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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. 

Our interests in the chemistry of atypical main group Lewis acids have led us to devise strategies that augment the affinity of chalcogen-bond donors for anionic guests. In this study, we describe the oxidative methylation of diaryltellurides as one such strategy along with its application to the synthesis of [Mes(C 6 F 5 )TeMe] + and [(C 6 F 5 ) 2 TeMe] + starting from Mes(C 6 F 5 )Te and (C 6 F 5 ) 2 Te, respectively. These new telluronium cations have been evaluated for their ability to complex and transport chloride anions across phospholipid bilayers. These studies show that, when compared to their neutral Te( ii ) precursors, these Te( iv ) cations display both higher Lewis acidity and transport activity. The positive attributes of these telluronium cations, which originate from a lowering of the tellurium-centered σ* orbitals and a deepening of the associated σ-holes, demonstrate that the redox state of the main group element provides a convenient handle over its chalcogen-bonding properties.