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Slow isotopic exchange of chelate compounds of indium in water and in anhydrous organic solvent
J.Inorg. Nucl. Clg~.. 1960, Vol. 13. pp. 334 to 335. PergamonPressLtd. Printedin Northern Ireland
L E T T E R TO T H E
EDITOR
Slow isotopic exchange of chelate compounds of indium in water and in anhydrous organic solvent (Received 12 October 1959; /n revised form 14 December 1959) As an extension of our work on the isotopic exchange of metal ions in co-ordination compounds,¢~ we have examined the exchange o f indium, by the use o f 11°'In (half-life, 49 days) as tracer, since the isotopic exchange reactions of the gallium group elements have not been studied, csj The exchange in water was examined between the indium ion and its chelate x~ith N-2-hydroxyethyl-ethylenediamineNN'N'-triacetic acid (EDTA-OH) labelled v/ith n ~ I n at various p H values, tl~ The indium ion is separated from its EDTA-OH complex by precipitating indium oxinate at pH 4. The indium oxinate is weighed on a sintered glass filter plate and submitted to 7-ray scintillation spectrometry for the specific counting rate to be measured by the use o f the photo-electric peak due to 0.192 MeV 7-rays. The results of the kinetic study arc summarized in Table 1, in which the exchange rate is expressed
by R = --2.303/t. ab/(a --Fb). log:0(I -- F) according to M c K A Y . c6~ Here a and b stand for the molar concentration of the indium ion and the E D T A - O H complex respectively, and t and F for the lapse of time and the fraction of exchange, respectively. TAnLE I.--RA~ OF ISOTOPIC EXCHANG~ OF I N D ~ M nETWEES THE INDIUM ION AND ITS E D T A - O H COMPLEX IN WATER pH
1-85" 2"62 2"85* 3.44 4-64 5"80
8.05?
Conch. of H +
1.4 2.4 1.4 3-6 2"3 1"6 8"9
× × × × × × ×
10-~ 10-s 10-s 10-4 10-6 I0 -6
10-'
Half-life
10min 138 rain 176 rain 6 hr 48 hr 7 days > 20 days
R mole/hr
1-8 1-4 1-0 6.1 5-9 1.8
× 10-3 × 10-' x 10-* x 10-6 × 10-6 × 10-* <10-*
R/[H+]( × I0)
1"3 0"6 0"6 0"7 2"6 11 > 108
Conditions: /~ ----0-1 (KNOa); [InS+I, 0.7 × 10-s; [In.EDTA-OH-HsO], 0.9 × 10-3. * Acetate buffer, 0.03 M, others tartrate buffer, 0.005 M. 1" Becomes turbid after 3 hr; temperature 25 4- I°C. It is obviously seen that at room temperature the isotopic exchange proceeds with a measurably slow rate, which depends on the hydrogen ion concentration. In an acid solution of p H less than 4, the rate appears to be proportional to the hydrogen ion concentration, but not at a p H more than 4. ~1~K. SArro and M. TAMUP.A,Bull. Chem. Soc. Japan 32, 532 (1959). es~e . g . D . R . STRANKSand R. (3. WILKINS, Chem. Rec. 57, 743 (1957). ca~A new compound prepared by K. SXITO; the composition is [In-EDTA-OH.HsO]HsO, the apparent dissociation constant of the co-ordinated water being 2.2 X 10-'. Bull. Chem. Soc. JapanIn preparation. ¢4~H. A. C. MCKAY, Nature, Lend. 142, 997 (1938). 334
Letter to the editor
335
This finding might be correlated with the facts that the formation of a metal chelate compound is favoured in a solution of higher pH value and that the indium EDTA-OH complex has one mole of co-ordinated water, which has an apparent dissociation constant of 2 × 10-6 and begins to produce a hydroxy complex at about pH 5. A similarly slow isotopic exchange appears to take place between the indium ion and its ethylenediaminetetraacetate complex: 5~ TABLE 2.--RATE OF ISOTOPIC EXCHANGE OF INDIUM BETWEENO~(INATE AND ACETYLACETONATEIN CHLOROFORM Concn. of oxinate
Concn. of acetylacetonate
Half-life (min)
R(mole/hr)
3.07 × 10-s M
2'51 × 10-s M
II
5"5 × I0 -s
Temperature, 25°C. The isotopic exchange was also studied between indium oxinate (labelled with n"~ln) and acetylacetonate in anhydrous chloroform. The former is precipitated free from the latter on addition of petroleum hydrocarbon. It is similarly weighed and the specific counting rate measured. Since indium acetylacetonate readily undergoes hydrolysis, care was taken to keep the compounds and the solvents completely anhydrous and the whole procedure was carried out in a dry box (relative humidity, less than 15 per cent). The result is shown in Table 2; the exchange proceeds with a measurably slow rate at this concentration. Because the solubility of the chelates in chloroform and the concentration range in which precipitation of pure oxinate is effected are limited, further kinetic study may involve some experimental difficulty.
Institute for Nuclear Study The University of Tokyo Tanashi, Tokyo ~b~ K. SAITOand the late H. TeRREY,J. Chem. Soc. 4701 (1956).
K. SAITO M. TAMURA
L E T T E R TO T H E
EDITOR
Slow isotopic exchange of chelate compounds of indium in water and in anhydrous organic solvent (Received 12 October 1959; /n revised form 14 December 1959) As an extension of our work on the isotopic exchange of metal ions in co-ordination compounds,¢~ we have examined the exchange o f indium, by the use o f 11°'In (half-life, 49 days) as tracer, since the isotopic exchange reactions of the gallium group elements have not been studied, csj The exchange in water was examined between the indium ion and its chelate x~ith N-2-hydroxyethyl-ethylenediamineNN'N'-triacetic acid (EDTA-OH) labelled v/ith n ~ I n at various p H values, tl~ The indium ion is separated from its EDTA-OH complex by precipitating indium oxinate at pH 4. The indium oxinate is weighed on a sintered glass filter plate and submitted to 7-ray scintillation spectrometry for the specific counting rate to be measured by the use o f the photo-electric peak due to 0.192 MeV 7-rays. The results of the kinetic study arc summarized in Table 1, in which the exchange rate is expressed
by R = --2.303/t. ab/(a --Fb). log:0(I -- F) according to M c K A Y . c6~ Here a and b stand for the molar concentration of the indium ion and the E D T A - O H complex respectively, and t and F for the lapse of time and the fraction of exchange, respectively. TAnLE I.--RA~ OF ISOTOPIC EXCHANG~ OF I N D ~ M nETWEES THE INDIUM ION AND ITS E D T A - O H COMPLEX IN WATER pH
1-85" 2"62 2"85* 3.44 4-64 5"80
8.05?
Conch. of H +
1.4 2.4 1.4 3-6 2"3 1"6 8"9
× × × × × × ×
10-~ 10-s 10-s 10-4 10-6 I0 -6
10-'
Half-life
10min 138 rain 176 rain 6 hr 48 hr 7 days > 20 days
R mole/hr
1-8 1-4 1-0 6.1 5-9 1.8
× 10-3 × 10-' x 10-* x 10-6 × 10-6 × 10-* <10-*
R/[H+]( × I0)
1"3 0"6 0"6 0"7 2"6 11 > 108
Conditions: /~ ----0-1 (KNOa); [InS+I, 0.7 × 10-s; [In.EDTA-OH-HsO], 0.9 × 10-3. * Acetate buffer, 0.03 M, others tartrate buffer, 0.005 M. 1" Becomes turbid after 3 hr; temperature 25 4- I°C. It is obviously seen that at room temperature the isotopic exchange proceeds with a measurably slow rate, which depends on the hydrogen ion concentration. In an acid solution of p H less than 4, the rate appears to be proportional to the hydrogen ion concentration, but not at a p H more than 4. ~1~K. SArro and M. TAMUP.A,Bull. Chem. Soc. Japan 32, 532 (1959). es~e . g . D . R . STRANKSand R. (3. WILKINS, Chem. Rec. 57, 743 (1957). ca~A new compound prepared by K. SXITO; the composition is [In-EDTA-OH.HsO]HsO, the apparent dissociation constant of the co-ordinated water being 2.2 X 10-'. Bull. Chem. Soc. JapanIn preparation. ¢4~H. A. C. MCKAY, Nature, Lend. 142, 997 (1938). 334
Letter to the editor
335
This finding might be correlated with the facts that the formation of a metal chelate compound is favoured in a solution of higher pH value and that the indium EDTA-OH complex has one mole of co-ordinated water, which has an apparent dissociation constant of 2 × 10-6 and begins to produce a hydroxy complex at about pH 5. A similarly slow isotopic exchange appears to take place between the indium ion and its ethylenediaminetetraacetate complex: 5~ TABLE 2.--RATE OF ISOTOPIC EXCHANGE OF INDIUM BETWEENO~(INATE AND ACETYLACETONATEIN CHLOROFORM Concn. of oxinate
Concn. of acetylacetonate
Half-life (min)
R(mole/hr)
3.07 × 10-s M
2'51 × 10-s M
II
5"5 × I0 -s
Temperature, 25°C. The isotopic exchange was also studied between indium oxinate (labelled with n"~ln) and acetylacetonate in anhydrous chloroform. The former is precipitated free from the latter on addition of petroleum hydrocarbon. It is similarly weighed and the specific counting rate measured. Since indium acetylacetonate readily undergoes hydrolysis, care was taken to keep the compounds and the solvents completely anhydrous and the whole procedure was carried out in a dry box (relative humidity, less than 15 per cent). The result is shown in Table 2; the exchange proceeds with a measurably slow rate at this concentration. Because the solubility of the chelates in chloroform and the concentration range in which precipitation of pure oxinate is effected are limited, further kinetic study may involve some experimental difficulty.
Institute for Nuclear Study The University of Tokyo Tanashi, Tokyo ~b~ K. SAITOand the late H. TeRREY,J. Chem. Soc. 4701 (1956).
K. SAITO M. TAMURA