Heavy Tetrel Clusters Based on the Bicyclobutane Framework: Bicyclo[1.1.0]butanes, [1.1.1]Propellanes, and Tricyclo[2.1.0.0 ]pentanes.

In this review, the current state of affairs in the novel field of the group 14 element clusters based on the bicyclo[1.1.0]butane framework, namely, bicyclo[1.1.0]butane, [1.1.1]propellane, and tricyclo[2.1.0.0 ]pentane derivatives, are overviewed. Structural similarities and differences between these three classes of highly strained polycyclic compounds are considered from the viewpoint of the critically important nature of their bridgehead bonds. Synthetic strategies towards bicyclo[1.1.0]butanes, [1.1.1]propellanes, and tricyclo[2.1.0.0 ]pentanes, as well as their peculiar structural and bonding features, and specific reactivity, are also presented and discussed in this review.