Question

(i) Write the IUPAC name of the complex $\left[Cr\right(N{H}_3{)}_{4}C{l}_2]Cl$.
(ii) What type of isomerism is exhibited by the complex $\left[Co\right(en{)}_3{]}^{3+}$?
(en= ethane-1,2-diamine)
(iii) Why is $[NiC{l}_4{]}^{2-}$ paramagnetic but $\left[Ni\right(CO{)}_4]$ is diamagnetic?
(At. Nos. : Cr = 24, Co = 27, Ni = 28)

Answer 1

(i) The IUPAC name of the complex $\left[Cr{\left({NH}_3\right)}_4{Cl}_2\right]Cl$ is Tetraamminedichlorochromium(III) chloride.

(ii) The complex ${\left[Co{\left(en\right)}_3\right]}^{3+}$ exhibits optical isomerism. Its optical isomers are shown in figure.

(iii) In ${\left[Ni{Cl}_4\right]}^{2-}$, the oxidation state of $Ni$ is +2. Chloride is weak field ligand and does not cause pairing up of electrons. As a result, two unpaired electrons are present in valence d-orbitals of $Ni$ which imparts paramagnetic character to the complex.

On the other hand, carbonyl is a strong field ligand and causes pairing up of electrons. As a result, no unpaired electrons are present. So, $\left[Ni\right(CO{)}_4]$ is diamagnetic complex.