Tantalum forms compounds in oxidation states −III to +V. Most commonly encountered are oxides of Ta(V), which includes all minerals. The chemical properties of Ta and Nb are very similar. In aqueous media, Ta only exhibit the +V oxidation state. Like niobium, tantalum is barely soluble in dilute solutions of hydrochloric, sulfuric, nitric and phosphoric acids due to the precipitation of hydrous Ta(V) oxide.[1] In basic media, Ta can be solubilized due to the formation of polyoxotantalate species.[2]
Oxides, nitrides, carbides, sulfides
editTantalum pentoxide (Ta2O5) is the most important compound from the perspective of applications. Oxides of tantalum in lower oxidation states are numerous, including many defect structures, and are lightly studied or poorly characterized.[3]
Tantalates, compounds containing [TaO4]3− or [TaO3]− are numerous. Lithium tantalate (LiTaO3) adopts a perovskite structure. Lanthanum tantalate (LaTaO4) contains isolated TaO3−
4 tetrahedra.[4]
As in the cases of other refractory metals, the hardest known compounds of tantalum are nitrides and carbides. Tantalum carbide, TaC, like the more commonly used tungsten carbide, is a hard ceramic that is used in cutting tools. Tantalum(III) nitride is used as a thin film insulator in some microelectronic fabrication processes.[5]
The best studied chalcogenide is TaS2, a layered semiconductor, as seen for other transition metal dichalcogenides. A tantalum-tellurium alloy forms quasicrystals.[4]
Halides
editTantalum halides span the oxidation states of +5, +4, and +3. Tantalum pentafluoride (TaF5) is a white solid with a melting point of 97.0 °C. The anion [TaF7]2- is used for its separation from niobium.[6] The chloride TaCl
5, which exists as a dimer, is the main reagent in synthesis of new Ta compounds. It hydrolyzes readily to an oxychloride. The lower halides TaX
4 and TaX
3, feature Ta-Ta bonds.[4][1]
Organotantalum compounds
edit
Organotantalum compounds include pentamethyltantalum, mixed alkyltantalum chlorides, alkyltantalum hydrides, alkylidene complexes as well as cyclopentadienyl derivatives of the same.[7][8] Diverse salts and substituted derivatives are known for the hexacarbonyl [Ta(CO)6]− and related isocyanides.
See also
editReferences
edit- ^ a b Agulyansky, Anatoly (2004). The Chemistry of Tantalum and Niobium Fluoride Compounds. Elsevier. ISBN 978-0-444-51604-6. Retrieved 2008-09-02.
- ^ Deblonde, Gauthier J. -P.; Chagnes, Alexandre; Bélair, Sarah; Cote, Gérard (2015-07-01). "Solubility of niobium(V) and tantalum(V) under mild alkaline conditions". Hydrometallurgy. 156: 99–106. doi:10.1016/j.hydromet.2015.05.015. ISSN 0304-386X.
- ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- ^ a b c Holleman, A. F.; Wiberg, E.; Wiberg, N. (2007). Lehrbuch der Anorganischen Chemie (in German) (102nd ed.). de Gruyter. ISBN 978-3-11-017770-1.
- ^ Tsukimoto, S.; Moriyama, M.; Murakami, Masanori (1961). "Microstructure of amorphous tantalum nitride thin films". Thin Solid Films. 460 (1–2): 222–226. Bibcode:2004TSF...460..222T. doi:10.1016/j.tsf.2004.01.073.
- ^ Soisson, Donald J.; McLafferty, J. J.; Pierret, James A. (1961). "Staff-Industry Collaborative Report: Tantalum and Niobium". Ind. Eng. Chem. 53 (11): 861–868. doi:10.1021/ie50623a016.
- ^ Schrock, Richard R. (1979-03-01). "Alkylidene complexes of niobium and tantalum". Accounts of Chemical Research. 12 (3): 98–104. doi:10.1021/ar50135a004. ISSN 0001-4842.
- ^ Morse, P. M.; et al. (2008). "Ethylene Complexes of the Early Transition Metals: Crystal Structures of [HfEt
4(C
2H
4)2−
] and the Negative-Oxidation-State Species [TaHEt(C
2H
4)3−
3] and [WH(C
2H
4)3−
4]". Organometallics. 27 (5): 984. doi:10.1021/om701189e.