es, either R6 sites or R7 sites, or either Y3 sites or Y4 sites. [0242] X??? represents a non-nucleophilic anion. [0243] The compounds represented by formula (III) are preferably compounds represented by the following formula (IV). [0244] Suitable examples of an aryl group represented by Ar in formula (III) include aryl groups containing 6 to 18 carbon atoms, such as a phenyl group, a naphthyl gro