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NitrideFrom Wikipedia, the free encyclopedia

In chemistry, a nitride is a compound of nitrogen where nitrogen has a formal oxidation state of −3. Nitrides are

a large class of compounds with a wide range of properties and applications.[1]

The nitride ion, N3–, is never encountered in solution because it is so basic that it would be protonated. Its ionic

radius is estimated to be 140 pm. Related to but distinct from nitride is pernitride, N22–.

Contents

1 Uses of nitrides

2 Examples

2.1 Nitrides of the s-block elements

2.2 Nitrides of the p-block elements2.3 Transition metal nitrides

2.4 Molecular nitrides

3 References

Uses of nitrides

Like carbides, nitrides are often refractory materials owing to their high lattice energy which reflects the strong

attraction of "N3−

" for the metal cation. Thus, titanium nitride and silicon nitride are used as cutting materials andhard coatings. Hexagonal boron nitride, which adopts a layered structure, is a useful high-temperature lubricantakin to molybdenum disulfide. Nitride compounds often have large band gaps, thus nitrides are usually insulatorsor 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.[2] Like some oxides, nitrides can absorbhydrogen 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 notassigned 3- oxidation state are not included, e.g. nitrogen trichloride, nor are ammonia and its many organicderivatives.

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.[3] Sodium nitride and potassium nitride have been generated in the laboratory,

however. The nitrides of the alkaline earth metals have the formula M3N2 and are numerous. Examples include

Mg3N2, Be3N2, Ca3N2, Sr3N2, and Ba3N2. The nitrides of electropositive metals (including Li, Zn, and the

alkaline earth metals) readily hydrolyze upon contact with air:

Mg3N2 + 6 H2O → 3 Mg(OH)2 + 2 NH3

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Nitrides of the p-block elements

Boron nitride exists as several forms (polymorphs). Nitrides of silicon and phosphorus are also known, but onlythe former is commercially important. The nitrides of aluminium, gallium, and indium adopt diamond-like wurtzitestructure in which each atom occupies tetrahedral sites. For example in aluminium nitride, each aluminium atomhas four neighboring nitrogen atoms at the corners of a tetrahedron and similarly each nitrogen atom has fourneighboring 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 anddiamond in the relative orientation of tetrahedra). Thallium(I) nitride, Tl3N is known, but thallium(III) nitride,

TlN, is not.

Transition metal nitrides

See also: Zirconium nitride, Tungsten nitride, Vanadium nitride, Tantalum nitride, and Niobiumnitride

For the group 3 metals, scandium nitride (ScN) is known. Yttrium nitride (YN) is also known. Group 4, 5, and6 transition metals, that is the titanium, vanadium and chromium groups all form nitrides. They are refractory,with high melting point and are chemically stable. Representative is titanium nitride. Sometimes these materialsare called "interstitial nitrides."

Nitrides of the Group 7 and 8 transition metals decompose readily. 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.[4][5]

See also: Silver nitride and Mercury nitride

Nitrides of heavier members from group 11 and 12 are less stable than copper nitride, Cu3N and Zn3N2: dry

silver nitride (Ag3N) is a contact explosive which may detonate from the slightest touch, even a falling water

droplet.[6]

Molecular nitrides

Main article: Transition metal nitrido complex

Many metals form molecular nitrido complexes, as discussed in the specialized article. The main group elementsalso form some molecular nitrides. Cyanogen ((CN)2) and tetrasulfur tetranitride (S4N4) are rare examples of a

molecular binary (containing one element aside from N) nitrides. They dissolve in nonpolar solvents. Bothundergo 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.

References

1. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.

2. ^ The Chemistry of Transition Metal Carbides and Nitrides S. T. Oyama, Ed. Blackie Academic, 1996 ISBN 0-7514-0365-2. H.O Pierson (1996). Handbook of refractory carbides and nitrides, William Andrew Inc. ISBN0-8155-1392-5

4/4/2014 Nitride - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Nitride 3/3

3. ^ Gregory, Duncan H (2001). "Nitride chemistry of the s-block elements". Coordination Chemistry Reviews

215: 301–345. doi:10.1016/S0010-8545(01)00320-4 (http://dx.doi.org/10.1016%2FS0010-8545%2801%2900320-4).

4. ^ L. Siller, N. Peltekis, S. Krishnamurthy, Y. Chao, S.J. Bull, M.R.C. Hunt (2005). "Gold film with gold nitride-

A conductor but harder than gold". Appl. Phys. Lett. 86 (22): 221912. Bibcode:2005ApPhL..86v1912S(http://adsabs.harvard.edu/abs/2005ApPhL..86v1912S). doi:10.1063/1.1941471(http://dx.doi.org/10.1063%2F1.1941471).

5. ^ J. A. Montoya, A.D Hernandez, C. Sanloup, E Gregoryanz, S Scandolo (2007). "OsN2: Crystal structure and

electronic properties". Appl. Phys. Lett. 90 (1): 011909. Bibcode:2007ApPhL..90a1909M(http://adsabs.harvard.edu/abs/2007ApPhL..90a1909M). doi:10.1063/1.2430631(http://dx.doi.org/10.1063%2F1.2430631).

6. ^ Edward S. Shanley, John L. Ennis (1991). "The Chemistry and Free Energy Formation of Silver Nitride".

Ind. Eng. Chem. Res. 30 (11): 2503. doi:10.1021/ie00059a023 (http://dx.doi.org/10.1021%2Fie00059a023).

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