Tris(indenyl)lanthanoid(III) Sulfoxide Adducts (1:1) in the Solid State and in Solution: Ligand Chirality as a Powerful Diagnostic Tool for Rapid Intermolecular Sulfoxide Exchange and Indenyl η5⇌η1 Fluxionality
✍ Scribed by Jingwen Guan; Jens Stehr; R. Dieter Fischer
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 369 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Me/4-MeC 6 H 4 (MTSO) or Ph/Ph (DPSO); Ln La, Pr, Nd, or Sm) have been prepared and characterized. While solid [Ln(C 9 H 7 ) 3 ´MTSO] (C 9 H 7 indenyl; Ln La, Pr) contains exclusively oxygen-bonded sulphoxide and three h 5coordinated indenyl ligands in a chiral arrangement around the metal ion, the C 9 H 7 ligands of the dissolved paramagnetic molecules (Ln Pr, Nd, Sm) are involved in rapid h 5 > h 1 fluxionality. Both variable-temperature 1 H NMR and f ± f circular dichroism (CD) spectroscopy indicate that a second chirogenic centre is generated that lies closer to the metal ion than the chiral sulphur atom of the MTSO ligand. In strict contrast, the congeners with Cp C 5 H 5 (Ln Pr, Nd, Yb) are practically CD-silent, although again the LnÀO distances are shorter by about 10 pm than in the corresponding THF adducts. Surprisingly, the NMR spectra of solutions of mixtures of [Ln(C 9 H 7 ) 3 ´MTSO] complexes with (R)-()-and (S)-(À)-MTSO, or/and with two different metals reveal rapid intermolecular sulphoxide exchange. On the other hand, mutual MTSO/THF exchange seems to be inhibited, which suggests that the facile sulphoxide exchange follows a special mechanistic pathway.