Fluoroborates by cleavage of trimethylamine-bis(trifluoromethyl)boranes with NE3 * 3 HF. Structures of C6F5(CF3)2B.NMe3, K[C6H5CH2(CF3)2BF], and K[C6H5(CF3)2BF].
Trimethylamine-bis(trifluoromethyl)boranes R(CF3)2B.NMe3 (R = cis/trans-CF3CF=CF (1/2), HC.tplbond.C (3), H2C=CH (4), C2H5 (5), C6H5CH2 (6), C6F5 (7), C6H5 (8)) react with NEt3 * 3 HF depending on the nature of R at 155-200 Deg under replacement of the trimethylamine ligand to form the corresponding fluoro-bis(trifluoromethyl)-borates [R(CF3)2BF]- (1a/2a-8a). The structures of 7, K[C6H5CH2(CF3)2BF] (K-6a), and K[C6H5(CF3)2BF] (K-8a) were investigated by single-crystal x-ray diffraction. In 7 the CF3 groups make short repulsive contacts with NMe3 and C6F5 entities - the B-CF3 bonds being unusually long. The B-F bond lengths of K-6a and K-8a (1.446(3) and 1.452(2) .ANG., resp.) are long for a fluoroborate. [on SciFinder (R)]
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