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Synthesis, Structure, and Reactivity of Anionic sp 2 –sp 3 Diboron Compounds: Readily Accessible Boryl Nucleophiles
Author(s) -
Pietsch Sabrina,
Neeve Emily C.,
Apperley David C.,
Bertermann Rüdiger,
Mo Fanyang,
Qiu Di,
Cheung Man Sing,
Dang Li,
Wang Jianbo,
Radius Udo,
Lin Zhenyang,
Kleeberg Christian,
Marder Todd B.
Publication year - 2015
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201500235
Subject(s) - chemistry , nucleophile , adduct , electrophile , lewis acids and bases , aryl , medicinal chemistry , borylation , reactivity (psychology) , nmr spectra database , reagent , organic chemistry , alkyl , physics , astronomy , spectral line , catalysis , medicine , alternative medicine , pathology
Lewis base adducts of tetra‐alkoxy diboron compounds, in particular bis(pinacolato)diboron (B 2 pin 2 ), 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 B 2 pin 2 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‐ t BuC 6 H 4 O)B 2 pin 2 ] − , 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.