Structural and Electronic Properties of Fluoride Complexes of Nb super(V), Ta super(V), and Pa super(V): The Influence of Relativistic Effects on Group V Elements

Aqueous fluorido complexes of niobium and tantalum were studied by using synchrotron-based extended X-ray absorption spectroscopy (EXAFS) as model systems for comparison of the structural and coordination chemistry of the group V metals Nb, Ta, and their pseudo-homologue Pa super(V). The EXAFS measu...

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Bibliographic Details
Published in:European journal of inorganic chemistry 2016-12, Vol.2016 (35), p.5467-5476
Main Authors: Wilson, Richard E, De Sio, Stephanie, Vallet, Valerie
Format: Article
Language:English
Subjects:
Absorption spectroscopy
Computation
Fluorides
Niobium
Protactinium
Relativistic effects
Speciation
Tantalum
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Summary:Aqueous fluorido complexes of niobium and tantalum were studied by using synchrotron-based extended X-ray absorption spectroscopy (EXAFS) as model systems for comparison of the structural and coordination chemistry of the group V metals Nb, Ta, and their pseudo-homologue Pa super(V). The EXAFS measurements indicate differences in the coordination chemistry of Nb and Ta in these systems that were not intuitively based on their similar charge and ionic radii. The Ta speciation is dominated by six- and seven-coordinate fluorido complexes, while the chemical speciation of Nb under the same conditions is dominated by its hydrolyzed oxyfluoride complexes. Quantum chemical computations were performed to more fully describe these observations, and these results are compared to our earlier study on the fluorido complexes of protactinium. Computations performed with and without the inclusion of scalar relativistic effects reveal that the differences in chemistry among the group V elements and their pseudo-homologue protactinium are due to the increasing influence of relativistic effects as Z increases from niobium to protactinium. A comparative study of fluoride complexes of Nb, Ta, and their pseudo-homologue protactinium with use of synchrotron-based X-ray absorption spectroscopy and quantum chemical calculations reveals various seemingly nonperiodic chemistries. Computational results demonstrate that this "nonperiodic" behavior is due to the increasing influence of relativistic effects as Z increases from Nb to Pa.
ISSN:1434-1948
1099-0682
DOI:10.1002/ejic.201600981