Structural and mechanistic studies on ion insertion into the molecular box {[CpCo(CN)3]4 [Cp*Ru]4}

Maya Ramesh, Thomas B. Rauchfuss

Research output: Contribution to journalArticle

Abstract

The molecular box [CpCo(CN)3]4[Cp*Ru] 4 (Co4Ru4) reacts readily with a variety of monocations to form M⊂Co4Ru4 + (M=K+, Cs+, Rb+). Ion competition experiments, monitored by ESI-MS, show that the molecular box binds the smaller K+ more rapidly than Cs+, but that thermodynamically Co4Ru4 prefers the larger ion. The rates of ion-insertion for K+ and Cs+ into Co4Ru4 were found to qualitatively follow second order kinetics with K+, 300 M-1 s-1 and Cs+, 36 M-1 s-1. The ratio kK/kCs qualitatively matched the ESI-MS results from ion competition experiments. The rates of ion-insertion into Co4Ru4 were found to depend on the counter anions. In particular, RbBF4 reacted with Co4Ru4 more slowly than did RbOTf. The slower rates allowed us to establish second order kinetics. 1H NMR studies reveal that the Cp signal for Co4Ru4 is very sensitive to the presence of entering ions, e.g., Rb+, whereas the corresponding Cp signal for Rb⊂Co4Ru4+ was insensitive to the presence of Rb+. The molecular structures of [Co4Ru4]·6MeCN, [K⊂Co4Ru4]BF4·7MeCN, [Cs⊂Co4Ru4]BF4·6MeCN and [Tl⊂Co4Ru4]BF4·6MeCN, determined by X-ray diffraction, showed that although the compounds crystallized in the same space group I 23, a correlation exists between the Ru-N/Co-C bond distances and the size of the interstitial ion.

Original languageEnglish (US)
Pages (from-to)1425-1430
Number of pages6
JournalJournal of Organometallic Chemistry
Volume689
Issue number8
DOIs
StatePublished - Apr 15 2004

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Keywords

  • Cage
  • Cobalt
  • Cyanide
  • Cyclopentadienyl
  • Ion-insertion
  • Kinetics
  • Molecular ionophilic box

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry
  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

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