[1] Pseudohalogens occur in pseudohalogen molecules, inorganic molecules of the general forms Ps–Ps or Ps–X (where Ps is a pseudohalogen group), such as cyanogen; pseudohalide anions, such as cyanide ion; inorganic acids, such as hydrogen cyanide; as ligands in coordination complexes, such as ferricyanide; and as functional groups in organic molecules, such as the nitrile group.
Well-known pseudohalogen functional groups include cyanide, cyanate, thiocyanate, and azide.
Well-known ones include (the true halogen chlorine is listed for comparison): (Gold dimer) (Gold(I) hydride) Au− is considered to be a pseudohalogen ion due to its disproportionation reaction with alkali and the ability to form covalent bonds with hydrogen.
For example, they can form strong acids of the type HX (compare hydrogen chloride HCl to hydrogen tetracarbonylcobaltate HCo(CO)4), and they can react with metals M to form compounds like MX (compare sodium chloride NaCl to sodium azide NaN3).
Nanoclusters of aluminium (often referred to as superatoms) are sometimes considered to be pseudohalides since they, too, behave chemically as halide ions, forming Al13I−2 (analogous to triiodide I−3) and similar compounds.