“…Other synthetic strategies for P,C cage structures include cycloaddition reactions of phosphaalkynes with cyclobutadienes6 ( III ), thermolysis of 1,2,3‐tris(pentamethylcyclopentadienyl)cyclotriphosphene7 ( IV ) and reactions of triphosphabenzene with phosphenium salts8 ( V ). P,C cage structures containing other heteroatoms directly bound to phosphorus,9 such as oxygen10 and nitrogen,11 are also known. In contrast to P,C cages, for which ring expansions, rearrangements and coordination chemistry have been reported, related N,P,C systems have not been studied intensively due to a lack of facile synthetic protocols.…”