[P3Se4]+: A Binary Phosphorus–Selenium Cation

Although a fairly large number of binary group 15/16 element cations have been reported, no example involving phosphorus in combination with a group 16 element has been synthesized and characterized to date. In this contribution is reported the synthesis and structural characterization of the first example of such a cation, namely a nortricyclane‐type [P₃Se₄]⁺. This cation has been independently discovered by three groups through three different synthetic routes, as described herein. The molecular and electronic structure of the [P₃Se₄]⁺ cage and its crystal properties in the solid state have been characterized comprehensively by using X‐ray diffraction, Raman, and nuclear magnetic resonance spectroscopies, as well as quantum chemical calculations.