What is a coordination complex?

A coordination complex is fundamentally characterized by the presence of a central metal atom or ion, typically a transition metal, that is surrounded by a variety of molecules or ions known as ligands. These ligands are capable of donating lone pairs of electrons to the metal, forming coordinate covalent bonds. The arrangement and variety of these ligands can significantly influence the properties of the complex, such as its color, reactivity, and stability.

Coordination complexes play crucial roles in various chemical processes, including catalysis, biological functions (like hemoglobin in oxygen transport), and materials science. This definition encompasses the specific structure and bonding characteristics unique to coordination complexes, distinguishing them from other types of compounds or mixtures.