MCQ
Which of the following is diamagnetic ?
  • A
    ${[Fe{(CN)_6}]^{3 - }}$
  • ${[Co{(C_2O_4)_3}]^{3 - }}$
  • C
    $[FeF_6]^{3-}$
  • D
    $[CoF_6]^{3-}$

Answer

Correct option: B.
${[Co{(C_2O_4)_3}]^{3 - }}$
b
$[Fe(CN)_6]^{3-}$ has magnetic moment of a single unpaired electron whereas $[FeF_6]^{3-}$ has a magnetic moment of five unpaired electrons. $[CoF_6]^{3-}$ is paramagnetic with four unpaired electrons while $[Co(C_2O_4)_3]^3$ is diamagnetic. This anomaly is explained by valence bond theory in terms of formation of inner and outer orbital coordination entities. $[Co(C_2O_4)_3]^{3-}$ is an inner orbital complexes having $d^2sp^3$ hybridization .

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