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We describe the synthesis of [o-Ph2P(＝O)(C6H4)SbPh3]+ ([2]+), an intramolecularly base-stabilized stibonium Lewis acid which was obtained by reaction of [o-Ph2P(C6H4)SbPh3]+ with NOBF4. This cation reacts with fluoride anions to afford the corresponding fluorostiborane o-Ph2P(＝O)(C6H4)SbFPh3, the structure of which indicates a strengthening of the P＝O → Sb interaction. When deployed in fluoride-containing POPC unilamellar vesicles, [2]+ behaves as a potent fluoride anion transporter whose activity greatly exceeds that of [Ph4Sb]+. [ABSTRACT FROM AUTHOR]

Bifunctional Lewis acidic group 15 compounds have emerged as appealing platforms for anion sensing and organocatalysis. As part of our interest in the chemistry of these compounds, we have now compared the catalytic properties of [o-(MePPh2)C6H4SbPh2]+ ([3]+), [o-(PPh2)C6H4SbPh3]+ ([4]+), [o-(MePPh2)C6H4SbPh3]2+ ([5]2+), and [o-C6H4(SbMePh2)2]2+ ([6]2+) using the transfer hydrogenation of 2-phenyl-quinoline and 3-bromoquinoline with a Hantzsch ester benchmark reactions. This study, which also involved an evaluation of the catalytic properties of [Ph4Sb]+ and [Ph3MeP]+, shows that antimony cations are generally more active than their phosphorus counterparts and neutral stiboranes. Our results also demonstrate that dicationic systems such as [6]2+ are superior activators. [ABSTRACT FROM AUTHOR]

In the context of our work on electron deficient group 15 cations as Lewis acid catalysts, we have synthesized the triflate salts of a series of tetraarylstibonium cations of general formula [ArSbPh3]+ with Ar = Mes (4+), o-(dimethylamino)phenyl (5+), and o-((dimethylamino)methyl)phenyl (6+). These new cationic antimony derivatives, along with the known [Ph4Sb]+ (1+), 1-naphthyltriphenylstibonium (2+), and [(Ant)SbPh3]+ (3+), have been evaluated as catalysts for the cycloaddition of oxiranes and isocyanates under mild conditions. While all stibonium cations favor the 3,4-oxazolidinone products, the reactivities of 5+ and 6+ are hindered by the ancillary amino donor which quenches the Lewis acidity of the antimony center. A comparison of the other stibonium cations shows that 4+ is the most selective catalyst. [ABSTRACT FROM AUTHOR]

In a continuation of our investigations into the unusual properties of antimony-based ligands, we have decided to investigate the structure of the complexes formed by the tetradentate ligands (o-(Ph2P)C6H4)3E (E = P (1), As (2), Sb (3)) with NiCl2. We observed that the structure of the resulting complexes depends on the nature of the central pnictogen atom E, with the phosphorus- and arsenic-based systems adopting ionic structures of the type [ClNi(o-(Ph2P)C6H4)3E][Cl] (E = P ([4][Cl]), As ([5][Cl])) while the known antimony complex ClNi(o-(Ph2P)C6H4)3SbCl (6-Cl) is molecular, with a chloride anion bound to the antimony atom trans from the nickel atom. Using both structural and computational arguments, we propose that the Lewis acidic behavior of the antimony atom in the cation [ClNi(o-(Ph2P)C6H4)3Sb]+ ([6]+) which as been structurally characterized as its [BPh4]− salt, originates in part from the steric compression imposed by the rigid ligand buttresses and the larger size of antimony. This steric compression pushes the antimony atom of [6]+ toward a geometry that is closer to that of a trigonal-base pyramid, setting the stage for the coordination of a ligand trans from the nickel atom as in 6-Cl. Coordination of the chloride ligand also benefits from an accumulation of positive character at the antimony atom of [6]+ which is a assigned to the polarizable and electron-releasing nature of this heavy pnictogen. [ABSTRACT FROM AUTHOR]

We describe the synthesis of [ o -Ph 2 P(O)(C 6 H 4 )SbPh 3 ] + ([2] + ), an intramolecularly base-stabilized stibonium Lewis acid which was obtained by reaction of [ o -Ph 2 P(C 6 H 4 )SbPh 3 ] + with NOBF 4 . This cation reacts with fluoride anions to afford the corresponding fluorostiborane o -Ph 2 P(O)(C 6 H 4 )SbFPh 3 , the structure of which indicates a strengthening of the PO → Sb interaction. When deployed in fluoride-containing POPC unilamellar vesicles, [2] + behaves as a potent fluoride anion transporter whose activity greatly exceeds that of [Ph 4 Sb] + .

In a continuation of our investigations into the unusual properties of antimony-based ligands, we have decided to investigate the structure of the complexes formed by the tetradentate ligands (o-(Ph 2 P)C 6 H 4 ) 3 E (E = P (1), As (2), Sb (3)) with NiCl 2 . We observed that the structure of the resulting complexes depends on the nature of the central pnictogen atom E, with the phosphorus- and arsenic-based systems adopting ionic structures of the type [ClNi(o-(Ph 2 P)C 6 H 4 ) 3 E][Cl] (E = P ([4][Cl]), As ([5][Cl])) while the known antimony complex ClNi(o-(Ph 2 P)C 6 H 4 ) 3 SbCl (6-Cl) is molecular, with a chloride anion bound to the antimony atom trans from the nickel atom. Using both structural and computational arguments, we propose that the Lewis acidic behavior of the antimony atom in the cation [ClNi(o-(Ph 2 P)C 6 H 4 ) 3 Sb] + ([6] + ) which as been structurally characterized as its [BPh 4 ] - salt, originates in part from the steric compression imposed by the rigid ligand buttresses and the larger size of antimony. This steric compression pushes the antimony atom of [6] + toward a geometry that is closer to that of a trigonal-base pyramid, setting the stage for the coordination of a ligand trans from the nickel atom as in 6-Cl. Coordination of the chloride ligand also benefits from an accumulation of positive character at the antimony atom of [6] + which is a assigned to the polarizable and electron-releasing nature of this heavy pnictogen.