C-66 is one of the smallest fullerenes that is able to encapsulate more than one metal atom, as in Sc-2@C-66, as well as to get chlorinated at a low level, C66Cl10 or C66Cl6. We show here, with the help of computations at density functional theory level, that these two means of obtaining derivatives of non-isolated pentagon rule fullerenes are dictated by different factors. Chlorination takes place at temperatures lower than 2000 K, once the neutral fullereries are formed: Encapsulation is, however, mainly governed by the charge transfer, although the Sc center dot center dot center dot Sc distance is also playing a tole in the stability of Sc-2@C-66.