Among the following complexes, the total number of diamagnetic species is ____. $[\mathrm{Mn}(\mathrm{NH}_{3})_{6}]^{3+}$, $[\mathrm{MnCl}_{6}]^{3-}$, $[\mathrm{FeF}_{6}]^{3-}$, $[\mathrm{CoF}_{6}]^{3-}$, $[\mathrm{Fe}(\mathrm{NH}_{3})_{6}]^{3+}$, and $[\mathrm{Co}(\mathrm{en})_{3}]^{3+}$ [Given, atomic number: $\mathrm{Mn}=25$, $\mathrm{Fe}=26$, $\mathrm{Co}=27$; $\mathrm{en}=\mathrm{H}_{2}\mathrm{NCH}_{2}\mathrm{CH}_{2}\mathrm{NH}_{2}$]

JEE Advanced · 2024 · 26 May 2024 · Paper 1 · Coordination Compounds

Among the following complexes, the total number of diamagnetic species is ____.

[Mn (NH_{3})_{6}]^{3 +}

[MnCl_{6}]^{3 -}

[FeF_{6}]^{3 -}

[CoF_{6}]^{3 -}

[Fe (NH_{3})_{6}]^{3 +}

, and

[Co (en)_{3}]^{3 +}

[Given, atomic number:

Mn = 25

Fe = 26

Co = 27

;

en = H_{2} NCH_{2} CH_{2} NH_{2}

]

Answer: 1

Mn^{3 +}

has

[Ar] 3 d^{4}

configuration. With

d^{4}

, there will always be unpaired electrons in both strong and weak field ligands.

Fe^{3 +}

has

[Ar] 3 d^{5}

configuration, which also always has unpaired electrons regardless of ligand field strength.

Co^{3 +}

has

[Ar] 3 d^{6}

configuration. With weak field ligand

F^{-}

, the configuration is

t_{2 g}^{4} e_{g}^{2}

(paramagnetic). With strong field ligand en, the configuration is

t_{2 g}^{6} e_{g}^{0}

(diamagnetic). Therefore, only

[Co (en)_{3}]^{3 +}

is diamagnetic.

JEE Advanced · 2024 · 26 May 2024 · Paper 1 · Integer answer