Single-crystal X-ray and neutron diffraction structure determination and inelastic neutron scattering study of the dihydrogen complex trans-[Ru(H2)(H)(dppe)2] [BPh4]

Alberto Albinati, Wim T. Klooster, Thomas F. Koetzle, Jeffrey B. Fortin, John S. Ricci, Juergen Eckert, Tina P. Fong, Alan J. Lough, Robert H. Morris, Adina P. Golombek

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Abstract

The structure of the complex trans-[Ru(η2-H2) (H)(dppe)2] [BPh4] (1), dppe = PPh2CH2CH2PPh2, has been determined by single-crystal X-ray diffraction at 123 K and neutron diffraction at 12 K. The core of the complex has a distorted octahedral geometry about ruthenium with the dihydrogen ligand trans to hydride and eclipsing a trans-P-Ru-P axis that is bent away from the hydrogens with a P-Ru-P angle of 167.9(4)°. The crystallographically determined H-H distance is 0.83(8)(X-ray) or 0.82(3) (neutron) Å. The latter value, when corrected for the shortening caused by the torsional libration of the H2 ligand, increases to about 0.94 Å. The long Ru-(H2) distance of 1.81(2) Å (neutron), compared to the terminal hydride to ruthenium distance of 1.64(2) A (neutron), is consistent with the lability of the dihydrogen ligand, which is partially lost from the crystal by treatment with vacuum. The analogous iron complex trans-[Fe(η2-H2)(H)(dppe) 2] [BPh4] (2) has similar features except that the Fe-H(H2) distances are much shorter and the H2 ligand is correspondingly less labile. An inelastic neutron scattering study of the powder of 1 at 5 K reveals two broad inelastic peaks flanking the elastic peak. With the assumption that the dihydrogen librates in a double-minimum potential, the barrier to dihydrogen reorientation is calculated to be 1.0 to 1.4 kcal mol-1 ',depending upon which of the H-H distances is used. This barrier is less than that for the iron analog, determined for its BF4 salt, therefore suggesting that there may be less dπ-» → σ* backbonding in 1 than 2.

Original languageEnglish
Pages (from-to)351-357
Number of pages7
JournalInorganica Chimica Acta
Volume259
Issue number1-2
DOIs
StatePublished - Jun 1997

Keywords

  • Crystal structures
  • Dihydrogen complexes
  • Hydride complexes
  • Neutron scattering
  • Ruthenium complexes

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    Albinati, A., Klooster, W. T., Koetzle, T. F., Fortin, J. B., Ricci, J. S., Eckert, J., Fong, T. P., Lough, A. J., Morris, R. H., & Golombek, A. P. (1997). Single-crystal X-ray and neutron diffraction structure determination and inelastic neutron scattering study of the dihydrogen complex trans-[Ru(H2)(H)(dppe)2] [BPh4]. Inorganica Chimica Acta, 259(1-2), 351-357. https://doi.org/10.1016/s0020-1693(97)05521-7