A solution of $(−)−1− chloro − 1− phenylethane$ in toluene racemises slowly in the presence of a small amount of $SbCl_5$ ,due to the formation of :

Question

$\begin{array}{1 1}(1) carbanion \\(2) carbene \\ (3) carbocation \\ (4) free \;radical \end {array}$