Molecular modelling of tantalum penta-halides during hydrolysis and oxidation reactions

Electronic transitions of tantalum monofluoride

“…The low-lying Λ-S states of TaF are listed in Table S2 of the supplementary material. Different from the ground L-S level 5 F of Ta + , the multiplicity of the ground Λ-S state of TaF is triplet instead of quintet. Three Λ-S states [1] 1 Σ + , [1] 1 Γ, and [1] 3 Σ − associated with the Ta + 5d 2 configurations have rather short equilibrium distances (around 1.8 Å), whereas the r e values of the Ta + 5d 3 dominated states are about 1.9 Å or much longer.…”

“…For comparison, although the lowest energy Ω = 0 and 2 sub-states of the TaCl molecule are quite similar to those of TaF, 6 the calculated energy for these two sub-states was reversed and the separation between them was too small to be conclusive. 5 Which of these is the ground state of TaCl is still not clear.…”

“…From x-ray crystal structural determination, the measured Ta-F bond length was found to be 1.951 Å for TaF 3 , and the bond length for equatorial and axial F atoms were determined to be 1.78 and 2.07 Å, respectively, for the TaF 5 molecule. 3,4 Recent densityfunctional theory (DFT) calculations by Ungerer et al 5 indicated that TaF 5 is a closed-shell molecule and has no first order spin-orbit effects and the calculated equatorial Ta-F bond length is 1.89 Å, and the highest calculated harmonic frequency (a 1 ) was 674 cm 1 . It would be interesting to a) Author to whom correspondence should be addressed.…”

Extraction of polyoxotantalate by Mg–Fe layered double hydroxides: elucidation of sorption mechanisms

“…4,6 Pyrometallurgy has been developed as an alternative process based on heat treatment at 725-773 K in air atmosphere followed by remelting or extraction of Ta from transition metals in the metallic state (liquid metal extraction), [7][8][9] or extraction of tantalum from tin slags by chlorination and carbochlorination using Cl 2 + N 2 and Cl 2 + CO + N 2 gas mixtures. 10 Despite the efficiency of these techniques, their industrialization is limited by the high investment costs due to the particular chemical conditions needed: the use of highly corrosive and toxic solutions of concentrated HF, 11 combined with H 2 SO 4 or HCl, 12 organic solvents such as MIBK, 13 or the different purication steps needed. Therefore, these processes represent a serious health hazard for the humans and the environment and recent efforts were focused on alkaline matrices to generate polyoxotantalates (POTas), which have a high solubility in alkaline medium.…”

Tantalum Recycling by Solvent Extraction: Chloride Is Better than Fluoride

“…To our knowledge, there are very few reports that describe the extraction of tantalum from chloride-based media; acids such as HCl were tested in the extraction of TaF5, but in these cases, significant solubility issues were seen [20]. Despite the limited speciation data available for tantalum in halide acids, previous theoretical studies have postulated that TaCl5 could behave in a similar manner to TaF5 in aqueous solution, so forming halidometalates such as TaCl6 − in the presence of excess chloride ion [21,22].…”