Organoantimony chemistry

Organoantimony chemistry is the chemistry of compounds containing a carbon to antimony (Sb) chemical bond. Relevant oxidation states are Sb^V and Sb^III. The toxicity of antimony ^[1] limits practical application in organic chemistry. ^[2]

Syntheses

Stibines

An organoantimony synthesis typically begins with tricoordinate antimony compounds, called stibines. Antimony trichloride reacts with organolithium or Grignard reagents to give compounds of the form R₃Sb:

SbCl₃ + 3 RLi (or RMgCl) → R₃Sb

Stibines are weak Lewis acids and do not form ate complexes. As soft Lewis donors, they see wide use in coordination chemistry ^{[3] : 348} and typically react through oxidative addition:

R₃Sb + Br₂ → R₃SbBr₂

R₃Sb + O₂ → R₃SbO

R₃Sb + B₂H₆ → R₃Sb·BH₃

This property also sensitizes them to air.

If reduced instead, stibanes typically release substituents (ligands): ^{[3] : 443}

R₃Sb + Na + NH₃ → R₂SbNa

R₂SbBr + Mg → (R₂Sb)₂ + MgBr₂

The cyclic compound stibole, a structural analog of pyrrole, has not been isolated, but substituted derivatives have. Antimony metallocenes are known as well:

14SbI₃ + 3 (Cp*Al)₄ → [Cp^∗
₂Sb]⁺[AlI₄]⁻ + 8Sb + 6 AlI₃

The Cp*-Sb-Cp* angle is 154°.

Stiboranes

Pentacoordinate antimony compounds are called stiboranes. They can be synthesised from stibines and halogens (Ph = C₆H₅):

Ph₃Sb + Cl₂ → Ph₃SbCl₂

As confirmed by X-ray crystallography, dichlorostiboranes feature pentacoordinate Sb(V) with trans-diaxial chloride ligands. ^[4] The dichlorostiborane reacts with phenyl lithium to give pentaphenylantimony:

Ph₃SbCl₂ + 2 PhLi → Ph₅Sb

Like the organobismuth compounds, stiboranes form onium compounds and ate complexes. Unsymmetrical stiboranes can also be obtained through the stibonium ions:

R₅Sb + X₂ → [R₄Sb]⁺[X]⁻ + RX

[R₄Sb]⁺[X]⁻ + R'MgX → R₄R'Sb

Pentaphenylantimony decomposes at 200 °C to triphenylstibine and biphenyl.

In the related Me₅Sb, proton NMR spectra recorded at -100 °C cannot resolve the two types of methyl protons. This observation is consistent with rapid Berry pseudorotation.

Distibines and antimony(I) compounds

Structure of (PhSb)₆

Distibines are formally Sb^II compounds, but feature tricoordinate Sb atoms with a single Sb-Sb bond. They may have interest as thermochromes. For example, tetramethyl­distibine is colorless when gas, yellow when liquid, red when solid just below the melting point of 18.5 °C, shiny-blue when cooler, and again yellow at cryogenic temperatures. ^{[6] [3] : 442} A typical synthesis first displaces an Sb^III halide with an alkali metal and then reduces the resulting anion with ethylene dichloride. ^{[3] : 781–783}

Like its lighter congener, arsenic, organoantimony compounds can be reduced to cyclic oligomers that are formally antimony(I) compounds. ^{[3] : 563–577}

With other substituents

Sb^V-N bonds are unstable, except where the N is also bonded to other electron-withdrawing substituents. ^[7]

Reactions

Stibine oxides undergo a sort of polarized-olefin metathesis. For example, they mediate a carbonyl-imine exchange (Ar is any activated arene): ^{[8] : 399}

Ph₃Sb=NSO₂Ar + PhC=O → Ph₃Sb=O + PhC=NSO₂Ar

The effect may extend vinylically: ^[9] $${\displaystyle {\ce {R2C=O{}+ HBrCHCO2R ->[{\ce {Bu3Sb}}] R2C=CHCO2R{}+ HBr}}}$$In contrast, unstabilized ylides (R₃Sb=CR'₂; R' not electron-withdrawing) form only with difficulty (e.g. diazo reagents). ^{[8] : 399–400}

Like other metals, stibanes vicinal to a leaving group can eliminate before a proton. For example, diphenyl(β-hydroxyphenethyl)stibine decomposes in heat or acid to styrene: ^{[8] : 400–402}

Ph₂SbCH₂CH(OH)Ph → CH₂=CHPh + Ph₂SbOH

As tertiary stibines also insert into haloalkyl bonds, tertiary stibines are powerful dehalogenating agents. ^{[8] : 403} However, stibanes poorly imitate active metal organometallics: only with difficulty do their ligands add to carbonyls or they power noble-metal cross couplings. ^{[8] : 403–405}

Stiboranes are gentle oxidants, converting acyloins to diketones and thiols to disulfides. ^{[8] : 406–408} In air, tris(thiophenyl)stibine catalyzes a Hunsdiecker-like decarboxylative oxidation of anhydrides to alcohols. ^{[8] : 411}

In ultraviolet light, distibines radicalize; the resulting radicals can displace iodide. ^{[3] : 766}

Lewis acids

Among pnictogen group Lewis acidic compounds, ^{[10] [11] [12] [13]} unusual lewis acidity of Lewis acidic antimony compounds have long been exploited as both stable conjugate acids of non-coordinating anions (SbF⁻
₆ and Sb
_²F⁻
₁₁), ^[14] and strong Lewis acid counterparts of well-known superacids (magic acids, fluoroantimonic acid). Also, Lewis-acidic antimony compounds have recently been investigated to extend the chemistry of boron because of the isolobal analogy between the vacant p orbital of borane and σ*(Sb–X) orbitals of stiborane, and the similar electronegativities of antimony (2.05) and boron (2.04). ^[15]

Origin of acidity

NBO of Sb(C₆F₅)₃-P(O)Ph₃ adduct describing donor–acceptor interaction between lp(O) and σ*(Sb-C₆F₅).

σ*(Sb–X), where X describes substituents on antimony, contributes to the Lewis acidity of antimony compounds in two ways: donor–acceptor orbital interaction and electrostatic interaction. These two contributions to the Lewis acidity have been evaluated. Both contributions are studied by calculations, and the acidities of theses compounds are quantified by the Gutmann–Beckett method, Hammett acidity function, pK_a, and fluoride ion affinity (FIA). FIA is defined as the amount of energy released upon binding a fluoride ion in the gas phase. The FIA of two popular strong Lewis acids, BF₃ and B(C₆F₅)₃, are 81 and 106 kcal/mol (340 and 440 kJ/mol) respectively. ^[14]

Donor–acceptor orbital overlap

Since Lewis adducts are formed by dative bond between Lewis bases and Lewis acids, the orbital overlap between the Lewis base and σ*(Sb–X) orbital is the source of the acidity. According to Gabbaï et al., NBO analysis of the Sb(C₆F₅)₃P(O)Ph₃ adduct indicates a donor-acceptor interaction between lp(O) and σ*(Sb–C₆F₅). ^{[16] [17]}

Lowering the LUMO (σ*(Sb–X)) energy increases the Lewis acidity. For example, Sb(C₆H₅)₃ has a higher LUMO energy (−0.55 eV) and weaker FIA (59 kcal/mol) than Sb(C₆F₅)₃ (−1.76 eV and 89 kcal/mol). ^[16]

Electrostatic interaction

Partial positive charges on the surface of antimony compounds interact with partial negative charges. For example, Sb(C₆F₅)₃(o-O₂C₆Cl₄) has a more positively charged site than Sb(C₆F₅)₃ as shown in its electrostatic potential map, corresponding to higher Lewis acidity (the FIA of Sb(C₆F₅)₃(o-O₂C₆Cl₄) and Sb(C₆F₅)₃ are 116 and 89 kcal/mol, respectively). ^[16]

Electrostatic potential map of (right) Sb(C₆F₅)₃ and (left) Sb(C₆F₅)₃(o-O₂C₆Cl₄). High electrostatic potential (blue region in the map) means partial positive charge.

Structure of Lewis acidic antimony compounds

Lewis acidic antimony complexes with a variety of oxidation states and coordination numbers are known. Several salient examples are introduced below.

FIA indicates fluoride ion affinity. δ indicates the P NMR shift of OPEt₃ adducts (Gutmann–Beckett method). The chemical shift of OPEt₃ is 51.0 ppm (in CH₂Cl₂), 51.2 ppm (in CHCl₃), and 47.6 ppm (in DFB (difluorobenzene)).

IBO of Sb-(η -Cp*) bondings in [Sb(tol)(Cp*)] (1).

3-coordinate Sb(III)

Although stibanes have a lone pair electrons, their antibonding orbitals with electron-withdrawing substituents renders them Lewis acidic. Sb(C₆F₅)₃ (3) has three σ*(Sb–C₆F₅) orbitals and three Lewis acidic sites. However, as shown in the electrostatic potential map of Sb(C₆F₅)₃, only one site is accessible to Lewis bases due to the asymmetric arrangement of the three aryl rings. ^[19]

In [Sb(tol)(Cp*)]²⁺ (1), the η⁵-Cp* binding mode is confirmed using IBO analysis. In the solid state structure, the Sb-C bond distances between Sb and carbons in the Cp* ring are 2.394(4) to 2.424(4) Å, but the Sb–C bond distances with the toluene are 2.993(5) to 3.182(5) Å. This longer Sb–toluene distance implies toluene lability in solution. ^[18]

Sb₂(o-catecholate)₂(μ-O) (2) had been predicted that a Lewis base would bind to two antimony centers in a bridging manner. However, it was observed that 2 binds with halide anions in various ratios (3:1, 2:1, 1:1, 1:2, 1:3). Cozzolono et al. suggested three reasons for its complex binding mode. First, rotational freedom around the bridge oxygen disrupts the Lewis base binding between two antimony centers. Second, intramolecular interactions between oxygen at catecholate and antimony competes with external Lewis base binding. Third, a high-polarity nucleophilic solvent, dimethylsulfoxide, is required to dissolve 2 due to the solubility and the solvent is also able to bind at antimony. ^[20]

3-coordinate Sb(V)

[SbPh₃]²⁺ (4) was not isolated. Instead, its Lewis adducts, [SbPh₃(OPPh₃)₂]²⁺ and [SbPh₃(dmap)₂(OTf)]⁺, were isolated. In the trigonal bipyramidal [SbPh₃(OPPh₃)₂]²⁺, two OPPh₃ are located in axial positions and the Sb–O bond distance (2.102(2) Å) is similar to the sum of the covalent radii of Sb and O (2.05 Å). In the distorted octahedral [SbPh₃(dmap)₂(OTf)]⁺, the Sb–N distance with the dmap (2.222(2) Å) is shorter than reported N–Sb⁺ distances. This bond distance implies Lewis adduct formation. In addition, a reaction between dmap and [SbPh₃(OPPh₃)₂]²⁺ forms [SbPh₃(dmap)₂(OTf)]⁺. The experimental results indicate that [SbPh₃]²⁺ is the Lewis acidic counterpart of these adducts. ^[21]

4-coordinate Sb(V)

Tetrahedral stibonium cations also show Lewis acidity. Since [Sb(C₆F₅)₄]⁺ (5) forms an adduct with triflate, the cation can be isolated as a [Sb(C₆F₅)₄][B(C₆F₅)₄] salt. Short Sb–C bond distances of 2.095(2) Å and a tetrahedral space group in the crystal proves that isolated [Sb(C₆F₅)₄]⁺ is completely free of external electron donors. This cationic antimony Lewis acid shows strong acidity: firstly, [Sb(C₆F₅)₄]⁺ abstracts fluoride anion from weakly coordinating anions, SbF⁻
₆, and secondly, the acidity measured by the Gutmann–Beckett method of [Sb(C₆F₅)₄]⁺ (5) is comparable with that of the B(C₆F₅)₃ adduct in CH₂Cl₂ (76.6 ppm). ^[22]

SbPh₃(Ant)⁺ (6) (where Ant is 9-anthryl) was isolated as triflate salt. 6 has a tetrahedral structure like 5. In a solid state structure of a fluoride adduct, AntPh₃SbF, the incoming fluoride occupies the axial position of a trigonal bipyramidal structure, and the sterically-demanding anthryl is located at the equatorial site. ^[23]

5-coordinate Sb(V)

Neutral Sb(V) complexes are also Lewis acids. ^[24] Compounds 7, 8 and 11 share the structure of spirocyclic stiborane. The LUMO of 8 mainly has its lobe at the antimony atoms and it renders 8 Lewis acidic. In detail, the LUMO can be assigned to as localized orbital on stiborafluorene moiety with larger nodes at the 9-position (Sb). Thus, Lewis bases bind towards trans to biphenylene and its fluoride adducts are asymmetric: 8·F⁻ has two enantiomers and 7·F⁻ has two diastereomers and four enantiomers.

A bisantimony complex (9) is synthesized starting from xanthene. 9 has C₂ symmetry and the Sb–Sb distance is 4.7805(7) Å. Both antimony(V) centers have distorted square pyramidal geometry with the geometry index τ₅ = 0.08. The base planes of the antimony centers meet face to face and this geometry allows 1:1 binding with F⁻, unlike 2. ^[25]

Trends in acidity

Inductive effect

Introduction of electron-withdrawing substituents on antimony results in increased acidity. For example, intramolecular donor–acceptor interactions of two stiboranes, o-C₆H₄(PPh₂)[SbPh₂(O₂C₆Cl₄)] and o-C₆H₄(PPh₂)[Sb(C₆F₅)₂(O₂C₆Cl₄)], have been analyzed by AIM. AIM analysis of electron density at the bond critical point (bcp) and delocalization index indicates that electron-withdrawing substituents on Sb(V) lead to an increased P–Sb bonding covalency. ^[26]

AIM analysis of the intramolecular donor-acceptor interactions of two stiboranes ^[26]

P-Sb bonding	o-C6H4(PPh2)(Sb(C6F5)2(O2C6Cl4)	o-C6H4(PPh2)(Sb(C6H5)2(O2C6Cl4)
Electron density at the bcp (e/rBohr3)	0.054	0.035
Delocalization index	0.38	0.24

Contour plots of the Laplacian of the electron density of (left) (o-C₆H₄(PPh₂)[Sb(C₆F₅)₂(O₂C₆Cl₄)] and (right) o-C₆H₄(PPh₂)[(SbPh₂(O₂C₆Cl₄)]. Blue dots are the bcp and brown lines are the bond paths.

Electrostatic potential map of a bisantimony(V) complex (9). Partial positive charges at antimony centers facing each other.

Bisantimony compounds vs mono-antimony compounds

A bisantimony complex (9) is a stronger Lewis acid than a monoantimony compound (8) because both Lewis acidic sites cooperatively contribute to the Lewis base binding. The electrostatic potential map of 9 shows positive charges on the Sb centers facing each other.

This cooperativity is supported by the Sb-(μ-F)-Sb moiety in solid state structure of F⁻ binding bisantimony compound 9. ^[25]

Reactions

Fluoride anion sensor

Fluoride binding turns on emission.

The 9-anthryltriphenylstibonium cation (5) shows weak fluorescent emission (Φ = 0.7%), but a corresponding fluoride adduct, fluorostiborane, shows a strong anthryl-based emission at 427 nm (Φ = 9.5% in CHCl₃). Owing to its stability in water, 5 could in principle be used as an aqueous fluoride sensor. ^{[23] [24] [27]} Fluoride-selective electrodes were developed by using Lewis acidic antimony compounds as ionophores. ^[28]

Catalysis

Examples of catalytic activity of Lewis acidic antimony compounds in (top) hydrogenation of quinoline using Hantzsch ester and (bottom) Ritter reaction.

Strongly acidic antimony compounds catalyze organic transformations such as the transfer hydrogenation and the Ritter reaction. ^[16]

Tetraarylstibonium cations catalyze cycloadditions between epoxides and CO₂ or isocyanate to produce oxazolidinones. ^[29]

Examples of Z-type ligand antimony compounds. Strong electron donation from gold to antimony decreases electron density on the Au center and the Au–Sb complex catalyzes (top) hydroamination and (bottom) polymerization of olefin.

Lewis acidic antimony compounds can act as Z-type ligands. Owing to the strong σ-accepting ability of dicationic Sb ligand, a gold-antimony complex can catalyze styrene polymerization and hydroamination after being activated by AgNTf₂. ^[30]

References

1. Filella, M. (2010). "Alkyl derivatives of antimony in the environment". Metal Ions in Life Sciences. 7. Cambridge: RSC publishing: 267–301. doi:10.1039/9781849730822-00267. ISBN   978-1-84755-177-1. PMID   20877810.
2. C. Elschenbroich, A. Salzer Organometallics : A Concise Introduction (2nd Ed) (1992) from Wiley-VCH: Weinheim. ISBN   3-527-28165-7
3. Patai, Saul, ed. (1994). The Chemistry of Organic Arsenic, Antimony, and Bismuth Compounds. Chemistry of Functional Groups. Chichester, UK: Wiley. doi:10.1002/0470023473. ISBN   047193044X.
4. Begley, M. J.; Sowerby, D. B. (1993). "Structures of triphenylantimony(V) dibromide and dichloride". Acta Crystallographica Section C Crystal Structure Communications. 49 (6): 1044–1046. Bibcode:1993AcCrC..49.1044B. doi:10.1107/S0108270192011958.
5. Breunig, Hans Joachim; Häberle, Karl; Dräger, Martin; Severengiz, Tevfik (1985). "(C₆H₅Sb)₆·(1,4-dioxane), the First Cyclohexastibane". Angewandte Chemie International Edition in English. 24: 72–73. doi:10.1002/anie.198500721.
6. Organoantimony compounds with element-element bonds H.J. Breunig, R. Rosler Coordination Chemistry Reviews 163 (1997) 33-53
7. Patai 1994 , p. 340, which immediately undercuts itself by giving an example of an -SbCl₃-NMe-... complex.
8. Freedman, Leon D.; Doak, George O. (1989). "The use of organoantimony and organobismuth compounds in organic synthesis". In Hartley, Frank Robinson (ed.). The Chemistry of the Metal—Carbon Bond. (Patai's) Chemistry of Functional Groups. Vol. 5. Chichester, UK: Interscience. pp. 397–413. doi:10.1002/9780470772263.ch9. ISBN   0471915564.
9. Freedman & Doak 1989 , p. 410, which ascribes the reaction instead to a Wittig-type reaction with an ylide.
10. Caputo, C. B.; Hounjet, L. J.; Dobrovetsky, R.; Stephan, D. W. (2013-09-20). "Lewis Acidity of Organofluorophosphonium Salts: Hydrodefluorination by a Saturated Acceptor" . Science. 341 (6152): 1374–1377. Bibcode:2013Sci...341.1374C. doi:10.1126/science.1241764. ISSN   0036-8075. PMID   24052304. S2CID   35796905.
11. Bayne, J. M.; Stephan, D. W. (2016). "Phosphorus Lewis acids: emerging reactivity and applications in catalysis" . Chemical Society Reviews. 45 (4): 765–774. doi:10.1039/C5CS00516G. ISSN   0306-0012. PMID   26255595.
12. Zhou, Jiliang; Liu, Liu Leo; Cao, Levy L.; Stephan, Douglas W. (2019-04-08). "The Arene-Stabilized η⁵-Pentamethylcyclopentadienyl Arsenic Dication [(η⁵-Cp*)As(toluene)] 2+" . Angewandte Chemie International Edition. 58 (16): 5407–5412. doi:10.1002/anie.201902039. ISSN   1433-7851. PMID   30802353. S2CID   73465935.
13. Ramler, Jacqueline; Hofmann, Klaus; Lichtenberg, Crispin (2019-12-31). "Neutral and Cationic Bismuth Compounds: Structure, Heteroaromaticity, and Lewis Acidity of Bismepines" . Inorganic Chemistry. 59 (6): 3367–3376. doi:10.1021/acs.inorgchem.9b03189. ISSN   0020-1669. PMID   31891491. S2CID   209523568.
14. Krossing, Ingo; Raabe, Ines (2004-04-13). "Noncoordinating Anions—Fact or Fiction? A Survey of Likely Candidates" . Angewandte Chemie International Edition. 43 (16): 2066–2090. doi:10.1002/anie.200300620. ISSN   1433-7851. PMID   5083452.
15. Marczenko, Katherine M.; Zurakowski, Joseph A.; Bamford, Karlee L.; MacMillan, Joshua W. M.; Chitnis, Saurabh S. (2019-12-09). "Hydrostibination" . Angewandte Chemie International Edition. 58 (50): 18096–18101. doi:10.1002/anie.201911842. ISSN   1433-7851. PMID   31591801. S2CID   242968313.
16. Yang, Mengxi; Tofan, Daniel; Chen, Chang-Hong; Jack, Kevin M.; Gabbaï, François P. (2018-10-15). "Digging the Sigma-Hole of Organoantimony Lewis Acids by Oxidation" . Angewandte Chemie International Edition. 57 (42): 13868–13872. doi:10.1002/anie.201808551. ISSN   1433-7851. PMID   30151881. S2CID   52099143.
17. Glendening, Eric D.; Landis, Clark R.; Weinhold, Frank (January 2012). "Natural bond orbital methods" . WIREs Computational Molecular Science. 2 (1): 1–42. doi:10.1002/wcms.51. ISSN   1759-0876. S2CID   95586513.
18. Zhou, Jiliang; Kim, Hyehwang; Liu, Liu Leo; Cao, Levy L.; Stephan, Douglas W. (2020). "An arene-stabilized η 5 -pentamethylcyclopentadienyl antimony dication acts as a source of Sb + or Sb 3+ cations" . Chemical Communications. 56 (85): 12953–12956. doi:10.1039/D0CC02710C. ISSN   1359-7345. PMID   32985631. S2CID   222166864.
19. Benz, Sebastian; Poblador-Bahamonde, Amalia I.; Low-Ders, Nicolas; Matile, Stefan (2018-05-04). "Catalysis with Pnictogen, Chalcogen, and Halogen Bonds". Angewandte Chemie International Edition. 57 (19): 5408–5412. doi:10.1002/anie.201801452. PMC   5947745 . PMID   29558562.
20. Qiu, J.; Song, B.; Li, X.; Cozzolino, A. F. (2018). "Solution and gas phase evidence of anion binding through the secondary bonding interactions of a bidentate bis-antimony(III) anion receptor" . Physical Chemistry Chemical Physics. 20 (1): 46–50. Bibcode:2018PCCP...20...46Q. doi:10.1039/C7CP05933G. ISSN   1463-9076. PMID   29226921.
21. Robertson, Alasdair P. M.; Burford, Neil; McDonald, Robert; Ferguson, Michael J. (2014-03-24). "Coordination Complexes of Ph₃Sb²⁺ and Ph₃Bi²⁺ : Beyond Pnictonium Cations" . Angewandte Chemie International Edition. 53 (13): 3480–3483. doi:10.1002/anie.201310613. PMID   24616180.
22. Pan, Baofei; Gabbaï, François P. (2014-07-09). "[Sb(C₆F₅)₄][B(C₆F₅)₄]: An Air Stable, Lewis Acidic Stibonium Salt That Activates Strong Element—Fluorine Bonds" . Journal of the American Chemical Society. 136 (27): 9564–9567. Bibcode:2014JAChS.136.9564P. doi:10.1021/ja505214m. ISSN   0002-7863. PMID   24946107.
23. Ke, Iou-Sheng; Myahkostupov, Mykhaylo; Castellano, Felix N.; Gabbaï, François P. (2012-09-19). "Stibonium Ions for the Fluorescence Turn-On Sensing of F – in Drinking Water at Parts per Million Concentrations" . Journal of the American Chemical Society. 134 (37): 15309–15311. Bibcode:2012JAChS.13415309K. doi:10.1021/ja308194w. ISSN   0002-7863. PMID   22954306.
24. Hirai, Masato; Gabbaï, François P. (2014). "Lewis acidic stiborafluorenes for the fluorescence turn-on sensing of fluoride in drinking water at ppm concentrations". Chem. Sci. 5 (5): 1886–1893. doi:10.1039/c4sc00343h. hdl: 1969.1/185530 . ISSN   2041-6520.
25. Hirai, Masato; Gabbaï, François P. (2015-01-19). "Squeezing Fluoride out of Water with a Neutral Bidentate Antimony(V) Lewis Acid" . Angewandte Chemie (in German). 127 (4): 1221–1225. Bibcode:2015AngCh.127.1221H. doi:10.1002/ange.201410085. PMID   25424599.
26. Tofan, Daniel; Gabbaï, François P. (2016). "Fluorinated antimony(V) derivatives: strong Lewis acidic properties and application to the complexation of formaldehyde in aqueous solutions". Chemical Science. 7 (11): 6768–6778. doi:10.1039/C6SC02558G. ISSN   2041-6520. PMC   5363782 . PMID   28451122.
27. Lee, Min Hyung; Agou, Tomohiro; Kobayashi, Junji; Kawashima, Takayuki; Gabba?, Fran?ois P. (2007). "Fluoride ion complexation by a cationic borane in aqueous solution" . Chemical Communications (11): 1133–5. doi:10.1039/b616814k. ISSN   1359-7345. PMID   17347716.
28. Li, Long; Zhang, Yihao; Li, Ying; Duan, Yinghui; Qian, Yi; Zhang, Peidong; Guo, Qingjie; Ding, Jiawang (2020-10-28). "Polymeric Membrane Fluoride-Selective Electrodes Using Lewis Acidic Organo-Antimony(V) Compounds as Ionophores". ACS Sensors. 5 (11): 3465–3473. doi:10.1021/acssensors.0c01481. PMID   33112603. S2CID   226054990.
29. Yang, Mengxi; Pati, Nilanjana; Bélanger-Chabot, Guillaume; Hirai, Masato; Gabbaï, François P. (2018). "Influence of the catalyst structure in the cycloaddition of isocyanates to oxiranes promoted by tetraarylstibonium cations" . Dalton Transactions. 47 (34): 11843–11850. doi:10.1039/C8DT00702K. ISSN   1477-9226. PMID   29697133.
30. Lo, Ying-Hao; Gabbaï, François P. (2019-07-22). "An Antimony(V) Dication as a Z-Type Ligand: Turning on Styrene Activation at Gold". Angewandte Chemie International Edition. 58 (30): 10194–10197. doi: 10.1002/anie.201903964 . ISSN   1433-7851. PMID   31111593.