Fluoride Ion Capture from Water with a Cationic Borane

Abstract

The reaction of the [Li(THF)4]+ salt of dimesityl-1,8-naphthalenediylborate with [Me2NCH2]I affords a borane (1-(Mes2B)-8-(Me2NCH2)-C10H6) which can be converted into a cationic borane [3]+ ([1-(Mes2B)-8-(Me3NCH2)-C10H6]+) by methylation with MeOTf. This cationic borane promptly complexes fluoride to afford the corresponding zwitterionic ammonium/fluoroborate 3-F (1-(Mes2FB)-8-(Me3NCH2)-C10H6). Cation [3]+ fails to react with chloride, bromide, and iodide indicating that fluoride complexation is selective. Structural, spectroscopic, and computational studies carried out on 3-F show the existence of an unusual C-H...F-B hydrogen bond. Remarkably, [3]+ captures fluoride from water under biphasic conditions (H2O/CHCl3) to form 3-F. The high fluoride affinity of [3]+ can be correlated to the Coulombic forces which stabilize the B-F bond against heterolysis.

Solubilizing Sodium Fluoride in Acetonitrile: Synthesis, Molecular Structure, and Complexation Behavior of Bis(organostannyl)methyl‐Substituted Crown Ethers

“…Recently there has been growing interest in designing hosts that are able to complex the fluoride ion in aqueous solution. [30,31] Attempts to study the ability of compound 2·H 2 O to capture sodium fluoride in water failed because of its rather limited solubility in this solvent. However, the fact that 2·H 2 O already contains water and that the acetonitrile was not specifically dried prior to use makes it likely that water will not preclude fluoride complexation by the organotin moiety.…”

A Phosphorescent Ir(III) Complex for Selective Fluoride Ion Sensing with a High Signal‐to‐Noise Ratio

“…[4] Recently, receptors based on a strong and selective boron-fluoride ion interaction have been found to achieve highly efficient fluoride ion detection. [5] In particular, sterically hindered boryl groups such as dimesitylboryl and tridurylboryl moieties showed enhanced size-selectivity toward fluoride ions. [5b-f,i,k-l,p,r,6] Moreover, some of them exhibited protic media tolerance, which is very advantageous compared with other receptors.…”

A class of fascinating optoelectronic materials: Triarylboron compounds

“…Studies of several groups have demonstrated that boron based receptors that are bidentate and cationic capitalize on both Coulombic and cooperative effects leading to a further enhancement of their F  affinity. Consequently, F  detection in aqueous media could be realized [37][38][39][40]. In order to recognize F  in water solution, Gabbaï et al [37][38][39][40] developed a number of cationic boranes (40-44 in Figure 12).…”

“…Consequently, F  detection in aqueous media could be realized [37][38][39][40]. In order to recognize F  in water solution, Gabbaï et al [37][38][39][40] developed a number of cationic boranes (40-44 in Figure 12). These compounds were able to bind with F  in organic solvent/ water mixed solution with high sensitivity and selectivity.…”

“…Addition of CN  to a THF solution of 64 changed the color from greenish to colorless, indicating the decomposition of BODIPY moiety. It also leads to the for- Figure 12) is one type of cationic boranes which serves to enhance the Lewis acidity of boron center by Coulombic effects [37]. Owing to favorable Coulombic effects, 40 has a very high affinity for CN  with a binding constant of 3.9 (± 0.1) × 10 8 .…”