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Stabilities, Solubility and Kinetics and Mechanism for Formation and Hydrolysis of some Palladium(II) and Platinum(II) Iodo Complexes in Aqueous Solution

Elding, Lars Ivar LU and Olsson, Lars Fride (1986) In Inorganica Chimica Acta 117(1). p.9-16
Abstract (Swedish)
Complex formation between Pd(II), Pt(II) and iodide has been studied at 25 °C for an aqueous 1.00 M perchloric acid medium. Measurements of the solubility of PdI2(s) in aqueous mercury(II) perchlorate and of AgI(s) and PdI2(s) in aqueous solutions of Pd2+(aq) and Ag+(aq) gave the solubility product of PdI2(s) as Kso=(7±3) × 10−32 M3, which is much smaller than previous literature values.

The stability constants β1=[MI(H2O)3+]/([M(H2O)42+][I−]) for the two systems were obtained as the ratio between rate constants for the forward and reverse reactions. The following values of k1 (s−1 M−1), k−1 (s−1) and β1 (M−1) were obtained at 25 °C: (1.14±0.11) × 106, (0.92±0.18), (12±4) × 105 for M=Pd, and (7.7±0.4), (8.0±0.7) × 10−5, (9.6±1.3)... (More)
Complex formation between Pd(II), Pt(II) and iodide has been studied at 25 °C for an aqueous 1.00 M perchloric acid medium. Measurements of the solubility of PdI2(s) in aqueous mercury(II) perchlorate and of AgI(s) and PdI2(s) in aqueous solutions of Pd2+(aq) and Ag+(aq) gave the solubility product of PdI2(s) as Kso=(7±3) × 10−32 M3, which is much smaller than previous literature values.

The stability constants β1=[MI(H2O)3+]/([M(H2O)42+][I−]) for the two systems were obtained as the ratio between rate constants for the forward and reverse reactions. The following values of k1 (s−1 M−1), k−1 (s−1) and β1 (M−1) were obtained at 25 °C: (1.14±0.11) × 106, (0.92±0.18), (12±4) × 105 for M=Pd, and (7.7±0.4), (8.0±0.7) × 10−5, (9.6±1.3) × 104 for M=Pt. Combination with previous literature data gives the following values of log(β1 (M−1)) to log(β4 (M−4)): 6.08, ∼22, 25.8 and 28.3 for M=Pd, and 4.98, ∼25, ∼28, and ∼30 for M=Pt. The present results show that the large overall stability constants β4 observed for the M2+ + I− systems are most likely due to a very large stability of the second complex MI2(H2O)2, which is probably a cis-isomer. A distinct plateau in the formation curve for mean ligand number 2 is obtained both for M=Pd and Pt. The other iodo complexes are not especially stable compared to those of chloride and bromide.

ΔH≠ (kJ mol−1) and ΔS≠ (JK−1 mol−1) for the forward reaction of (i), M=Pd, are (17.3±1.7) and (−71±5), and for the reverse reaction of (i) M=Pd, (45±3) and (−95±6), respectively. The kinetics are compatible with associative activation (Ia). The contribution from bond-breaking in the formation of the transition state seems to be less important for Pd than for Pt. (Less)
Abstract
Complex formation between Pd(II), Pt(II) and iodide has been studied at 25 °C for an aqueous 1.00 M perchloric acid medium. Measurements of the solubility of PdI2(s) in aqueous mercury(II) perchlorate and of AgI(s) and PdI2(s) in aqueous solutions of Pd2+(aq) and Ag+(aq) gave the solubility product of PdI2(s) as Kso=(7±3) × 10−32 M3, which is much smaller than previous literature values.
The stability constants β1=[MI(H2O)3+]/([M(H2O)42+][I−]) for the two systems were obtained as the ratio between rate constants for the forward and reverse reactions.

The following values of k1 (s−1 M−1), k−1 (s−1) and β1 (M−1) were obtained at 25 °C: (1.14±0.11) × 106, (0.92±0.18), (12±4) × 105 for MPd, and (7.7±0.4), (8.0±0.7) × 10−5,... (More)
Complex formation between Pd(II), Pt(II) and iodide has been studied at 25 °C for an aqueous 1.00 M perchloric acid medium. Measurements of the solubility of PdI2(s) in aqueous mercury(II) perchlorate and of AgI(s) and PdI2(s) in aqueous solutions of Pd2+(aq) and Ag+(aq) gave the solubility product of PdI2(s) as Kso=(7±3) × 10−32 M3, which is much smaller than previous literature values.
The stability constants β1=[MI(H2O)3+]/([M(H2O)42+][I−]) for the two systems were obtained as the ratio between rate constants for the forward and reverse reactions.

The following values of k1 (s−1 M−1), k−1 (s−1) and β1 (M−1) were obtained at 25 °C: (1.14±0.11) × 106, (0.92±0.18), (12±4) × 105 for MPd, and (7.7±0.4), (8.0±0.7) × 10−5, (9.6±1.3) × 104 for MPt. Combination with previous literature data gives the following values of log(β1 (M−1)) to log(β4 (M−4)): 6.08, ∼22, 25.8 and 28.3 for MPd, and 4.98, ∼25, ∼28, and ∼30 for MPt. The present results show that the large overall stability constants β4 observed for the M2+I− systems are most likely due to a very large stability of the second complex MI2(H2O)2, which is probably a cis-isomer. A distinct plateau in the formation curve for mean ligand number 2 is obtained both for MPd and Pt. The other iodo complexes are not especially stable compared to those of chloride and bromide.

ΔH≠ (kJ mol−1) and ΔS≠ (JK−1 mol−1) for the forward reaction of (i), MPd, are (17.3±1.7) and (−71±5), and for the reverse reaction of (i) MPd, (45±3) and (−95±6), respectively. The kinetics are compatible with associative activation (Ia). The contribution from bond-breaking in the formation of the transition state seems to be less important for Pd than for Pt. (Less)
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published
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keywords
Gold(III), Iodide, Palladium(II), Platinum(II), Complex formation, Solubility, Thermodynamic stability, Kinetiks, Reaction mechanism, Pd/Pt comparison, Palladium(II), Platinum(II), Iodide, Complex formation, Stabilities, Kinetics, Reaction mechanism
in
Inorganica Chimica Acta
volume
117
issue
1
pages
9 - 16
publisher
Elsevier
external identifiers
  • scopus:0039615558
ISSN
0020-1693
DOI
10.1016/S0020-1693(00)88059-7
language
English
LU publication?
yes
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c3e7c6a7-d804-41bb-b3ef-cb6f4d97310d
date added to LUP
2017-01-11 19:10:26
date last changed
2017-07-30 05:20:03
@article{c3e7c6a7-d804-41bb-b3ef-cb6f4d97310d,
  abstract     = {Complex formation between Pd(II), Pt(II) and iodide has been studied at 25 °C for an aqueous 1.00 M perchloric acid medium. Measurements of the solubility of PdI2(s) in aqueous mercury(II) perchlorate and of AgI(s) and PdI2(s) in aqueous solutions of Pd2+(aq) and Ag+(aq) gave the solubility product of PdI2(s) as Kso=(7±3) × 10−32 M3, which is much smaller than previous literature values.<br/>The stability constants β1=[MI(H2O)3+]/([M(H2O)42+][I−]) for the two systems were obtained as the ratio between rate constants for the forward and reverse reactions.<br/><br/>The following values of k1 (s−1 M−1), k−1 (s−1) and β1 (M−1) were obtained at 25 °C: (1.14±0.11) × 106, (0.92±0.18), (12±4) × 105 for MPd, and (7.7±0.4), (8.0±0.7) × 10−5, (9.6±1.3) × 104 for MPt. Combination with previous literature data gives the following values of log(β1 (M−1)) to log(β4 (M−4)): 6.08, ∼22, 25.8 and 28.3 for MPd, and 4.98, ∼25, ∼28, and ∼30 for MPt. The present results show that the large overall stability constants β4 observed for the M2+I− systems are most likely due to a very large stability of the second complex MI2(H2O)2, which is probably a cis-isomer. A distinct plateau in the formation curve for mean ligand number 2 is obtained both for MPd and Pt. The other iodo complexes are not especially stable compared to those of chloride and bromide.<br/><br/>ΔH≠ (kJ mol−1) and ΔS≠ (JK−1 mol−1) for the forward reaction of (i), MPd, are (17.3±1.7) and (−71±5), and for the reverse reaction of (i) MPd, (45±3) and (−95±6), respectively. The kinetics are compatible with associative activation (Ia). The contribution from bond-breaking in the formation of the transition state seems to be less important for Pd than for Pt.},
  author       = {Elding, Lars Ivar and Olsson, Lars Fride},
  issn         = {0020-1693},
  keyword      = {Gold(III),Iodide,Palladium(II),Platinum(II),Complex formation,Solubility,Thermodynamic stability,Kinetiks,Reaction mechanism,Pd/Pt comparison,Palladium(II),Platinum(II),Iodide,Complex formation,Stabilities,Kinetics,Reaction mechanism},
  language     = {eng},
  number       = {1},
  pages        = {9--16},
  publisher    = {Elsevier},
  series       = {Inorganica Chimica Acta},
  title        = {Stabilities, Solubility and Kinetics and Mechanism for Formation and Hydrolysis of some Palladium(II) and Platinum(II) Iodo Complexes in Aqueous Solution},
  url          = {http://dx.doi.org/10.1016/S0020-1693(00)88059-7},
  volume       = {117},
  year         = {1986},
}