Chemists are, by and large, fascinated with cyclic structures (blame Kekule falling asleep in front of the fire and dreaming of serpents if you wish…) and I think it’s fair to say that benzene is the granddaddy of them all. Although it’s now possible to make really big molecular rings and to interlock macrocycles in almost any way imaginable (catenanes, rotaxanes, Borromean rings, knots, etc…), the bonding of six carbon atoms to form a perfect planar hexagon is somewhat sacred in organic chemistry.
I’m always a little perturbed, therefore, when I see how people fiddle about with this magic structure, this bastion of aromaticity, and substitute one of the carbon atoms for something a little more exotic… a metal for example. Metallabenzenes are certainly not new, but in the Early View articles posted at Angewandte Chemie, Zhang and co-workers report the first thermally stable ruthenabenzenes – benzene analogues in which a carbon atom has been replaced by ruthenium (and all of the associated spinach hanging off it).
According to the authors, they know of no other first- or second row transition metal-containing metallabenzenes that are stable at room temperature, making these examples the first of their kind. Perhaps there’s a reason for that, I don’t know… it just has an eerie ring to it.
Stuart Cantrill (Associate Editor, Nature Nanotechnology)