A NEW TYPE OF COMPOUND CONTAINING ARSENIC. 1373 CXL1X.-A New of Compound containing Arsenic. By GEOEGE JOSEPH BURROWS and EUSTACE EBENEZER TURNER. HITHERTO our knowledge of additive compounds formed from arsines has been restricted to those of the cacodyl series and the compounds in question are of the co-ordination type and contain such elements as platinum mercury and copper. The authors have found that many arsines of the type R,R,R,As where R1, R, and R may be similar or dissimilar alkyl or aryl groups, combine readily with methyldi-iodoarsine and with the corre-sponding ethyl and phenyl derivatives to give brightly-coloured substances varying in shade from pale yellow to deep orange and of the general type R,R,R,As,RAsI,. They are completely dis-sociated into their parent substances 011 dissolving in benzene but evaporation of such solutions gives the pure additive compoun 1374 BURROWS AND TURNER: once more.They react in benzene solution with methyl iodide, with precipitation of the methiodide of the arsine the alkyl- or aryl-di-iodoarsine remaining in solution. The solid additive com-pounds cannot be said to be unstable remaining unchanged indefinitely under ordinary conditions but they crystallise only with difficulty from some solvents apparently owing to the retard-ing influence of the latter on the rate of addition of the two substances giving rise to the additive compound. The authors hesitate without further experimental work to suggest definite formula for the additive compounds. These may evidently be simple '' molecular compounds '' or compounds analogous to those formed between arsines and methylene iodide, and of the type R,R,R,IAs*AsRI.I n support of this structure can be cited the fact that as a rule an additive compound is paler than the di-iodoarsine from which it is formed and the further fact that iodine attached to arsenic in the quinquevalent condition has no chromophoric properties. Against the structure given above however is the fact of ready dissociation in benzene solution. Phenyldimethylarsine phenylmethylethylarsine and phenyldi-ethylarsine in their behaviour towards di-iodoarsines illustrate well the subject under discussion and the melting points of the various substances involved are tabulated below : MeAsI PhAsI EtAsI (30"). (19).(-9"). PhMe,As (liquid) ......... 94" 69" 44" PhMeEtAs (liquid) ...... 84 55" -PhEt,As (liquid) ......... 79 - -I n each of the nine cases allowed for by this table combination undoubtedly occurred since on mixing the pair of substances in quest'ion heat was evolved. Only six compounds were actually isolated and from the melting-point regularities this fact can no doubt be attributed to the low melting points of the three com-pounds which could not be isolated. Attention should perhaps be drawn to the isomerism of the additive compounds PhMeEtAs,MeAsI and PhMe2As,EtAsI,. On the other hand certain arsines show no tendency t o form additive compounds with di-iodoarsines no heat being evolved on mixing the substances in question. Thus diphenylmethylarsine, triphenylarsine and other aromatic arsines could not be caused to combine with di-iodoarsines under a wide range of experimental conditions.Phenyldichloroarsine has also been found to form an additive compound with the most reactive of the arsines in our possession A NEW TYPE OF COMPOUND CONTAINING ARSENIC. 1375 namely phenyldimethylarsine. The compound is strictly analogous to t)he iodo-compounds just described and the effect of heat on chloro-additive coinpounds generally if they can be pre-pared will be investigated since some light might thus be thrown on the interaction between say triphenylarsine and arsenious chloride which proceeds in a very irregular manner and is greatly influenced by temperature (compare Michaelis and Loesner Ber., 1891 27 294 etc.).The iodo-derivatives of arsenic have been found to be the most suitable for the preparation of the various types of arsines. They react almost quantitatively with Grignard reagents giving the expected arsines in all cases so far studied. The use of arsenious chloride or bromide (Auger and Billy C’ompt. rend. 1904 139, 597; Hibbert Ber. 1906 39 160) is t o be avoided as very low temperatures are necessarily involved. EX P E R I M E N TAL. Methyldiiodoarsine. This substance was prepared by Auger’s method (Compt. rend., 1906 142 1151) and was purified by distillation under diminished pressure. It boiled without decomposition at 128O/16 mm. and gave on cooling a bright yellow solid melting a t 30° (Auger, loc. c i t . gives 25O). On one occasion 320 grams of arsenious oxide converted into sodium methylarsinate by the method described by Klinger and Kreutz (Annalen 1888 249 149) gave more than 500 grams of pure redistilled methyldi-iodoarsine (Found M.W.[by cryoscopic method in benzene] = 331 340. Calc. M.W. = 344). In view of certain results obtained in other directions i t is considered possible that in other solvents methyldi-iodoarsine may be associated although a t present no direct evidence can be put forward in connexion with this point. The ease with which methyldi-iodoarsine may be prepared renders this substance a very convenient starting material for the preparation of arsenic deriv-atives. I n this connexion it is of interest to note that whereas methyl iodide reacts almost quantitatively in the course of a few hours with sodium arsenite in aqueous-alcoholic solution ethyl iodide reacts much more slowly a 57 per cent.conversion of sodium arsenite into ethyldi-iodoarsine (see below) being the maximum so far obtained. E thcyldi-iodoarsine . The product obtained (compare McKenzie and Wood this vol., p. 408) by the reduction of ethylarsinic acid was dried ove 1376 BURROWS AND TURNER: calcium chloride and the sulphur dioxide present removed by gentle warming under diminished pressure the whole of the liquid finally being distilled under the same conditions. Ethyldi-iodo-arsine was obtained in this way as a reddish-yellow oil boiling a t 1 2 6 O / 1 1 rnm. and setting to a pale yellow crystalline solid (m. p. -9") on cooling in solid carbon dioxide.Ph eny Zdi-iodoarsine . A mixture of phenyldichloroarsine (34 grams) 90 grams (a large excess) of finely powdered sodium iodide and 100 C.C. of absolute alcohol was shaken for three hours in the cold filtered and the filtrate evaporated to dryness under diminished pressure. The residue was extracted with qhloroform and the filtered extract evaporated under diminished pressure until quite free from chloro-form. A brownish-red oil in amount corresponding with an almost theoretical conversion of dichloro- into di-iodo-arsine was obtained and was purified by crystallisation from alcohol using solid carbon dioxide as an external refrigerant. In this way pure phenyldi-iodoarsine was obtained in lemon-yellow clusters of needles melting (after remaining in contact wiih porous porcelain a t a low temperature) a t 1 5 O (Found 1=62-9." M.W.[by cryo-scopio method in benzene] = 393 401. C,H,I,As requires I= 62.6 per cent. M.W. =406). Phenyldi-iodoarsine resembles the corresponding methyl and ethyl derivatives in odour and physiological properties. It under-goes slight decomposition when distilled under diminished pressure, boiling a t 190°/12 mm. The effect of heat on the product obtained by Michaelis and Schulte ( B e y . 1881 14 913) by the action of hydriodic acid on phenylarsenious oxide shows that this product was even before heating a mixture of several substances. Dime thyliodoarsine . The difficulty of obtaining derivatives of cacodyl has now been removed by the discovery that Auger's method for the reduction of methylarsinic acid to methyldi-iodoarsine (Zoc.cit .) may be applied to the conversion of dirnethylarsinic (cacodylic) acid into dimethyliodoarsine (cacodyl iodide). A solution of 250 grams of cacodylic acid and 800 grams of potassium iodide in 1 litre of water was saturated with sulphur dioxide dilute hydrochloric acid (500 C.C. of concentrated acid and * All these compounds in which iodine and arsenic are directly combined (whether the arsenic be ter- or quinque-valent) react quantitatively with silver nitrato in alcoholic solution A NEW TYPE OF COMPOUND CONTAININU ARSENIC. 1377 500 C.C. of water) being added from time to time. Reduction pro-ceeded rapidly with the separation of dimethyliodoarsine as a yellow oil the end of the process being indicated by the separation also of sulphur.The oily layer was separated dried over calcium chloride and distilled when pure dimethyliodoarsine (380 grams, corresponding with a 90 per cent. conversion) was obtained as a yellow liquid boiling a t 154-157O and freezing to a pale yellow, crystalline solid at about - 3 5 O . From . dimethyliodoarsine cacodyl oxide chloride etc. may readily be prepared without the production of intermediate com-pounds which are spontaneously inflammable. Phenylmethyliodoarsiize and Phenylmethylchloroarsine. By a similar reduction process phenylmethylarsinic acid (Bertheim Ber. 1915 48 350) has been converted into phenyl-met h y liod oarsin e . The plienylarsenious oxide required was prepared by treating phenyldichloroarsine with excess of powdered sodium hydrogen sulphite in the presence of a little water.On removing the inorganic matter by repeated extraction with hot water the pure oxide was left behind and when cold could be ground up and was then used without further purification for conversion int'o phenylmethyliodoarsine. Phenylarsenious oxide (50 grams) was dissolved in a solution of 30 grams of sodium hydroxide in 240 C.C. of rectified spirit and 60 C.C. of water the solution cooled and treated with 30 C.C. of methyl iodide. A vigorous reaction set in and was allowed to complete itself overnight. The mixture was acidified freed from alcohol by distillation treated with 50 grams of potassium iodide, and saturated with sulphur dioxide. The dark oil formed was separated dried over calcium chloride and distilled when 54 grams of phenylmethyliodoarsine a yellow oil boiling a t 138-140°/ 12 mm.were obtained (Found 1=43*7. C7H81As requires I = 43.2 per cent.). It is interesting t o note that in this preparation sodium hydr-oxide gives better results than potassium hydroxide. The preparation of the corresponding chloro-arsine is readily effected by treating the iodo-compound with the calculated amount of sodium hydroxide washing the oily oxide so obtained with water and subsequently shaking repeatedly with small quantities of concentrated hydrochloric acid. The oil after being dried over calcium chloride distils a t 113.5'/14 mm. (Found C1= 17.6. C7€18C1As requires C1= 17.5 per cent.) 1378 BURROWS AND TCTRNER: Plzenylme thykhloroarsine is a pale yellow liquid resembling phenyldichloroarsine in appearance and physiological properties.The so-called Bart reaction (D.R.-P. 250264) for the preparation of arsinic acids is unsatisfactory in the case of phenylmethylarsinic acid and therefore of its reduction products although a small quantity of phenylmethyliodoarsine was prepared in this manner, benzenediazonium chloride being combined with methylarsenious oxide in alkaline solution. The ethylation of phenylarsenious oxide proceeds very much more slowly than the methylation and is only partial under con-ditions that allow of quantitative methylation. Pheny Zdime thylamine. This arsine was obtained in 75 per cent. yield by Winmill (T., 1912 101 722) by the action of magnesium methyl iodide on phenyldichloroarsine in the presence of light petroleum.The following method gave even more satisfactory results. A Grignard reagent made by the interaction of 19 grams of bromobenzene 2.9 grains of magnesium and 50 C.C. of ether was gradually treated with a solution of 23.2 grams of dimethyliodo-arsine in 50 C.C. of ether. A vigorous reaction accompanied each addition of iodo-compound and after allowing the mixture to remain a t the ordinary temperature for two hours ice and dilute hydrochloric acid were added the ethereal layer separated and dried over anhydrous sodium sulphate. The ether was evaporated and the residue distilled under diminished pressure when 16 grams of phenyldimethylarsine were obtained as a colourless oil boiling a t 85O/14 mm.and possessing the properties ascribed to the arsine by Michaelis and Link ( A ~ ~ n a l e n 1881 207 205). The methiodide melted a t 2500 (Michaelis and Link Zoc. c i t . give 244O). The ethiodide is obtained a t water-bath temperatures and crystallises from alcohol in colourless needles melting a t 142O ; mixtures with the methiodide of phenylmethylethylarsine melted a t the same temperature indicating the identity of the two substances. The benziodide is readily formed and crystallises from a mixture of acetone and ether in colourless needles melting at 115-116O (Found I=31*5. Phenyldimethylarsine combines energetically with equimolecular quantities of certain halogenated arsines. Compound PhMe,As,MeAsI .-This compound is formed from the arsine aod methyldi-iodoarsine when the two substances are C,,H,,IAs requires 1=31.8 per cent.) NEW TYPE OF COMPOUND CONTAINING ARSENIC.1379 mixed in equimolecular quantities. Heat is generated and after a few moments the whole becomes solid. The product crystallises from a mixture of acetone and ether in lemon-yellow needles melt-ing a t 93-94O (Found I=48*3. M.W. [by cryoscopic method in benzene] = 259 264. C,IP,,I,As requires I = 48.3 per cent. The compound is theref ore completely dissociated into phenyl-dimethylarsine and methyldi-iodoarsine in benzene solution a t concentrations up to 5 per cent. M.W. =526). Action of Methyl Iodide on the Compound PhMe,As,MeAsI,. A solution of a small quantity of the compound in benzene, mixed with an excess of methyl iodide deposited after some hours, slender colourless needles which melted a t 243O without purifi-cation a mixture with pure phenyltrimethylarsonium iodide melt-ing a t 248O.The additive compound is quantitatively converted by methyl iodide into the methiodide of the arsine originally used. Compound PhMe,As,EtAsT2.-Phenyldimethylarsine combines readily with ethyldi-iodoarsine to give a yellow solid which when crystallised from alcohol melts a t 44O (Found 1 ~ 4 7 . 2 . M.W. [by cryoscopic method in bemenel= 364 266. C,,W,,I,As requires I=47*0 per cent. M.W. ~ 5 4 0 ) . Compound PhMe,As PhAsI,.-This compound prepared by mixing the arsine and iodo-arsine in calculated quantities crystal-lises from alcohol or acetone in orange-coloured prisms melting a t 69" (Found I = 43.3.M.W. [by cryoscopic method in benzene] = 286 287. C,,€11612A~L requires 1 ~ 4 3 . 2 per cent. M.W. ==588). This compound is of a deeper shade than those of the corre-sponding compounds from alkyldi-iodoarsines. Compound P hMe,As,PhAsCl,. -P henyldimethylarsine com bines readily with phenyldichloroarsine to give a colourless solid crystal-lising from alcohol in colourless needles melting a t 36O (Found: C1 17.7. M.W. [by cryoscopic method in benzene] = 215 212. C,,H,,Cl,As requires Cl = 17.5 per cent. M.W. = 405). Phenyldiet hylarsine. Michaelis and La Coste (Annalen 1880 201 212) first obtained this arsine from zinc diethyl and phenyldichloroarsine in ethereal solution Winmill (loc. cit .) subsequently showing that the reac-tion proceeded more satisfactorily in the presence of light petroleum.We have now by the following method eliminated the difficulty attached to these methods of preparation. A Grignard reagent prepared from 26.2 grams of ethyl bromide 1380 BURROWS AND TURNER: 5.8 grains of magnesium and 40 C.C. of ether was gradually treated with a solutioii of 22.3 grams of phenyldichloroarsine in 100 C.C. of benzene the mixture finally heated to boiling for two hours, and the ether allowed to distil off slowly. The resulting mixture was decomposed with ice and dilute sulphuric acid the benzene layer separated dried and evaporated and the residue distilled under diminished pressure when 12 grams of pE enyldiethylarsine were obtained as a colourless oil boiling a t 111-115°/14 mm. a further 3 grams of slightly less pure arsine distilling a t 115-120°/ 14 mm.The arsiiie possessed the properties ascribed t o i t in the literature. The methiodide was described by Michaelis (Annalen 1902, 328 296) as melting a t 1 2 2 O . We have been unable to confirm his statements our results being as follows. When phenyldiethylarsine and methyl iodide are mixed heat is evolved and a dark oil separates which only becomes crystalline after a considerable time or after scratching vigorously. This substance after thorough purification by repeated crystallisation from alcohol in the presence or absence of ether was obtained as a colourless crystalline solid melting a t 75-770 (Found I = 36.1, C,,H,,PAs requires T = 36.1 per cent.). The ethiodide and the methylene iodide additive compound were found to possess the propert,ies ascribed to them by Michaelis Cornpound PhEtl,As,Me Ad,.-This was formed readily and crystallised from alcohol or acetone in bright yellow needles melt-ing a t ‘78-79O (Found I=45*4.M.W. [by cryoscopic method in benzene]=271 27.3. C,,H,,T,As2 requires 1-45.8. M.W. =544). (ZOC. cit.). Phenylmethylethylarsine. Phenylmethyliodoarsine or the corresponding chloro-compound reacts vigorously with magnesium ethyl bromide to give the desired mixed arsine. Phenylmethyliodoarsine (19 grams) dissolved in 50 C.C. of benzene was gradually added to a Grignard reagent prepared from 7.8 grams of ethyl bromide 1.7 grams of magnesium and 20 C.C. of ether. When the whole of the iodo-compound had been added the mixture was heated to boiling for two hours decom-posed and worked up in the usual manner when 8 grams of phenylmethylethylarsine were obtained as a colourless oil boiling at 97O/12-13 mm.(Found [by Ewins’ method] As=37-8. C,H13As requires As = 38.3 per cent.). The arsine as might be expected possesses physical and chemica A NEW TYPE OF COMP0U;ND CONTAINING ARSENIC. 1381 properties intermediate between those of the dimethyl- and diethyl-arsine. The methiodide is readily formed and crystallises froni alcohol in colourless needles melting a t 142O (Found I = 37.5. C1,H161As requires I = 37.6 per cent.). Contpozcnd PhMeEtAs,MeAs12.-This compound crystallises from alcohol in yellow needles melting a t 84O (Found I=46.8. C,,,H1612As2 requires I = 47.0 per cent.).Compound PhMeEtAs,PhAsI,.-This substance separates from alcohol in orange-yellow prisms melting a t 55O (Found I = 42.3. M.W. [by cryoscopic method in benzene]=315 322 327. C,,H,,I,As requires I = 42.2 per cent. M. W. = 602). DZ~F.en~lmethylarsirLe. The preparation of this arsine by the action of zinc dimethyl on diphenylchloroarsine (Michaelis and Link Zoc. cit.) is less satis-factory than the following. A Grignard reagent prepared from 34.6 grams of bromobenzene, 5.4 grams of magnesium and 80 C.C. of ether was gradually treated with 34 grams of methyldi-iodoarsine after removal of unchanged magnesium by decantation. The product was worked up in the usual manner and gave 17.5 grams of diphenylmethyl-arsine boiling a t 163-1'iOO / 15 mm. and possessing the properties described in the literature.This arsine possesses only to a slight degree the property of forming additive compounds and so far 110 compounds have been obtained with alkyl- or phenyl-di-iodoarsines. The benziodide melts a t 1 9 3 O (Found I=27*5. C,,H,,IAs requires I = 27.5 per cent.). a-Naplz thyldime t hylarsin e . Dimethyliodoarsine (46.4 grains) was gradually added to a Grignard reagent prepared from 50 grams of a-bromonaphthalene, 5.34 grams of magnesium and 200 C.C. of ether (if small quantities of ether are used the magnesium a-naphthyl bromide separates out as a crystalline solid) 1,he reaction allowed to become complete by heating to boiling for an hour and the cooled product decom-posed and worked up in the usual manner. I n this way 37 grams (instead of the theoretical quantity of 46 grams) of a-naphthyl-dimethylarsine were obtained boiling at 163-165O/ 13 mm.The medkiodide is formed very readily and crystallises from alcohol in colourless needles melting at 330° (Found I = 33.7. Cl3HI6IAs requires I= 34.0 per cent.) 1382 A NEW TYPE OF COMPOUND CONTAINING ARSENIC. The ethzodzde is formed a t 90-looo and crystallises from alcohol in colourless leaflets melting a t 2 1 8 O (Found I=32.5. C',4H,81As requires I= 32.7 per cent.). Compound C,,H7*Me,As,MeAs12.-This compound is readily formed and crystallises from alcohol in yellow needles melting a t 76-77O (Found I = 44.0. C,3H,,12As2 requires I = 44.1 per cent.). Triphenytarsine , Although triphenylarsine is readily prepared by the action of sodium on a mixture of chlorobenzene and arsenic chloride the following method has been found to be the most convenient for the preparation of small quantities.More than 90 per cent. of the theoretical conversion can be effected and the arsine requires very little purification. Powdered arsenic iodide (22 grams) was gradually added with shaking to a Grignard reagent prepared from 26 grams of bromo-benzene 4 grams of magnesium and 50 C.C. of ether. The vigorous reaction having abated the mixture was heated to the boiling point for half an hour and then decomposed etc. the more volatile products beiog removed by heating finally to 200' under 12. mm. pressure. The residue practically pure triphenyl-arsine when once crystallised from alcohol melted correctly a t 5 8 O .No additive compounds could be obtained between the arsine and any of the di-iodoarsines a fact which falls in line with the difficulty of preparing the methiodide. Tri-o-tolytarsine. Arsenic iodide (22.8 grams) was added gradually to a Grignard reagent prepared from 26 grams of o-bromotoluene 3.7 grams of magnesium and 80 C.C. of ether the reaction completed by heating for a short time and the product worked up as in the case of triphenylarsine. Ten grams of tri-o-tolylursine were obtained and were crystallised from alcohol when colourless needles were formed melting at 9 8 O (Found As = 20.9. C,,H2,As requires As = 21.5 per cent.). The methiodide crystallises from water in colourless needles melting a t 1 6 6 O . Owing to the small quantity of matmerial avail-able for analysis the determination of iodine was unsatisfactory (Found I =24*2.C,,H,,IAs requires I= 25.9 per cent.) DERIVATIVES OR PHENYLDIHYDRORESORCIN. 1383 Di-o-tolylinethylarsine. A Grignard reagent was prepared from 22 grams of o-bromo-toluene 3.2 grams of magnesium and 50 C.C. of ether. A solution of 18 grams of niethyldi-iodoarsine in 100 C.C. of benzene was gradually added the reaction completed by heating under reflux, and the product decomposed with ice and dilute sulphuric acid. The separated ether-benzene layer was washed with aqueous sodium hydroxide to remove unchanged methyldi-iodoarsine dried over calcium chloride evaporated and the residue distilled under diminished pressure. In this way 8 grams of a very pale yellow oil were obtained boiling a t 178-18Z0/12 mm. and setting on cooling to a solid melting a t 4 2 O (Found As=27.3. C,,H17As requires As=27*6 per cent.). The methiodide is formed readily and crystallises from water in colourless needles melting a t 195O (Found I =31*2. Cl,H,oIAs requires I = 30.7 per cent.). TETE UNIVERSITY CE~EMIIYAL LABORATORIES, SYDNEY. [Received September 27th 1920.