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working currently to explore these factors Mr. Norman B. Colthup in the design of the high further. temperature infrared cell and in the interpretation Acknowledgments.-The authors gratefully ac- of spectra. The authors also are indebted to Dr. knowledge the assistance of Mrs. Elisabeth C. (3. Warren Kennerly for helpful discussions. Colthup in the preparation of the complexes and STAMFORD, CONNECTICUT
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The Reactions of Nickel(I1) with 2,3-Dimercapto-1-propanol' BY D. L. LEUSSING RECEIVEDFEBRUARY 2, 1959 .4 spectrophotometric investigation of the reactions in alkaline solutions of 2,3-dimercapto-l-propanolwith nickel( 11) ions has revealed the existence of two complexes, Ni2(DMP)?OH' and Xi( DMP)2=. The first of these complexes is brown and the second is green. The cc,nstants for the reactions 2 N i + + OH3DMP= ~2 S 2 ( D M P ) ? 0 H ' and S i + + 2D M P = + Ni(DMP)?=are calculated t o be 4 X 10+46and 6 X 10f22. The absorption spectra of the complexes have been determined and are discussed. The Ni-S bond appears to be predominantly U.
+
The high stability of complexes of heavy metals with 2,3-dimercapto-l-propanol (British Anti Lewisite, B.IL) has been recognized since its preparation. Little, however, is known quantitatively of the nature and stabilities of the complexes t h a t are formed in solution. ;Is one of a series of investigations into the nature of metal ion-mercaptide complexes a study was undertaken of the nickel(11)-2,3-dimercapto-l-propanolreactions. Hereafter, in this paper the latter will be referred to as DRIP. Zuman and Zumanova' have investigated by means of polarometric titrations the nature of the compounds formed by many heavy metal ions with DILIP. They report that with nickel(I1) an insoluble compound with a 1: 1 ratio of metal to DMP is formed in slightly acid and alkaline solutions. They state also that in ammoniacal solutions a soluble complex is formed which is indicated to have a ratio of 1:1.5. Pribil and Rouba13 report that nickel(I1) reacts in alkaline solutions containing excess DRIP to form an olive green complex. The formation of the insoluble compound prevents the use of the conventional PH-titration method of determining stability constants. In the present work, the equilibria involving the soluble complexes which exist in alkaline solutions were investigated spectrophotometrically. It was found that the olive-green solutions are mixtures of two complexes, a brown one and a green one. Their absolute stabilities were obtained from the results of experiments in which DlZP and ethylenediaminetetraacetate ions were allowed to compete for limited amounts of nickel ions. In this connection, Pribil and Rouba13 who have proposed the use of DRIP in chelatometric titrations of mixtures of metal ions report that DAIP does not replace EDTA bound to Ki(II), although the EDTA is replaced readily by DLIP with the other ( I ) Presented a t t h e 1SJth National hleeting of t h e American Chemical S o c i e t y , Boston, Massachusetts, April, 1939. Financial assistance f o r this work was made available b y a grant f r o m t h e h-ational Science Foundation ( 2 J P Zuman a n d R . Zuman 2[NiIt give essentially a straight line for a plot of A.45?/ [Nilt versus [Ni]t/([DiCIPIt - 2[Ni]t). The plots for each buffer are illustrated in Fig. 1. The lines for the three buffers converge to a value on the intercept of e2,4b2 equal to 104 f 1 JT-lcm.-l. Values of the slopes are 8, 5 and 3 a t pH 9.28, 9.85 and 10.14. The estimated uncertainty is about f 1 unit in the slope. For such plots to be linear indicates that in the region [DMP]t> 2 [Ni ] t, [Ni ( DR.1P)2 = ] [Ni It and [DM P I z [ D M P It -2 [Nilt. Similar plots for the measurements a t 550 and 610 rnp also yield straight lines but because of smaller spectral changes give less precise slopes. N
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(7) J . J. Draney and M . Cefola, THISJOURNAL., 76, 1975 (1954). (8) J. M. White, T. J. Weismann and iY.C. Li, J . P h y s . Chem., 61, 126 (1957). (9) D. L. Leussing, THISJ O U R N A L , 80, 4180 (1958). (10) These equations assume that the concentrations of the ammino nickel(I1) complexes are negligible. T h e formation constants given below verify the validity of this assumption in solutions n h m t h e ratio of D M P t to Nit i s greater t h a n 1 : 1
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value of 3.1 X 10f3M-'cm.-l is calculated. Using this value and those for the slopes of Fig. 1and, also, correcting for the ratio [DMPH-]/ [DMPIz, values of @a,.? are calculated to be 5 ?C 0.7 X lo+', 8 1.7 X and 14 j= 4 X 10f2 a t pH 9.28, 9.88 and 10.14. One solution was made up to contain 0.00103 M Ni(II), 0.00904 M D M P in 0.10 X KOH (A462 equaled 0.135 ern.-' after 68 hours). A value of Qd,2 equal to 19 -f 3 X l o t 2 was calculated from this result ( 9 H c a l c d equals 12.70)." A plot similar to that in Fig. 1 was made based on the postulated composition, NiDhlPOH-, for the lower complex. For a 1 : 1 complex, a plot of A/[Ni]t versus l/[DhZP]t - 2[Ni]t should yield a straight line. Thus, only by considering the effect of Nit on the slope is i t possible to distinguish the monomer from the dimer, Because of experimental variations a clearcut distinction between the two models is not had with the present data. However, the points in Fig. l do give less deviation from I I I 2 4 6 a straight line than when plotted for the 1: 1 case. Also, for the 1 : l plot the points at the two lower [Nil, nickel concentrations show a definite tendency to [DMPIt- 2 [Nil, fall below the straight line passed through points a t the highest nickel concentration. In Fig. 1, Fig. 1.-The absorbance of Ni( 11) solutions as a function on the other hand, the points for the low nickel of the concentration of excess DMP: 0,pH 9.27, 0.00206 JI Kit (except lowest point which was 0.00103 M): (3, PH 9.88, concentrations scatter about equally between high 0.00052 M Sit; 8 , pH 9.88, 0.00103 Af Nit; 0 , pH 9.88, and low deviations. 0.00206 d l Nit; 0, PH 10.14, 0.00206 N Nit. The error Evidence which more clearly favors the dimer is limits were drawn on the basis of j=lyouncertainty in A45S obtained from the absorption spectra of ammoniacal and DMP,. solutions from which the ammonium chloride was omitted. I n these solutions i t is possible to achieve For the data in the region [DMP]t
