Question

Consider the complex ions $\mathbf{CO}{{\left({\mathrm{NH}}_3\right)}_{\mathbf{6}}}^{\mathbf{3}\mathbf{+}}$, $\mathbf{Co}{{\left(\mathrm{CN}\right)}_{\mathbf{6}}}^{\mathbf{3}\mathbf{-}}$and ${{\mathbf{COF}}_{\mathbf{6}}}^{\mathbf{3}\mathbf{-}}$.The wavelengths of absorbed electromagnetic radiation for these compounds are (in no specific order) 770 nm, 440 nm and 290 nm. Match the complex ion to the wavelength of the absorbed electromagnetic radiation

Short answer

$\mathbf{Co}{{\mathbf{\left(}\mathbf{CN}\mathbf{\right)}}_{\mathbf{6}}}^{\mathbf{3}\mathbf{-}}$-290nm

$\mathbf{CO}{{\mathbf{\left(}{\mathbf{NH}}_{\mathbf{3}}\mathbf{\right)}}_{\mathbf{6}}}^{\mathbf{3}\mathbf{+}}$-440nm

${{\mathbf{COF}}_{\mathbf{6}}}^{\mathbf{3}\mathbf{-}}$-770nm

Step-by-step solution

Cyanate complex has high splitting energy ∆ than amine and fluoride complexes.

Hence the cyanate complex absorbs at shorter wavelength of electromagnetic radiation than the cobalt complexes with amine and fluoride ligands.

Fluoride complex has low splitting energy ∆ than amine and cyanate complexes.

Hence the fluoride complex absorbs at higher wavelength of electromagnetic radiation than the amine and cyanate complexes of cobalt.