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Synthesis, Coordination Behavior, and Reduction Chemistry of Cymantrenyl‐1,3‐bis(2,3,4,5‐tetraphenyl)borole
Author(s) -
Braunschweig Holger,
Damme Alexander,
Gamon Daniela,
Kelch Hauke,
Krummenacher Ivo,
Kupfer Thomas,
Radacki Krzysztof
Publication year - 2012
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.201200284
Subject(s) - chemistry , lewis acids and bases , adduct , pyridine , boron , medicinal chemistry , oxidation state , boranes , stereochemistry , metal , organic chemistry , catalysis
We describe the synthesis of base‐free bisborole [Cym † (BC 4 Ph 4 ) 2 ]—Cym † =(OC) 3 Mn(η 5 ‐C 5 H 3 )—and its transformation into two fully characterized Lewis acid–base adducts with pyridine bases of the type 4‐RNC 5 H 4 (R= t Bu, NMe 2 ). The results of electrochemical, as well as NMR and UV/Vis spectroscopic studies on [Cym † (BC 4 Ph 4 ) 2 ] and the related monoborole derivative [Cym(BC 4 Ph 4 )]—Cym=(OC) 3 Mn(η 5 ‐C 5 H 4 )—provided conclusive evidence for 1) the enhanced Lewis acidity of the two boron centers that result from conjugation of two borole fragments, and 2) the fact that MnB bonding interactions between the Lewis acidic borole moieties and the Mn center are considerably less pronounced for bisborole [Cym † (BC 4 Ph 4 ) 2 ]. In addition, the reduction chemistry of [Cym † (BC 4 Ph 4 ) 2 ] has been studied in detail, both electrochemically and chemically. Accordingly, chemical reduction of [Cym † (BC 4 Ph 4 ) 2 ] with magnesium anthracene afforded the corresponding tetraanion, which features a rare MgOC bonding mode in the solid state.