Consider the following metal complexes :
${[Co ({NH}_{3})]}^{3 +}$
${[CoCl {({NH}_{3})}_{5}]}^{2 +}$
${[Co (CN)_{6}]}^{3 -}$
${[Co {({NH}_{3})}_{5} (H_{2} O)]}^{3 +}$
The spin-only magnetic moment value of the complex that absorbs light with shortest wavelength is B.M. (Nearest integer)

Question

Consider the following metal complexes :

${[Co ({NH}_{3})]}^{3 +}$

${[CoCl {({NH}_{3})}_{5}]}^{2 +}$

${[Co (CN)_{6}]}^{3 -}$

${[Co {({NH}_{3})}_{5} (H_{2} O)]}^{3 +}$

The spin-only magnetic moment value of the complex that absorbs light with shortest wavelength is B.M. (Nearest integer)

TestHub · Accepted Answer

The complex that absorbs minimum wave length of light has maximum splitting
$Δ_{0} \propto \frac{1}{λ} Δ_{0} = Crystal field stabilization energy$
Here, ${CN}^{-}$ being $strong field ligand$ ,It will have cause CFSE So, ${[Co (CN)_{6}]}^{3 -}$ will absorb minimum wavelength.
The hybridization of Co in ${[Co (CN)_{6}]}^{3 -}$ will be $d^{2} {sp}^{3}$
As, the complex has no unpaired electrons, spin only magnetic moment will be zero and it is diamagnetic in nature.

Chemistry - Coordination Chemistry Question with Solution | TestHub

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