We report cationic complexes of arsenic and antimony with the tris(2-pyridyl)phosphine ligand. Chloride ion abstraction from AsCl using TMSOTf in the presence of the ligand gives [P(Pyr)As][OTf], in which the trication adopts a C symmetric cage structure. The reaction proceeds via the intermediate [P(Pyr)AsCl][OTf], which undergoes chloride exchange to give [P(Pyr)As][OTf] and [P(Pyr)AsCl][OTf]. The rearrangement reaction has been supported by the isolation of the antimony mono fluoride derivative [P(Pyr)SbF][OTf]. The asymmetric axial lone pairs in derivatives of [P(Pyr)Pn] are electronically separated. The HOMO-1 (for arsenic) and HOMO (for antimony) represent the major contribution to the phosphine lone pair indicating the possibility for nucleophilic behaviour despite the +3 charge. Less accessible is the HOMO-7, which represents the lone pair at arsenic or antimony, respectively.

Compounds of the generic formula [PhPL][OTf]2 with L = bipyridine (bipy) and 4,4′-di(tert-butyl)-2,2′-bipyridine (Bbipy) and [PhPL2][OTf]2 with L = 4-dimethylaminopyridine (dmap), tricyclohexyl-thiophosphine, and tricyclohexyl-selenophosphine have been prepared by the reaction of dichlorophenylphosphine with two equivalents of trimethylsilyl triflate and the respective ligand. The new complexes of the phenylphosphine dication with this variety of ligands expands the scope of coordination complexes involving phosphorus as an acceptor.

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