Molecular pyramids - from tetrahedranes to [6]pyramidanes

The study of 3D architectures at a molecular scale has fascinated chemists for generations. This includes molecular pyramids with all-carbon frameworks, such as trigonal, tetragonal and pentagonal pyramidal geometries. A small number of substituted tetrahedranes and all-carbon [4]-[5]pyramidanes have been experimentally generated and studied. Although the hypothetical unsubstituted parent [3]-[6]pyramidanes have only been explored computationally, the formal replacement of carbon vertices with isolobal main group element fragments has provided a number of examples of stable hetero[m]pyramidanes, which have been isolated and amply characterized. In this Review, we highlight the synthesis and chemical properties of [3]-[6]pyramidanes and summarize the progress in the development of chemistry of pyramid-shaped molecules. Pyramidanes are curious molecules. The tetrahedranes and the [4]-[6]pyramidanes exhibit molecular structures derived from trigonal to hexagonal pyramids. Examples of these pyramidanes are presented and their structural, spectroscopic and chemical features are described.

Automated summary

The study of 3D architectures at a molecular scale, specifically molecular pyramids with all-carbon frameworks and various geometries, has been a fascinating subject for chemists. While some substituted forms of tetrahedranes and all-carbon [4]-[5]pyramidanes have been experimentally generated and explored, the hypothetical unsubstituted parent [3]-[6]pyramidanes have primarily been studied computationally. However, the replacement of carbon vertices with isolobal main group element fragments has resulted in stable hetero[m]pyramidanes that have been successfully synthesized and characterized.