Organoboranes have recently advanced ring-opening(co)polymerization(ROP)with high controllability,offering diverse polymer structures.Following the pioneering use of triethylborane(BEt_(3))in ROP,the categories of org...Organoboranes have recently advanced ring-opening(co)polymerization(ROP)with high controllability,offering diverse polymer structures.Following the pioneering use of triethylborane(BEt_(3))in ROP,the categories of organoborane have been updated to functional borane-based catalysts,borinane,multiboranes integrated into small organic scaffolds or macromolecular frameworks,which circumvent some limitations of BEt_(3)such as dilution effect,limited activity,and sensitivity to moisture and oxygen.In this study,well-defined nanoscopic polyhedral oligomeric silsesquioxanes(POSS)with eight vinyl groups serving as a substrate to create nanoscopic multiborane(POSS-B8)Lewis acid.This design offered high local density and closely positioned active sites for targeting the high-activity ROP of epoxides.Various initiators combined with POSS-B8 and chain transfer agents(CTAs)were investigated to endow diverse structures and molecular weights of polyethers.Density functional theory(DFT)calculations revealed exceptional catalytic behavior,with a turnover frequency(TOF)=3750 h^(−1)per borane of the POSS-B8.This was due to a much lowered activation energy for the chain propagation(15.0 kcal mol−1)and“intramolecular”propagation mode,assisted by one borane paired with three identical boranes in a concerted manner.A“self-concentrating synergistic effects”model was proposed to explain the structure-activity relationships.This work provides a newly designed strategy for creating a remarkably active and thermally robust borane catalyst for the ROP of epoxides.展开更多
基金supported by the National Natural Science Foundation of China(grant nos.22175105 and 22473047)the National Key R&D Program of China(grant no.2021YFA1501600)the Natural Science Foundation of Shandong Province,China(grant no.ZR2024MB019).
文摘Organoboranes have recently advanced ring-opening(co)polymerization(ROP)with high controllability,offering diverse polymer structures.Following the pioneering use of triethylborane(BEt_(3))in ROP,the categories of organoborane have been updated to functional borane-based catalysts,borinane,multiboranes integrated into small organic scaffolds or macromolecular frameworks,which circumvent some limitations of BEt_(3)such as dilution effect,limited activity,and sensitivity to moisture and oxygen.In this study,well-defined nanoscopic polyhedral oligomeric silsesquioxanes(POSS)with eight vinyl groups serving as a substrate to create nanoscopic multiborane(POSS-B8)Lewis acid.This design offered high local density and closely positioned active sites for targeting the high-activity ROP of epoxides.Various initiators combined with POSS-B8 and chain transfer agents(CTAs)were investigated to endow diverse structures and molecular weights of polyethers.Density functional theory(DFT)calculations revealed exceptional catalytic behavior,with a turnover frequency(TOF)=3750 h^(−1)per borane of the POSS-B8.This was due to a much lowered activation energy for the chain propagation(15.0 kcal mol−1)and“intramolecular”propagation mode,assisted by one borane paired with three identical boranes in a concerted manner.A“self-concentrating synergistic effects”model was proposed to explain the structure-activity relationships.This work provides a newly designed strategy for creating a remarkably active and thermally robust borane catalyst for the ROP of epoxides.
