Frustrated radicals

Persistent nitroxide radicals can be generated by exploiting the ability of a frustrated Lewis pair (FLP) to capture nitric oxide through the synergistic action of the acid-base species. FLPs have both an acid and a base component but their bulky substituents preclude them from getting close enough to neutralize one another, hence their frustration. This frustration is equivalent to pent up reactivity, of course. Now, researchers in Germany and the US have shown that FLPs comprising dimesitylphosphanes and bis(pentafluorophenyl)borane can trap nitric oxide to form novel radicals. These materials can in turn abstract hydrogen from cyclohexadiene and toluene, leading to O-substituted alkoxyamine derivatives, a potentially useful step for organic synthesis.