Issue 23, 2022

Tantalum, easy as Pi: understanding differences in metal–imido bonding towards improving Ta/Nb separations

Abstract

The separation and purification of niobium and tantalum, which co-occur in natural sources, is difficult due to their similar physical and chemical properties. The current industrial method for separating Ta/Nb mixtures uses an energy-intensive process with caustic and toxic conditions. It is of interest to develop alternative, fundamental methodologies for the purification of these technologically important metals that improve upon their environmental impact. Herein, we introduce new Ta/Nb imido compounds: M(tBuN)(TriNOx) (1-M) bound by the TriNOx3− ligand and demonstrate a fundamental, proof-of-concept Ta/Nb separation based on differences in the imido reactivities. Despite the nearly identical structures of 1-M, density functional theory (DFT)-computed electronic structures of 1-M indicate enhanced basic character of the imido group in 1-Ta as compared to 1-Nb. Accordingly, the rate of CO2 insertion into the M[double bond, length as m-dash]Nimido bond of 1-Ta to form a carbamate complex (2-Ta) was selective compared to the analogous, unobserved reaction with 1-Nb. Differences in solubility between the imido and carbamate complexes allowed for separation of the carbamate complex, and led to an efficient Ta/Nb separation (STa/Nb = 404 ± 150) dependent on the kinetic differences in nucleophilicities between the imido moieties in 1-Ta and 1-Nb.

Graphical abstract: Tantalum, easy as Pi: understanding differences in metal–imido bonding towards improving Ta/Nb separations

Supplementary files

Article information

Article type
Edge Article
Submitted
02 Apr 2022
Accepted
10 May 2022
First published
12 May 2022
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2022,13, 6796-6805

Tantalum, easy as Pi: understanding differences in metal–imido bonding towards improving Ta/Nb separations

A. B. Weberg, S. Chaudhuri, T. Cheisson, C. Uruburo, E. Lapsheva, P. Pandey, M. R. Gau, P. J. Carroll, G. C. Schatz and E. J. Schelter, Chem. Sci., 2022, 13, 6796 DOI: 10.1039/D2SC01926D

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. You can use material from this article in other publications, without requesting further permission from the RSC, provided that the correct acknowledgement is given and it is not used for commercial purposes.

To request permission to reproduce material from this article in a commercial publication, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party commercial publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements