Cyclic Bis(trifluoromethyl)borates [ cyclo-O(CH 2) nB(CF 3) 2] − ( [formula omitted]): structure of Cs[ cyclo-O(CH 2) 4B(CF 3) 2

Abstract

Hydroboration of H 2CCH(CH 2) ( n−2) (CF 3) 2B·NMe 3 ( n=3 ( 1), 4 ( 2), 5 ( 3)) with 9-BBN followed by alkaline oxidation with H 2O 2 yields HO(CH 2) n (CF 3) 2B·NMe 3 ( n=3 ( 4), 4 ( 5), 5 ( 6)). Upon heating HO(CH 2) n (CF 3) 2B·NMe 3 rearranges under elimination of HNMe 3 + to form the cyclic borates [ cyclo-O(CH 2) n B(CF 3) 2] − ( n=3 ( 7), 4 ( 8), 5 ( 9)). In case of n=4 and 5 side products [ cyclo-O(CH 2) n C(CF 3)BF 3] − ( 10) and ( 11) could be identified and the Cs salts of 7, 8, 9 and 11 have been isolated. The constitution of the novel boron compounds has been deduced from multinuclear NMR, Raman and mass spectra. The structure of Cs[ cyclo-O(CH 2) 4B(CF 3) 2] has been determined by X-ray diffraction.