Synthesis and structure of heavy alkali metal pentalenides

Hugh Sanderson, Sumanta Banerjee, Mandeep Kaur, Alan Kennedy, Gabriele Kociok-Köhn, Ulrich Hintermair, Stuart Robertson

Research output: Contribution to journalArticlepeer-review


The solid‐state structures of the first rubidium and caesium pentalenides, [Rb(THF)]2[Ph4Pn] and [Cs(THF)]­­2[Ph4Pn] have been determined by single crystal X‐ray diffraction. Both were found to be polymeric in the solid state through interactions of the cations with the phenyl substituents, in contrast to their lighter group 1 congeners which are monomeric for lithium and sodium and THF‐bridged for potassium. Both [Rb(THF)]2[Ph4Pn] and [Cs(THF)]2[Ph4Pn] displayed increased η8 coordination, demonstrating a shift towards higher hapticities down the group as previously predicted computationally for the parent M2[Pn] complexes (M = group 1 metal). The solid‐state structures of the polydentate donor adducts [M(DME)x]2[Ph4Pn] (M = Li, x = 1; M = Na, x = 2) and [M(Me6TREN)]2[Ph4Pn] (M = K, Rb, Cs) were all monomeric and displayed increased metal‐carbon distances and decreased ring slippage values relative to the THF adducts.
Original languageEnglish
Article numbere202400039
Early online date6 May 2024
Publication statusE-pub ahead of print - 6 May 2024


  • pentalenides
  • rubidium
  • caesium
  • alkali metal coordination


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