Which is the most basic oxygen in [Ta6O19]8−? — Synthesis and structural characterization of [H2Ta6O19]6−

The first protonated hexatantalate, [H2Ta6O19]6−, has been synthesized and structurally characterized. X-ray diffraction analysis revealed that the protons are selectively attached to the O atoms that bridge two Ta atoms. The overall structure of the [H2Ta6O19]6− anion is virtually identical to that predicted by a DFT calculation.