Every once in a while, one encounters a molecule which instantly makes an interesting point. Thus Ruthenium is ten electrons short of completing an 18-electron shell, and it can form a complex with benzene on one face and a ligand known as trimethylenemethane on the other.
- G.E. Herberich, and T.P. Spaniol, "Trimethylenemethane complexes of ruthenium via the trimethylenemethane dianion", Journal of the Chemical Society, Chemical Communications, pp. 1457, 1991. http://dx.doi.org/10.1039/C39910001457