Pseudohalide

Pseudohalide is a term in inorganic chemistry describing an anion or neutral ligand whose chemistry parallels that of a halide ion in salts and coordination compounds. Like halides, pseudohalides can participate in ionic lattice formation and act as ligands that coordinate to metal centers.

Common pseudohalide anions include cyanide (CN-), azide (N3-), thiocyanate (SCN- or NCS-), and cyanate (OCN-). These species can substitute for halides in ionic lattices and frequently serve as ligands that bind to metals, often by bridging between centers or adopting multiple binding modes.

Pseudohalides sometimes form salts with lattice behaviors similar to halides, and they contribute to the formation of coordination polymers and metal clusters. Their coordination chemistry often shows greater versatility than simple halides, with examples of ambidentate binding in some cases (for example, cyanate can bind through N or O, and thiocyanate through N or S).

In synthesis and materials science, pseudohalides are used to prepare metal cyanides, azido complexes, and thiocyanate-bridged frameworks. Safety considerations are important, as cyanide and azide salts are highly toxic or potentially explosive and require appropriate handling and precautions.