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Structures of polynuclear complexes of palladium(II) and platinum(II) formed by slow hydrolysis in acidic aqueous solution

Torapava, Natallia ; Elding, Lars Ivar LU ; Maendar, Hugo ; Roosalu, Kaspar and Persson, Ingmar (2013) In Dalton Transactions 42(21). p.7755-7760
Abstract
The aqua ions of palladium(II) and platinum(II) undergo extremely slow hydrolysis in strongly acidic aqueous solution, resulting in polynuclear complexes. The size and structures of these species have been determined by EXAFS and small angle X-ray scattering, SAXS. For palladium(II), the EXAFS data show that the Pd-O and Pd center dot center dot center dot Pd distances are identical to those of crystalline palladium(II) oxide, but the intensities of the Pd center dot center dot center dot Pd distances in the Fourier transform at 3.04 and 3.42 angstrom are significantly lower compared to those of crystalline PdO. Furthermore, no Pd center dot center dot center dot Pd distances beyond 4 angstrom are observed. These observations strongly... (More)
The aqua ions of palladium(II) and platinum(II) undergo extremely slow hydrolysis in strongly acidic aqueous solution, resulting in polynuclear complexes. The size and structures of these species have been determined by EXAFS and small angle X-ray scattering, SAXS. For palladium(II), the EXAFS data show that the Pd-O and Pd center dot center dot center dot Pd distances are identical to those of crystalline palladium(II) oxide, but the intensities of the Pd center dot center dot center dot Pd distances in the Fourier transform at 3.04 and 3.42 angstrom are significantly lower compared to those of crystalline PdO. Furthermore, no Pd center dot center dot center dot Pd distances beyond 4 angstrom are observed. These observations strongly indicate that the polynuclear palladium(II) complexes are oxido- and hydroxido-bridged species with the same core structure as solid palladium(II) oxide. Based on the number of Pd center dot center dot center dot Pd distances, as derived from the EXAFS data, their size can be estimated to be approximately two unit cells, or ca. 1.0 nm(3). For platinum(II), EXAFS data of the polynuclear species formed in the slow hydrolysis process show Pt-O and Pt center dot center dot center dot Pt distances identical to those of amorphous platinum(II) oxide, precipitating from the solution studied. The Pt center dot center dot center dot Pt distances are somewhat different from those reported for crystalline platinum(II) oxide. The polynuclear platinum(II) complexes have a similar structure to the palladium ones, but they are somewhat larger, with an estimated diameter of 1.5-3.0 nm. It has not been possible to precipitate any of these species by ultracentrifugation. They are detectable by SAXS, indicating diameters between 0.7 and 2 nm, in excellent agreement with the EXAFS observations. The number of oxido- relative to hydroxido bridges will increase with increasing size of the complex. The charge of the complexes will remain about the same, +4, at growth, with approximate formulas [Pd10O4(OH)(8)(H2O)(12)](4+) and [Pt14O8(OH)(8)(H2O)(12)](4+) for complexes with a size of 2 and 3 unit cells of the corresponding solid metal oxide, respectively. Their high ionic charge in acidic aqueous solution will result in a stabilizing hydration shell. (Less)
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Aqua Ions, Palladium(II), Platinum(II), Hydrolysis, Polynuclear complexes, Nano particles
in
Dalton Transactions
volume
42
issue
21
pages
7755 - 7760
publisher
Royal Society of Chemistry
external identifiers
  • wos:000318792400030
  • scopus:84877725199
  • pmid:23549750
ISSN
1477-9234
DOI
10.1039/c3dt32859g
language
English
LU publication?
yes
id
1c6fbf20-a2bd-402f-bed1-1da6137dfd7f (old id 3815543)
date added to LUP
2016-04-01 10:35:00
date last changed
2022-03-19 22:12:16
@article{1c6fbf20-a2bd-402f-bed1-1da6137dfd7f,
  abstract     = {{The aqua ions of palladium(II) and platinum(II) undergo extremely slow hydrolysis in strongly acidic aqueous solution, resulting in polynuclear complexes. The size and structures of these species have been determined by EXAFS and small angle X-ray scattering, SAXS. For palladium(II), the EXAFS data show that the Pd-O and Pd center dot center dot center dot Pd distances are identical to those of crystalline palladium(II) oxide, but the intensities of the Pd center dot center dot center dot Pd distances in the Fourier transform at 3.04 and 3.42 angstrom are significantly lower compared to those of crystalline PdO. Furthermore, no Pd center dot center dot center dot Pd distances beyond 4 angstrom are observed. These observations strongly indicate that the polynuclear palladium(II) complexes are oxido- and hydroxido-bridged species with the same core structure as solid palladium(II) oxide. Based on the number of Pd center dot center dot center dot Pd distances, as derived from the EXAFS data, their size can be estimated to be approximately two unit cells, or ca. 1.0 nm(3). For platinum(II), EXAFS data of the polynuclear species formed in the slow hydrolysis process show Pt-O and Pt center dot center dot center dot Pt distances identical to those of amorphous platinum(II) oxide, precipitating from the solution studied. The Pt center dot center dot center dot Pt distances are somewhat different from those reported for crystalline platinum(II) oxide. The polynuclear platinum(II) complexes have a similar structure to the palladium ones, but they are somewhat larger, with an estimated diameter of 1.5-3.0 nm. It has not been possible to precipitate any of these species by ultracentrifugation. They are detectable by SAXS, indicating diameters between 0.7 and 2 nm, in excellent agreement with the EXAFS observations. The number of oxido- relative to hydroxido bridges will increase with increasing size of the complex. The charge of the complexes will remain about the same, +4, at growth, with approximate formulas [Pd10O4(OH)(8)(H2O)(12)](4+) and [Pt14O8(OH)(8)(H2O)(12)](4+) for complexes with a size of 2 and 3 unit cells of the corresponding solid metal oxide, respectively. Their high ionic charge in acidic aqueous solution will result in a stabilizing hydration shell.}},
  author       = {{Torapava, Natallia and Elding, Lars Ivar and Maendar, Hugo and Roosalu, Kaspar and Persson, Ingmar}},
  issn         = {{1477-9234}},
  keywords     = {{Aqua Ions; Palladium(II); Platinum(II); Hydrolysis; Polynuclear complexes; Nano particles}},
  language     = {{eng}},
  month        = {{03}},
  number       = {{21}},
  pages        = {{7755--7760}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{Dalton Transactions}},
  title        = {{Structures of polynuclear complexes of palladium(II) and platinum(II) formed by slow hydrolysis in acidic aqueous solution}},
  url          = {{http://dx.doi.org/10.1039/c3dt32859g}},
  doi          = {{10.1039/c3dt32859g}},
  volume       = {{42}},
  year         = {{2013}},
}