Sulfonium Boranes for the Selective Capture of Cyanide Ions in Water

Abstract

Owing to the presence of low lying s* orbitals, sulfonium ions are inherently Lewis acidic and can interact with electron-rich substrates to form donor-acceptor complexes. Although this phenomenon has been documented, [1] efforts to use sulfonium ions as a binding site in Lewis acidic hosts have not been reported. As part of our fundamental interest in the chemistry of polydentate Lewis acidic boranes, [2] we have become interested in probing the synthesis and properties of anion receptors containing accessible sulfonium ions. As an added motivation for these studies, we anticipated that the anion binding properties of sulfonium boranes would also benefit from attractive Coulombic effects similar to those occurring in other cationic boron-based anion receptors. [3,4] To test the validity of the aforementioned concepts, we synthesized the cationic boranes [1] + and [2] + which feature adjacent sulfonium and boryl moieties connected by a 1,8-naphthalenediyl or o-phenylene linker, respectively (Scheme 1). The salt [1]OTf was obtained by reaction of the tetrakis(THF)lithium salt of dimesityl-1,8-naphthalenediylborate [5] with dimethyldisulfide and subsequent methylation of the resulting sulfide with MeOTf (Scheme 1). The salt [2]OTf could also be conveniently prepared in two steps by reaction of o-lithiothioanisole [6] with dimesitylboron fluoride and subsequent methylation with MeOTf.Both [1]OTf and [2]OTf have been isolated in an analytically pure form and characterized by multinuclear NMR spectroscopy, UV/Vis spectroscopy, and single-crystal X-ray diffraction. The detection of a 11 B NMR resonance near d = 70 ppm (d = 67 ppm for [1] + or d = 77 ppm for [2] + ) and the presence of a low energy UV/Vis absorption band at 340 nm in MeOH for both [1] + (e = 16 350 m À1 cm À1 ) and [2] + (e = 9300 m À1 cm À1 ) indicate the presence of a coordinatively unsaturated boron center, which mediates p conjugation of the aromatic ligands. [7] The resulting boron-centered chromophores are fluorescent and give rise to a broad emission band at 464 nm for [1] + (f = 0.02) and 450 nm for [2] + (f = 0.12) when excited at 350 and 340 nm in MeOH, respectively. As reported for other sulfonium salts, [8] [1] + and [2] + are sensitive to UV light and should therefore not be irradiated for extended periods of time. The crystal structures of these salts clearly show that: 1) the boron center adopts a trigonalplanar coordination geometry (S (C-B-C) = 359.68 for [1] + and 360.08 for [2] + ); 2) that the boron-sulfur separation in [1] + (3.07 ) is slightly shorter than in [2] + (3.12 ) (Figure 1). [9] Despite the similarity of this boron-sulfur separation, the two cationic boranes differ by the respective disposition of the boryl and sulfonio moieties which are oriented in a more convergent fashion in [1] + . A natural bond orbital (NBO) analysis carried out at the density functional theory (DFT) optimized geometry of [1] + indicates the presence of a lp(S)! p(B) donor-acceptor interaction (Figure 1) whose deletion leads to an increase of the ...

Synthesis and Structure of a 1‐Phospha‐2‐boraacenaphthene Derivative and Its Chalcogenation Reactions

“…The 1 H NMR spectra also suggested such facile chalcogen exchange in 10 SeSe in solution. In both cases of 9 S and 9 Se, the six methyl groups of the two mesityl groups were observed independently at room temperature in 1 H NMR spec- (8), P2-Se3-B2, 99.72 (11). b) 10'SeSe: Crystallographic pseudo-C 2 axis passes through the center of the molecule: Definitive structural parameters could not be obtained due to the severe disorder with pseudo-C 2 symmetry.…”

“…It should be noted that compounds 9 S and 9 Se are the first examples of the new heterocycles with phosphorus, boron, and chalcogen atoms in the phenalene backbone. [11] A further selenization reaction of 9 Se with 1.5 equiv of Se in C 6 D 6 at 100 8C for 3.5 days resulted in the formation of 2-selena-1-phospha-3-boraphenalene-1-selenide 10 SeSe in 80 % yield. Alternatively, long-term heating of C 6 D 6 solution of 1 with elemental selenium at 100 8C for five days directly gave 10 SeSe isolated in 54 % yield.…”

“…All results of the analyses supported their structures with reasonable structural parameters. During the investigation on the molecu- (11), SÀB, 1.802(4), P-S-B, 105.64(12); b) 9 Se: PÀSe, 2.2607(10), SeÀB, 1.938 (4), P-Se-B, 101.52 (13); c) 10 SS: Two independent molecules were found in the unit cell: P1ÀS1, 2.1125(10), S1ÀB1, 1.814 (3), P1ÀS2, 1.9524(9), P1-S1-B1, 102.51(11), P2ÀS3, 2.0948(10), S3ÀB2, 1.808 (3), P2ÀS4, 1.9514(10), P2-S3-B2, 103.49 (11). d) 10 SSe: Two independent molecules were found in the unit cell: P1ÀS1, 2.1112(8), S1ÀB1, 1.817(3), P1ÀSe1, 2.1056(6), P1-S1-B1, 102.15(9), P2ÀS2, 2.0970(8), S2ÀB2, 1.799(3), P2ÀSe2, 2.1051(6), P2-S2-B2, 103.00(9).…”

A Label‐Free Gold‐Nanoparticle‐Based SERS Assay for Direct Cyanide Detection at the Parts‐per‐Trillion Level

“…[1][2][3][4] Long-term exposure to smaller concentrations of cyanide can damage the central nervous system. [1][2][3][4][5][6][7][8][9] For this reason, the environmental protection agency (EPA) set the drinking water standard at 200 ppb. [1][2][3][4] Accidental leaks and spills of cyanide are common from gold mining.…”

“…[1][2][3][4] Accidental leaks and spills of cyanide are common from gold mining. [1][2][3][4][5][6][7][8][9] Also, cyanide is still used in electroplating, metal mining, and the plastic industry. [1][2][3][4][5][6][7][8][9] Current technology can detect cyanide ions at the level of EPA limit, but they are not suitable for field detection due to tedious sample pretreatment or measurements.…”