Long Hydrogen-Bonded Rod of Molecular Oxide: A Hexatantalate Tetramer

A tetra-n-butylammonium (TBA) salt of [H4.5(Ta6O19)]3.5– was synthesized by reacting hydrous tantalum oxide with TBAOH. X-ray structural analysis of TBA3.5[H4.5(Ta6O19)]·2THF·5.5H2O (THF = tetrahydrofuran) revealed that this compound consists of a hydrogen-bonded, rod-shaped tetramer of hexatantalate that is almost 30 Å long together with TBA cations and solvent molecules of crystallization [a = 20.6354(5) Å, b = 25.5951(7) Å, c = 37.2058(8) Å, α = 77.092(1)°, β = 86.177(1)°, γ = 88.683(1)°, V = 19110.9(8) Å3, Z = 8, and space group P1̅]. 1H NMR spectra showed that this tetrameric structure is maintained in solution.