Model compounds for polymeric redox-switchable hemilabile ligands

Thomas B. Higgins, Chad A. Mirkin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

The syntheses and characterization of two new tetradentate hemilabile ligands 1,2-bis(2-diphenylphosphinoethoxy)benzene (5) and 2,2′-bis(2-diphenylphosphinoethoxy)-1,1′-binaphthalene (10) are reported. Ligands 5 and 10 were synthesized as models to test the suitability of specific phosphinoether coordination environments for complexing Rh(I) in high surface area thiophene-based, redox-active polymeric systems. Ligands 5 and 10 react with the product formed from the reaction between (bicyclo[2.2.1]hepta-2,5-diene)rhodium(I) chloride dimer and AgBF4 to form [η2-(1,2-bis(2-diphenylphosphinoethoxy)benzene) η4-norbornadiene rhodium(I)] tetrafluoroborate (6) and [η2-(2,2′-bis(2-diphenylphosphinoethoxy)-1,1′-binaphthalene) η4-norbornadiene rhodium(I)] tetrafluoroborate (11), respectively. Complexes 6 and 11 react with H2 in CD2Cl2 to form the two new square-planar cis-phosphine, cis-ether Rh(I) complexes 7 and 12, respectively. Compound 7, which could be characterized on the basis of its 31P NMR spectrum, is extremely reactive and decomposes in CD2Cl2. In THF compounds 6 and 11 react with H2 to form the dihydride, bis-THF adducts 8 and 16, respectively, which upon removal of solvent form 7 and 12, respectively. Compound 12 is a stable, isolable complex that reacts with acetonitrile to form a cis-phosphine, cis-acetonitrile adduct 15. Removal of solvent from 15 leads to the quantitative reformation of 12. Compound 12 does not react to a detectable extent with gross excesses of benzene or even thiophene, demonstrating the suitability of this ligand environment for implementation into a thiophene-based polymeric system. Compound 12 does catalyze the hydrogenation of cyclohexene to form cyclohexane, and mechanistic implications of such a transformation are discussed.

Original languageEnglish (US)
Pages (from-to)347-353
Number of pages7
JournalInorganica Chimica Acta
Volume240
Issue number1-2
DOIs
StatePublished - Dec 1995

Keywords

  • Catalysis
  • Hemmilabile ligand complexes
  • Hydrogenation
  • Olefins
  • Rhodium complexes
  • Tetradentate ligand complexes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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