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Equilibria, Kinetics and Mechanism for Complex Formation Between Hydrogen Sulfate/Sulfate and Palladium(II). Hydrolysis of Tetraaquapalladium(II)

Shi, Tiesheng LU and Elding, Lars Ivar LU (1998) In Acta Chemica Scandinavica 52 (1998). p.897-902
Abstract
Spectrophotometric equilibrium measurements indicate formation of the complexes [Pd(H2O)(3)HSO4](+) and [Pd(H2O)(3)SO4] in the reaction between [Pd(H2O)(4)](2+) and hydrogen sulfate/sulfate in the region: 0.10 less than or equal to [H+] less than or equal to 0.80 M. The stability constants are 0.7 +/- 0.2 and 19 +/- 6 M-1, respectively, at 25 degrees C and 1.00 M ionic strength. The protolysis constant for coordinated hydrogen sulfate, i.e. the equilibrium constant for the reaction [Pd(H2O)(3)HSO4](+) +H2O reversible arrow[Pd(H2O)(3)SO4] + H3O+, is 2.5 +/- 1.0 M. The stability constant for [Pd(H2O)(3)HSO4](+) and the protolysis constant for coordinated HSO4- are also derived from kinetic measurements as 0.6 +/- 0.2 M-1 and 2.3 +/- 1.3 M,... (More)
Spectrophotometric equilibrium measurements indicate formation of the complexes [Pd(H2O)(3)HSO4](+) and [Pd(H2O)(3)SO4] in the reaction between [Pd(H2O)(4)](2+) and hydrogen sulfate/sulfate in the region: 0.10 less than or equal to [H+] less than or equal to 0.80 M. The stability constants are 0.7 +/- 0.2 and 19 +/- 6 M-1, respectively, at 25 degrees C and 1.00 M ionic strength. The protolysis constant for coordinated hydrogen sulfate, i.e. the equilibrium constant for the reaction [Pd(H2O)(3)HSO4](+) +H2O reversible arrow[Pd(H2O)(3)SO4] + H3O+, is 2.5 +/- 1.0 M. The stability constant for [Pd(H2O)(3)HSO4](+) and the protolysis constant for coordinated HSO4- are also derived from kinetic measurements as 0.6 +/- 0.2 M-1 and 2.3 +/- 1.3 M, respectively. The kinetics for the reversible complex formation reaction, studied by use of stopped-flow spectrophotometry, is first order with respect to palladium complex and total concentration of sulfate, [S(VI)], with an observed pseudo-first-order rate constant k(obsd) = k(f)[S(VI)] + k(r) for excess sulfate. Here k(f) and k(r) denote observed forward second-order and reverse first-order rate constants, respectively. The kinetic data are interpreted in terms of a reaction mechanism which involves parallel and reversible reactions between [Pd(H2O)(4)](2+) and HSO4- and SO42-, respectively, and between [Pd(H2O)(3)OH](+) and HSO4-. Forward and reverse rate constants for complex formation between [Pd(H2O)(4)](2+) and HSO4- are 119 +/- 6 M-1 s(-1) and 210 +/- 60 s(-1) at 25 degrees C, indicating that HSO4- has a similar nucleophilicity as other oxygen-donor ligands. The rate constants for the reactions of [Pd(H2O)(4)](2+) with SO42- and of [Pd(H2O)(3)OH](+) with HSO4- cannot be resolved because of a proton ambiguity. The mononuclear protolysis constant of [Pd(H2O)(4)](2+) is pK(h) = 3.0 +/- 0.1 at 25 degrees C and 1.00 M ionic strength as determined from rapid spectrophotometric equilibrium measurements.
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Contribution to journal
publication status
published
subject
keywords
Palladium(II), Tetraaquapalladium(II), Hydrolysis, Complex formation, Sulfate, Palladium(II) tetraaqua ion, Protolysis constant, Sulfate, Complex formation, Kinetics, Reaction mechanism, Tetraaqua ion
in
Acta Chemica Scandinavica
volume
52 (1998)
pages
6 pages
publisher
Munksgaard International Publishers
external identifiers
  • scopus:0001259235
ISSN
0904-213X
DOI
10.3891/acta.chem.scand.52-0897
language
English
LU publication?
yes
id
d0b3ed6d-d91a-4659-bcbe-cfe3d36ed6d5
date added to LUP
2016-12-27 20:41:53
date last changed
2018-05-29 09:47:17
@article{d0b3ed6d-d91a-4659-bcbe-cfe3d36ed6d5,
  abstract     = {Spectrophotometric equilibrium measurements indicate formation of the complexes [Pd(H2O)(3)HSO4](+) and [Pd(H2O)(3)SO4] in the reaction between [Pd(H2O)(4)](2+) and hydrogen sulfate/sulfate in the region: 0.10 less than or equal to [H+] less than or equal to 0.80 M. The stability constants are 0.7 +/- 0.2 and 19 +/- 6 M-1, respectively, at 25 degrees C and 1.00 M ionic strength. The protolysis constant for coordinated hydrogen sulfate, i.e. the equilibrium constant for the reaction [Pd(H2O)(3)HSO4](+) +H2O reversible arrow[Pd(H2O)(3)SO4] + H3O+, is 2.5 +/- 1.0 M. The stability constant for [Pd(H2O)(3)HSO4](+) and the protolysis constant for coordinated HSO4- are also derived from kinetic measurements as 0.6 +/- 0.2 M-1 and 2.3 +/- 1.3 M, respectively. The kinetics for the reversible complex formation reaction, studied by use of stopped-flow spectrophotometry, is first order with respect to palladium complex and total concentration of sulfate, [S(VI)], with an observed pseudo-first-order rate constant k(obsd) = k(f)[S(VI)] + k(r) for excess sulfate. Here k(f) and k(r) denote observed forward second-order and reverse first-order rate constants, respectively. The kinetic data are interpreted in terms of a reaction mechanism which involves parallel and reversible reactions between [Pd(H2O)(4)](2+) and HSO4- and SO42-, respectively, and between [Pd(H2O)(3)OH](+) and HSO4-. Forward and reverse rate constants for complex formation between [Pd(H2O)(4)](2+) and HSO4- are 119 +/- 6 M-1 s(-1) and 210 +/- 60 s(-1) at 25 degrees C, indicating that HSO4- has a similar nucleophilicity as other oxygen-donor ligands. The rate constants for the reactions of [Pd(H2O)(4)](2+) with SO42- and of [Pd(H2O)(3)OH](+) with HSO4- cannot be resolved because of a proton ambiguity. The mononuclear protolysis constant of [Pd(H2O)(4)](2+) is pK(h) = 3.0 +/- 0.1 at 25 degrees C and 1.00 M ionic strength as determined from rapid spectrophotometric equilibrium measurements.<br/> },
  author       = {Shi, Tiesheng and Elding, Lars Ivar},
  issn         = {0904-213X},
  keyword      = {Palladium(II),Tetraaquapalladium(II),Hydrolysis,Complex formation,Sulfate,Palladium(II) tetraaqua ion,Protolysis constant,Sulfate,Complex formation,Kinetics,Reaction mechanism,Tetraaqua ion},
  language     = {eng},
  pages        = {897--902},
  publisher    = {Munksgaard International Publishers},
  series       = {Acta Chemica Scandinavica},
  title        = {Equilibria, Kinetics and Mechanism for Complex Formation Between Hydrogen Sulfate/Sulfate and Palladium(II). Hydrolysis of Tetraaquapalladium(II)},
  url          = {http://dx.doi.org/10.3891/acta.chem.scand.52-0897},
  volume       = {52 (1998)},
  year         = {1998},
}