Monday, June 18, 2012

Boron Joins Triple Bond Club

Scientific American:

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 bonds.

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 temperatures. This compound seemed to incorporate a boron–boron triple bond, surrounded by CO groups, but fell apart at temperatures above about -263 °C.
Braunschweig’s compound, by contrast, is stable up to 234 °C, if kept isolated from the air. “Under inert conditions, this is a very stable molecule,” says Braunschweig.
It's interesting to me that it has taken so long for somebody to manage the feat, considering that theory had predicted the possibility.  It sounds like it is pretty tough to do thus far.

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