Issue 20, 2018

The role of electronegativity on the extent of nitridation of group 5 metals as revealed by reactions of tantalum cluster cations with ammonia molecules

Abstract

Reactions of the free tantalum cation, Ta+, and tantalum cluster cations, Tan+ (n = 2–10), with ammonia are presented. The reaction of the monomer cation, Ta+, with two molecules of NH3 leads to the formation of TaN2H2+ along with release of two H2 molecules. The dehydrogenation occurs until the formal oxidation number of the tantalum atom reaches +5. On the other hand, all the tantalum cluster cations, Tan+, react with two molecules of NH3 and form TanN2+ with the release of three H2 molecules. Further exposure to ammonia showed that TanNmH+ and TanNm+ are produced through successive reactions; a pure nitride and three H2 molecules are formed for every other NH3 molecule. The nitridation occurred until the formal oxidation number of the tantalum atoms reaches +5 as in the case of TaN2H2+ in contrast to other group 5 elements, i.e., vanadium and niobium, which have been reported to produce nitrides with lower oxidation states. The present results on small gas-phase metal-nitride clusters show correlation with their bulk properties: tantalum is known to form bulk nitrides in the oxidation states of either +5 (Ta3N5) or +3 (TaN), whereas vanadium and niobium form nitrides in the oxidation state of +3 (VN and NbN). Along with DFT calculations, these findings reveal that nitridation is driven by the electron-donating ability of group 5 elements, i.e., electronegativity of the metal plays a key role in determining the composition of the metal nitrides.

Graphical abstract: The role of electronegativity on the extent of nitridation of group 5 metals as revealed by reactions of tantalum cluster cations with ammonia molecules

Supplementary files

Article information

Article type
Paper
Submitted
19 yan 2018
Accepted
29 apr 2018
First published
01 may 2018

Phys. Chem. Chem. Phys., 2018,20, 13974-13982

The role of electronegativity on the extent of nitridation of group 5 metals as revealed by reactions of tantalum cluster cations with ammonia molecules

M. Arakawa, K. Ando, S. Fujimoto, S. Mishra, G. N. Patwari and A. Terasaki, Phys. Chem. Chem. Phys., 2018, 20, 13974 DOI: 10.1039/C8CP00424B

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