From the parent phosphinidene–carbene adduct NHCPH to cationic P4-rings and P2-cycloaddition products

Abstract

Reactions of the parent phosphinidene–carbene adduct ^DippNHCPH with chlorophosphanes are reported herein. The obtained ^DippNHC-substituted chlorodiphosphanes, ^DippNHCP–PClR, and the formation of their cationic derivatives, [^DippNHC–PPR]⁺, were also explored. Depending on the steric demand of their substituents, these cations were found to be monomeric [^DippNHC–PP–NⁱPr₂][GaCl₄] or to dimerise to cyclotetraphosphanes [^DippNHC–PP–R]₂[GaCl₄]₂ (R = Ph, NMe₂). For R = NMe₂, this dication is the first isolated example of a tetrasubstituted all-σ³ cyclotetraphosphane. Finally, the hetero-Diels–Alder reactivity of these cations was studied with 2,3-dimethylbuta-1,3-diene and cyclopentadiene, resulting in the isolation of a number of cationic 1,2-diphosphinanes.