Coordination Entity

A coordination entity is an ion or a neutral molecule made up of a central atom (usually a metal) together with the array of other atoms or groups of atoms, called ligands, that are directly attached to it; in a formula it is always the part enclosed in square brackets, for example [Fe(CN)₆]⁴⁻ inside potassium ferrocyanide K₄[Fe(CN)₆], or the whole neutral molecule [Ni(CO)₄] in …