Cyanide exchange on Tl(CN)4- in aqueous solution studied by 205Tl and 13C NMR spectroscopy

István Bányai, Julius Glaser, Imre Tóth

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Abstract

Dynamics of cyanide exchange between Tl(13CN)4- and 13CN- was studied by means 205Tl and 13C NMR. The rate law consists of two parts: w = kCN[Tl(CN)4-][CN-] + kOH[Tl(CN)4-][CN-][OH -] with kCN = 9.7(±0.4) ×106 M-1S-1 and kOH = 5.4(±0.4) ×1010 M-2S-1. It was shown that the exchange between the two cyano species can be studied, not only by 13C NMR, but also by 205Tl NMR using the heteronuclear carbon-thallium scalar coupling as an indicator, despite the fact that only one Tl site is present in the system. The reaction mechanism is discussed in terms of an associative interchange mechanism, IA. Penetration of the incoming cyanide ion into the coordination sphere of Tl(CN)4- and Tl(CN)4(OH)- is suggested to be the rate-determining step for the two parallel reactions paths. Possible reasons for the strong labilizing effect of the cyanide ligand is discussed in the light of thermodynamic and structural data. The possibility of detection of an exceptional exchange reaction, namely cyanide exchange between two Tl(CN)4- entities by a direct encounter was theoretically settled, but found to be too slow to be detected.

Original languageEnglish
Pages (from-to)1709-1717
Number of pages9
JournalEuropean Journal of Inorganic Chemistry
Issue number7
Publication statusPublished - Jul 16 2001

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Keywords

  • Cyanides
  • Ligand exchange
  • Thallium
  • Tl NMR

ASJC Scopus subject areas

  • Inorganic Chemistry

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