For 10 points, name these compounds that act as electron acceptors in a namesake American's acid-base theory.
Ralph Pearson classified these entities as "hard" if they contained a high-energy LUMO and "soft" if they contained a low-energy one. These compounds include a common catalyst for the Friedel-Crafts reactions and for halogenating benzene; other examples include (*) carbocations and the central atom in any coordination compound. These compounds are useful for removing halogen atoms from molecules, as they act as electrophiles in nucleophilic addition. For 10 points, name these compounds that act as electron acceptors in a namesake American's acid-base theory.
Ralph Pearson classified these entities as "hard" if they contained a high-energy LUMO and "soft" if they contained a low-energy one.
Lewis acids [prompt on acids]