Polyhedral cluster

A connected molecular framework described by a polyhedral vertex graph. Terminal ligands are distinguished from atoms belonging to the skeletal framework.

A polyanionic main-group cluster whose electron count can support delocalized skeletal bonding. Localized lone pairs must be separated before applying a polyhedral count.

An open cluster framework formally obtained by removing two vertices from a closo parent. Its usual electron count is $n+3$ skeletal pairs; hydrogen positions and cage distortions require additional structural information.

An open cluster framework formally obtained by removing one vertex from a closo parent. In the usual electron-counting model, an $n$-vertex nido framework has $n+2$ skeletal pairs.

A closed deltahedral cluster described by $n+1$ skeletal electron pairs in the usual Wade model. borane examples include $[{\mathrm{B}}_{12}{\mathrm{H}}_{12}{]}^{2-}$.