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Nonclassical Titanocene Silyl Hydrides

  1. Stanislav K. Ignatov Dr.3,
  2. Nicholas H. Rees Dr2,
  3. Ben R. Tyrrell2,
  4. Stuart R. Dubberley Dr.2,
  5. Alexei G. Razuvaev Dr.3,
  6. Philip Mountford Dr.2,
  7. Georgii I. Nikonov Dr.1

Article first published online: 23 AUG 2004

DOI: 10.1002/chem.200400230

Issue

Chemistry - A European Journal

Chemistry - A European Journal

Volume 10, Issue 20, pages 4991–4999, October 18, 2004

Additional Information

How to Cite

Ignatov, S. K., Rees, N. H., Tyrrell, B. R., Dubberley, S. R., Razuvaev, A. G., Mountford, P. and Nikonov, G. I. (2004), Nonclassical Titanocene Silyl Hydrides. Chem. Eur. J., 10: 4991–4999. doi: 10.1002/chem.200400230

Author Information

  1. 1

    Chemistry Department, Moscow State University, Vorob'evy Gory, 119992 Moscow, Russia, Fax: (+7) 095-9328846

  2. 2

    Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Oxford OX1 3TA, UK, Fax: (+44) 8165-272690

  3. 3

    University of Nizhnii Novgorod, 23, Gagarin Avenue, Nizhnii Novgorod 603600, Russia

Publication History

  1. Issue published online: 7 OCT 2004
  2. Article first published online: 23 AUG 2004
  3. Manuscript Revised: 25 MAY 2004
  4. Manuscript Received: 10 MAR 2004

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Keywords:

  • density functional calculations;
  • hydride ligands;
  • hypervalent compounds;
  • silicon;
  • titanium

Abstract

The titanocene silyl hydride complexes [Ti(Cp)2(PMe3)(H)(SiR3)] [SiR3=SiMePhCl (6), SiPh2Cl (7), SiMeCl2 (8), SiCl3 (9)] were prepared by HSiR3 addition to [Ti(Cp)2(PMe3)2] and were studied by NMR and IR spectroscopy, X-ray diffraction (for 6, 8, and 9), and DFT calculations. Spectroscopic and structural data established that these complexes exhibit nonclassical Ti-H-Si-Cl interligand hypervalent interactions. In particular, the observation of silicon–hydride coupling constants J(Si,H) in 6–9 in the range 22–40 Hz, the signs of which we found to be negative for 8 and 9, is conclusive evidence of the presence of a direct Si[BOND]H bond. The analogous reaction of [Ti(Cp)2(PMe3)2] with HSi(OEt)3 does not afford the expected classical silyl hydride complex [Ti(Cp)2(PMe3)(H){Si(OEt)3}], and instead NMR-silent titanium (apparently TiIII) complex(es) and the silane redistribution product Si(OEt)4 are formed. The structural data and DFT calculations for the compounds [Ti(Cp)2(PMe3)(H)(SiR3)] show that the strength of interligand hypervalent interactions in the chlorosilyl complexes decreases as the number of chloro groups on silicon increases. However, in the absence of an Si-bound electron-withdrawing group trans to the Si[BOND]H moiety, a silane σ complex is formed, characterized by a long Ti[BOND]Si bond of 2.658 Å and short Si[BOND]H contact of 1.840 Å in the model complex [Ti(Cp)2(PMe3)(H)(SiMe3)]. Both the silane σ complexes and silyl hydride complexes with interligand hypervalent interactions exhibit bond paths between the silicon and hydride atoms in Atoms in Molecules (AIM) studies. To date a classical titanocene phosphane silyl hydride complex without any Si[BOND]H interaction has not been observed, and therefore titanocene silyl hydrides are, depending on the nature of the R groups on Si, either silane σ complexes or compounds with an interligand hypervalent interaction.

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