In the brown ring complex [Fe(H₂O)₅(NO)]SO₄ nitric oxide behaves as:

• A) NO⁺
• B) neutral NO molecule
• C) NO⁻
• D) NO₂⁺

In the brown ring complex [Fe(H₂O)₅(NO)]SO₄, nitric oxide (NO) acts as a neutral molecule. This is because it coordinates to the iron center without carrying a formal charge, allowing it to stabilize the complex effectively.

Understanding the Role of NO

Nitric oxide can exist in different forms, but in this complex, it does not contribute a charge. Instead, it participates in bonding through its ability to donate a pair of electrons.

Key Points

• NO is neutral in this complex.
• It coordinates to iron, enhancing the stability of the complex.
• This behavior is typical for nitric oxide in coordination chemistry.

Thus, the correct answer is B) neutral NO molecule.