P5X2+ (X=Br, I), a Phosphorus-Rich Binary P−X Cation with a C2v-Symmetric P5 Cage This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie. We thank Prof. H. Schnöckel for valuable discussions.

Insertion of the intermediately formed carbene-analoguous PX2+ ion (X=Br, I) into one of the P−P bonds of the P4 tetrahedron led to the P5X2+ ion (see structure of the Br derivative)—the first example of the previously unknown class of phosphorus-rich binary P−X cations.