Henry Rzepa's Blog

Whilst clusters of carbon atoms are well-known, my eye was caught by a recent article describing the detection of a cluster of boron atoms, B₄₀ to be specific.[cite]10.1038/nchem.1999[/cite] My interest was in how the σ and π-electrons were partitioned. In a C₄₀, one can reliably predict that each carbon would contribute precisely one π-electron. But boron, being more electropositive, does not always play like that. Having one electron less per atom, one might imagine that a fullerene-like boron cluster would have no π-electrons. But the element has a propensity[cite]10.1039/B911817A[/cite] to promote its σ-electrons into the π-manifold, leaving a σ-hole. So how many π-electrons does B₄₀ have? These sorts of clusters are difficult to build using regular structure editors, and so coordinates are essential. The starting point for a set of coordinates with which to compute a wavefunction was the supporting information. Here is the relevant page: The coordinates are certainly there (that is not always the case), but you have to know a few tricks to make them usable.

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