Reactions of trifluorovinyl-trifluoromethylboron derivatives, structure of (F2CCF)(F3C)2B·NHMe2 and (HOOC)(F3C)2B·NHMe2

Dimethylamino-bis(trifluoromethyl)borane, (F3C)2BNMe2 (1) reacts with 1,1,1,2-tetrafluoroethane in the presence of tBuLi to yield the dimethylamine borane (F2CCF)(F3C)2B·NHMe2 (2). Compound 2 was alkylated at nitrogen with CH3I/KOH or benzyl chloride/KOH in ether to yield the amine boranes (F2CCF)(F3C)2B·NMe3 (2a) or (F2CCF)(F3C)2B·NMe2Bzl (2b). Both 2 and 2a add bromine across the CC bond to form the respective F2BrCCFBr derivatives 3 and 3a. A solution of 2 in CHCl3 reacts with ozone to give a 9:1 mixture of (cyclo-O-CF2CF)(F3C)2B·NHMe2 (4) and (HOOC)(F3C)2B·NHMe2 (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 the oxocarboxyborane (HOOCCO)(F3C)2B·NHMe2 (6). The BN bond of 2a is cleaved by either NEt3×3HF or NMe4F to form the fluoroborate anion [(F2CCF)B(CF3)2F]− (7). The structures of 2 and 5 have been investigated by single-crystal X-ray diffraction. The BC bond involving the trifluorovinyl group in 2 is 1.598(3) Å long, and the associated BCC bond angle of 134.4(2)° is remarkably large. The BC linkage to the carboxy group in 5 is 1.620(2) Å long.