How to insulate a reactive site from a perfluoroalkyl group: Photoelectron spectroscopy, calorimetric, and computational studies of long-range electronic effects in fluorous phosphines P((CH2)m (CF2)7CF3)3

Haijun Jiao, Sylvie Le Stang, Tibor Soós, Ralf Meier, Klaus Kowski, Paul Rademacher, Laleh Jafarpour, Jean Benoit Hamard, Steven P. Nolan, J. A. Gladysz

Research output: Contribution to journalArticle

70 Citations (Scopus)

Abstract

This study advances strategy and design in catalysts and reagents for fluorous and supercritical CO2 chemistry by defining the structural requirements for insulating a typical active site from a perfluoroalkyl segment. The vertical ionization potentials of the phosphines P((CH2)mRf8)3 (m = 2 (2) to 5 (5)) are measured by photoelectron spectroscopy, and the enthalpies of protonation by calorimetry (CF3SO3H, CF3C6H5). They undergo progressively more facile (energetically) ionization and protonation (P(CH2CH3)3 > 5 > 4 ≈ P(CH3)3 > 3 > 2), as expected from inductive effects. Equilibrations of trans-Rh(CO)(Cl)(L)2 complexes (L = 2, 3) establish analogous Lewis basicities. Density functional theory is used to calculate the structures, energies, ionization potentials, and gas-phase proton affinities (PA) of the model phosphines P((CH2)mCF3)3 (2′-9′). The ionization potentials of 2′-5′ are in good agreement with those of 2-5, and together with PA values and analyses of homodesmotic relationships are used to address the title question. Between 8 and 10 methylene groups are needed to effectively insulate a perfluoroalkyl segment from a phosphorus lone pair, depending upon the criterion employed. Computations also show that the first carbon of a perfluoroalkyl segment exhibits a much greater inductive effect than the second, and that ionization potentials of nonfluorinated phosphines P((CH2)mCH3)3 reach a limit at approximately nine carbons (m = 8).

Original languageEnglish
Pages (from-to)1516-1523
Number of pages8
JournalJournal of the American Chemical Society
Volume124
Issue number7
DOIs
Publication statusPublished - Feb 20 2002

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Fingerprint Dive into the research topics of 'How to insulate a reactive site from a perfluoroalkyl group: Photoelectron spectroscopy, calorimetric, and computational studies of long-range electronic effects in fluorous phosphines P((CH<sub>2</sub>)<sub>m</sub> (CF<sub>2</sub>)<sub>7</sub>CF<sub>3</sub>)<sub>3</sub>'. Together they form a unique fingerprint.

  • Cite this