Nuclear magnetic resonance study of fluorine exchange in the system

Abstract

p>Intermolecular fluorine exchange in the [Formula: see text] system has been studied by 31P nmr spectroscopy. The anion [Formula: see text] was prepared insitu from PhPF4 and KF in 18-crown-6, or from PhPF4 and [Formula: see text]. Exchange was found to be first-order in PhPF4, first-order in [Formula: see text], and slowed down by donor solvents such as acetonitrile, in support of a mechanism involving a fluorine-bridged intermediate. Experimental difficulties are probably due to HF impurities.

Phenylfluorophosphoranes: axial–equatorial fluorine exchange in RC6H4PF3H and intermolecular exchange in the PhPF2(H)OMe–MeOH–base system

“…Addition of small amounts of Et3N to RC6H4PF3H leads to the formation of RC6H4PF2 and the onset of intermolecular fluorine exchange, and reactions [2] and [3] are consistent with the behavior reported for PhPF3H (1).…”

“…Stereoselective bond-cleavage is difficult to observe in fiveand six-coordinate compounds if accompanied by axialequatorial scrambling of ligands, as illustrated by the PhPF3H-PhPF4HP or PhPF4-PhPFSP systems (1,2), although the introduction of three phenyl substituents can avert this problem, as demonstrated by the Ph3TeF3-Ph3TeF2+ or Ph3TeF2C1-Ph3~eFCl+ systems (3). In this paper we describe another, albeit unsuccessful, attempt at slowing down axial-equatorial ligand exchange, namely, by the introduction of trifluoromethyl or methyl substituents into the phenyl ring of PhPF3H.…”