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Selective Synthesis of Stannoles by 1,1‐Carboboration of Bis(trimethylsilylethynyl)tin Compounds Using Weakly and Strongly Electrophilic Triorganoboranes: Characterization of a Zwitterionic Intermediate
Author(s) -
Wrackmeyer Bernd,
Thoma Peter,
Marx Simone,
Bauer Tobias,
Kempe Rhett
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201400028
Subject(s) - chemistry , electrophile , tin , nuclear magnetic resonance spectroscopy , intramolecular force , spectroscopy , medicinal chemistry , stereochemistry , reactivity (psychology) , crystallography , organic chemistry , catalysis , medicine , physics , alternative medicine , pathology , quantum mechanics
The triorganoboranes BEt 3 , BPh 3 , and B(C 6 F 5 ) 3 were allowed to react with bis(trimethylsilylethynyl)diorganotin compounds [R 1 2 Sn(C≡C–SiMe 3 ) 2 ; R 1 2 = –(CH 2 ) 5 – ( a ), R 1 = n Bu ( b ), n Oct ( c ), Ph ( d )] to give selectively and quantitatively stannoles. The reactions proceeded by 1,1‐carboboration in two consecutive steps (inter‐ and intramolecular) and intermediates were detected by NMR spectroscopy. In one case, using the strongly electrophilic B(C 6 F 5 ) 3 , a zwitterionic intermediate was isolated and structurally characterized by X‐ray diffraction analysis. The question of reversibility of the 1,1‐carboboration is addressed. Multinuclear magnetic resonance spectroscopy ( 1 H, 11 B, 13 C, 19 F, 29 Si, 119 Sn NMR) was used to characterize the intermediates and the stannoles as the final products. Some of the NMR parameters ( 11 B, 13 C, 29 Si) of the intermediates were calculated by DFT methods using the optimized gas‐phase geometries.