US 2020/0209747 Al  15  Jul. 2, 2020  [0088]  In formula (AL-3),  RL 5 ,  RL 6  and  Rn  are each  independently a C$_{1 }$-C$_{20 }$ monovalent hydrocarbon group  which may contain a heteroatom such as oxygen, sulfur,  nitrogen or fluorine. The monovalent hydrocarbon group  may be straight, branched or cyclic and examples thereof  include C$_{1 }$-C$_{20 }$ alkyl groups and C$_{2}$-C$_{20 }$ alkenyl groups. A  pair  ofRL 5  and  RL 6 ,  RL 5  and  Rn,  or  RL $^{6 }$and  RL $^{7 }$may bond  together to form a C$_{3}$ -C$_{20 }$aliphatic ring with the carbon atom  to which they are attached.  [0089]  Examples of the group having formula (AL-3)  include  tert-butyl,  1,1-diethylpropyl,  1-ethylnorbomyl,  1-methy lcyclohexy  1,  1-methy lcyclopenty  1,  2-(2-methy  1  )ada› manty  l,  2-(2-ethyl)adamantyl, and tert-pentyl.  [0090]  Examples of the group having formula (AL-3) also  include groups having the formulae (AL-3)-1 to (AL-3)-18.  -continued  (AL-2)-77  itf1  ib 1  RL15  X  ~  itf1  (AL-3)-1  (AL-3)-2  (AL-3)-3  (AL-3)-4  (AL-3)-5  (AL-3)-6  -continued  iii]  iftil  (AL-3)-7  (AL-3)-8  (AL-3)-9  (AL-3)-10  (AL-3)-11  (AL-3)-12  (AL-3)-13 