Difluorination at Boron Leads to the First Electrophilic Ligated Boryl Radical (NHC‐BF2.). Issue 32 (17th 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 international edition. Volume 57:Issue 32(2018)
• Page Start: 10251
• Page End: 10256
• Publication Date: 2018-07-17
• Subjects: boron -- laser flash photolysis -- photochemistry -- polymerization -- radical reactions; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201806476
• Languages: English
• ISSNs: 1433-7851

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. Abstract : Radical reactions : 1, 3‐Dimethylimidazol‐2‐ylidene difluoroborane (NHC‐BF2 H) leads to the radical NHC‐BF2 . . The transient difluoroboryl radical was generated by laser flash photolysis experiments. It is the first electrophilic ligated boryl radical. NHC‐BF2 H serves as a co‐initiator in bulk photopolymerizations for both electron‐poor and electron‐rich monomers.