A cobalt salen pentenoate complex [salen = (R,R)-N,N'-bis(3,5-di-tertbutylsalicylidene)-1,2-cyclohexanediamine] is rationally designed as the catalyst for the ring-opening copolymerization (ROCOP) of epoxides/anhydrides/CO 2 . Via migratory insertion of carbon monoxide (CO) into the Co À O bonds, the ROCOP-active species a-alkene-w-O-Co III (salen) can be rapidly and quantitatively transformed into a-alkene-w-O 2 C-Co III (salen) telechelic linear precursors. Upon dilution of reaction mixtures, the homolytic cleavage of CoÀC bonds induced by visible light generates a-alkene acyl radicals that spontaneously undergo intramolecular radical addition to afford organocobalt-functionalized cyclic polyesters and CO 2 -based polycarbonates with excellent regioselectivity. The cyclic products can either react with radical scavengers to generate metal-free cyclic polymers or serve as photo-initiators for organometallic-mediated radical polymerization (OMRP) to produce tadpole-shaped copolymers.
A cobalt salen pentenoate complex [salen = (R,R)-N,N'-bis(3,5-di-tertbutylsalicylidene)-1,2-cyclohexanediamine] is rationally designed as the catalyst for the ring-opening copolymerization (ROCOP) of epoxides/anhydrides/CO 2 . Via migratory insertion of carbon monoxide (CO) into the Co À O bonds, the ROCOP-active species a-alkene-w-O-Co III (salen) can be rapidly and quantitatively transformed into a-alkene-w-O 2 C-Co III (salen) telechelic linear precursors. Upon dilution of reaction mixtures, the homolytic cleavage of CoÀC bonds induced by visible light generates a-alkene acyl radicals that spontaneously undergo intramolecular radical addition to afford organocobalt-functionalized cyclic polyesters and CO 2 -based polycarbonates with excellent regioselectivity. The cyclic products can either react with radical scavengers to generate metal-free cyclic polymers or serve as photo-initiators for organometallic-mediated radical polymerization (OMRP) to produce tadpole-shaped copolymers.
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