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Updated: Jul 15, 2026

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of Phosphorus(I)
Published on: November 22, 2016
Monocyclic di- and triphosphinophosphonium cations: new foundational frameworks for catena-phosphorus chemistry
C Adam Dyker1, Neil Burford, Gabriel Menard
1Department of Chemistry and Atlantic Region Magnetic Resonance Center, Dalhousie University, Halifax, Nova Scotia B3H 4J3, Canada.
Abstract:
The synthesis and characterization for trifluoromethanesulfonate (triflate) salts of the first definitive examples of cyclotriphosphinophosphonium and cyclodiphosphinophosphonium cations are described, representing new prototypical frameworks in the rational and systematic development of catena-phosphorus chemistry. Addition of methyl triflate (MeOTf) or triflic acid (HOTf) to cyclotetraphosphines (tBuP)4 (1a) or (CyP)4 (1b) gives [(tBuP)3PtBuMe][OTf] (2a[OTf]), [(CyP)3PCyMe][OTf] (2b[OTf]), [(tBuP)3PtBuH][OTf] (3a[OTf]), and [(CyP)3PCyH][OTf] (3b[OTf]), respectively. Cyclotriphosphine (tBuP)3 (4a) reacts with HOTF or Me2PCl/Me3SiOTf to give the ring expanded cations 3a[OTf] and [(tBuP)3PMe2][OTf] (5[OTf]), respectively, but reactions with MeOTf and HCl give cyclic diphosphinophosphonium cation [(tBuP)2PtBuMe][OTf] (6a[OTf]) and ring-opened triphosphine HtBuP-PtBu-PtBuCl (7), respectively. The analogous diphosphinophosphonium cation [(CyP)2PCyMe][OTf] (6b[OTf]) is formed along with 2b[OTf] in reactions of MeOTf with (CyP)3 (4b). Compounds 2a[OTf], 2b[OTf], 3a[OTf], 5[OTf], and 6a[OTf] have been crystallographically characterized. 1H NMR spectra of 2a[OTf], 2b[OTf], 5[OTf], and 6a[OTf] demonstrate that 3JPH coupling is only observed for methyl protons if they are in a cis orientation to the lone pairs on the adjacent phosphine sites.
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