Tetrel Cyclic Polyene Dianions as Precursors for the Pyramidal Clusters and Multi‐Decker Sandwiches

Abstract In this review, the current state of affairs in the application of tetrel cyclic polyene dianions, such as cyclobutadiene dianion and cyclopentadiene dianion, in the preparation of pyramidal clusters (pyramidanes) and multi‐decker sandwiches is overviewed. The synthesis of both main group element and transition metal derivatives of the latter complexes is presented, along with a discussion of their peculiar structural and bonding features. The preference for either pyramidanes or sandwiches, depending on the nature of the central atom (main group element vs. transition metal), is also discussed.