Fluoride ion affinity of some Lewis acids

Abstract

The negative ion icr spectra of SO,, HC1, HBr, BC13, BF3, PF5, SiF4, AsF5, SF6, and combinations thereof were studied at various electron energies and pressures in an effort to obtain evidence for ion-molecule reactions yielding halide ion adducts. Only primary negative ions were observed with pure samples except for the previously reported SiF=r, BFr, and AsF,-~and the additional species Si2F8~and B.Fr. Addition of SFe greatly enhanced halide adduct formation and was utilized in the reaction mixtures for all systems investigated. The relative order of fluoride ion affinity has been found to be: SF4, SF3• < SO,, HC1, AsF3 < SiF4 < BF3 < PF3 < BC13 < AsF3. Fluoride ion affinities of these compounds and the enthalpies of formation of the corresponding fluoroanions have been estimated.

Matrix isolation studies of reactive intermediate complexes

“…This formalism has been effective in describing a large number of intermediate complexes, both neutral and ionic. At the same time, gas phase ion cyclotron resonance (ICR) studies have provided significant data on relative basicities [21][22][23] (by constructing a table of gas phase proton affinities), and gas phase Lewis acidities [24][25][26] (by constructing a table of fluoride ion affinities). These have proved very useful in guiding condensed phase spectroscopic studies.…”

Fluoride affinities of fluorinated alanes

“…Theoretical fluoride affinities were calculated using an isodesmic approach, calculating the 298K enthalpy for the fluoride transfer reaction with tetrafluoroaluminate, shown in Eq. (2).…”

“…Fluoride affinity (FA) is also an important thermochemical property, serving as a measure of the Lewis acidity. The measurements of FAs have been determined experimentally using a variety of techniques [2][3][4]. Haartz and McDaniel used ion cyclotron resonance spectroscopy to determine the relative order of the fluoride affinity to be SF 4 , SF 5 < SO 2 , HCl, AsF 3 < SiF 4 < BF 3 < PF 5 < BCl 3 < ASF 5 [2].…”

“…The measurements of FAs have been determined experimentally using a variety of techniques [2][3][4]. Haartz and McDaniel used ion cyclotron resonance spectroscopy to determine the relative order of the fluoride affinity to be SF 4 , SF 5 < SO 2 , HCl, AsF 3 < SiF 4 < BF 3 < PF 5 < BCl 3 < ASF 5 [2]. Larson and McMahon related fluoride affinities to the hydrogen bond strengths of various chemical species [3], which enabled them to create a wide-range fluoride affinity scale.…”

General Aspects

“…Numerous techniques have been applied: conductivity measurements, 74-79 cryoscopy, [80][81][82][83] aromatic hydrocarbon extraction, 53,84 solubility measurements, [85][86][87] kinetic parameters determinations, 52,88,89 electroanalytical techniques (hydrogen electrode), [90][91][92][93] quinones systems as pH indicators, [94][95][96][97] or other electrochemical systems, 98,99 IR, 100,101 and acidity function (H 0 ) determinations with UV-visible spectroscopy, 8,9,14,19,[102][103][104][105] or with NMR spectroscopy. [109][110][111] Comparison of the results obtained by different methods shows large discrepancies (Table 1.2). [109][110][111] Comparison of the results obtained by different methods shows large discrepancies (Table 1.2).…”