Titanium diselenide

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Titanium diselenide
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Names
IUPAC name
bis(selanylidene)titanium
Other names
titanium selenide, titanium diselenide
Identifiers
3D model (JSmol)
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PubChem CID
  • [Se]=[Ti]=[Se]
Properties
TiSe2
Molar mass 205.787
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Titanium diselenide (TiSe2) also known as titanium(IV) selenide, is an inorganic compound of titanium and selenium. In this material selenium is viewed as selenide (Se2−) which requires that titanium exists as Ti4+. Titanium diselenide is a member of metal dichalcogenides, compounds that consist of a metal and an element of the chalcogen column within the periodic table. Many exhibit properties of potential value in battery technology, such as intercalation and electrical conductivity, although most applications focus on the less toxic and lighter disulfides, e.g. TiS2.

Contents

Structure

Within the titanium-selenium system, many stoichiometries have been identified. Titanium diselenide crystallizes with the CdI2 -type structure, in which the octahedral holes between alternating hexagonal closely packed layer of Se2− layers (that is half of the total number of octahedral holes) are occupied by Ti4+ centers. The CdI2 structure is often referred to as a layer structure as the repeating layers of atoms perpendicular to the close packed layer form the sequence Se-Ti-SeSe-Ti-SeSe-Ti-Se with weak van der Waals interactions between the selenium atoms in adjacent layers. The structure has (6,3)-coordination, being octahedral for the cation and trigonal pyramidal for the anions. The structure type is found commonly for many transition metal halides as well. [1] This layered structure is known to undergo intercalation by alkali metals (M), resulting in the formation of MxTiSe2 (x ≤ 1), thereby expanding the weak van der Waals gaps between the 2D layered sheets. [2]

Synthesis

A mixture of titanium and selenium are heated under argon atmosphere to produce crude samples. The crude product is typically purified by chemical vapor transport using iodine as the transport agent. [3]

Ti + 2 Se → TiSe2

Related Research Articles

Carbide Inorganic compound group

In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece.

A selenide is a chemical compound containing a selenium anion with oxidation number of −2 (Se2−), much as sulfur does in a sulfide. The chemistry of the selenides and sulfides is similar. Similar to sulfide, in aqueous solution, the selenide ion, Se2−, is prevalent only in very basic conditions. In neutral conditions, hydrogen selenide ion, HSe, is most common. In acid conditions, hydrogen selenide, H2Se, is formed.

Intercalation (chemistry) Reversible insertion of an ion into a material with layered structure

In chemistry, intercalation is the reversible inclusion or insertion of a molecule into layered materials with layered structures. Examples are found in graphite and transition metal dichalcogenides.

Chalcogenide

A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term chalcogenide is more commonly reserved for sulfides, selenides, tellurides, and polonides, rather than oxides. Many metal ores exist as chalcogenides. Photoconductive chalcogenide glasses are used in xerography. Some pigments and catalysts are also based on chalcogenides. The metal dichalcogenide MoS2 is a common solid lubricant.

Organoselenium compounds are chemical compounds containing carbon-to-selenium chemical bonds. Organoselenium chemistry is the corresponding science exploring their properties and reactivity. Selenium belongs with oxygen and sulfur to the group 16 elements or chalcogens, and similarities in chemistry are to be expected. Organoselenium compounds are found at trace levels in ambient waters, soils and sediments.

Selenol

Selenols are organic compounds that contain the functional group with the connectivity C–Se–H. Selenols are sometimes also called selenomercaptans and selenothiols. Selenols are one of the principal classes of organoselenium compounds. The best known member of the group is the amino acid selenocysteine.

Selenium tetrafluoride Chemical compound

Selenium tetrafluoride (SeF4) is an inorganic compound. It is a colourless liquid that reacts readily with water. It can be used as a fluorinating reagent in organic syntheses (fluorination of alcohols, carboxylic acids or carbonyl compounds) and has advantages over sulfur tetrafluoride in that milder conditions can be employed and it is a liquid rather than a gas.

Tin selenide Chemical compound

Tin selenide, also known as stannous selenide, is an inorganic compound with the formula SnSe. Tin(II) selenide is a typical layered metal chalcogenide as it includes a group 16 anion (Se2−) and an electropositive element (Sn2+), and is arranged in a layered structure. Tin(II) selenide is a narrow band-gap (IV-VI) semiconductor structurally analogous to black phosphorus. It has received considerable interest for applications including low-cost photovoltaics, and memory-switching devices.

In chemistry, crystallography, and materials science, the coordination number, also called ligancy, of a central atom in a molecule or crystal is the number of atoms, molecules or ions bonded to it. The ion/molecule/atom surrounding the central ion/molecule/atom is called a ligand. This number is determined somewhat differently for molecules than for crystals.

Carbon diselenide Chemical compound

Carbon diselenide is an inorganic compound with the chemical formula CSe2. It is a yellow-orange oily liquid with pungent odor. It is the selenium analogue of carbon disulfide (CS2). This light-sensitive compound is insoluble in water and soluble in organic solvents.

Titanium disulfide Inorganic chemical compound

Titanium disulfide is an inorganic compound with the formula TiS2. A golden yellow solid with high electrical conductivity, it belongs to a group of compounds called transition metal dichalcogenides, which consist of the stoichiometry ME2. TiS2 has been employed as a cathode material in rechargeable batteries.

Iron(II) selenide refers to a number of inorganic compounds of ferrous iron and selenide (Se2−). The phase diagram of the system Fe–Se reveals the existence of several non-stoichiometric phases between ~49 at. % Se and ~53 at. % Fe, and temperatures up to ~450 °C. The low temperature stable phases are the tetragonal PbO-structure (P4/nmm) β-Fe1−xSe and α-Fe7Se8. The high temperature phase is the hexagonal, NiAs structure (P63/mmc) δ-Fe1−xSe. Iron(II) selenide occurs naturally as the NiAs-structure mineral achavalite.

Molybdenum diselenide Chemical compound

Molybdenum diselenide is an inorganic compound of molybdenum and selenium. Its structure is similar to that of MoS
2
. Compounds of this category are known as transition metal dichalcogenides, abbreviated TMDCs. These compounds, as the name suggests, are made up of a transition metals and elements of group 16 on the periodic table of the elements. Compared to MoS
2
, MoSe
2
exhibits higher electrical conductivity.

Tungsten diselenide Chemical compound

Tungsten diselenide is an inorganic compound with the formula WSe2. The compound adopts a hexagonal crystalline structure similar to molybdenum disulfide. Every tungsten atom is covalently bonded to six selenium ligands in a trigonal prismatic coordination sphere while each selenium is bonded to three tungsten atoms in a pyramidal geometry. The tungsten–selenium bond has a length of 0.2526 nm, and the distance between selenium atoms is 0.334 nm. It is a well studied example of a layered material. The layers stack together via van der Waals interactions. WSe2 is a very stable semiconductor in the group-VI transition metal dichalcogenides.

Platinum diselenide is a transition metal dichalcogenide (TMDC) consisting of the metal platinum and the non-metal selenium with the formula PtSe2. Being a layered substance, PtSe2 can be split into thin layers down to three atoms thick called monolayers. PtSe2 is a semimetal or semiconductor depending on thickness.

Niobium diselenide Chemical compound

Niobium diselenide or niobium(IV) selenide is a layered transition metal dichalcogenide with formula NbSe2. Niobium diselenide is a lubricant, and a superconductor at temperatures below 7.2 K that exhibit a charge density wave (CDW). NbSe2 crystallizes in several related forms, and can be mechanically exfoliated into monatomic layers, similar to other transition metal dichalcogenide monolayers. Monolayer NbSe2 exhibits very different properties from the bulk material, such as of Ising superconductivity, quantum metallic state, and strong enhancement of the CDW.

Rhenium diselenide Chemical compound

Rhenium diselenide is an inorganic compound with the formula ReSe2. It has a layered structure where atoms are strongly bonded within each layer. The layers are held together by weak Van der Waals bonds, and can be easily peeled off from the bulk material.

Indium (II) selenide (InSe) is an inorganic compound composed of indium and selenium. It is a III-VI layered semiconductor. The solid has a structure consisting of two-dimensional layers bonded together only by van der Waals forces. Each layer has the atoms in the order Se-In-In-Se.

Layered materials

In material science, layered materials are solids with highly anisotropic bonding, in which two-dimensional sheets are internally strongly bonded, but only weakly bonded to adjacent layers. Owing to their distinctive structures, layered materials are often suitable for intercalation reactions.

Tantalum diselenide Chemical compound

Tantalum diselenide is a compound made with tantalum and selenium atoms, with chemical formula TaSe2, which belongs to the family of transition metal dichalcogenides. In contrast to molybdenum disulfide (MoS2) or rhenium disulfide (ReS2, tantalum diselenide does not occur spontaneously in nature, but it can be synthesized. Depending on the growth parameters, different types of crystal structures can be stabilized.

References

  1. Riekel, C (1976). "Structure Refinement of TiSe2 by Neutron Diffraction". Journal of Solid State Chemistry. 17 (4): 389–92. Bibcode:1976JSSCh..17..389R. doi:10.1016/S0022-4596(76)80008-4.
  2. Bouroushian, M. "Electrochemistry of Metal Chalcogenides" ISBN   978-3-642-03967-6
  3. Hagenmuller, P. "Preparative Methods in Solid State Chemistry" ISBN   978-0-323-14436-0