Abstract: Two crystalline tantalum polyselenides, Ta4Se17 and Ta4Se18, were synthesized in reactions of the elements at temperatures 360-380°C. Crystals of Ta4Se17 (1) were obtained by heating of a mixture Ta:Se at a molar ratio of 1:6 at 380°С, while crystals of Ta4Se18 (2) were produced from the same mixture in the presence of either ammonium chloride or ammonium bromide, at 360°С. Crystal structure of Ta4Se17 (1) (space group C2, a = 11.680(5), b = 11.870(5), c = 7.793(4) Å, β = 100.36(2)°, Z=2) is a packing of layers which consists of chains with a repeating sequence {-Ta(Se2)2-Ta(Se2)2-Ta(Se2)2-Ta(Se2)(Se3)-}, where Ta atoms are bridged by di- and tri-selenide groups, with Ta…Ta distances 3.15, 3.05, 3.15, 3.68 Å. These chains are connected in layers by means of Se–Se bonds in the (Se3) groups which form infinite chains of Se atoms. Crystal structure of Ta4Se18 (2) (space group I422, a = 9.2876(2), c = 12.7133(3) Å, Z=2) is a packing of chains {Ta(Se2)2}½+ and anions (Se2)2-, the interatomic distances Ta…Ta in the chains are all 3.18 Å. The experimental observations were supported by DFT calculations of the formation enthalpies of binary tantalum selenides. The syntheses, structures and stability of Ta4Se17 and Ta4Se18 are discussed in this paper.

Cite: Poltarak A. , Poltarak P. , Artemkina S.
Synthesis and crystal structure of binary tantalum polyselenides Ta4Se17 and Ta4Se18
Inorganic Chemistry. 2025. V.64. N49. P.23939–23946. DOI: 10.1021/acs.inorgchem.5c03595

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Dec 4, 2025

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