Question

Which of the following are outer orbital octahedral complexes?
(1) $\left[ FeF _{6}\right]^{3-}$
(2) $\left[ Fe ( CN )_{6}\right]^{4-}$
(3) $\left[ Fe \left( H _{2} O \right)_{6}\right]^{2+}$
(4) $\left[ Fe ( CN )_{6}\right]^{3-}$

• A. 1, 2 and 3 are correct
• B. 1 and 2 are correct
• C. 2 and 4 are correct
• D. 1 and 3 are correct

Answer 1

Answer: (D)

Weak field ligands like $F ^{-}, H _{2} O$ etc are unable to cause pairing of $d$-electrons of the central metal atom/ion, thus they usually result in the formation of outer orbit complexes (in case metal ion contains atleast $5$ electrons in its d-orbital).
Thus, $\left[ FeF _{6}\right]^{3-}$ and $\left[ Fe \left( H _{2} O \right)_{6}\right]^{2+}$ are outer orbital octahedral complexes.