NMR and DFT study of chemical bonding of the titanyl ion in pentafluoro complexes (NH4)3TiOF5 and Rb2KTiOF5

19F NMR and DFT methods are used to study the electronic structure and chemical bonding of titanyl ions in pentafluoro titanyl complexes (NH₄)₃TiOF₅ and Rb₂KTiOF₅. The experimental values of the anisotropy of ¹⁹F NMR chemical shifts (CSs) are shown to be consistent with the calculated parameters within the DFT method. At normal temperatures orientational disordering of octahedral TiOF₅]^3- anions occurs, fluorine atoms steadily occupying cis- and trans-positions with respect to the O^2- ion. In both complexes, trans-position is not fully occupied; the occupation ratio does not exceed ~4:0.9. When the temperature is decreased to 150 K, the value of the CS anisotropy of the fluorine atom resonance line in trans-position is found to be smaller than the dipole-dipole broadening, whereas the line from fluorine atoms in cis-positions transforms into an asymmetric broad line characterized by the triaxial anisotropy of the CS tensor. It is shown that the found anisotropy corresponds to violation of the axial symmetry of Ti—F cis bonds because of strong delocalization of the electron density of Ti—O bonds in the titanyl ion.