From Bidentate Gallium Lewis Acids to Supramolecular Complexes

• Published in: Angewandte Chemie International Edition 2017-05, Vol.56 (22), p.6107-6111
• Main Authors: Horstmann, Jan, Hyseni, Mentor, Mix, Andreas, Neumann, Beate, Stammler, Hans‐Georg, Mitzel, Norbert W.
• Format: Article
• Language: English
• Subjects: Acids; Adducts; alkane elimination; bidentate Lewis acids; diethynyldiphenylsilane; Gallium; Lewis acid; Magnetic resonance spectroscopy; Nitrogen; NMR spectroscopy; Pyridines; supramolecular adducts; X-ray diffraction
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201701303

Bidentate gallium Lewis acids were prepared by the reaction of diethynyldiphenylsilane with neat trimethyl‐ or triethylgallium. Bis[(dimethylgallyl)ethynyl]diphenylsilane (1) and diethylgallyl derivative 2 were characterized as Et2O or pyridine adducts by NMR spectroscopy; 2⋅2Py was isolated. Lewis acids 1 and 2 form host–guest adducts with bidentate nitrogen bases, but defined cyclic 1:1 adducts are only formed between 1 and bases with matching N⋅⋅⋅N distances: 4,4′‐dimethyl‐3,3′‐bipyridinylacetylene (3), bis[(pyridin‐3‐yl)ethynyl]diphenylsilane (4), and bis[(2‐methylpyridin‐5‐yl)ethynyl]diphenylsilane (5). The structures of adducts 1⋅3, 1⋅4, and 1⋅5 were established by X‐ray diffraction experiments. 2⋅2Py reacts with DABCO to afford polymeric (DABCO‐2‐)n. Matchmaking: Supramolecular host–guest formation between the bidentate Lewis acid bis[(dialkylgallyl)ethynyl]diphenylsilane (alkyl=Me, Et) with defined Ga⋅⋅⋅Ga distances and tailor‐made bidentate pyridine bases with various N⋅⋅⋅N distances were studied. An insufficient match of the distances leads to either no reaction or polymeric compounds, while a good match gives defined cyclic 1:1 adducts.