nido ‐Five‐Vertex Clusters: In and Out of Boron Chemistry

During the early days of borane chemistry B 5 H 9 was considered to be the stable pentaborane and although a BH vertex is isolobal with a naked P vertex, it is only recently that the first nido ‐five‐vertex compounds with a naked phosphorus atom at the apical position were discovered. The most recent example is a valence isomer of the hitherto unknown triphosphacyclopentadienyl cation. These results shed light on the relative stability of planar and three‐dimensional Cp + derivatives (see picture).