$[\text{Co(NH}_3)_6]^{3+}$

$[\text{CoF}_6]^{3-}$

$[\text{NiCl}_4]^{2-}$

$[\text{Ni(CN)}_4]^{2-}$

$\text{CN}^-$

$\text{H}_2\text{O}$

$\text{Cl}^-$

$\text{NH}_3$

Alcohol

Ether

Phenol

Ketone

The $\text{SN}^2$ mechanism proceeds mainly with racemization.

The $\text{SN}^2$ mechanism includes a transition state with penta coordinating carbon.

The $\text{SN}^2$ mechanism involves formation of planar carbocation intermediate in the first step.

The $\text{SN}^2$ mechanism involves formation of carbocation with $\text{SP}^2$ hybridized carbon.