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How do neutral ligands such as water and ammonia affect the charge of a complex ion?

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Structural diagram of the vitamin B12 coenzyme molecule, highlighting its organometallic core with five nitrogen-cobalt bonds and one cobalt-carbon bond at the center, surrounded by complex organic groups. — coordination compound Coordination compounds contain a central metal atom surrounded by nonmetal atoms or groups of atoms, called ligands. For example, vitamin B₁₂ is made up of a central metallic cobalt ion bound to multiple nitrogen-containing ligands.

In chemistry, neutral ligands such as water ( $H_{2} O$ ) and ammonia ( $N H_{3}$ ) do not contribute to the electrical charge of a complex ion. Because these ligands are electrically neutral, the overall charge of the complex is determined solely by the oxidation state of the central metal atom or ion.1

For example, in the hexaaquanickel(2+) ion, $[N i (H_{2} O)_{6}]^{2 +}$ , the water ligands are neutral, meaning the +2 charge of the complex is derived entirely from the nickel ion. Similarly, in the hexaamminecobalt(3+) ion, $[C o (N H_{3})_{6}]^{3 +}$ , the neutral ammonia ligands allow the +3 charge of the cobalt ion to define the charge of the entire complex.12

When neutral ligands are present alongside charged ligands, the total charge of the complex is the sum of the metal's oxidation state and the charges of any anionic or cationic ligands. Consequently, neutral ligands serve to coordinate with the metal without altering the net charge of the resulting species.1