CBSE Class 12 · 2017 · Coordination CompoundsShort Answer

(a) What type of isomerism is shown by the complex [Co(NH

_{3}

)

_{5}

(SCN)]

^{2 +}

?
(b) Why is [NiCl

_{4}

]

^{2 -}

paramagnetic while [Ni(CN)

_{4}

]

^{2 -}

is diamagnetic? (Atomic number of Ni = 28)
(c) Why are low-spin tetrahedral complexes rarely observed?

Solution

(a) SCN

^{-}

is ambidentate (S- or N-bonded) → the complex shows \textbf{linkage isomerism}.
(b) Ni

^{2 +}

= 3d

^{8}

.
[NiCl

_{4}

]

^{2 -}

: Cl

^{-}

is weak-field — no pairing, sp

^{3}

tetrahedral, 2 unpaired electrons → paramagnetic.
[Ni(CN)

_{4}

]

^{2 -}

: CN

^{-}

is strong-field — the electrons pair, dsp

^{2}

square planar, 0 unpaired → diamagnetic.
(c) In a tetrahedral field the splitting is small, Δ

_{t}

= (4/9)Δ

_{0}

; it never exceeds the pairing energy P, so electrons always occupy the upper set rather than pair — low-spin tetrahedral complexes are therefore rarely observed.

CBSE Class 12 Board · 2017 · Subjective

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CBSE Class 12 · 2017 · Coordination CompoundsShort Answer

Solution

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