Question

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

Answer 1

(i) The IUPAC name of the complex$\left[Cr\right(N{H}_3{)}_{4}C{l}_2]Cl$ is Tetraamminedichlorochromium(III) chloride.

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

(iii) In $[NiC{l}_4{]}^{2-}$, the oxidation state of Ni is +2. Chloride is a weak field ligand and does not cause pairing up of electrons against the Hund's rule of maximum multiplicity. As a result, two unpaired electrons are present in the valence d-orbitals of Ni which impart paramagnetic character to the complex. On the other hand, carbonyl is a strong field ligand and causes pairing up of electrons against the Hund's rule of maximum multiplicity. As a result, no unpaired electrons are present and hence, the complex is diamagnetic.