Making acids behave like bases
A research team lead by Guy Bertrand, a distinguished professor of chemistry at the University of California at Riverside,
recently reported on the use of boron-based compounds to build Lewis bases.
The researchers reported on the synthesis and characterization of a neutral tricoordinate organoboron isoelectronic with amines.
The neutral tricoordinate boron derivative acted as a Lewis base and underwent one-electron oxidation into the corresponding
radical cation. These compounds were the parent borylene and borinylium, respectively, stabilized by two cyclic (alkyl)(amino)
carbenes. Ab initio calculations showed that the highest occupied molecular orbital of the borane and the singly occupied molecular orbital of
the radical cation were essentially a pair and a single electron, respectively, in the p(p) orbital of boron (7).
"The result is totally counterintuitive," said Bertrand, in an July 28, 2011, University of California at Riverside press
release. "...But we have achieved it. We have transformed boron compounds into nitrogen-like compounds. In other words, we
have made acids behave like bases."
Nitrogen- or phosphorus-based compounds are commonly used as ligands in catalysts. "The trouble with using phosphorus-based catalysts is that phosphorus is toxic and it can contaminate
the end products," Bertrand said. "Our work shows that it is now possible to replace phosphorus ligands in catalysts with
boron ligands. And boron is not toxic," he added. Researchers at Philipps–Universitat in Marburg, Germany, also contributed
to the study.
References
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2. S. Ritter, Chem. & Eng. News
89 (42), 13 (2011).
3. J.M. John and S.H. Bergens, Angew. Chem. Int. Ed.
50 (44), 10377–10380 (2011).
4. K.C. Harper and M.S. Singer, Science
333 (6051), 1875–1878 (2011).
5. F. Meyer nd C. Limber, eds., "Preface" in Organometallic Oxidation Catalysis (Springer, New York, 2007).
6. J.T. Yates, Jr., et al., Science
333 (6043), 736–739 (2011).
7. G. Bertrand, Science
333 (6042), 610–613 (2011).
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