CBSE Class 12 · Coordination CompoundsShort Answer

a) For the complex [Fe(CN)

_{6}

]

^{3 -}

, write the hybridisation type, magnetic character and spin nature. (Atomic number: Fe = 26)
b) Draw one of the geometrical isomers of the complex [Pt(en)

_{2}

_{2}

]

^{2 +}

which is optically active.

Answer: (a) d²sp³; paramagnetic (1 unpaired); low-spin. (b) The cis-isomer (both Cl adjacent) — chiral, hence optically active.

Solution

(a) Fe

^{3 +}

= 3d

^{5}

; strong-field CN

^{-}

pairs to t

_{2 g}^{5}

: hybridisation \textbf{d

^{2}

^{3}

}; \textbf{paramagnetic} with 1 unpaired electron (μ ≈ 1.73 BM); \textbf{low-spin} (inner-orbital).
(b) \textit{cis}-[Pt(en)

_{2}

_{2}

]

^{2 +}

— the two Cl

^{-}

on adjacent octahedral vertices; this arrangement has no symmetry plane, so it is chiral (optically active). Draw the octahedron with the two Cl cis and the two en chelate rings completing the sphere.

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CBSE Class 12 · Coordination CompoundsShort Answer

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