Polyhedral skeletal electron pair theory
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In chemistry, the polyhedral skeletal electron pair theory or Wade's rules or Wade / Mingos rules are electron counting rules that apply to electron-poor cages such as boron hydrides which consist of many boron atoms linked together.
For clusters of transition metals the rules are
- closo or closed structures have 12n + 2(n +1) electrons
- nido or nest structures have 12(n-1) + 2(n+1) electrons
- arachno or spider web like structures have 12(n-2) + 2(n+1) electrons
While for main group clusters such as boranes and carboranes the rules are
- closo or closed structures have 2n + 2(n +1) electrons
- nido or nest structures have 2(n-1) + 2(n+1) electrons
- arachno or spider web like structures have 2(n-2) + 2(n+1) electrons
The number of electrons per cluster are worked out using the same rules as are used for the 18-Electron rule.