page_title: Nitrogen
section_title: Nitrides, azides, and nitrido complexes
hierarchical_section_title: Nitrogen / Chemistry and compounds / Nitrides, azides, and nitrido complexes
caption_attribution_description: Borazin Mesomers
context_page_description: Nitrogen is the chemical element with the symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772. Although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about the same time, Rutherford is generally accorded the credit because his work was published first. The name nitrogène was suggested by French chemist Jean-Antoine-Claude Chaptal in 1790 when it was found that nitrogen was present in nitric acid and nitrates. Antoine Lavoisier suggested instead the name azote, from the Greek ἀζωτικός "no life", as it is an asphyxiant gas; this name is instead used in many languages, such as French, Italian, Russian, Romanian and Turkish, and appears in the English names of some nitrogen compounds such as hydrazine, azides and azo compounds.
  Nitrogen is the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at about seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bind to form dinitrogen, a colourless and odorless diatomic gas with the formula N₂.
context_section_description: Nitrogen bonds to almost all the elements in the periodic table except the first three noble gases, helium, neon, and argon, and some of the very short-lived elements after bismuth, creating an immense variety of binary compounds with varying properties and applications. Many binary compounds are known: with the exception of the nitrogen hydrides, oxides, and fluorides, these are typically called nitrides. Many stoichiometric phases are usually present for most elements (e.g. MnN, Mn₆N₅, Mn₃N₂, Mn₂N, Mn₄N, and MnₓN for 9.2 < x < 25.3). They may be classified as "salt-like" (mostly ionic), covalent, "diamond-like", and metallic (or interstitial), although this classification has limitations generally stemming from the continuity of bonding types instead of the discrete and separate types that it implies. They are normally prepared by directly reacting a metal with nitrogen or ammonia (sometimes after heating), or by thermal decomposition of metal amides:
  3 Ca + N₂ → Ca₃N₂
  3 Mg + 2 NH₃ → Mg₃N₂ + 3 H₂ (at 900 °C)
  3 Zn(NH₂)₂ → Zn₃N₂ + 4 NH₃
  Many variants on these processes are possible.The most ionic of these nitrides are those of the alkali metals and alkaline earth metals, Li₃N (Na, K, Rb, and Cs do not form stable nitrides for steric reasons) and M₃N₂ (M = Be, Mg, Ca, Sr, Ba). These can formally be thought of as salts of the N³⁻ anion, although charge separation is not actually complete even for these highly electropositive elements. However, the alkali metal azides NaN₃ and KN₃, featuring the linear N⁻
  ₃ anion, are well-known, as are Sr(N₃)₂ and Ba(N₃)₂. Azides of the B-subgroup metals (those in groups 11 through 16) are much less ionic, have more complicated structures, and detonate readily when shocked.
  Many covalent binary nitrides are known. Examples include cyanogen ((CN)₂), triphosphorus pentanitride (P₃N₅), disulfur dinitride (S₂N₂), and tetrasulfur tetranitride (S₄N₄). The essentially covalent silicon nitride (Si₃N₄) and germanium nitride (Ge₃N₄) are also known: silicon nitride in particular would make a promising ceramic if not for the difficulty of working with and sintering it. In particular, the group 13 nitrides, most of which are promising semiconductors, are isoelectronic with graphite, diamond, and silicon carbide and have similar structures: their bonding changes from covalent to partially ionic to metallic as the group is descended. In particular, since the B–N unit is isoelectronic to C–C, and carbon is essentially intermediate in size between boron and nitrogen, much of organic chemistry finds an echo in boron–nitrogen chemistry, such as in borazine ("inorganic benzene"). Nevertheless, the analogy is not exact due to the ease of nucleophilic attack at boron due to its deficiency in electrons, which is not possible in a wholly carbon-containing ring.
  The largest category of nitrides are the interstitial nitrides of formulae MN, M₂N, and M₄N (although variable composition is perfectly possible), where the small nitrogen atoms are positioned in the gaps in a metallic cubic or hexagonal close-packed lattice. They are opaque, very hard, and chemically inert, melting only at very high temperatures (generally over 2500 °C). They have a metallic lustre and conduct electricity as do metals. They hydrolyse only very slowly to give ammonia or nitrogen.
  The nitride anion (N³⁻) is the strongest π donor known amongst ligands (the second-strongest is O²⁻). Nitrido complexes are generally made by thermal decomposition of azides or by deprotonating ammonia, and they usually involve a terminal {≡N}³⁻ group. The linear azide anion (N⁻
  ₃), being isoelectronic with nitrous oxide, carbon dioxide, and cyanate, forms many coordination complexes. Further catenation is rare, although N⁴⁻
  ₄ (isoelectronic with carbonate and nitrate) is known.
caption: Mesomeric structures of borazine, (–BH–NH–)3
exif: {}