Difluorination at Boron Leads to the First Electrophilic Ligated Boryl Radical (NHC‐BF2.). (18th July 2018)

• Record Type: Journal Article
• Authors: Subervie, Daniel; Graff, Bernadette; Nerkar, Swapnil; Curran, Dennis P.; Lalevée, Jacques; Lacôte, Emmanuel
• Is Part Of: Angewandte Chemie. Volume 130:Number 32(2018)
• Page Start: 10408
• Page End: 10413
• Publication Date: 2018-07-18
• Subjects: Bor -- Laserblitzphotolyse -- Photochemie -- Polymerisation -- Radikalreaktionen; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201806476
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: 1, 3‐Dimethylimidazol‐2‐ylidene difluoroborane (NHC‐BF2 H) was prepared in a one‐pot, two‐step reaction from the parent ligated borane (NHC‐BH3 ). The derived difluoroboryl radical (NHC‐BF2 . ) was generated by laser flash photolysis experiments and characterized by UV spectroscopy and rate‐constant measurements. It is transient and reacts quickly with O2 . Unusually, it also reacts more rapidly with ethyl vinyl ether than with methyl acrylate. By this measure, it is the first electrophilic ligated boryl radical. Both NHC‐BH3 and NHC‐BF2 H serve as co‐initiators in bulk photopolymerizations, converting both electron‐poor and electron‐rich monomers at roughly similar rates. However, the difluorinated coinitiator provides polymers with dramatically increased chain lengths from both monomers.