When is used as a catalyst, a neutral Lewis acid or a cationic Lewis or {TAIL ~ Bronsted acid} whose counterion is {HEAD ~ a weakly coordinating anion} is also present as part of the catalyst system  
When is used as a catalyst , a neutral Lewis acid or a cationic Lewis or { TAIL ~ Bronsted acid } whose counterion is { HEAD ~ a weakly coordinating anion } is also present as part of the catalyst system
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH