Periodic Terpolymerization of Cyclooligoarsine, Cyclooligostibine, and Acetylenic Compound

The ring-collapsed radical terpolymerization of pentamethylcyclopentaarsine ( 1a ), hexaphenylcyclohexastibine ( 2 ), and dimethyl acetylenedicarboxylate ( 3 ) provided a periodic terpolymer containing both antimony atom and arsenic atom in the polymer chain. In the case of a 1:1:2 ratio of 1a: 2: 3, the obtained polymer has 1:1:2 structure of arsine, stibine, and vinylene unit. Employing excess 1a did not affect the periodic structure of the terpolymerization. On the other hand, employing excess 2 resulted in the terpolymer with more stibine units. The arsenic radical was more reactive toward 3 forming the vinyl radical, while the antimony radical was more reactive toward the vinyl radical forming the terpolymer. After the arsenic radicals were consumed, the antimony radical also reacted with 3 thereby affecting the periodic structure of the terpolymerization. Different reactivity of pnictogen radicals made it possible to construct the periodic vinylene−arsine−vinylene−stibine backbone.