A solution of 1-chloro-2-phenylethane in toluene racemises slowly in the presence of a small amount of SbCl5, due to the formation of:

The racemization of 1-chloro-2-phenylethane in the presence of SbCl5 is due to the formation of a carbocation intermediate. SbCl5 is a Lewis acid, and it accepts a pair of electrons from the chlorine atom of 1-chloro-2-phenylethane. This leads to the formation of a carbocation. The carbocation is planar and can be attacked from either side by a nucleophile (like Cl-), leading to a racemic mixture of products. Therefore the answer is Carbocation.