Coordinated compounds form through coordinate covalent bonds. The coordinate covalent bond is when one of the atoms or ions donates both the shared electrons. In the usual covalent bond, each of the atoms shares an electron, but in the coordinate covalent bond, one atom shares both of the electrons.
When scientists talk about coordination chemistry, they refer to a few terms you should know. One is the coordination number, which is the number of ligands attached to the central metal atom or ion. The other is the coordination sphere. The coordination sphere is all the ligands bonded to the central metal atom.
Coordinated compounds are made of a central metal atom that acts as a Lewis acid, and a Lewis base as a ligand (containing one atom that acts as a donor).
Examples of coordinated compounds: