From lead thiocyanate and an alcoholic solution of triphenyl- bismut hine dichloride, diphenylt hiocyanobismut hine, phen yl thiocyanate, and polymerised thiocyanogen, (SCN), (Soderback, Annulen, 1919, 419, 317) were isolated. An attempt to obtain triphenylbismuthine dithiocyanate by the addition of free thiocyanogen, (SCN),, prepared according to the method of Soderback (Zoc. cit.), to triphenylbisrnuthine in ethereal solution wits also unsuccessful, the products being bismuth thiocyan- ate (Bender, Ber., 1887, 20, 723), phenyl thiocyanate, and diphenyl- thiocyanobismuthine, which has therefore been prepared by three different methods. This is analogous to the action of thiocyanogen on mercury diphenyl, giving mercury phenyl thiocyanate and phenyl thiocyanate (Soderbiick, Zoc. cit.). The production of the small quantity of bismuth thiocyanate might be caused by further substitution, or decomposition of the diphenylthiocyanobismuthine as above. From these results, it is obvious that triphenylbismuthine dicyanide and dithiocyanate-as well as the di-iodide-are extremely unstable compounds, a property which is shared by the correspond- ing salts of copper. Published on 01 January 1922. Downloaded by University of Western Ontario 31/10/2014 11:40:05. This being the case, it was of interest to determine whether the cyano- or the thiocyano-radicle possesses the greater affinity for bismuth. For this purpose, cyanogen sulphide, (CN),S (Schneider, J. pr. Chem., 1885, [ii], 32, 187), and triphenylbismuthine were shaken with dry ether for eleven hours, yielding bismuth thiocyanate, unchanged triphenylbismuthine, diphenylthiocyanobismuthine, and phenyl thiocyanate. No diphenylcyanobismuthine was isolated. Other experiments confirmed these results, and the reaction is being further investigated. A similar lack of success attended our efforts to prepare the dicyanide and dithiocyanate of tri-cc-naphthylbismuthine. Lead thiocyanate and tri-cc-naphthylbismuthine dichloride in boiling alcohol gave a-naphthyl thiocyanate, and tri-a-naphthylbismuthine. No a-naphthylthiocyanobismuthines were detected, due probably to their instability. View Article Online 04 CHALLENGER AND WILKINSON : The hypothetical dithiocyanate probably breaks down thus :- (C10H7)3Bi(SCN)2= (CloH,),Bi*SCN+ CloH7*SCN. 3(C1,H,),Bi*SCN = 2(CloH7),Bi + Bi(SCN),. a-NaphthyZ thiocyanate does not appear to have been described.* It was also obtained from tri-a-naphthylbismuthine and thiocyano- gen, together with bismuth thiocyanate, thus :- (C1,H7),Bi + 3(SCN), = 3CloH7*SCN+ Bi(SCN),. With potassium cyanide in boiling alcohol, tri-a-naphthylbismuthine dichloride gave the bismuthine. This may be due to the action of alkali, arising from the hydrolysis of potassium cyanide, on di-a- naphthylcyanobismuthine (compare p. 92 ; and Challenger and Allpress, T., 1921, 119, 914). Triphenylbismuthine dichloride was prepared by Michaelis and Marquardt (Zoc. cit.) by the action of chlorine on the bismuthine in chloroform, but no mention is made of the simultaneous produc- tion of a small quantity of diphenylchlorobismuthine, which may be isolated on crystallisation from acetone, in which it is sparingly soluble. This probably explains the low m. p. of the dichloride, when recrystallised from chloroform-light petroleum. The m. p. of the pure dichloride has, however, been shown to depend on the rate of heating, being somewhat higher when rapidly heated, and in the case of large crystals. Potassium cyanate and triphenylbismuthine dichloride, when heated with alcohol, regenerated the free bismuthine, this being probably due to hydrolysis of the potassium cyanate. No reaction occurred in the cold. Kipping and Sands (T.,1921, 119, 842) have shown that with Published on 01 January 1922. Downloaded by University of Western Ontario 31/10/2014 11:40:05. s-tetrachloroethane, certain silico-hydrocarbons give dichloro- additive products. Its action on tertiary bismuthines has been investigated, triphenylbismuthine yielding diphenylchlorobismuth- ine. No dichloride was isolated, even on heating for only a few seconds, although this compound is probably formed in the first instance. No reaction occurred in the case of tri-cr-naphthyl-