KINETIC EPR STUDIES OF THE DECAY OF TERT-BUTYL ALKOXY, SILYLOXY, GERMYLOXY, AND STANNYLOXY NITROXIDES

The kinetics of decomposition of oxynitroxides Me3CN(O.)OMR3, with R3M = Me3C, Bu3Sn, Ph3Ge, and Ph3Si, has been studied by EPR at different temperatures, and the activation parameters have been determined. While the first nitroxide undergoes cleavage at the nitrogen-oxygen bond more readily than at the nitrogen-carbon bond, the organometallic nitroxides essentially fragment with elimination of a tert-butyl radical with rates of fragmentation increasing, at ordinary temperatures, along the sequence Ph3Ge < Ph3Si < Ph3Sn. A very large reduction of the frequency factor for the decomposition was observed on descending the periodic table. This has been explained in terms of an equilibrium between the nitroxide adduct and its dimer; experimental evidence supporting the existence of this equilibrium has been obtained.