Question

Complex which does not show $d^{2}s{p}^3$ hybridisation is:

• A. $\left[Co\right(en{)}_3]C{l}_3$
• B. $K_3\left[Co\right(ox{)}_3]$
• C. $\left[Co\right(H_{2}O{)}_6]B{r}_3$
• D. $K_3\left[Co{F}_6\right]$

Answer 1

The correct option is D $K_3\left[Co{F}_6\right]$

In all the complexes given, $Co$ is in the +3 oxidation state. For this case, ethylenediamine, oxalate and $H_{2}O$ act as strong field ligands which can pair up the electrons in inner d orbitals and form $d^{2}s{p}^3$ hybridisation.
In $K_3\left[Co{F}_6\right]$ hybridisation is $s{p}^3{d}^2$ because $F$ is a weak field ligand and can not pair up the inner d electrons.