New class of oligonuclear platinum - Thallium compounds with a direct metal-metal bond. 5. Structure determination of heterodimetallic cyano complexes in aqueous solution by EXAFS and vibrational spectroscopy

F. Jalilehvand, M. Maliarik, M. Sandström, J. Mink, I. Persson, P. Persson, I. Tóth, J. Glaser

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The structures of three closely related heterodimetallic cyano complexes, [(NC)5Pt-Tl(CN)n]n- (n = 1-3), formed in reactions between [PtII(CN)4]2- and TlIII cyano complexes, have been studied in aqueous solution. Multinuclear NMR data (205Tl, 195Pt, and 13C) were used for identification and quantitative analysis. X-ray absorption spectra were recorded at the Pt and Tl LIII edges. The EXAFS data show, after developing a model describing the extensive multiple scattering within the linearly coordinated cyano ligands, short Pt-Tl bond distances in the [(NC)5Pt-Tl(CN)n]n- complexes: 2.60(1), 2.62(1), and 2.64(1) Å for n = 1-3, respectively. Thus, the Pt-Tl bond distance increases with increasing number of cyano ligands on the thallium atom. In all three complexes the thallium atom and five cyano ligands, with a mean Pt-C distance of 2.00-2.01 Å, octahedrally coordinate the platinum atom. In the hydrated [(NC)5Pt-Tl(CN)(H2O)4]- species the thallium atom coordinates one cyano ligand, probably as a linear Pt-Tl-CN entity with a Tl-C bond distance of 2.13(1) Å, and possibly four loosely bound water molecules with a mean Tl-O bond distance of about 2.51 Å. In the [(NC)5Pt-Tl(CN)2]2- species, the thallium atom probably coordinates the cyano ligands trigonally with two Tl-C bond distances at 2.20(2) Å, and in [(NC)5Pt-Tl(CN)3]3- Tl coordinates tetrahedrally with three Tl-C distances at 2.22(2) Å. EXAFS data were reevaluated for previously studied mononuclear thallium(III)-cyano complexes in aqueous solution, [Tl(CN)2(H2O)4]+, [Tl(CN)3(H2O)], and [Tl(CN)4]-, and also for the solid K[Tl(CN)4] compound. A comparison shows that the Tl-C bond distances are longer in the dinuclear complexes [(NC)5Pt-Tl(CN)n]n- (n = 1-3) for the same coordination number. Relative oxidation states of the metal atoms were estimated from their 195Pt and 205Tl chemical shifts, confirming that the [(NC)5Pt-Tl(CN)n]n- complexes can be considered as metastable intermediates in a two-electron-transfer redox reaction from platinum(II) to thallium(III). Vibrational spectra were recorded and force constants from normal-coordinate analyses are used for discussing the delocalized bonding in these species.

Original languageEnglish
Pages (from-to)3889-3899
Number of pages11
JournalInorganic Chemistry
Issue number16
Publication statusPublished - Jul 30 2001


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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