1956 MAY: AROMATIC ANTIMONY COMPOUNDS. PART I.CCVI1.-Aromatic Antimony Compounds. Part I.The Oxidation and Nitration of Triphenylstibine.By PERCY MAY.VARIOUS aromatic derivatives of antimony of the type R,Sb andR,SbX,, in which R represents phenyl, tolyl, anisyl, etc., and Xrepresents C1, Br, NO,, or OH, have been prepared by Michaelisand his pupils (Michaelis and Reese, AnmaZen, 1886, 233, 5 2 ;Michaelis and Genzken, Annalen, 1887,242,176; Loloff, Ber., 1897,30, 2834), but nevertheless far less work has been carried out withthese compounds than with the corresponding derivatives of arsenic.Michaelis and Reese showed that the compound (C,H,),Sb(OH), isamphoteric in character, and it therefore appeared to be of interestto observe the effect of the introduction of a nitro-group on therelative stability of the various compounds, such as R,SbCI,,R,Sb(OR),, R,Sb(NO,),.Michaelis and Reese prepared the com-pound (C,H,),Sb(N03)2 by the action of nitric acid on triphenyl-stibine, but if, at the same time, a nitregroup could be introducedinto the benzene nuclei, the basicity of the compound R,Sb(OH),might be so depressed that a nitrate such its R,Sb(NO,), could nolonger be formed, and the resulting compound might be of the typeR,Sb(NO,) (OH).On nit ration, triphenylstibine yields t rinit ro t riphenyls ti b i n e di-hydroxide, (C,H,*NO,),Sb(OI~),. It does not appear to be capableof forming a stable sulphate or nitrate, but a chloride has beenprepared, and it therefore appeared to be desirable to obt,ain somefurther information as to the relative stability of the parentsubstance, (C,H,),Sb~OH),, and its salts, and, if possible, to preparethe hitherto unknown normal sulphate, (C,H,),SbSO,.Triphenyl-stibine readily reduces concentrated sulphuric acid, with theformation of the desired sulphate, thus :(C6H,),Sb + 2H2S04 = (C6H,),SbSO4 + so, + 2H20,and this compound could also be obtained by dissolving the correMAY : AROMATIC ANTIMONY COMPOUNDS. PART I. 1057sponding hydroxide in concentrated sulphuric acid. Dilutesulphuric acid does not attack triphenylstibine, but permanganateand dilute sulphuric acid oxidise it to the hydroxide,(C,H,),Sb(OH),. This reaction is of interest from a twofold pointof view. On the one hand, it indicates that the sulphate is far lessstable than the chloride,* and, on the other hand, it affords freshevidence of the great stability of the molecule of triphenylstibineas a whole.I f alkaline permanganate be used as the oxidisingagent, a better yield of the dihydroxide is obtained. Michaelis andReese state that solutions of this substance in alkali are repre-cipitated by mineral acids, but on repeating these experiments itwas found that dilute nitric or sulphuric acids produced noprecipitate, whilst hydrochloric acid caused precipitation even invery dilute solutions. Probably the experiments of Michaelis andReese were confined t o halogen acids. Similarly, solutions of tri-phenylstiibine sulphate and nitrate in the corresponding con-centrated acids can be diluted indefinitely, although these substancesthemselves are insoluble in dilute acids, but, on addition of dilutehydrochloric acid t o their dilute solutions, an immediate precipitateof the chloride is obtained.The introduction of a nitro-group into the benzene nuclei of thecomplex R,Sb(OH), not only reduces the salt-forming power ofthe molecule, but also lowers its stability as a, whole.This isshown by the fact that the trinitro-derivative is partly decomposedwhen boiled with aqueous alkali, yielding a, small quantity ofnitrobenzene.EXPERIMENTAL.The triphenylstibine used in this investigation was prepared byMichaelis and Reese’s method, shortened and simplified in some ofits detai1s.t The long method of purification after extraction withalcoholic hydrochloric acid, described by these authors, was omitted,the product being instead directly recrystallised from lightpetroleum.Pure triphenylstibine was thus obtained, the yieldbeing 70 per cent.. of the theoretical. The material contained inthe petroleum mother liquor was converted into the dichloride,which, after recrystallisation, was still contaminated with traces ofan impurity having an extremely irritant action on the mucousmembrane. This was finally removed by dissolving the product inconcentrated sulphuric acid, pouring the product into aqueousalcohol, and setting aside to crystallise.* Triphenylstibine hydroxide combines readily with dilute hydrochloric acid,forming the dichloride.f A stock solution of dry antimony chloride in dry benzene, made up for thesepreparations, gradually acquired a deep magenta collour cven in the dark1958 MAY: AROMATIC ANTIMONY COMPOUNDS.PART I.A7itration of Triphenylstibine and Preparation of Trinitrophenpl-s t i b in e Dih y dr o xid e, (C0H,-N02)3Sb (OH),.Triphenylstibine was added, in small quantities a t a time, to anexcess of a mixture of three parts of sulphuric acid and one partof nitric acid, a t about 40°. When cold, the mixture was pouredinto ice-water, the temperature being kept below 25O. Theyellow precipitate thus obtained was recrystallised from glacialacetic acid, in which it is very soluble, and separates in flat,transparent, pale yellow crystals, melting at 190-191O. It is alsosoluble to some extent in alcohol or ether, but does not crystallisewell from these solvents.It is insoluble in water, and almostinsoluble in benzene, light petroleum, etc. :Found, C= 41.74 ; H = 2-91 ; N = 7.79, 7.91 ; Sb = 22-06.C,,H,,O,N,Sb requires C = 41.5 ; H = 2.72 ; N = 8.07 ;Sb = 23.11 per cent.On treatment with Devarda’s alloy no ammonia is evolved.When boiled with glacial acetic acid and zinc dust, or with alcohol,hydrochloric acid, and tin, it yields an easily diazotisable amine,which was not further investigated, as work on this compound isbeing carried out by Morgan, Micklethwait, and Whitby (Proc.,1910, 26, 151).TTinit rop henylstib ine Dichloride, (C,H,~NO,),SbCl,.This compound is formed, together with the hydroxy-chloride, byboiling trinitrophenylstibine dihydroxide with alcoholic hydro-chloric acid.After recrystallising, the product still appeared tobe impure, and analysis indicated that it was a mixture of thedichloride and the hydroxy-chloride. The pure dichloride wasobtained by the direct nitration of triphenylstibine dichloride,which was dissolved in concentrated sulphuric acid, and thennitrated in the same manner as triphenylstibine. It separatesfrom glacial acetic acid in clusters of small crystals, melting at157O, which are readily soluble in concentrated nitric acid or glacialacetic acid. As this substance was only obtained in small amount,its properties were not further investigated.Found, C1= 12.37.C,8H,,06N,C1,Sb requires c1= 12.73 per cent.Triphenylstibine Sulphate, (C6H,)3SbS0,.Five grams of triphenylstibine were warmed with an excess ofconcentrated sulphuric acid on the water-bath.A vigorous reactionsuddenly set in, sulphur dioxide being evolved, and a white p r MAY: AROMATIC ANTIMONY COMPOUNDS. PART I. 1959cipitate formed, which was filtered on asbestos, and washed withcold alcohol, a portion being afterwards extracted with this solvent-,in which it is only very sparingly soluble. Sniall crystals were thusobtained, and similar crystals separated on evaporation of themother liquor after dilution with water. These crystals melt above300°, and are soluble in concentrated sulphuric acid, very sparinglyso in alcohol, and insoluble in water, dilute sulphuric acid, and mostother solvents.The substance is decomposed by warming withaqueous sodium hydroxide, forming sodium sulphate and triphenyl-stibine hydroxide, the latter dissolving in the excess of alkali :Found, S = 7-30.Cl8H1,O4SSb requires S = 7-17 per cent.A solution of the sulphate in sulphuric acid may also be obtainedby dissolving triphenylstibine hydroxide in the concentrated acid,and this solution, as also the sulphuric acid mother liquor mentionedabove, can be largely diluted without any precipitation occurring,but on adding a drop of hydrochloric acid t o solutions of anyconcentration, a precipitate is formed, which, after recrystallisationfrom alcohol, was found to have the characteristic crystalline formand melting point of triphenylstibine dichloride.Oxidution of Triphenylstibine with Permanyanate.(1) In Alkaline Solution.-Triphenylstibine was boiled for threehours with alkaline permanganate, the manganese dioxide removed,and a portion of the filtrate acidified with hydrochloric acid.Awhite precipitate was produced, wb?ch was recrystallised from alcoholand found to be triphenylstibine dichloride. Another portion ofthe filtrate was acidified with dilute sulphuric acid, and in thiscase no precipitate was formed. Evidently the first product ofthe oxidation is triphenylstibine hydroxide, which dissolves in thealkali, giving solutions from which hydrochloric acid precipitatesthe chloride, but which are not precipitated by sulphuric or nitricacids.(2) In, A cid Solution.-Five grams of triphenylstibine werewarmed on the water-bath with an excess of 1 per cent. per-manganate and dilute sulphuric acid.The permanganate wasgradually decolorised with a slight evolution of carbon dioxide ;more permanganate was added from time t o time, and finally theprecipitate was collected and extracted with alcohol. I n this way,a small quantity of a substance was obtained which melted at210°, contained no sulphur, and appeared to be identical withtriphenylstibine hydroxide, as prepared by Michaelis and Reese.This substance was obtained by them in the form of an amorphouspowder, but a modification of their method of preparation led t1960 KENNER AND WITHAM : TOLANE DERlVATIVES FROMits being obtained in a well-crystallised state. An alcoholic solutionof triphenylstibine dichloride was added t o an equal volume of2177-aqueous sodium hydroxide, and the mixture set aside. Aftersome days, triphenylstibise hydroxide crystallised out in beautifulleaflets, which were washed with water and dried. The productwas then found to melt at 210°, and resembled the productobtained by Michaelis and Reese in its behaviour towards reagents.I wish to express my thanks to Sir William Ramsay and toProfessor Collie for the interest they have taken in this work, andto the Research Fund Committ.ee of the Chemical Societ,y for agrant towards the expenses thereof.UNIVERSITY COLLEGE,LONDON