For The First Time, A Five-fold Bond

Muchof chemistry is about understanding how bonds are made and broken. Formost of the history of chemistry, only single, double or triple bondswere known. Multiple bonds are particularly important in carbonchemistry, but only certain metals are theoretically capable of morethan triple bonds, said Philip Power, professor of chemistry at UCDavis and senior author on the paper.

The dark red crystals weresynthesized by Tailuan (Peter) Nguyen, a graduate student in Power'slaboratory. The chromium-based compound is stable at room temperaturebut decomposes in the presence of water, and spontaneously ignites whenexposed to air.

To make the compound, Nguyen and Power attachedlarge carbon-based molecules to chromium atoms, constraining how theycould behave. They were then able to coax the chromium atoms to bondwith each other. The multiple bonding was confirmed by X-raycrystallography and magnetic measurements.

As far as we know, no comparable compound exists in nature, Power said.

Inaddition to Nguyen and Power, other authors on the paper werepostdoctoral researcher Andrew Sutton, theorist Marcin Brynda andcrystallographer James Fettinger at the UC Davis chemistry department;and Gary Long, professor of chemistry at the University of Missouri,Rolla. Peter Klavins and Long Pham at the UC Davis physics departmentcarried out magnetic measurements for the study.

The work is published online in Science Express and will appear in the print version of the journal Science later this year.