For 10 points, identify these compounds which act as electron pair acceptors according to a theory posited by a namesake American scientist.
In Pearson's theory, these entities can be classified as either hard or soft, and one of these functions as a catalyst for the Friedel-Crafts reaction. Crown ethers attract metal cations because the cations effectively function as these. Antimony Pentafluoride is a strong one of these, and compounds such as Zinc Chloride and electron deficient Boron compounds can also act as these. For 10 points, identify these compounds which act as electron pair acceptors according to a theory posited by a namesake American scientist.
In Pearson's theory, these entities can be classified as either hard or soft, and one of these functions as a catalyst for the Friedel-Crafts reaction.
{Lewis acid} (prompt on {acids})