An Acyclic Arsenium Cation Stabilised by a Single P–As π‐Interaction and a Cyclic Diphosphinophosphonium Salt

Abstract

Stable acyclic arsenium cations R 2 As + ,isoelectronic analogues of germylenes,a re rare in comparison to the corresponding phosphenium cations.T he first example of ad iphosphaarsenium salt, [{(Dipp) 2 P} 2 As][Al{OC-(CF 3 ) 3 } 4 ]·1 1 = 2 PhMe,isdescribed. This salt exhibits remarkable stability due to the delocalisation of alone pair from aplanar phosphorus centre into the vacant p-orbital at arsenic;t he bonding in 2 has been probed by DFT calculations.Anattempt to synthesise an analogous diphosphaphosphenium salt unexpectedly generated the cyclic phosphonium salt [cyclo-{(Mes)P} 2 P(Mes) 2 ][BAr F 4 ]·CyMe through the cyclisation of ap utative phosphine-substituted diphosphene cation intermediate.

Kinetically Stabilized Diarylpnictogenium Ions

“…Unlike those, pnictogenium ions are also strong electrophiles, which can be attributed to the positive charge that attracts any nucleophile present. Consequently, the vast majority of phosphenium ions, [R 2 P] + , [2–33] arsenium ions, [R 2 As] + , [34–51] stibenium ions, [R 2 Sb] +[52–59] and bismuthenium ions, [R 2 Bi] + , [60–72] reported in the literature are either affected by ion pairing or stabilized by electron‐rich ligands or substituents, which inter‐ or intramolecularly fill the vacant p‐orbital. These electronically stabilized pnictogenium ions often have a dramatically reduced Lewis acidity and cannot be regarded as genuine 6 VE species as they fulfill or even exceed the octet rule.…”