Experimental Characterization of an Electron-Rich (σ2π4δ2δ*2) Metal-Metal Triple Bond. Synthesis, Reactivity, and Photoelectron Spectral Studies of Trimethylphosphine Complexes of Dirhenium(II)

Dawn R. Root, Richard A. Walton, Charles H. Blevins, Dennis L. Lichtenberger, Alfred P. Sattelberger

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The reaction of (n-Bu4N)2Re2X8(X = Cl or Br) with PMe3 gives high yields of the triply bonded complexes Re2X4(PMe3)4. These compounds are oxidized by NOPF6 to give paramagnetic [Re2X4(PMe3)4]PF6, and the chloro derivative reacts with Ph2PCH2PPh2 (dppm) and Ph2PNHPPh2 (dppa) to give Re2Cl4(PMe)2(dppm) and Re2Cl4(PMe3)2(dppa), respectively. NMR spectroscopy (1H and 31P{1H}) shows that the latter complexes possess fairly symmetrical structures in which the PMe3 ligands are in cis dispositions with respect to the bridging dppm and dppa ligands. The volatility of Re2Cl4(PMe3)4has permitted the measurement of its gas-phase photoelectron spectrum which accords with this compound possessing a σ2π4δ2δ*2configuration. The δ* ionization band is slightly narrower than the δ ionization band and occurs at about 0.9 eV lower binding energy. The π ionization gives evidence of spin-orbit splitting as expected for the heavy-atom rhenium character. An ionization assigned to removal of an electron from the valence a orbital is observed at a binding energy 1 eV higher than the ir ionization. Comparison of these ionizations with those of the corresponding W2Cl4(PMe3)42π4δ2) complex is especially informative. In particular, these observations support a strong interaction between the valence a density on one metal atom and the core density on the neighboring metal atom in these complexes.

Original languageEnglish (US)
Pages (from-to)953-959
Number of pages7
JournalJournal of the American Chemical Society
Issue number5
StatePublished - Jan 1 1986


ASJC Scopus subject areas

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

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