B. 19 F NMR Fig. shows the 19 F MAS solid-state NMR spectrum for ReO 3 -type TiOF 2 , which provides additional information about the local environments of the F -anions. The spectrum shows a broad, slightly asymmetric main feature. We have reconstructed the experimental spectrum using two resonances (lines 1 and 2), which we assign to bridging Ti-F-Ti fluorine atoms. Additionally, our reconstruction reveals a broader and less intense line (line 3) at δ iso ≈ 170 ppm, which we attribute to Ti-F-□ "non-bridging" fluorine atoms, where one adjacent titanium site is vacant .