772-94-1Relevant academic research and scientific papers
Mixed Boron Trihalide Adducts of Amines: A Multinuclear Nuclear Magnetic Resonance Study
Fox, Arnold,Hartman, Stephen J.,Humphries, Robyn E.
, p. 1275 - 1284 (2007/10/02)
The (19)F chemical shifts of mixed boron trihalide adducts of tertiary amines have a marked dependence on the steric effects of amine substituents, as estimated from the 'cone angle' of the amines.Base strength of the amine has little effect on adduct (19)F shifts, but does have a pronounced effect on the rate of halogen redistribution.The (11)B and (13)Cchemical shifts and (11)B-(19)F coupling constants of the adducts are discussed.Amines NRR'R'' become chiral when complexed to Lewis acids, since complexation stops the rapid inversion process.Because of this the fluorines in R''R'RN*BF2X (X=Cl, Br, or I) adducts are diastereotopic and magnetically non-equivalent, differing in chemical shift by up to 2 p.p.m.The four-adduct system of benzyl(ethyl)methylamine with BF(n)I(3-n)(n=0-3) gives rise to the cation B(PhCH2NMeEt)2F2(1+) which, because of the chirality of the co-ordinated amines, exists in meso and optically active forms distinguishable by (19)F n.m.r. spectroscopy.
