Charge-separated and molecular heterobimetallic rare earth-rare earth and alkaline earth-rare earth aryloxo complexes featuring intramolecular metal-π-arene interactions

Glen B. Deacon, Peter C. Junk, Graeme J. Moxey, Karin Ruhlandt-Senge, Courtney St Prix, Maria F. Zuniga

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

Treatment of a rare earth metal (Ln) and a potential divalent rare earth metal (Ln′) or an alkaline earth metal (Ae) with 2,6-diphenylphenol (HOdpp) at elevated temperatures (200-250 °C) afforded heterobimetallic aryloxo complexes, which were structurally characterised. A charge-separated species [(Ln′/Ae)2(Odpp)3][Ln-(Odpp)4] was obtained for a range of metals, demonstrating the similarities between the chemistry of the divalent rare earth metals and the alkaline earth metals. The [(Ln′/Ae)2(Odpp)3]+ cation in the heterobimetallic structures is unusual in that it consists solely of bridging aryloxide ligands. A molecular heterobimetallic species [AeEu(Odpp)4] (Ae = Ca, Sr, Ba) was obtained by treating an alkaline earth metal and Eu metal with HOdpp at elevated temperatures. Similarly, [BaSr-(Odpp)4] was prepared by treating Ba metal and Sr metal with HOdpp. Treatment of [Ba 2(Odpp)4] with [Mg-(Odpp)2(thf)2] in toluene afforded [Ba2(Odpp)3][Mg(Odpp)3(thf)]. Analogous solution-based syntheses were not possible for [(Ln′/Ae) 2(Odpp)3][Ln-(Odpp)4] complexes, for which the free-metal route was essential. As a result of the absence of additional donor ligands, the crystal structures of the heterobimetallic complexes feature extensive π-Ph-metal interactions involving the pendant phenyl groups of the Odpp ligands, thus enabling the large electropositive metal atoms to attain coordination saturation. The charge-separated heterobimetallic species were purified by extraction with toluene/thf mixtures at ambient temperature (Ba-containing compounds) or by extraction with toluene under pressure above the boiling point of the solvent (other products). In donor solvents, heterobimetallic complexes other than those containing barium were found to fragment into homometallic species.

Original languageEnglish (US)
Pages (from-to)5503-5519
Number of pages17
JournalChemistry - A European Journal
Volume15
Issue number22
DOIs
StatePublished - May 25 2009

Keywords

  • Alkaline earth metals
  • Heterobimetallic complexes
  • O ligands
  • Pi interactions
  • Rare earths

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Organic Chemistry

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