An elite chemical club has a new member, after a team in Germany found a way to link two boron atoms together with a stable triple bond. Boron joins carbon and nitrogen as one of the few elements in the periodic table known to form stable compounds featuring triple bonds1.
Theory had predicted that such boron structures should be possible, says Holger Braunschweig, a chemist at the University of Würzburg who led the research. After all, nitrogen–nitrogen and carbon–carbon triple bonds are stable: the nitrogen molecules that make up the majority of our air are held together by a triple bond, for example. And boron is next to carbon and nitrogen in the periodic table, so should have comparable properties. “One would expect something similar for boron,” says Braunschweig. “The major problem has been the synthesis.”
Until now, the closest that anyone had come was a molecule made by using a laser to vaporize boron in the presence of carbon monoxide (CO) at very low temperatures2. This compound seemed to incorporate a boron–boron triple bond, surrounded by CO groups, but fell apart at temperatures above about -263 °C.