Novel (n + 1 + 1) cycloaddition reactions; the formation of cyclic tetraphosphonium dications with four linked phosphorus atoms and an organic backbone.

In the presence of SnCl(2), a novel cycloaddition of two moles of R'PCl(2) (R' = Et or Ph) to a diphosphane has been achieved, forming a cyclic dication with four linked phosphorus atoms and an organic backbone; two of these species have been characterised by single-crystal X-ray diffraction, and the mechanism of the reaction has been established.