Synthesis and study of tetramethylammonium hexafluoridozirconate and hexafluoridohafnate solvated by H2O·HF adducts and [N(CH3)4]2ZrF6

A new type of zirconium and hafnium fluoride complexes of the composition [N(CH3)4]2AF6·(H2O·HF) (A = Zr, Hf) solvated by H2O·HF adducts and the compound [N(CH3)4]2ZrF6 have been synthesized. The synthesized compounds were studied by X-ray diffraction, vibrational spectroscopy, quantum chemical calculations and differential thermal analysis. The crystal structures of [N(CH3)4]2AF6·(H2O·HF) (A = Zr, Hf) are built up from N(CH3)4+ cations, octahedral complex anions [AF6]2−, and solvate adducts H2O·HF linked by strong hydrogen bonds FH⋯O. The compound [N(CH3)4]2ZrF6 is built up from N(CH3)4+ cations and complex anions [ZrF6]2−. In the investigated structures, the complex anions, cations, and adducts are linked by ionic interactions and a branched system of hydrogen bonds OH⋯F and СH⋯F.