INTERACTION OF MERCURIC AND CUPRIC CHLORIDES, ETC. a71

IIXXII.-Intei*action of Mercuric and Cupric Chlorides Respectively and the Mercaptans and Potential Mewxiptans.

By PRAFULLA CHANDRA RAY. SOME four years ago, the author ventured. t o put forth the view that the compounds which mercuric, platinic, and cupric chlorides, respectively, yield with thiocarbamide and thioacetamide, etc., are of the same nature as those obtained by the interaction of these

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972 RA$Y: INTERACTION OF MERCURIC AND

haloids and real mercaptans, that is, they are chlorcrmsrcaptides (P., 1914, 30, 304), and it seemed desirable to undertake a systematic study of the behaviour of mercuric, cupric, and platinic chlorides towards some of the typical mono- and di-mercapbns, namely, ethyl and ethylene mercaptans (dithimthylene glycol) arid 2-thiol-5-thio-4-phenyl-4 : 5-dihydro-l : 3 : 4-thiodiazole.

Ethyl mercaptsaii yields under normal conditions chluroplatinum mercaptide, (EtS),PtCl, and under exceptional conditions platinous memaptide, (EtS),Pt. Dithioethylene glycol also yields a chloro-

mercaptide of the formula C2H4<s>PtC1*S*CzH4*SH. I n the

formation of this remarkable compound, two molecules of dithie ethylene glycoj simultaneously take part in the reaction; one atom of chlorine of the platinic chloride remains, however, intact.

The potassium salt of 2-thiol-5-thio-4-phenyl-4 : 5-dihydro-l : 3 : 4- thiodiazole has been found to be equally reactive towards platink chloride, and it readily yields mercaptides in which platinum func- tions both as a triad and a dyad element, as in the case of the simple ethyl mercaptan.

The salh of the type MX, are scarcely represented among the platinum corn- pounds. ,In the formula (EtS),PtCl, no doubt platinum may be made to appear as quadrivaleiit by doubling it. Platinum has its proper place in the eighth or transitional group in the periodic system, which also includes iron and iridium. Now, the chlorides of these metals are represented by the simple formula MCI,, and not by M,Cl,. Moreover, platinum, with the high atomic.weight of 194, will scarcely permit of the coalescence of two. atoms into the complex IPt-Pti. Salts containing two atoms of platinum in the molecule have no doubt been described, but they are of a very complex character (Cossa, Ber., 1890, 23, 2503 ; Cleve, ‘Bztbt. Soc. chim., 1872, 17, 289). The product of the reaction of mercuric chloride with thiocarb-

amide has been assigned the formula HgCl,,@SN,H, (Rosenheim and Meyer, Zeitsch. anorg. Chem., 1903, 34, 62; 1906, 49, 13). In &her words, it has been regarded as a mere additive or mole- cular compound. From considerations based on analogy, the author suggested that it should be formulated as

[NH2*C( :NR)*S*Hg@l]HCl, that is, tha t it is the product of the reaction of mercuric chloride on $-thiocarbamide. The hydrogen chloride which is formed is not liberated in the free state, but is simply fixed by the basic complex. It is well known that formamidine disulphide exista as a salt of a diacidic base, because of the presence of two amino- and

S

T h e valency of platinum calls for a few remarks.

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CUPRIC CHLORIDES RESPECTIVELY, ETC. 873

imino-groups. support of the been found to

Convincing proof has recently been obtained in above formula. The compound in question has

be sufficitmtly soluble in water to admit of con- ductivity measurements. If -it were an additive one, it would dis- sociate into its components on dissolution. Now, thiocarbamide is practically a non-electrolyte, and mercuric chloride is very feebly ionised in solution (compare Rgy and Dhar, T., 1913, 103, 8).

The aqueous solution, however, shows an enormous increase in the dissociation, which is of the same order as that of ammonium chloride, proving that the salt is the hydrochloride of a base.

Thiocarbamide may be expected to behave in like manner towards platinic chloride and yield a compound of the same

type, thus : 2CS(NHZ), + [(NH2*C(:NH)*S),PtCl2]HCl. Both Reynolds and Pratorious-Seidler (compare Rathke, Ber., 1884, 17, 307), however, regard the compound as an additive one of thio- carbamide with platinous chloride, and assign to it the formula (CSN,H&PtCl,,HCl or (CSN2H4),PtHC1,. That this view is erroneous is evident' from another consideration. The platinic chloride on being reduced t o the platinolus state would set free chlorine, which would in turn act on a portion of the thiocarb- amide, and f ormamidine disulphide hydrochloride would be simultaneously formed ; * the derivative in queetion is, however, free from it.

Cupric chloride is analogous in its behavioiur towards thiocarb-

amide, CS(NH,), + NH,*C(:NH)*S*CuCl. In this case, how- ever, the hydrogen chloride is liberated in the f rw state and can be detected in the filtzate. This is what might have been expected. The, chlorides of mercury, platinum, and cobalt are capable of forming complex compounds with lammonia, amines, and amino- groups, which, on account of their basic character, can fix a mole- cule of hydrogen chloride, whilst copper, being a more positive metal, doee not possess &his property.

The view taken above offers also a ready interpretation of the reaction between platinic chloride and thioacetamide, first studied by Kurnakov (J. Buss. Phys. Chem. Soc., 1893, 25, 613), who formulatea the compound as PtCl,,4C,H,NS,PtCl4, that is, as an additive one of four molecules of thioacetamide with one of platinous bhloride and another of platinic chloride. This formula, when halved, stands as PtC13,2C,H,NS,HC1, and is in reality [ (CH,-C( :NH)oS)2PtCl,]HCl, t he platinic chloride functioning

* It has been actually found that sulphuryl dichloride, which acts as a mild chlorinating agent, behaves exactly like iodine towards thiocarbamide and yields the hydrochloride of the base.

PtC14

CUClZ

VOL. cxv K K

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874 RAY: INTEBACTION OF MERUURIC AND

exactdy like mercuric chloride. Thioawtamide here alm simply undergoes tautomeric change. One strong argument in favour of the suggested constitution is afforded by the fact that i f platinic chloride were actually to be reduced to the platinous form, the available atoms of chlorine would act on two other molecules of thimoetamide. It has already been shown that iodine completely decomposes thioacetamide, the whole of the sulphur being pre: cipitated (T., 1916, 109, 698). The product ir question when heated with carbon tlisulphide, however, did not yield any sulphur. The corresponding cupric chloride derivative has been found to conform to the formula CH,*C(:NH)*&CuCl; it is, in fact, a chlor omercaptide.

The reaction between platinic chloride and thiosemicarbazide is of special interest. The compound obtained has the formula C,H,N,Cl,S,Pt. Here also a tautomeric change of the thiecom- pound evidently takes place under the influence of the haloid, resulting in the formation of a cyclic compound with the elimina- tion of a m01wule of ammonia, thus:

NH,*CS*NH*NH, --+ NH:C(SH)-NH*NH, + NH*C*SH N H O S

\/ N pt$? I( L \g )pt”’l”’. The mercaptan now acts on platinic chloride in the usual manner,

the product being a chloromercaptide. Of the three molecules of hydrogen chloride generated, one is fixed by the complex sub- stance because of its basic character, due t o the presence of several irnino-residues.

E X P E R I M E N T A L . Mercaptans and Metallic Haloids.

Ethyl Mercaptan and Platinic Chloride.-Hofmann and Rabe , (Zeitsch. anorg. Chem., 1897, 14, 294) state that i f to chloro- platinic acid is added ethyl mercaptan in alcoholic solution, a t first an orangeyellow platinic mercaptide, (EtS)4Pt, is formed which, when heated to looo in a vacuum, readily yields platinous aercaptide. It has been found, however, that by the interaction of platinic chloride and ethyl mercaptan, chloroplatinum mereaptide, (EtS),PtCI, is almost invariably formed, and that it is only under exceptional conditions that platinous mercaptide, (EtS),Pt, can be obtained. The method is therefore given here somewhat in detail. To a concentrated alcoholic solution of chlore platinic acid is added a very dilute alcoholic solution of ethyl mercaptan from time to time with vigorous shaking; for t-he first

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CWPRIC CRLORIDES RESPECTIVELY, ETC. 875

few momenta, only a deep orange coloration is n o t M , but shortly after an orangeyellow precipitate begins to appear. Care should be taken tha t the platinic chloride is always in sufficient excess. If the conditions of reaction are reversed, tha t is, if a dilute solu- tion of platinic chloride is added in small quantities a t a time to an excem of a concenbrated alcoholic solution of ethyl mercaptan with vigorous shaking, for a few minutee the solution remains clear, after which a yellow salt begins t o separate, which is v0ry marly pure platinoua mercaptide.

Chlwoplatirmm mercaptide : I. 0.050 gave 0.0276 Pt, 0.022 AgC1, and 0.065 BaSO,.*

11. 0.0502 gave 0.0283 Pt and 0.0675 BaSO,. Pt=56*37;

111. 0.0226 gave 0.0126 Pt. IV. 0.0191 gave Om0081 AgCl and 09242 BaS0,.

Pt = 56.2 ; C1= 11.33 ; S = 17.85.

S=18*47. Pt=55*75.

C1=10-51; S= 17.44.

C4H,,C1S,Pt requires Pt

Platinow mercaptide : 0.1317 gave 0-0814 Pt, 0.012 A@, and 0.1985 BaSO,.

55.02 ; C1= 10.09; S = 18.19 per cent.

Pt = 61.81 ; C1= 2.25 ; S = 20.71. C4H,,S2Pt requires Pt = 61.43 ; S= 20.24 per cent.

which is invariably formed, accounts for the presence of chlorine. Contarninaf$;ion with distinct traces of the previous compound,

2-Thid-5-thio-4-phem?/l-4 : 5-dihydro-l : 3 : &thiodiazok,

and Platinic ChZoride.-To a concentrated aqueous solution of the potassium salt was added, with stirring, a dilute solution of chloro platinic acid in a thin stream. A yellow precipitate was obtained which, on drying, became orange. Here also, as in the case of ethyl mercaptan, the platinum atom functions as hrvalent and bivalent: -

0.080 gave 0.0213 Pt and 0.1805 BaSO,. A second preparation gave Pt = 25-32.

Pt=26*63; S=31*00.

(C,H,N,S,),Pt requires Pt = 22.33 ; S = 33.14. (C,H,N,S&Pt requires Pt = 30-12 ; S= 29.18.

Mean: Pt=26*23; S=31-16 per cent. It will thus be seen tha t here also a compound containing quadri-

* The estimation throughout was pffected by fusion with sodium nitrate and sodium carbonate,

K K a

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876 RAY: INTERACTION OF MERCURIC AND

valent platinum is never formed, but a mixture of almost equal proportions of the compounds containing tervaient and bivalent platinum. In the above reactions, the free hydrogen chloride of chloro-

platinic acid, acting on a portion of the potassium mercaptide, liberates the corresponding mercaptan, which is insoluble in water, and the available chlorine atoms of the quadrivalent platinum chloride also acting on the potassium mercaptide give rise to the disulphide, which is equally insoluble. The dried precipitate was therefore exhausted first with alcohol and afterwards with benzene in order t o extract impurities. The colour of the compound changed from yellow to orange under this treatment.

Dimercaptans artd Xetallic Haloids.

Dithjoethylerue Glycd and Pla t ink Chlm'de.-A dilute alcoholic solution of platinic chloride was gradually added, with vigorous stirring, to a concentrated alcoholic solution of dithioethylene glycol. A yellowish-brown precipitate was obtained, which was washed with alcohol and dried in a vacuum. It conforms to the

formula C,H, <;>PtCl*S*C,H,*SH :

0.0788 gave 0,0373 Pt, 0.032 AgCl, and 0.1608 BaSO,.

C,H,ClS,Pt requires Pt 246.96 ; Cl = 8.58 ; S = 30.93 per cent. There is reason to conclude that a simpler mercaptide of the

Pt= 47.34 ; Cl = 10.05 ; S = 28.03.

formula C2H4<S>PtC12 S (Pt=54*39; C1=19*88; S=17.91) is

simultaneously formed in small quantities ; the higher results for platinum and chlorine and the lower result for sulphur are thus accounted for. Attempts to obtain the chloromercaptide in a purer form proved unsuccessful.

Potential Mercaptans and Metallic HdOial.6:.

Thiocarbamide artd Mercuric Chloride.-The catnponents inter- acted both in alcoholic and in aqueous solution; a copious white precipitate was obtained, which was washed with alcohol and dried in a vacuum. The filtrate was neutral. (Found: C=3-82;

CH,N2Cl,$Hg requires C = 3.46 ; H = 1.18 ; N = 8.07 ; C1= 20.46 ; S=9*22; Hg=57.64 per cent.)

H = 1.63; N = 8.14; C1 = 20.45; S = 10.03; Hg = 56.62.

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CUPRIC CHLORIDES RESPECTIVELY, ETC. 577

Conductivity Measurement.

V. T . E r a

256 21.6 98.96

There w0re evidently two ions in solution, and the dissociation is of the order of that of ammonium chloride.

T hiocarbamide and Platinic Chl wide.-An acetone solution of thiocarbarnide was cautiously added, with constant stirring, to platinic chloride solution. An orange-yellow precipitate was obtained, which was washed with alcohol and driad in a vacuum:

I. 0.0838 gave 0.0365 Pt, 0.0910 BaSO,, and 0.0804 AgCl. Pt=43*56; S=14.91; C1=23*74.

0.0582 gave 6-6 C . C . N, a t 33O and 760 mm. N=12-39. 11. 09496 gave 0.0540 BaSO, and 0.0482 AgCl. S=14*95;

C1= 24.03. C,H,N,Cl,S,Pt requires Pt = 43.01 ; S = 14.17 ; c1= 23.57 ;

N=12*40 per cent. Thiocadamide and Cupric Chloride.-To an alcoholic solution

of cupric chloride was added, with constant stirring, an alcoholic solution of the carbamide. The granular precipitate when dried in a vacuum was white with a faintly blue t int :

0.0608 gave 0.0275 CuO. Cu=36.09. 0.0443 ,, 6.2 C.C. N, a t 31° and 760 m. N=15.41. 0-0588 ,, 0.0483 AgCl and 0.0780 BaS0,. Cl=20*31;

CH,N,ClSCu requires Cu = 36-38 ; N = 16-12 ; Cl= 20.44 ; S = 18.43 per cent.

Thioacetamide a/nd Platinic Chtloride .-Thioacetamide in alcoholic solution was added, with stirring, to platinio chlorido solution, and the brownish-yellow precipitate was treated as before :

I. 0-0852 gave 0.0360 Pt; 0.0782 AgC1. Pt=42-26;

S = 18-22.

C1= 22.79. 11. 0.0334 gave 0.0144 Pt. Pt=43.11.

0.0813 ,, 5.2 C.C. N, a t 32O and 760 mm. N='i.01. 111. 0.1457 gave 0.0630 Pt, 0-1697 BaSO,, and 0.1313 AgC1.

Pt = 43.83 ; S = 15.99 ; C1= 22.29. C4H,N2CI,S,Pt requires Pt = 43.20 ; S = 14-23 ; C1= 23.68 ;

N=6.23 per cent.

Thioacetamide und Czcpic Chloride.-The method of preparation was exactly the same as in the preceding case, the salt being almost white. The alcoholic filtrate, when distilled off, was found t o contain free hydrogen chloride :

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78 INTERACTlON OF MERCURIC AND CUPRIC CHLORIDES, ETC.

I. 0.0555 gave 0.0250 CuO. Cu=35.95. 0,0595 ,, 4.6 C.C. N, a t 29.5O and 760 mm. N=8*57.

11. 0.2818 ,, 0.1261 CuO, 0.42 BaSO,, and 0.2250 AgCl.

C,H,NClSCu requires Cu = 36.59 ; S = 18.53 ; C1= 20.55 ; N = 8.11 per cent.

Thiosemicarbazide and Platink Cltloride .-A dilute solution of platinic chloride was added t o a concentrahd aqueous solution* of thiosemicarbazide. I n the course of half an hour, a granular precipitate began t o be deposited, and the solution was allowed t o remain overnight. The granules, when collschd and dried, were yellowish-white :

0.2864 gave 0.1171 Pt, 0.1719 AgCl, and 0.387 BaSO,.

0.0381 gave 6.2 C.C. N, a t 30° and 760 mm.

CU = 35-78 ; S =20*44 ; C1= 19-75.

Pb=40.89 ; C1= 14.85 ; S = 18.56. N=17*97.

C,H,N,Cl,S,Pt~ requires Pt = 40.04 ; C1= 14.63 ; S = 19-78 ; N=17-31 per cent.

Sunznaary and Conclusiow (1) Whilst mercuric chloride reacts with a mercaptan to yield

a chlormercaptide, thus, R*SH + HgCl,=R*S*HgCl+ HC1, cupric and platinic chlorides generally give mercaptides or mercaptides with only a slight admixture of chloromercapt.ides.

(2) Platinum in relation to monomercaptanic radicles functions either as tervalent or bivalent.

(3) The above chlorides bring about tautomeric changes in thio- carbamide and thioacetamide. Thiosemicarbazide with platinic chloride also undergoes similar transformation and yields a cyclic

degradation product, \/ . N H*C SH

N (4) The chloromercaptides of the potential mercaptans, inasmuch

as they contain one or more imino-groups, are capable of fixing a molecule of hydrogen chloride, and in fact are hydroehlorides of complex bases.

CHEMICAL LABORATORY, COLLEGE OF SCIENCE,

UNIVERSITY OF CALCUTTA. [Received, June Z h t , 1918.3

* Thiosemicarbazide is almost insoluble in cold dcohol, ether, or acetone.

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INTERNATIONAL COMMITTEE ON ATOMIC WEIGHTS, 1920. 879

THE Council has ordered the following letter and report to be prinbd in the Journal of the Society:

WHINFIPLD, SALCOMBE,

S. DEVON. June 23rd, 1919.

GENTLEMEN, I have the honour to submit a Report from the International

Committee on Atomic Weights relative to such accounts of experi- ' mental work on atomic weights as have been published since their last regular Report of 1916, together with a table which it is sug- gested should be a d o p w in place of that now in use.

It will be seen hhat the Report deals with the atomic weights of hydrogen, carbon, bromine, boron, fluorine, lead, gallium, zirconium, tin, tellurium, yttrium, samarium, dysprosium, erbium, thorium, uranium, helium, and argon.

In the accompanying table for 1920, changes from the values hitherto adopted are recommended for argon, boron, gallium, thorium, and yttrium, and the atomic weight of nitrogen should be changed from 14.01 t o the more precise value 14.008, which is probably accurate t o within 1 in the third decimal place.

I am, Gentlemen, Your obedient; Servant,

T. E. THORPE. The Hon. Secretam'es,

The Chemical: Society, Londm.

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