Issue Date: June 27, 2016
Stable phosphorus carbene analog debuts
Carbenes were once thought to be transient species featuring a neutral carbon with a pair of unshared electrons that formed during chemical reactions. Given the instability, the best chemists could do was invoke them by proposed reaction mechanisms. With time, researchers designed molecular frameworks to house carbenes so that they were persistent enough to be isolated, namely N-heterocyclic carbenes and cyclic alkyl-amino carbenes. These molecules now serve as ligands to bind and stabilize metals and as organocatalysts. Phosphinidenes, the phosphorus analogs of carbenes, are now following a similar course of development. After years of working with transient phosphinidenes, a team led by Guy Bertrand of the UCSD-CNRS Joint Research Chemistry Laboratory at the University of California, San Diego, has prepared the first phosphinidene that’s stable for weeks at room temperature (Chem 2016, DOI: 10.1016/j.chempr.2016.04.001). As with carbenes, the secret to making a stable phosphinidene has been finding just the right combination of substituents––a π-donating phosphorus substituent and superbulky aryl groups. Without the steric protection, the phosphinidene dimerizes and extinguishes itself. In preliminary reactions, the team found that the electron lone pair enables the phosphinidene to undergo addition reactions with alkenes and isonitriles.
- Chemical & Engineering News
- ISSN 0009-2347
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