Fluoroborates by Cleavage of Trimethylamine-bis(trifluoromethyl)boranes with NEt3 × 3 HF. Structures of C6F5(CF3)2B · NMe3, K[C6H5CH2(CF3)2BF], and K[C6H5(CF3)2BF]

✍ Scribed by David J. Brauer; Hans Bürger; Regina Hübinger; Gottfried Pawelke

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: German
• Weight: 183 KB
• Volume: 627
• Category: Article
• ISSN: 0372-7874
• DOI: 10.1002/1521-3749(200104)627:4<679::aid-zaac679>3.0.co;2-1

✦ Synopsis

Trimethylamine-bis(trifluoromethyl)

boranes R(CF 3 ) 2 B ´NMe 3 (R = cis/trans-CF 3 CF=CF (1/2), HCºC (3), H 2 C=CH (4), C 2 H 5 (5), C 6 H 5 CH 2 (6), C 6 F 5 (7), C 6 H 5 (8)) react with NEt 3 ´3 HF depending on the nature of R at 155±200 °C under replacement of the trimethylamine ligand to form the corresponding fluoro-bis(trifluoromethyl)borates [R(CF 3 ) 2 BF] ± (1 a/2 a±8 a). The structures of 7, K[C 6 H 5 CH 2 (CF 3 ) 2 BF] (K-6 a), and K[C 6 H 5 (CF 3 ) 2 BF] (K-8 a)

have been investigated by single-crystal X-ray diffraction. In 7 the CF 3 groups make short repulsive contacts with NMe 3 and C 6 F 5 entities ± the B±CF 3 bonds being unusually long. The B±F bond lengths of K-6 a and K-8 a (1.446(3) and 1.452(2) A Ê , respectively) are long for a fluoroborate.