Question

Which of the following is not correct about $\text{tetraamminedithiocyanato-S-cobalt(III) tris(oxalato)cobaltate(III)}?$

• A. Formula of complex is $\left[Co\right(SCN{)}_2\left(N{H}_3{)}_4\right]\left[Co\right(ox{)}_3]$
• B. It is a chelating complex and show linkage isomerism
• C. It show optical isomerism
• D. It show geometrical isomerism

Answer 1

The correct option is A Formula of complex is $\left[Co\right(SCN{)}_2\left(N{H}_3{)}_4\right]\left[Co\right(ox{)}_3]$

(A) The formula of the complex $\text{tetraamminedithiocyanato-S-cobalt(III) tris(oxalato)cobaltate(III)}$
is $\left[Co\right(SCN{)}_2\left(N{H}_3{)}_4{]}_3\right[Co\left(ox{)}_3\right]$ and not $\left[Co\right(SCN{)}_2\left(N{H}_3{)}_4\right]\left[Co\right(ox{)}_3]$ because to balance the charge, three units of complex cation and one unit of complex anion are present in one formula unit.Thus option (A) is incorrect.

(B) Linkage isomerism is possible as $SCN$ ligand is ambidentate ligand and has two donor atoms N and S.
Thus option B is correct.

(C) The complex ion $\left[Co\right(ox{)}_3{]}^{3-}$ will have 2 optical isomers but have no geometrical isomers. Thus option C is correct.

(D) The complex cation $\left[Co\right(SCN{)}_2(N{H}_3{)}_4{]}^{+}$ shows geometrical isomerism. Two geometrical isomers cis and trans are possible. In the cis isomer, the two $SCN$ ligands are adjacent to each other and in the trans isomer, they are opposite to each other.
Thus option (a) is correct.