The development of practical carbon-heteroatom bond formation as well as new polymerization methods for heteroatom-containing polymers is not only of considerable scientific interest but also important for preparing useful materials with unusual properties. Safe and facile reactions for As-C bond formation protocols promote further advancement in organoarsenic chemistry. We have developed several practical methods for As-C bond formation based on the arsenic homocycles, cyclo-(AsMe)5 and cyclo-(AsPh)6 (Scheme 1). Organoarsenic electrophiles and nucleophiles are generated in situ from the arsenic homocycles by addition of iodine and organolithium reagents, respectively. The in situ generation methods do not require isolation and purification of the arsenic intermediates because neither salts nor by-products are formed. Without isolation, the obtained solution of the arsenic intermediates can be subsequently used for the next substitution reaction to produce various organoarsenic compounds such as 9-arsafluorenes, 2,5-diaryl-1-phenylarsoles, and dithienoarsoles. These compounds can be used as monomers for preparation of arsole-containing p-conjugated polymers. The coordination direction of arsenic atom is more versatile than that of phosphorus, and various complex forms can be attained by organoarsenic ligands. In addition, trivalent arsenic compounds are stereochemically stable because of the higher inversion barrier relative to that of phosphorus compounds. Furthermore, organoarsenic compounds are much less reactive to oxygen compared with phosphorus analogues, which are generally prone to oxidation, and thus most phosphines are spontaneously oxidized even under the ambient atmosphere. Therefore, arsenic-containing polymers are a promising alternative to open a new door toward trivalent-pnictogen-based materials.

Organoarsenic polymers by practical As-C bond formation techniques

ACS Spring Meeting 2021

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