(a) (i) Explain the bonding in co-ordination compounds in terms of Werner's postulate. (ii) $CuSO_4Cl.5NH_3$ exists in two isomeric forms (A) and (B). Isomer (A) reacts with $AgNO_3$ to give white precipitate but does not react with $BaCl_2$. Isomer (B) gives white precipitate wi

Question

(a) (i) Explain the bonding in co-ordination compounds in terms of Werner's postulate. (ii) $CuSO_4Cl.5NH_3$ exists in two isomeric forms (A) and (B). Isomer (A) reacts with $AgNO_3$ to give white precipitate but does not react with $BaCl_2$. Isomer (B) gives white precipitate with $BaCl_2$ but does not react with $AgNO_3$. Give the structural formula of isomers (A) and (B).

**OR**

(b) (i) Discuss briefly the use of co-ordination compounds in metallurgy of gold, estimation of hardness of water and photosynthesis. (ii) Name the type of structural isomerism when ambidentate ligands are attached to central metal ion. (iii) Why is $[Co(NH_3)_6]^{3+}$ called low spin complex ?

Accepted Answer

>

> [!TLDR]
> This question offers a choice between Werner's coordination theory plus a linkage-isomer identification (primary), or three short applications/naming questions on coordination chemistry (the alternative). Both are answered below.
>
> **(Primary, a):**
>
> **(i) Werner's postulates (bonding in coordination compounds):** Werner proposed that a metal ion in a coordination compound exhibits two types of valency: a **primary (ionisable) valency**, satisfied by negative ions and equal to the metal's oxidation state, and a **secondary (non-ionisable, coordinate) valency**, satisfied by neutral or negatively charged ligands occupying a **fixed number of positions in space** around the metal (its coordination number), giving the complex a definite geometry (e.g. octahedral for CN 6). Only the primary-valency-satisfying ions (outside the coordination sphere) dissociate into free ions in solution; ligands bound by the secondary valency (inside the coordination sphere) do not ionise and stay bound to the metal.
>
> **(ii) Identifying isomers (A) and (B) of $CuSO_4Cl\cdot5NH_3$:**
> …

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