Tantalum(IV) iodide is an inorganic compound with the chemical formula TaI₄. It dissolves in

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

to give a green solution, but the color fades when left in the air and produces a white precipitate.

Preparation

Tantalum(IV) iodide can be prepared by the reduction reaction of

tantalum(V) iodide Tantalum(V) iodide is the inorganic compound with the formula Ta2I10. Its name comes from the compound's empirical formula, TaI5. It is a diamagnetic, black solid that hydrolyses readily. The compound adopts an edge-shared bioctahedral structure, ...

and

tantalum Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as ''tantalium'', it is named after Tantalus, a villain in Greek mythology. Tantalum is a very hard, ductile, lustrous, blue-gray transition metal that is ...

. If

pyridine Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a d ...

is used as the reducing agent, there is an adduct TaI₄(py)₂. Tantalum(IV) iodide can also be obtained by reacting tantalum(V) iodide with aluminum, magnesium or calcium at 380 °C. Ta₆I₁₄ is also formed. This makes it difficult to produce a very pure crystallized tantalum(IV) iodide. :

Properties

Tantalum(IV) iodide is a black solid. It has a crystal structure isotypic to that of

niobium(IV) iodide Niobium(IV) iodide is an iodide of niobium, with the chemical formula of NbI4. Preparation Niobium(IV) iodide can be obtained by the decomposition of niobium(V) iodide Niobium(V) iodide is the inorganic compound with the formula Nb2I10. It ...

. Single-crystalline tantalum(IV) iodide was first obtained in 2008 by Rafal Wiglusz and Gerd Meyer as a chance product of a reaction in a tantalum ampoule that was supposed to lead to the product Rb(Pr₆C₂)I₁₂. The single crystal has a triclinic crystal structure with space group P1 (space group no. 2) with two formula units per unit cell (a = 707.36 pm, b = 1064.64 pm, c = 1074.99 pm, α = 100.440°, β = 89.824° and γ = 104.392°). The crystal structure differs from that of other transition metal tetraiodides, which usually have a MI_4/2I_2/1 chain structure, as it consists of TaI₆ octahedra bridged over a common surface to form a dimer. Two such dimers bridge over a common edge to form a tetramer.

References

{{Iodides Tantalum compounds Iodides Metal halides