論文

査読有り 国際誌
2019年9月

Terminal and bridging fluorine ligands in TiF4 as studied by 19F NMR in solids.

Solid state nuclear magnetic resonance
  • Miwa Murakami
  • ,
  • Yasuto Noda
  • ,
  • K Takegoshi

101
開始ページ
82
終了ページ
88
記述言語
英語
掲載種別
研究論文(学術雑誌)
DOI
10.1016/j.ssnmr.2019.05.007

To examine bonding nature of fluorine ligands in a metal coordinated system, 19F high-resolution solid-state NMR has been applied to TiF4, which bears both bridging and terminal fluorines. Observed 12 isotropic signals are assigned to 12 crystallographically different fluorines (6 terminal and 6 bridging fluorines) in TiF4 by referring to the calculated isotropic shifts using density functional theory (DFT). The isotropic chemical shift (δiso) for terminal F (FT) appears at high frequency (420-480 ppm from δ(CCl3F) = 0 ppm) with large shielding anisotropy Δσ ∼ 850 ppm. Whereas the δiso and Δσ values for bridging F (FB) are moderate; δiso ∼ 0-25 ppm and Δσ ∼ 250 ppm. The origin of the observed high-frequency shift for FT is ascribed to the second-order paramagnetic shift with increased covalency, shorter Ti-F bonds, and smaller energy difference between the occupied and vacant orbitals. Examination of the orientation of the shielding tensor relative to the molecular structure shows that the most deshielded component of the shielding tensor is oriented along the Ti-F bond. The characteristic orientation is consistent with a Ti-F σ bond formed by dYZ of Ti and pz of F. Further, we show that the selectively observed spinning sideband patterns and the theoretical patterns with the calculated Δσ and η (shielding asymmetry) values are not consistent with each other for FB, indicating deficiency of the present DFT calculation in evaluating Δσ.

リンク情報
DOI
https://doi.org/10.1016/j.ssnmr.2019.05.007
PubMed
https://www.ncbi.nlm.nih.gov/pubmed/31132715

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