Sept. 20, 1954
COMPLEXES BETWEEN METALIONS AND AMINESCONTAINING SULFUR
with a mole ratio of one to one may be because the tetrahydropyran molecule cannot act as a bidentate group and form such a bicyclic structure with dinitrogen tetroxide. The fact that neither a stable dinitrogen tetroxide.2( 1,4-dioxane) nor a stable ternary compound is formed may be due
[CONTRIBUTION FROM
THE
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to the high stability of such a bicyclic structure for the compound N204.1,4-dioxane. I n such a structure there are no bonding orbitals on the nitrogen atoms available for coordinating a second ether molecule. COLUMBUS, OHIO
SCHOOL O F CHEMISTRY AND PHYSICS, THEPENNSYLVANIA STATE UNIVERSITY]
Equilibrium Constants for the Formation of Complexes between Metal Ions and Amines Containing
w.CONARD FERNELIUS AND BODIEE. D O U G L A S 3
BY ELYGONICK,
RECEIVED OCTOBER 13, 1953 The complexes of copper, nickel, cobalt(I1) and zinc with methyl 2-aminoethyl sulfide, bis-(2-aminoethyl) sulfide, 1,8diamino-3,6-dithiaoctane and bis-(2-aminoethyl) disulfide have been studied. Formation constants were calculated for the complexes of nickel and copper with methyl 2-aminoethyl sulfide, those of nickel and cobalt( 11) with bis-(2-aminoethyl) at 30". Formation constants were sulfide, and those of nickel, copper and cobalt( 11) with 1,8-diamino-3,6-dithiaoctane also obtained at 0 and 50' for complexes of nickel with each of the ligands for which constants were obtained a t 30' and for the complex of cobalt(I1) with bis-(2-aminoethyl) sulfide. From the data at different temperatures AH and A S values were calculated for the reactions involved. I n all cases the sulfur-containing amines give less stable complexes than the analogous polyamines containing no sulfur.
Experimental Bjerrum4 has shown that the formation of complexes between metal cations and ammonia or amBis-(2-aminoethyl) sulfide, bis-(2-aminoethyl) disulfide,'6 ines is a stepwise process. Further, he has shown methyl 2-aminoethyl sulfide and 1,8-diamino-3,6-dithiaochow measurements of the hydrogen ion concentra- tanel8 were prepared according t o published methods and purified. tions of solutions containing amines and salts of carefully The general procedure involved the titration of 100 ml. complex-forming metals may be used to determine of solution, 1 Ad in neutral electrolyte (either KCI or KXOr) the successive formation constants and the compo- and containing known concentrations of metal salt and minsition of the coordinatively saturated complex ion.5 eral acid. The titrant was either pure amine or a standardaqueous solution of amine. I n the case where the There are presently available data on ammoniaI4 ized amine was in the form of the acid salt, a weighed amount of monoamines,6 ethylenediamine,4J propylenediam- the salt was placed in the solution to be titrated and a standardized solution of sodium hydroxide was the titrant. d i e t h ~ l e n e t r i a m i n e , ~triethylenetetram~~ The PH measurements were made with the Beckman ine,*tlO 1,2,3-propanetriamine,11 tris-(2-aminoModel G PH meter using a glass electrode with a saturated ethyl)-amine,12 and N-alkylethylenediarnine~.~~~~~ calomel electrode as the reference electrode. A nitrogen This paper reports the results of a study of the atmosphere was maintained over all the solutions titrated formation constants of complexes of copper, nickel, and the titrant was protected from atmospheric carbon diby means of a soda lime tube. Measurements were cobalt and zinc ions with methyl 2-aminoethyl sul- oxide made a t 0 i 0.1", 30 i 0.1"and 50 i 0.1". The 30 and fide, bis-(2-aminoethyl) sulfide and 1,B-diamino-3,6- 50' baths were regulated by means of thermoregulators condithiaoctane. trolled by mercury switches. The 0" bath was obtained by (1) T h i s investigation was carried out under contract N6-onr 26913 between T h e Pennsylvania S t a t e University a n d T h e Office of Naval Research. (2) A portion of a thesis presented b y E l y Gonick in partial fulfillment of t h e requirements for t h e degree of Doctor of Philosophy, August, 1951. (3) University of Pittsburgh, P i t t s b u r g h 13, Pennsylvania. (4) J. Bjerrum, "Metal Ammine Formation in Aqueous Solution," P . Haase a n d Son, Copenhagen, 1941. (5) For definition of terms a n d method for t h e calculation of cons t a n t s see G. A. Carlson, J. P. hIcReynolds a n d F. H. Verhoek, THIS JOURNAL, 67, 1334 (1945). ( 6 ) R . V. Bruehlman a n d F. H. Verhoek, i b i d . , 7 0 , 1401 (1948). (7) H. B. Jonassen, R. B. LeBlanc a n d R . M . Rogan, ibid., 72, 4968 (1950).
(8) H. B. Jonassen, G. G. Hurst, R . B. LeBlanc and A. W. Meibohm, J . P h y s . Chem., 66, 16 (1952). (9) J. E. P r u e and G. Schwarzenbach, Helv. Chim. A d a , 33, 985 (1950). (10) G.Schwarzenbach, i b i d . , 33, 974 (1950). (11) J. E. P r u e and G . Schwarzenbach, ibid., 33, 995 (1950). (12) J. E. P r u e and G . Schwarzenbach, i b i d . , 3 3 , 963 (1950). (13) F. Basolo a n d R. K. h l u r m a n n , THIS JOURNAL,74, 5243 (1952). (14) H. Irving, Report No. BRL/146, M a y . 1951. Presented a t
Discussions on Coordination Chemistry held b y Imperial Chemical Industries Limited a t Welwyn, Herts, September, 1951.
means of a stirred water-ice mixture. Aqueous solutions of the acids and metal salts used were prepared and analyzed by means of generally accepted methods. The pH meter was standardized both before and after the titrations against buffer solutions prepared from National Bureau of Standards buffer salts. I n the titrations it was found that equilibrium was obtained in most cases as rapidly as the solution could be stirred atid the heat of reaction dissipated to the bath. From twenty to forty PH readings were taken in each titmtion. The acid dissociation constants of the amines were determined in similar titrations substituting barium ion, a noncoordinating ion, for the coordinating metal ions.
Data and Results Dissociation Constants of the Amines.-The results are given in Table I. Complexes of Sulfur-containing Amines.-The measurements of pH and calculation of fi and A yield the results which are recorded as formation curves in Figs. 1-3. From these curves the formation constants given in Table I1 were calculated. (15) E . J. Mills, Jr., and M . T. Bogert, THISJOURNAL, 62, 1173 (1940). (16) E. Gonick and W. C. Frrnelius, submitted for publication.
E. GONICK, W. C. FERNELIUS AND B. E. DOUGLAS
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Vol. 76
TABLE I ACID DISSOCIATION CONSTANTS OF SULFUR-COXTAINING AMINESIN 1 M KNOa SOLUTIONS (SOLUTIONS CONTAINING HCl WERE 1 i?f IN KC1) Barium salt concentration 0.020 Jf except in solutions marked by an asterisk which contain 0.004 M barium ion. Amine
Salt
Acid
PKAH PKAH~ PKAA PK.AH, PKAH PKm, PKAU PKAE, PKAH PKAH% PK~H
CHaSCHzCHzNHe S(CHzCHzNHz)z
S(C H ~ C H Z S H Z ) ~ (-CHeSCHiCHzKH?)s (-CHnSCH?CHzNH2)2 (-SCH*CH,NIiJl
1 . 0 0 M KN03 1 . 0 0 M KSOa
,07872 A' HNOj
1 . 0 0 LIf KNOa*
,1419 N HSOa
1 . 0 0 ilf KNOs
,3286 ,V HCI
1 .OO ,% KCl .I
0827 S HC1
1 . 0 0 M KCl*
For certain Combinations of amine and cation it is not possible to determine the formation curve because precipitates form before appreciable coordination takes place in solution. This situation obtains for methyl 2-aminoethyl sulfide with zinc and cobalt(II), for 1,8-diamino-3,6-dithiaoctanewith zinc, and for bis-(2-aminoethyl) disulfide with all of the metal ions investigated except barium. No
10.43 9.84 10.60 9.81 10.65
9.45 8.84 9.64 8.84 9.64 8.89 9.73 9.00 9.61 8.82 9.58
9.97 10.59
8.85 8.26 9.11 8.28 9.10
8.45 9.07
constants were calculated for the complexes of copper and zinc with bis-(2-aminoethyl) sulfide because of irregularities in the formation curves, particularly after FZ = 1. The plots of log KNvs, 1/T for the various complexes are shown in Fig. 4. The thermodynamic quantities calculated from these data are presented in Table 111. The AF values were calculated from the constants determined a t 30". The AH values are the average of the values calculated for the intervals 0-30 and 30-50". The A S values were calculated using the AF and AH values in the tables. The pH readings a t 0 and 50" were corrected using the formula supplied by the Beckman Instrument Company: any error arising from the use of this formula would be reflected in the A H and A S values.
3 00 7 00 1-41 Fig 1 -Formation curves for cornplexei of methyl 2-nminoethyl sulfide a t 30": A4,Xi, B, Cu 100
50'
30'
00
0.07112 N H S O j 0295 N HNOa
3 00
P
15 14 13
12
48 2.00
4.00
6.00 8.00 10.00 [*41. Fig. 2.-Formation curves for complexes of bk(2-aminoethyl) sulfide at 30': A, Co(I1); B, Zii; C , S i ; L), Cu.
11
I
i
3.0
3.1
l
l
l
i
l
l
10
P
8
7 1
0 00
4 00
8 uo
13 00
16 00
P 1.41 Fig. 3 -Formation curves for complexes of 1,8-didmino-3,6dithiaoctane a t 30': -4,Co(I1); B, S i ; C, Cu.
3.2
3.3 3.1 3.5 3.6 3.7 1 / T X lo?. Fig. 4.--Plots of log K N as a function of the reciprocal of the absolute temperature for the following complexes: I, 2 and 4 nickel complexes with CH3SCH2CH2NHz,(-CH*3, SCH~CH~NHZ and ) ~ S(CH2CH2iYH2)a,respectively; cobalt complex with S(CHzCH&H2)9.
Sept. 20, 1954
COMPLEXES BETWEEN METALIONS
AND
AMINESCONTAINING SULFUR
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TABLE I1 FORMATION CONSTANTS OF VARIOUS COMPLEXES OF SULFUR-CONTAINING AMINES The formation constants for corresponding polyamines without sulfur are given in parentheses for comparison. 30'
00
N i + + with CH~SCHZCHZNHZ and ( H z N C H Z C H Z N H Z ) ~
C u + + with C H ~ S C H Z C H Z N H Z and ( HzNCHZCHZNHZ)~ Co + + with S( C H Z C H Z N H Z ) ~ and (HN( C H Z C H Z N H Z ) ~ ) ~ N i + + with S(CHzCHzNHz)z and H N ( C H Z C H Z N H Z ) ~ ) ~
log ki log kz log k3 log Kn log ki log Kz log Kn log ki log k z log Kn log k i log kz log Kn log k
C o + + with (-CHZSCHZCHZNHZ)~ and (-CHZNHCH~CHZNHZ)~)'O N i + + with (-CH*SCHzCHzNHz)z log k and (-CH~XHCH~CH~SHZ)Z)'O C u + + with (-CH~SCHZCHZNHZ)Z log k and ( - C H Z ~ ~ " C H ~ C H ~ S H ~ ) Z ) ' O
3.64 3.26 2.00 8.90
5.56 4.63 10.19 8.05 6.96 15.01
8.86
3.23 2.79 1.73 7.75 5.58 5.10 10 68 5.09 3.92 9.01 7.27 6.10 13.37 4.89
200
50'
(7.52) (6.28) (4.26) (18.06) (10.55) (9.05) (19.60)
2.98 2.50 1.48 6.96
4.70 3.58 8.28 6.81 5.53 12.34
(8.1) (6.0) (14.1) (10.7) (8.25) (18.95) (11.0)
7.38
7.90
(14.0) (20.4)
11.32
TABLE I11 THERMODYNAMIC QUANTITIES FOR THE STEPWISE FORMATION OF VARIOUS COMPLEXES AT 30' The values in parentheses are for the complexes of corresponding polyamines without sulfur. n value
N i + + with ( N H z C H Z C H ~ N H Zand )~' (CH3NHCH2CHzKH2)"
X i + + with S(CHzCHzKHz)2and (NH( C H ~ C H Z N H ~ ) ~ ) X i + + with ( - C H ~ S C ~ H ~ X Hand Z)Z (( - C H ~ N H C Z H ~ N H Z ) Z ) Co++ with S(CHZCHZNHZ)Z and (NH(CHzCHzNHz)z)
Discussion
1 2 3 Total 1 2 3 Total 1 2 Total 1
- A F , kcal./mole 4.5 3.9 2.4 10.7 (10.1)( 9 . 7 ) ( 8.5)( 7 . 5 ) ( 5.8)( 3.3) (24.4)(20.5) 10.1 (15.0) 8 . 4 (11.2) 18.5 (26.2) 1 0 . 9 (19.8)
1 2 Total
7 . 0 (11.8) 5.4 ( 8.4) 1 2 . 4 (20.2)
-AH, kcal./mole
5 6 4 15 ( 8.8)( 8 . 5 ) ( 7.5)( 8 . 5 ) ( 8.9)( 7.1)
(25.2)(24.1) 10 (12) 12 (13) 22 (25) 12 (13) 7 (9) 8 (10) 15
(19)
A S , cal./degree mole
-3 -8 -7 - 17 ( +4)( +4) ( +3)( -3) ( - l o ) ( - 13) ( -3X-12) 0 (+lo) -11 ( - 6 ) -11 ( + 4) - 3 (4-23)
-9 -9
0 (+9) (-5) (+4)
The constants reported here are considered to be reliable to a t least 0.1 log unit as concentration conThe complete parallel between the values of N (the characteristic coordination number) for CH3- stants for the conditions specified. The data obSCH2CH2NH2 and H2NCH2CH2NH2,for S(CH2- tained a t different temperatures were used to calcuC H Z N H Zand ) ~ HN(CHL!H2NH2)2, and for (-CH2- late the thermodynamic quantities presented in S C H Z C H Z N Hand ~ ) ~ (-CH2NHCH2CH2NH~)2 indi- Table 111. The AF values should be reliable to ca. cates that the sulfur atom is active in coordination. f0.2 kcal., since the only uncertainty is that in the A comparison of the actual values for the formation log K values. The error in the A F values would be constants for each of the pairs listed above shows slightly greater if the values of the concentration clearly that coordination through sulfur for the sys- constants differ from those of the activity contems studied is not as strong as through nitrogen. stants to a greater extent than is anticipated. The This is further indicated by the failure to obtain average error in A H is probably of the order of *2 complexes with the sulfide amines in certain in- kcal. The A S values are probably valid to within stances] whereas the corresponding imine com- ca. f 7 cal./degree. The results of McIntyre" indicate that the acpounds form readily. The colors of the complexes formed between the various metal ions and the am- tivity constants in general are slightly lower than ines containing sulfur as a sulfide linkage are much the concentration constants determined under conthe same as those formed with amines containing a (17) G. McIntyre. Jr., Ph.D. Thesis, Pennsylvania S t a t e Universecondary amino group in place of the sulfur atom. sity, 1853.
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THOR RUBINAND ROBERT0. LEACH
ditions similar to those used in this study. The slope of the plots of log K vs. 1/T seem to be slightly greater for the activity constants. If this relationship is assumed to be general, the A F values can be interpreted as maximum values and the A N values as minimum values. This interpretation of the limits of the A H and A F values would indicate that the correct A S values are probably no more positive than those given in Table 111. There are rather large differences in the thermodynamic quantities reported by various worke r ~ for~ nickel ~ *with~ ethylenediamine. ~ ~ ~ ~ The conditions used by HaresI8 in this Laboratory are very nearly the same as those used in this investigation and the constants obtained by Hares are in closer agreement with the activity constants obtained by McIntyre17 than any other values which have been reported. The thermodynamic data of McIntyre are used for comparisons rather than those of BasoloI3 because of the close agreement between the results of Hares and 11cIntyre and the wide discrepancies between the results of Basolo and McIntyre. Baso10'~has since reported that the SII values obtained by calorimetric measurement are in much closer agreement with those of Mclntyre. The lower A F values indicate clearly that the sulfur-containing amines give much less stable complexes than the corresponding polyamines without sulfur. However, the decreased stability is not due entirely to a decrease in bond strength, although the A I 2 values are generally lower for the complexes of the sulfur-containing amines. The stability is decreased appreciably by the less favorable entropy changes accompanying the formation of the coinplexes of the sulfur-containing amines. The irregularities in the formation curves of zinc and copper with bis-(2-aminocthyl) sulfide are prob(18) G. Hares, Ph D. Thesis, P e n n s ~ l v a n i dStdte University, 1052 (19) F. B a s d o dnd R K Murrnan, T i m J O C K N A L , 76, 313 (1964)
[COSTRIBUTIOX FROM THE
Vol. 76
ably due to other equilibria which apparently are not important in the formation of the cobalt and nickel complexes. In the case of zinc there might be an intermediate complex with a ratio of three ligands to two zinc ions, or perhaps the second molecule of amine is not coordinated through all three points of attachment initially. In the adjustment from a tetrahedral to an octahedral arrangement accompanying the change in the coordination number some alteration in the shape of the formation curve might be more likely in the case of the sulfur-containing amines because of the greater variety in the means of attachment of a second molecule of amine to the zinc ion with a tetrahedral configuration. The formation curve for copper might be drawn out because not all of the sulfur and nitrogen atoms are active in coordination and perhaps there is a change in the ratio of the number of copper-nitrogen to copper-sulfur bonds. No formation constants are given for zinc or copper with bis(2-aminoethyl) sulfide because of the irregularities. Xore information is needed for an understanding of these cases. The slope of the formation curve of copper with l,S-diamin0-3,G-dithiaoctane differs from the expected theoretical slope. However, the deviation is slight and the formation constant presented in Table I1 is probably not appreciably less reliable than the other constants given. The slope of the formation curve of nickel with l,S-diamino-3,G-dithiaoctane shows no appreciable deviation from the theoretical slope for a one to one complex. However, the curve is somewhat unusual in that it levels off slightly above an ii value of 1. In each of these cases the slight irregularities are probably due to equilibria of iiiinor importance as compared to the simple addition reaction to form the one to one complex. PITTSBURGH, PENNA.
MCPHERSON CHEMICAL LABORATORY, THEOHIO STATE UNlVERSITY]
An Investigation of the Low Pressure Photolysis of Acetone by Means of the Mass Spectrometer BY TIIORRUBINAND ROBERT 0. LEACH RECEIVED NOVEMBER 19, 1951 The photolysis of acetone iii the wave leiigth region 2800 to 3100 A. has bcen studied by incans of mass spectrometric technique. The pressure includes those in the range from 5 to 100 @. Additional steps in the mechanism proposed by Dorfniari and Noyes and Herr and r i o y e s appear to be demanded by the data
In the photolysis of acetone, the formation of ethane, methane, carbon nionoxide and biacetyl as maior products has been substantiated by many a ~ t h o r s . l - ~The quantum yields of carbon monoxide and ethane under varying conditions of light intensity and pressure have been studied in great detail.4-7 However, the direct measurement of (1) G. 1%.Darncm and I.' h n i e l s . T H i s J O U K N A L . 6 5 , 23G3 (1!)331. (2) hl. Burak a n d U . W .G S t y l e , . V O ~ I L1!3P6,, 307 (108:). ( 3 ) R. Spence a n d W. Wild, ibid., 138, 206 (1936). (41 R. Spence a n d W. Wild, J . Chem Soc., 352 (1937). ( 5 ) D. S. H e r r a n d W A Noyes. J r , THISJ O U R N A L , 62, 2032 ( I O LO). (6) H W. Anderson a n d G K . R d I e f x w i b i d , 6 3 , 81G (1041J ( i ) J. J. Howland and W . A. N u y e s , J r . , i b i d . , 6 6 , 974 (lY44j
the quantum yield for biacetyl has been made infrequently and the measured quantum yield of acetone decomposition has been determined only from the total amounts of the major product^.^ Indirect estimates of the number of molecules of acetone decomposed per quantum and yield of biacetyl per quantum have been in general based upon the two net r e a c t i o r ~ s ~ ~ ~ (CI-I3)pCO--+ CrH6 -t CO 2(CHa)zCO +(CH3CO)z f CzHa
I t has been fou11d5r6too in the most successful niechanisni explaining the results that both a het-
