1032 D. A. BUCKINGHAM, P.A. MARZILLI,AND A. A I . SARGESON the equilibrium constant for the over-all reaction AjCoOkl28+
+ s-
K
A j C O X ~i-
-+-
1Zam
ASD
Inorgcinic Chemistry
-
TABLE \'I EQLXLIBRIUM CONSTANTS FOR ' r m IZEACTICIX
1120
(KHa).,CoOHz"'
+ X.-
k,,
f-
(SA8)jCoX2
+ I9997,) and was markedly dependent on [ H + ] , temperature, and ionic strength. The first~order~ rate ~ constants ~ obtained polarimetrically a t 640 mp are given in Table I. Those given in Table I1 show that reaction 5 is independent of [Hgz+]. The product D-P-[Co(trien)(H2O)2Ia+ was shown to be spectrophotometrically indistinguishable (€487 124) from D-P-SS[Co(trien)(HZ0);]l3+ obtained by acidification of D-p-SS[Co(trien)C03]C104, but the polarimetric results showed considerable differences a t various acid concentrations. The products were optically more active a t wavelengths below 560 mp than optically pure D-,B-SS[Co(trien)(HZ0)2l3+obtained from D-p-SS[Co(trien)CO3]C104 (reaction 3). These results are given in Table 111. Figure 6 shows the RD curves of the products from reaction 5 after a t least 6 half-lives as a function of the HCIO, concentration. It can be seen that a t all acid strengths they are optically more active than the product obtained from reaction 3 with the largest differences occurring a t the lowest acid strengths. That these anomalous rotations were due to the presence of some D-P-SR-[Co(trien)(H20),l3+and were not due merely to the presence of Hg2+ was established by the experiment illustrated in eq ti. (7) A. M. Sargeson and G. H. Searle, Naluve. 200, 356 (1968).
1036 D.
A.UUCKINGIIAX, 1'. A.MARZILLI, A N D A.M. SAIZCESON
Inorganic Chernislry
n ni- I O JI HClOn D-P-SS-[Co(trien)C1(Hzo)lY'runs-SS- [Co(trien)Clz] -- -+ [Jr]D $3000° 3CI min, 30' +
Hg'+
( 2 equiv)
vuiis-S'S-[Cu(tricii)Cl~] Clod ___ -++ tl.u?zs-SS-[C~(trieii)ClbHpO)] + [Jf]D 4-3000" 1 .If HCIOI, 15' [ ~ k f ] D4-3040 (after 6 min) I15'
(after 41 min) 0 1 Jrl Hg2+
tmns-SS- [ Co( trieii)Cld] -___ +tic~ns-SS-[Co(trien)o(H,O)*] j[ k f ] D +3000° 1-11 HClOn, 15' [.v!]D +750 (after 12 min) +
415'
0 1 21 H g 2 +
+n-p-SSil.ens-SS-[Co(trien)Clo(HeO)]I[ ~ l l ] D4-2930 1 .VI HClOa, 15' (after 6 min)
I t was established also by the following set of experiments that the D-p-SR-[Co(trien)(H20)2I3+ ion is formed only via trans-SS-[Co(trien)(H20)2I3+ (eq 7-9). The R D curves of the trans-SS-[Co(trien)C1(H20)12+, trans-SS- [Co(trien)(Hz0)2]3f,and D-p-SS[Co(trien)C1(H20)]2+ions formed in reactions 8 and 9 are given in Figure 7. The trans products almost certainly contain some of the p species but they are predominantly as stated (>80yo). Furthermore, it was shown that similar treatment of L-p-RR-[Co(trien)C12]Clod over the acid range 0.01-1.0 A4 HC104 gave no evidence for the formation of the "high-rotation'' L-p-RS-[Co(trien)(H,O)n] + product, and only a single product identical spectrophotometrically and polarimetrically with t h a t obtained from optically pure L-B-RR-[Co(trien)COa]C104was formed (eq 10). From the above sequence of experiments (eq 7-10), it is evident that the D-P-SR-[Co(trien) (H20)p]3' ion is produced only during the isomerization of trans-SS-
+ ~-p-sR-[Co(trien)(Hao)1] 3+
[XI i10 122'75O (after 6 hr)
[Co(trien)( H z O ) ~ L.] ~ This "high-rotation' ' u-p-SR form vias found to mutarotate completely (>99Yc) to the "low-rotation" (D-p-SS)isomer
and the rate of this reaction was shon-n to be acid dependent, Table IV. The optical rotation of the ~ may be final diaquo product, [ M ] 5 1+1400-1550°, compared n i t h that obtained on acidification of optically [Co(trien)CO3]C104, [ M ] 5 1 0 1440°, and pure D-6-SSi t should be noted that p-SS- [Co(trien)(OH*)2l3+ racemizes too slowly to affect the mutarotation signifisec-l in 1.0 AI HC104 a t cantly (klaC = 1.4 X 400, p = 1). The polarimetric rate data for the isomerization of trans-SS- [Co(trien)(Hz0)2l3+ (Table I) fit the rate kp/[H+].and the last column in law kabsd = k1
+
+
Vol. G , No. 5, ilday 1967
TRIETIIYLENETETRAMINE DISUBSTITUTED c O U A L T ( I I 1 )
[MI io-'
TABLE I1 RATECONSTANTS
FOR THE ISOMERIZATION O P
tran~-SS-[Co(trien)(H~O)z]~+ IN 1 M HClO4 AT 15'
([co]=
[Hg2t],a
IONS 1037
1.33
x
1041+~b~d, sec-1
a
M
3
10-3 M )
0 . 1 (P) 1.3 3.3 0.1 (s) 1.3 2.7 0.1 ( s ) 1.3 3.0 0 . 5 (s) 2.5 2.5 1.0 (s) 4.0 2.6 0.1 (P) 4.0 2.5 s = obtained spectrophotometrically a t 415 mp; p polarimetrically a t 510 mp. Q
2 =
obtained
TABLE I11 FINAL MOLECULAR ROTATIONS A T 510 mp FOR THE ISOMERIZATION REACTION trans-SS- [Co(trien)( HzO),] 3 + -+
1
+
D-P-SS- ~-p-SR-[Co(trien)(H~o)~]3+ ( [Hg2+] = 0.1 M ) Time of measure-
[H+l, M
0.05 0.10 0.10 0.10 0.3 0.5 1.0 1.0 0.10 1.0 2.0 3.0 3.0 3.0 3.0 5.89 a [Hg2+] =
Temp, 'C
15 15
8 1 15 15 15 8 15 15 15 15 15 15 15 15 0.5 M .
ment,
-[IVI]SIQ,deg M - ' cm-r-
P
min
Obsd
Calcd
1.3 1.3 1.3 1.3 1.3 1.3 1.3 1.3 4.0
26 38 9.5 236 80 233 360 300 130 360 180 100 107 270 105 50
2700 2720 2750 2740 2490 2240 2275 2190 2030 1990 1580 1490 1570 1430 1500 1580
2700 2640
4.0 4.0 4.0 4.0 4.0
4.5a 6.2
0
I
I
400
600
mp
1
2470 2340 2130
Figure 6.-RD curves for the o-P-SS-[Co(trien)(oH~)~] 3 + and o - p - ~ ~ - [ C o ( t r i e n ) ( o H3 ~ + )products z] of reaction 5 as a function of [HClOa]: 1.0 M , - . 0.1 and 0.05 M , -' , 0.3 M , - - - _., 0.5 M , a t p = 1.3, 15O, and 6ti/,. The 0.1 M curve () mutarotates to the 0.1 M curve (- -) a t 40'. e ;
1
a ;
[MIX
3
TABLE IV FOR THE OBSERVED RATECONSTANTS ~ - p - S X - [ c ot (r i e n ) ( H ~ O )3~+ ]-+ o-P-SS-[Co(trien)(HzO)z] + REACTION ([Hg(C10&] = 0.1 M,p = 1.3, FOLLOWED POLARIMETRICALLY AT 510 mp) W+I, M 0.05 0.10
Temp, O C
kcalcd,a sec-1
kobsd,
sec-1
40.0 1 . 7 x 10-3 1.7 X 40.0 9 . 2 x 10-4 9 . 1 x 10-4 34.3 4.1 x 10-4 25.0 8.2 X 0.30 40.0 3 . 9 x 10-4 3 . 6 x 10-4 1.0 50.0 4.9 x 10-4 40.0 1 . 4 x 10-4 1.7 x 10-4 34.3 6.5 X IOw6 a koalod was obtained from the rate law k = k'1 k'z/[H+], sec-] and k'z = 0.83 X where k'' = 0.83 X sec-l.
+
Table I gives values of k,,lod, a t 15' and an ionic sec-' and kz = strength of 1 3, using k , = 1.33 X 1.53 X sec-I. The agreement obtained and the [H+] 3.0 M a t the insensitivity to [H+] for 1.0 higher ionic strength (p = 4.0) eliminate the possibility of a term directly proportional to [H+], except possibly a t the highest acid strengths. Furthermore, the final product distribution (column 5 , Table 111) agrees with this rate law where kl corresponds to that path leading
