| Autor: |
Réant, Benjamin L. L., Mackintosh, Fraser J., Gransbury, Gemma K., Mattei, Carlo Andrea, Alnami, Barak, Atkinson, Benjamin E., Bonham, Katherine L., Baldwin, Jack, Wooles, Ashley J., Vitorica-Yrezabal, Iñigo J., Lee, Daniel, Chilton, Nicholas F., Liddle, Stephen T., Mills, David P. |
| Zdroj: |
JACS Au; July 2024, Vol. 4 Issue: 7 p2695-2711, 17p |
| Abstrakt: |
The paramagnetism of f-block ions has been exploited in chiral shift reagents and magnetic resonance imaging, but these applications tend to focus on 1H NMR shifts as paramagnetic broadening makes less sensitive nuclei more difficult to study. Here we report a solution and solid-state (ss) 29Si NMR study of an isostructural series of locally D3h-symmetric early f-block metal(III) tris-hypersilanide complexes, [M{Si(SiMe3)3}3(THF)2] (1-M; M = La, Ce, Pr, Nd, U); 1-Mwere also characterized by single crystal and powder X-ray diffraction, EPR, ATR-IR, and UV–vis–NIR spectroscopies, SQUID magnetometry, and elemental analysis. Only one SiMe3signal was observed in the 29Si ssNMR spectra of 1-M, while two SiMe3signals were seen in solution 29Si NMR spectra of 1-Laand 1-Ce. This is attributed to dynamic averaging of the SiMe3groups in 1-Min the solid state due to free rotation of the M–Si bonds and dissociation of THF from 1-Min solution to give the locally C3v-symmetric complexes [M{Si(SiMe3)3}3(THF)n] (n= 0 or 1), which show restricted rotation of M–Si bonds on the NMR time scale. Density functional theory and complete active space self-consistent field spin–orbit calculations were performed on 1-Mand desolvated solution species to model paramagnetic NMR shifts. We find excellent agreement of experimental 29Si NMR data for diamagnetic 1-La, suggesting n= 1 in solution and reasonable agreement of calculated paramagnetic shifts of SiMe3groups for 1-M(M = Pr and Nd); the NMR shifts for metal-bound 29Si nuclei could only be reproduced for diamagnetic 1-La, showing the current limitations of pNMR calculations for larger nuclei. |
| Databáze: |
Supplemental Index |
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