Lead joins the aromatic ring club

Scientists in Japan have successfully incorporated an atom of lead into an aromatic molecule - the heaviest metal so far to be 'aromatised'. The finding could result in novel structures with useful electron-donating characteristics, with potential applications in areas such as catalysis or optoelectronics.

Forming a stable aromatic ring with an element such as lead is difficult because of the wide discrepancy in the size of the electronic orbitals of the metal and the carbon atoms (6p and 2p orbitals, respectively) in the ring. A certain degree of overlap is needed for electrons to be shared evenly around the ring - a requirement for aromaticity. If one orbital is huge and the other tiny, getting overlap is a tall order.  More...

http://www.rsc.org/chemistryworld/News/2010/April/15041002.asp