title: On the synthesis, characterization and reactivity of N-heteroaryl-boryl radicals, a new radical class based on five-membered ring ligands.
abstract: The synthesis and physical characterization of a new class of N-heterocycle-boryl radicals is presented, based on five membered ring ligands with a N(sp(2) ) complexation site. These pyrazole-boranes and pyrazaboles exhibit a low bond dissociation energy (BDE; BH) and accordingly excellent hydrogen transfer properties. Most importantly, a high modulation of the BDE(BH) by the fine tuning of the N-heterocyclic ligand was obtained in this series and could be correlated with the spin density on the boron atom of the corresponding radical. The reactivity of the latter for small molecule chemistry has been studied through the determination of several reaction rate constants corresponding to addition to alkenes and alkynes, addition to O2 , oxidation by iodonium salts and halogen abstraction from alkyl halides. Two selected applications of N-heterocycle-boryl radicals are also proposed herein, for radical polymerization and for radical dehalogenation reactions.
authors.affiliation: Institut de Science des Matériaux de Mulhouse IS2M, UMR CNRS 7361, UHA, 15, rue Jean Starcky, 68057 Mulhouse Cedex (France).
authors.forename: Mohamad-Ali
authors.initials: MA
authors.lastname: Tehfe
authors.forename: Stéphane
authors.initials: S
authors.lastname: Schweizer
authors.forename: Anne-Caroline
authors.initials: AC
authors.lastname: Chany
authors.forename: Cédric
authors.initials: C
authors.lastname: Ysacco
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Clément
authors.forename: Didier
authors.initials: D
authors.lastname: Gigmes
authors.forename: Fabrice
authors.initials: F
authors.lastname: Morlet-Savary
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Fouassier
authors.forename: Markus
authors.initials: M
authors.lastname: Neuburger
authors.forename: Théophile
authors.initials: T
authors.lastname: Tschamber
authors.forename: Nicolas
authors.initials: N
authors.lastname: Blanchard
authors.forename: Jacques
authors.initials: J
authors.lastname: Lalevée
keywords: N-heterocycle-boranes; boryl radicals; co-initiator; dehalogenation; polymerization; radical chemistry