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Question: Which of the following will give the maximum number of isomers? A. \([Co{(N{H_3})_4}C{l_2}]\) B....

Which of the following will give the maximum number of isomers?
A. [Co(NH3)4Cl2][Co{(N{H_3})_4}C{l_2}]
B. [Ni(en)(NH3)4]2+{[Ni(en){\left( {N{H_3}} \right)_4}]^{2 + }}
C. [Ni(C2O4)(en)2][Ni\left( {{C_2}{O_4}} \right){(en)_2}]
D. [Cr(SCN)2(NH3)4]2+{[Cr{\left( {SCN} \right)_2}{\left( {N{H_3}} \right)_4}]^{2 + }}

Explanation

Solution

Hint: We know that two or more than two different compounds having the same formula are known as isomers. Thus isomers have different arrangements of atoms in space. In coordination compounds there are two main types of isomerism, these are Stereoisomers and structural isomerism.

Step-By-Step answer:
If the arrangement of atoms of two isomers are nonsuperimposable mirror images of each other then they are called optical isomers. If coordination compounds possess plane of symmetry that means their isomers will have superimposable mirror image hence symmetric coordination compounds do not show optical isomerism, thus we can identify optical isomers. [Co(NH3)4Cl2][Co{(N{H_3})_4}C{l_2}] has two geometrical isomers that are cis and trans form. It has no optical isomers due to a plane of symmetry. [Ni(en)(NH3)4]2+{[Ni(en){\left( {N{H_3}} \right)_4}]^{2 + }} will show optical isomerism. [Ni(C2O4)(en)2][Ni\left( {{C_2}{O_4}} \right){(en)_2}] will show optical isomerism. [Cr(SCN)2(NH3)4]2+{[Cr{\left( {SCN} \right)_2}{\left( {N{H_3}} \right)_4}]^{2 + }} shows geometrical isomerism in cis and trans form as well as linkage isomerism due to presence of thiocyanate or SCN−SC{N^ - } ligand. SCN−SC{N^ - } is an ambidentate ligand so it can coordinate with either sulphur or nitrogen atom. Hence [Cr(SCN)2(NH3)4]2+{[Cr{\left( {SCN} \right)_2}{\left( {N{H_3}} \right)_4}]^{2 + }} will have maximum number of isomers. So option D is correct answer to this problem which is [Cr(SCN)2(NH3)4]2+{[Cr{\left( {SCN} \right)_2}{\left( {N{H_3}} \right)_4}]^{2 + }}.

Note: The number of optical isomers of a compound is determined by the number of chiral centres. In linkage isomers coordination compounds have the same composition but differ in the connectivity of ligands to the metals. Geometric isomers of coordination compounds differ from one another by the spatial distribution of ligands. Cis and trans isomers of a compound have different properties due to difference in dipole moment of molecule or the different spatial arrangement of atoms.