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Reversible Dihydrogen Activation by Reduced Aryl Boranes as Main‐Group Ambiphiles
Author(s) -
von Grotthuss Esther,
Diefenbach Martin,
Bolte Michael,
Lerner HansWolfram,
Holthausen Max C.,
Wagner Matthias
Publication year - 2016
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201608324
Subject(s) - homolysis , boranes , chemistry , boron , reactivity (psychology) , borylation , aryl , halide , metalation , main group element , medicinal chemistry , leaving group , metal , transition metal , carbon group , crystallography , photochemistry , inorganic chemistry , group (periodic table) , radical , organic chemistry , catalysis , medicine , alkyl , alternative medicine , pathology
A new approach to main‐group H 2 activation combining concepts of transition‐metal and frustrated Lewis pair chemistry is reported. Ambiphilic, metal‐like reactivity toward H 2 can be conferred to 9,10‐dihydro‐9,10‐diboraanthracene (DBA) acceptors by the injection of two electrons. The resulting [DBA] 2− ions cleave the H−H bond with the formation of hydridoborates under moderate conditions ( T= 50–100 °C; p <1 atm). Depending on the boron‐bonded substituents R, the addition is either reversible (R=C≡C t Bu) or irreversible (R=H). The reaction rate is strongly influenced by the nature and the coordination behavior of the countercation (Li + slower than K + ). Quantum‐chemical calculations support the experimental observations and suggest a concerted, homolytic addition of H 2 across both boron atoms. As proven by the successful conversion of Me 3 SiCl into Me 3 SiH, the system Li 2 [DBA]/H 2 appears generally relevant for the hydrogenation of element–halide bonds.