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1. Distiboranes based on ortho -phenylene backbones as bidentate Lewis acids for fluoride anion chelation

   https://doi.org/10.1039/D1OB00536G  

   You, Di; Zhou, Benyu; Hirai, Masato; Gabbaï, François P. (June 2021, Organic & Biomolecular Chemistry)

   null (Ed.)

   As part of our efforts in the chemistry of main group platforms that support anion sensing and transport, we are now reporting the synthesis of anitmony-based bidentate Lewis acids featuring the o -C 6 F 4 backbone. These compounds can be easily accessed by reaction of the newly synthesized o -C 6 F 4 (SbPh 2 ) 2 ( 5 ) with o -chloranil or octafluorophenanthra-9,10-quinone, affording the corresponding distiboranes 6 and 7 of general formula o -C 6 F 4 (SbPh 2 (diolate)) 2 with diolate = tetrachlorocatecholate for 6 and octafluorophenanthrene-9,10-diolate for 7 , respectively. While 6 is very poorly soluble, its octafluorophenanthrene-9,10-diolate analog 7 readily dissolves in CH 2 Cl 2 and undergoes swift conversion into the corresponding fluoride chelate complex [ 7 -μ 2 -F] − which has been isolated as a [ n Bu 4 N] + salt. The o -C 6 H 4 analog of 7 , referred to as 8 , has also been prepared. Although less Lewis acidic than 7 , 8 also forms a very stable fluoride chelate complex ([ 8 -μ 2 -F] − ). Altogether, our experiental results, coupled with computational analyses and fluoride anion affinity calculations, show that 7 and 8 are some of the strongest antimony-based fluoride anion chelators prepared to date. Another notable aspect of this work concerns the use of the octafluorophenanthrene-9,10-diolate ligand and its ablity to impart advantageous solubility and Lewis acidity properties. 

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2. Tetragonal phosphorus( v ) cations as tunable and robust catalytic Lewis acids

   https://doi.org/10.1039/C9SC02463H  

   Gilhula, James C.; Radosevich, Alexander T. (July 2019, Chemical Science)

   The synthesis and catalytic reactivity of a class of water-tolerant cationic phosphorus-based Lewis acids is reported. Corrole-based phosphorus( v ) cations of the type [ArP(cor)][B(C 6 F 5 ) 4 ] (Ar = C 6 H 5 , 3,5-(CF 3 ) 2 C 6 H 3 ; cor = 5,10,15-(C 6 H 5 ) 3 corrolato 3− , 5,10,15-(C 6 F 5 ) 3 corrolato 3− ) were synthesized and characterized by NMR and X-ray diffraction. The visible electronic absorption spectra of these cationic phosphacorroles depend strongly on the coordination environment at phosphorus, and their Lewis acidities are quantified by spectrophotometric titrations. DFT analyses establish that the character of the P-acceptor orbital comprises P–N antibonding interactions in the basal plane of the phosphacorrole. Consequently, the cationic phosphacorroles display unprecedented stability to water and alcohols while remaining highly active and robust Lewis acid catalysts for carbonyl hydrosilylation, C sp3 –H bond functionalization, and carbohydrate deoxygenation reactions. 

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3. Phosphonium Boranes for the Selective Transport of Fluoride Anions across Artificial Phospholipid Membranes

   https://doi.org/10.1002/anie.201914958  

   Park, Gyeongjin; Gabbaï, François P. (February 2020, Angewandte Chemie International Edition)

   Abstract With the view of developing selective transmembrane anion transporters, a series of phosphonium boranes of general formula [p‐RPh₂P(C₆H₄)BMes₂]⁺have been synthesized and evaluated. The results demonstrate that variation of the R group appended to the phosphorus atom informs the lipophilicity of these compounds, their Lewis acidity, as well as their transport activity. Anion transport experiments in POPC‐based large unilamellar vesicles show that these main‐group cations are highly selective for the fluoride anion, which is transported more than 20 times faster than the chloride anion. Finally, this work shows that the anion transport properties of these compounds are extremely sensitive to the steric crowding about the boron atom, pointing to the crucial involvement of the Group 13 element as the anion binding site. 

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4. Assessing the Possibility and Properties of Types I and II Chalcogen Bonds

   https://doi.org/10.3390/cryst13050766  

   Scheiner, Steve (May 2023, Crystals)

   Type I and II halogen bonds are well-recognized motifs that commonly occur within crystals. Quantum calculations are applied to examine whether such geometries might occur in their closely related chalcogen bond cousins. Homodimers are constructed of the R1R2C=Y and R1R2Y monomers, wherein Y represents a chalcogen atom, S, Se, or Te; R1 and R2 refer to either H or F. A Type II (T2) geometry wherein the lone pair of one Y is closely aligned with a σ-hole of its partner represents a stable arrangement for all except YH2, although not all such structures are true minima. The symmetric T1 geometry in which each Y atom serves as both electron donor and acceptor in the chalcogen bond is slightly higher in energy for R1R2C=Y, but the reverse is true for R1R2Y. Due to their deeper σ-holes, the latter molecules engage in stronger chalcogen bonds than do the former, with the exception of H2Y, whose dimers are barely bound. The interaction energies rise as the Y atom grows larger: S < Se < Te. 

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5. Cationic Complexes with Au→Ge Bonds – Synthesis and Carbophilic Reactivity

   https://doi.org/10.1002/ijch.202200036  

   Karimi, Mohammadjavad; Litle, Elishua; Gabbaï†, François P. (September 2022, Israel Journal of Chemistry)

   Abstract As part of our efforts to interface late transition metals with Lewis acidic main group fragments, we have decided to investigate gold complexes bearing halogermanes as Z‐type ligands. Toward this end, we have synthesized complexes of general formula [(o‐(Ph₂P)C₆H₄)₂(Ph)(X)GeAuCl] (X = F, Cl). Experimental and computational analyses indicate the presence of an Au→Ge interaction in both cases. Chloride abstraction reactions have also been investigated. In the case of X = Cl, double chloride abstraction with AgSbF₆affords a putative dication that gradually abstracts fluoride from its counterion. This putative dication is also significantly more active as a catalyst than its monocationic analog in alkyne hydroamination reactions. 

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