Nitride

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In chemistry, a nitride is a chemical compound of nitrogen. Nitrides can be inorganic or organic, ionic or covalent. The nitride anion, N3- ion, is very elusive but compounds of nitride are numerous, although rarely naturally occurring. Some nitrides have a found applications, [1] such as wear-resistant coatings (e.g., titanium nitride, TiN), hard ceramic materials (e.g., silicon nitride, Si3N4), and semiconductors (e.g., gallium nitride, GaN). The development of GaN-based light emitting diodes was recognized by the 2014 Nobel Prize in Physics. [2] Metal nitrido complexes are also common.

Contents

Synthesis of inorganic metal nitrides is challenging because nitrogen gas (N2) is not very reactive at low temperatures, but it becomes more reactive at higher temperatures. Therefore, a balance must be achieved between the low reactivity of nitrogen gas at low temperatures and the entropy driven formation of N2 at high temperatures. [3] However, synthetic methods for nitrides are growing more sophisticated and the materials are of increasing technological relevance. [4]

Uses of nitrides

Like carbides, nitrides are often refractory materials owing to their high lattice energy, which reflects the strong bonding of "N3−" to metal cation(s). Thus, cubic boron nitride, titanium nitride, and silicon nitride are used as cutting materials and hard coatings. Hexagonal boron nitride, which adopts a layered structure, is a useful high-temperature lubricant akin to molybdenum disulfide. Nitride compounds often have large band gaps, thus nitrides are usually insulators or wide-bandgap semiconductors; examples include boron nitride and silicon nitride. The wide-band gap material gallium nitride is prized for emitting blue light in LEDs. [5] [6] Like some oxides, nitrides can absorb hydrogen and have been discussed in the context of hydrogen storage, e.g. lithium nitride.

Examples

Classification of such a varied group of compounds is somewhat arbitrary. Compounds where nitrogen is not assigned −3 oxidation state are not included, such as nitrogen trichloride where the oxidation state is +3; nor are ammonia and its many organic derivatives.

Nitrides of the s-block elements

Only one alkali metal nitride is stable, the purple-reddish lithium nitride (Li3N), which forms when lithium burns in an atmosphere of N2. [7] Sodium nitride and potassium nitride has been generated, but remains a laboratory curiosity. The nitrides of the alkaline earth metals that have the formula M3N2 are however numerous. Examples include beryllium nitride (Be3N2), magnesium nitride (Mg3N2), calcium nitride (Ca3N2), and strontium nitride (Sr3N2). The nitrides of electropositive metals (including Li, Zn, and the alkaline earth metals) readily hydrolyze upon contact with water, including the moisture in the air:

Mg3N2 + 6 H2O → 3 Mg(OH)2 + 2 NH3

Nitrides of the p-block elements

Boron nitride exists as several forms (polymorphs). Nitrides of silicon and phosphorus are also known, but only the former is commercially important. The nitrides of aluminium, gallium, and indium adopt the hexagonal wurtzite structure in which each atom occupies tetrahedral sites. For example, in aluminium nitride, each aluminium atom has four neighboring nitrogen atoms at the corners of a tetrahedron and similarly each nitrogen atom has four neighboring aluminium atoms at the corners of a tetrahedron. This structure is like hexagonal diamond (lonsdaleite) where every carbon atom occupies a tetrahedral site (however wurtzite differs from sphalerite and diamond in the relative orientation of tetrahedra). Thallium(I) nitride (Tl3N) is known, but thallium(III) nitride (TlN) is not.

Transition metal nitrides

Most metal-rich transition metal nitrides adopt a relatively ordered face-centered cubic or hexagonal close-packed crystal structure, with octahedral coordination. [8] Sometimes these materials are called "interstitial nitrides". They are essential for industrial metallurgy, because they are typically much harder and less ductile than their parent metal, and resist air-oxidation. [9] For the group 3 metals, ScN and YN are both known. Group 4, 5, and 6 transition metals (the titanium, vanadium and chromium groups) all form [10] chemically stable, refractory nitrides with high melting point. Thin films of titanium nitride, zirconium nitride, and tantalum nitride protect many industrial surfaces.

Nitrides of the group 7 and 8 transition metals tend to be nitrogen-poor, and decompose readily at elevated temperatures. For example, iron nitride, Fe2N decomposes at 200 °C. Platinum nitride and osmium nitride may contain N2 units, and as such should not be called nitrides. [11] [12]

Nitrides of heavier members from group 11 and 12 are less stable than copper nitride (Cu3N) and zinc nitride (Zn3N2): dry silver nitride (Ag3N) is a contact explosive which may detonate from the slightest touch, even a falling water droplet. [13]

Nitrides of the lanthanides and actinides

Nitride containing species of the lanthanides and actinides are of scientific interest as they can provide a useful handle for determining covalency of bonding. Nuclear magnetic resonance (NMR) spectroscopy along with quantum chemical analysis has often been used to determine the degree to which metal nitride bonds are ionic or covalent in character. One example, a uranium nitride, has the highest known nitrogen-15 chemical shift. [14]

Molecular nitrides

S4N4 is a prototypical binary molecular nitride. Tetrasulfur-tetranitride.png
S4N4 is a prototypical binary molecular nitride.

Many metals form molecular nitrido complexes, as discussed in the specialized article. The main group elements also form some molecular nitrides. Cyanogen ((CN)2) and tetrasulfur tetranitride (S4N4) are rare examples of a molecular binary (containing one element aside from nitrogen) nitrides. They dissolve in nonpolar solvents. Both undergo polymerization. S4N4 is also unstable with respect to the elements, but less so that the isostructural Se4N4. Heating S4N4 gives a polymer, and a variety of molecular sulfur nitride anions and cations are also known.

Related to but distinct from nitride is pernitride diatomic anion (N2−2) and the azide triatomic anion (N3-).

Related Research Articles

<span class="mw-page-title-main">Boron nitride</span> Refractory compound of boron and nitrogen with formula BN

Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal form corresponding to graphite is the most stable and soft among BN polymorphs, and is therefore used as a lubricant and an additive to cosmetic products. The cubic variety analogous to diamond is called c-BN; it is softer than diamond, but its thermal and chemical stability is superior. The rare wurtzite BN modification is similar to lonsdaleite but slightly softer than the cubic form.

<span class="mw-page-title-main">Boron</span> Chemical element, symbol B and atomic number 5

Boron is a chemical element; it has symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the boron group it has three valence electrons for forming covalent bonds, resulting in many compounds such as boric acid, the mineral sodium borate, and the ultra-hard crystals of boron carbide and boron nitride.

<span class="mw-page-title-main">Carbide</span> 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.

<span class="mw-page-title-main">Nitrogen</span> Chemical element, symbol N and atomic number 7

Nitrogen is a chemical element; it has symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N2, a colorless and odorless diatomic gas. N2 forms about 78% of Earth's atmosphere, making it the most abundant uncombined element in air. Because of the volatility of nitrogen compounds, nitrogen is relatively rare in the solid parts of the Earth.

<span class="mw-page-title-main">Refractory</span> Materials resistant to decomposition under high temperatures

In materials science, a refractory is a material that is resistant to decomposition by heat or chemical attack that retains its strength and rigidity at high temperatures. They are inorganic, non-metallic compounds that may be porous or non-porous, and their crystallinity varies widely: they may be crystalline, polycrystalline, amorphous, or composite. They are typically composed of oxides, carbides or nitrides of the following elements: silicon, aluminium, magnesium, calcium, boron, chromium and zirconium. Many refractories are ceramics, but some such as graphite are not, and some ceramics such as clay pottery are not considered refractory. Refractories are distinguished from the refractory metals, which are elemental metals and their alloys that have high melting temperatures.

<span class="mw-page-title-main">Aluminium nitride</span> Chemical compound

Aluminium nitride (AlN) is a solid nitride of aluminium. It has a high thermal conductivity of up to 321 W/(m·K) and is an electrical insulator. Its wurtzite phase (w-AlN) has a band gap of ~6 eV at room temperature and has a potential application in optoelectronics operating at deep ultraviolet frequencies.

<span class="mw-page-title-main">Superhard material</span> Material with Vickers hardness exceeding 40 gigapascals

A superhard material is a material with a hardness value exceeding 40 gigapascals (GPa) when measured by the Vickers hardness test. They are virtually incompressible solids with high electron density and high bond covalency. As a result of their unique properties, these materials are of great interest in many industrial areas including, but not limited to, abrasives, polishing and cutting tools, disc brakes, and wear-resistant and protective coatings.

<span class="mw-page-title-main">Titanium nitride</span> Ceramic material

Titanium nitride is an extremely hard ceramic material, often used as a physical vapor deposition (PVD) coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface properties.

<span class="mw-page-title-main">Magnesium nitride</span> Chemical compound

Magnesium nitride, which possesses the chemical formula Mg3N2, is an inorganic compound of magnesium and nitrogen. At room temperature and pressure it is a greenish yellow powder.

Boron trichloride is the inorganic compound with the formula BCl3. This colorless gas is a reagent in organic synthesis. It is highly reactive towards water.

Aluminium carbide, chemical formula Al4C3, is a carbide of aluminium. It has the appearance of pale yellow to brown crystals. It is stable up to 1400 °C. It decomposes in water with the production of methane.

<span class="mw-page-title-main">Boron compounds</span>

Boron compounds are compounds containing the element boron. In the most familiar compounds, boron has the formal oxidation state +3. These include oxides, sulfides, nitrides, and halides.

The chemical element nitrogen is one of the most abundant elements in the universe and can form many compounds. It can take several oxidation states; but the most common oxidation states are -3 and +3. Nitrogen can form nitride and nitrate ions. It also forms a part of nitric acid and nitrate salts. Nitrogen compounds also have an important role in organic chemistry, as nitrogen is part of proteins, amino acids and adenosine triphosphate.

Silicon compounds are compounds containing the element silicon (Si). As a carbon group element, silicon often forms compounds in the +4 oxidation state, though many unusual compounds have been discovered that differ from expectations based on its valence electrons, including the silicides and some silanes. Metal silicides, silicon halides, and similar inorganic compounds can be prepared by directly reacting elemental silicon or silicon dioxide with stable metals or with halogens. Silanes, compounds of silicon and hydrogen, are often used as strong reducing agents, and can be prepared from aluminum–silicon alloys and hydrochloric acid.

Metal nitrido complexes are coordination compounds and metal clusters that contain an atom of nitrogen bound only to transition metals. These compounds are molecular, i.e. discrete in contrast to the polymeric, dense nitride materials that are useful in materials science. The distinction between the molecular and solid-state polymers is not always very clear as illustrated by the materials Li6MoN4 and more condensed derivatives such as Na3MoN3. Transition metal nitrido complexes have attracted interest in part because it is assumed that nitrogen fixation proceeds via nitrido intermediates. Nitrido complexes have long been known, the first example being salts of [OsO3N]−, described in the 19th century.

Ultra-high-temperature ceramics (UHTCs) are a type of refractory ceramics that can withstand extremely high temperatures without degrading, often above 2,000 °C. They also often have high thermal conductivities and are highly resistant to thermal shock, meaning they can withstand sudden and extreme changes in temperature without cracking or breaking. Chemically, they are usually borides, carbides, nitrides, and oxides of early transition metals.

<span class="mw-page-title-main">Aluminium compounds</span>

Aluminium (British and IUPAC spellings) or aluminum (North American spelling) combines characteristics of pre- and post-transition metals. Since it has few available electrons for metallic bonding, like its heavier group 13 congeners, it has the characteristic physical properties of a post-transition metal, with longer-than-expected interatomic distances. Furthermore, as Al3+ is a small and highly charged cation, it is strongly polarizing and aluminium compounds tend towards covalency; this behaviour is similar to that of beryllium (Be2+), an example of a diagonal relationship. However, unlike all other post-transition metals, the underlying core under aluminium's valence shell is that of the preceding noble gas, whereas for gallium and indium it is that of the preceding noble gas plus a filled d-subshell, and for thallium and nihonium it is that of the preceding noble gas plus filled d- and f-subshells. Hence, aluminium does not suffer the effects of incomplete shielding of valence electrons by inner electrons from the nucleus that its heavier congeners do. Aluminium's electropositive behavior, high affinity for oxygen, and highly negative standard electrode potential are all more similar to those of scandium, yttrium, lanthanum, and actinium, which have ds2 configurations of three valence electrons outside a noble gas core: aluminium is the most electropositive metal in its group. Aluminium also bears minor similarities to the metalloid boron in the same group; AlX3 compounds are valence isoelectronic to BX3 compounds (they have the same valence electronic structure), and both behave as Lewis acids and readily form adducts. Additionally, one of the main motifs of boron chemistry is regular icosahedral structures, and aluminium forms an important part of many icosahedral quasicrystal alloys, including the Al–Zn–Mg class.

Gallium compounds are compounds containing the element gallium. These compounds are found primarily in the +3 oxidation state. The +1 oxidation state is also found in some compounds, although it is less common than it is for gallium's heavier congeners indium and thallium. For example, the very stable GaCl2 contains both gallium(I) and gallium(III) and can be formulated as GaIGaIIICl4; in contrast, the monochloride is unstable above 0 °C, disproportionating into elemental gallium and gallium(III) chloride. Compounds containing Ga–Ga bonds are true gallium(II) compounds, such as GaS (which can be formulated as Ga24+(S2−)2) and the dioxan complex Ga2Cl4(C4H8O2)2. There are also compounds of gallium with negative oxidation states, ranging from -5 to -1, most of these compounds being magnesium gallides (MgxGay).

Hafnium compounds are compounds containing the element hafnium (Hf). Due to the lanthanide contraction, the ionic radius of hafnium(IV) (0.78 ångström) is almost the same as that of zirconium(IV) (0.79 angstroms). Consequently, compounds of hafnium(IV) and zirconium(IV) have very similar chemical and physical properties. Hafnium and zirconium tend to occur together in nature and the similarity of their ionic radii makes their chemical separation rather difficult. Hafnium tends to form inorganic compounds in the oxidation state of +4. Halogens react with it to form hafnium tetrahalides. At higher temperatures, hafnium reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Some compounds of hafnium in lower oxidation states are known.

Lanthanide compounds are compounds formed by the 15 elements classed as lanthanides. The lanthanides are generally trivalent, although some, such as cerium and europium, are capable of forming compounds in other oxidation states.

References

  1. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  2. ↑ "The Nobel Prize in Physics 2014". The Nobel Prize. Nobel Prize Outreach. Retrieved 13 January 2021.
  3. ↑ Sun, Wenhao; Bartel, Christopher J.; Arca, Elisabetta; Bauers, Sage R.; Matthews, Bethany; Orvañanos, Bernardo; Chen, Bor-Rong; Toney, Michael F.; Schelhas, Laura T.; Tumas, William; Tate, Janet; Zakutayev, Andriy; Lany, Stephan; Holder, Aaron M.; Ceder, Gerbrand (2019). "A map of the inorganic ternary metal nitrides". Nature Materials. 18 (7): 732–739. arXiv: 1809.09202 . doi:10.1038/s41563-019-0396-2. ISSN   1476-4660. PMID   31209391. S2CID   119461695.
  4. ↑ Greenaway, Ann L.; Melamed, Celeste L.; Tellekamp, M. Brooks; Woods-Robinson, Rachel; Toberer, Eric S.; Neilson, James R.; Tamboli, Adele C. (2021-07-26). "Ternary Nitride Materials: Fundamentals and Emerging Device Applications". Annual Review of Materials Research. 51 (1): 591–618. arXiv: 2010.08058 . doi:10.1146/annurev-matsci-080819-012444. ISSN   1531-7331. S2CID   223953608.
  5. ↑ Oyama, S. T., ed. (1996). The Chemistry of Transition Metal Carbides and Nitrides. Blackie Academic. ISBN   0-7514-0365-2.
  6. ↑ Pierson, H. O. (1996). Handbook of refractory carbides and nitrides. William Andrew. ISBN   0-8155-1392-5.
  7. ↑ Gregory, Duncan H. (2001). "Nitride chemistry of the s-block elements". Coord. Chem. Rev. 215: 301–345. doi:10.1016/S0010-8545(01)00320-4.
  8. ↑ Toth, Louis (2014-04-11). Transition Metal Carbides and Nitrides. Elsevier. ISBN   978-0-323-15722-3.
  9. ↑ Leineweber, Andreas; Niewa, Rainer; Jacobs, Herbert; Kockelmann, Winfried (2000). "The manganese nitrides η‐Mn3N2 and θ‐Mn6N5 + x: nuclear and magnetic structures". Journal of Materials Chemistry. 10 (12): 2827–2834. doi:10.1039/b006969h.
  10. ↑ Mei, A. B.; Howe, B. M.; Zhang, C.; Sardela, M.; Eckstein, J. N.; Hultman, L.; Rockett, A.; Petrov, I.; Greene, J. E. (2013-10-18). "Physical properties of epitaxial ZrN/MgO(001) layers grown by reactive magnetron sputtering". Journal of Vacuum Science & Technology A. 31 (6): 061516. Bibcode:2013JVSTA..31f1516M. doi:10.1116/1.4825349. ISSN   0734-2101.
  11. ↑ Siller, L.; Peltekis, N.; Krishnamurthy, S.; Chao, Y.; Bull, S. J.; Hunt, M. R. C. (2005). "Gold film with gold nitride—A conductor but harder than gold" (PDF). Appl. Phys. Lett. 86 (22): 221912. Bibcode:2005ApPhL..86v1912S. doi:10.1063/1.1941471.
  12. ↑ Montoya, J. A.; Hernández, A. D.; Sanloup, C.; Gregoryanz, E.; Scandolo, S (2007). "OsN2: Crystal structure and electronic properties". Appl. Phys. Lett. 90 (1): 011909. Bibcode:2007ApPhL..90a1909M. doi:10.1063/1.2430631.
  13. ↑ Shanley, Edward S.; Ennis, John L. (1991). "The Chemistry and Free Energy Formation of Silver Nitride". Ind. Eng. Chem. Res. 30 (11): 2503. doi:10.1021/ie00059a023.
  14. ↑ Du, Jingzhen; Seed, John A.; Berryman, Victoria E. J.; Kaltsoyannis, Nikolas; Adams, Ralph W.; Lee, Daniel; Liddle, Stephen T. (2021). "Exceptional uranium(VI)-nitride triple bond covalency from 15N nuclear magnetic resonance spectroscopy and quantum chemical analysis". Nat. Commun. 12 (1): 5649. Bibcode:2021NatCo..12.5649D. doi:10.1038/s41467-021-25863-2. PMC   8463702 . PMID   34561448.
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