Reactions of trifluorovinyl-trifluoromethylboron derivatives, structure of(F2C = CF)(F3C)(2)B center dot NHMe2 and (HOOC)(F3C)(2)B center dot NHMe2

Dimethylamino-bis(trifluoromethyl)borane, (F3C)(2)BNMe2 (1) reacts with 1,1 ,1,2-tetrafluoroethane in the presence of tBuLi to yield the dimethylamine borane (F2C=CF)(F3C)(2)B . NHMe2 (2). Compound 2 was alkylated at nitrogen with CH3I/KOH or benzyl chloride/KOH in ether to yield the amine boranes (F 2C=CF)(F3C)(2)B . NMe3 (2a) or (F2C=CF)(F3C)(2)B . NMe(2)Bzl (2b). Both 2 a nd 2a add bromine across the C=C bond to form the respective F2BrC-CFBr der ivatives 3 and 3a. A solution of 2 in CHCl3 reacts with ozone to give a 9:1 mixture of (cyclo-O-CF2-CF)(F3C)(2)B . NHMe2 (4) and (HOOC)(F3C)(2)B . NHM e2 (5), and the reaction of ozone with 2a yields a mixture of the analogous trimethylamine adducts 3b and 5a. Compound 4 further hydrolyzes to form th e oxocarboxyborane (HOOC-CO)(F3C)(2)B . NHMe2 (6). The B-N bond of 2a is cl eaved by either NEt3 x 3HF or NMe4F to form the fluoroborate anion [(F2C=CF )B(CF3)(2)F](-) (7). The structures of 2 and 5 have been investigated by si ngle-crystal X-ray diffraction. The B-C bond involving the trifluorovinyl g roup in 2 is 1.598(3) Angstrom long, and the associated B-C-C bond angle of 134.4(2)degrees is remarkably large. The B-C linkage to the carboxy group in 5 is 1.620(2) Angstrom long. (C) 2000 Elsevier Science S.A. All rights r eserved.