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An Axially Chiral, Electron‐Deficient Borane: Synthesis, Coordination Chemistry, Lewis Acidity, and Reactivity
Author(s) -
Mewald Marius,
Fröhlich Roland,
Oestreich Martin
Publication year - 2011
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.201100724
Subject(s) - chemistry , lewis acids and bases , borane , transmetalation , substituent , adduct , medicinal chemistry , reactivity (psychology) , nuclear magnetic resonance spectroscopy , polymer chemistry , boron , inorganic chemistry , catalysis , stereochemistry , organic chemistry , medicine , alternative medicine , pathology
An axially chiral dihydroborepine with a binaphthyl backbone and a C 6 F 5 substituent at the boron atom was prepared by transmetalation from the corresponding tin precursor. This novel motif was structurally characterized by X‐ray diffraction analysis as its THF and its PhCN Lewis acid/base complex. 1 H NMR measurements at variable temperatures of the former adduct revealed a remarkable dynamic behavior in solution. Several more Lewis pairs with oxygen, nitrogen, carbon, and phosphorus σ‐donors were synthesized and analyzed by multinuclear NMR spectroscopy. The determination of the borane’s Lewis acidity with the Gutmann–Beckett method attests its substantial Lewis acidity [85 % with Et 3 PO as well as 74 % with Ph 3 PO relative to the parent B(C 6 F 5 ) 3 ]. Representative examples of SiH bond activation (carbonyl reduction and dehydrogenative SiO coupling) are included, demonstrating the chemical stability and the synthetic potential of the new chiral boron‐based Lewis acid.