Alkali metal cation-pi interactions stabilized solely by [M{N(SiMe3)(2)}(3)](-) anions (M = Mg or Zn): The competing influence of alkali metal center dot center dot center dot C(Me) agostic interactions

G.C. Forbes, A.R. Kennedy, R.E. Mulvey, B.A. Roberts, R.B. Rowlings

Research output: Contribution to journalArticle

78 Citations (Scopus)

Abstract

A series of [K(ar)(2)](+) and [Rb(toluene)(3)](+) cations (ar = benzene, toluene, o-xylene, or p-xylene) has been synthesized and crystallized in the presence of [M{N(SiMe3)(2)}(3)](-) anions (M = Mg or Zn). In the solid state all form either extended supermolecular, dimeric or supramolecular, polymeric structures. Only [K(toluene)(2)][Mg{N(SiMe3)(2)}(3)] was found to exist as both suprastructural isomers. Introducing cyclopentadienyl to the system gave a similar zincate with the unusual [K2CP](+) cation. The absence of any traditional Lewis bases facilitates' short metal-to-arene contact distances and makes these species excellent candidates for the study of alkali metal cation-pi interactions. It is shown that K-pi interactions and to a lesser extent Rb-pi interactions are heavily influenced by the number and nature of agostic methyl interactions, especially when the electron-donating ability of these is maximized by adoption of near-linear geometries. These features combine so that the weakest potassium-to-arene interaction observed is that with benzene.
Original languageEnglish
Pages (from-to)5115-5121
Number of pages6
JournalOrganometallics
Volume21
Issue number23
DOIs
Publication statusPublished - 11 Nov 2002

Keywords

  • crown-ether complexes
  • crystal-structures
  • chemistry
  • amide
  • potassium
  • group-12
  • benzene

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