title: Synthesis, Structure, and Reactivity of Anionic sp(2) -sp(3) Diboron Compounds: Readily Accessible Boryl Nucleophiles.
abstract: Lewis base adducts of tetra-alkoxy diboron compounds, in particular bis(pinacolato)diboron (B2 pin2 ), have been proposed as the active source of nucleophilic boryl species in metal-free borylation reactions. We report the isolation and detailed structural characterization (by solid-state and solution NMR spectroscopy and X-ray crystallography) of a series of anionic adducts of B2 pin2 with hard Lewis bases, such as alkoxides and fluoride. The study was extended to alternative Lewis bases, such as acetate, and other diboron reagents. The B(sp(2) )-B(sp(3) ) adducts exhibit two distinct boron environments in the solid-state and solution NMR spectra, except for [(4-tBuC6 H4 O)B2 pin2 ](-) , which shows rapid site exchange in solution. DFT calculations were performed to analyze the stability of the adducts with respect to dissociation. Stoichiometric reaction of the isolated adducts with two representative series of organic electrophiles-namely, aryl halides and diazonium salts-demonstrate the relative reactivities of the anionic diboron compounds as nucleophilic boryl anion sources.
authors: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany).
authors: Sabrina
authors: S
authors: Pietsch
authors: Emily C
authors: EC
authors: Neeve
authors: David C
authors: DC
authors: Apperley
authors: Rüdiger
authors: R
authors: Bertermann
authors: Fanyang
authors: F
authors: Mo
authors: Di
authors: D
authors: Qiu
authors: Man Sing
authors: MS
authors: Cheung
authors: Li
authors: L
authors: Dang
authors: Jianbo
authors: J
authors: Wang
authors: Udo
authors: U
authors: Radius
authors: Zhenyang
authors: Z
authors: Lin
authors: Christian
authors: C
authors: Kleeberg
authors: Todd B
authors: TB
authors: Marder
mesh_terms: D000838:Anions / Q000138:chemical synthesis / Q000737:chemistry; D001896:Boron Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003979:Diazonium Compounds / Q000138:chemical synthesis / Q000737:chemistry; D005459:Fluorides / Q000138:chemical synthesis / Q000737:chemistry; D054879:Halogenation; D058115:Lewis Bases / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D000838:Anions; D001896:Boron Compounds; D003979:Diazonium Compounds; D058115:Lewis Bases; D005459:Fluorides
keywords: Lewis bases; boron; boronic acids; cross-coupling; metal-free borylation