14  13  US 9,665,002 B2  -continued  (A-37)  0  N-N"CQ  H  I  #  #  CO2- (A-38)  o(i  \_,-N"CQ  #  #  CO2- (A-39)  s(i  \_,-N"CQ  #  #  CO2- (A-40)  "Nl  ~N"C»co,  o]  ~N~co,  (A-42)  "Nl  ~N"C»co,  (A-43)  s]  ~N"CQC~  Of the anions of structural formulae (A-1) to (A-43), those  of formulae (A-1) to (A-23) are especially preferred for  availability of starting carboxylic acids and ease of synthe- 55  SIS.  In formula (a), R 100 , R $^{200 }$and R$^{300 }$are each independently  a straight C$_{1}$-C$_{20 }$or branched or cyclic C$_{3}$-C$_{20 }$monovalent  hydrocarbon group which may be substituted with or sepa› rated by a heteroatom. Examples of the monovalent hydro- carbon group are as exemplified for R 11 , R 22 , R 33 , R 44 , R 55  and R$^{01 }$in formula (1). Also, any two or more ofR 100 , R 200  and R$^{300 }$may bond together to form a ring with the sulfur  atom in formula (a), and the ring may have a carbonyl  moiety, sulfur atom, S(=O) moiety, S0$_{2 }$ moiety, oxygen 65  atom, or NH moiety interposed therein. In this case, exem› plary structures are shown below.  0  oo6cx:D  I+  I+  I+  I+  R6oo  R6oo  R6oo  R6oo  0  0  0  II  ~/  (XSX)(XSX)  s  #  ~  s  #  I+  I+  R6oo  R6oo  (XOX)C(X)  s  #  ~  s  #  I+  I+  R6oo  R6oo  H  CC:OCXNX)  s  ~  s  #  I+  I+  R6oo  R6oo  Herein, R$^{600 }$is a monovalent hydrocarbon group as exem- plified above for  R 100 ,  R $^{200 }$and  R 300 .  Preferred structures for the sulfonium cation having for- mula (a) are shown below although the invention is not  limited thereto.  Q  ¢  usuusu 