Ligand-Enhanced Aliphatic Carbon-Carbon Bond Activation of Nitroxides by Rhodium(H) Porphyrin

Rh(tmp) underwent Ph3P-enhanced aliphatic carbon carbon bond activation with various nitroxides. (Ph3P)Rh(tmp), rapidly formed from Rh(tmp) and Ph3P, enhanced the rate, selectivity, and yield in comparison to Rh(tmp). From kinetic studies, the rate of reaction showed a first-order dependence on both Rh(tmp) and TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-1-oxyl) and saturation kinetics on Ph3P. The rate enhancement of (Ph3P)Rh(tmp) over Rh(tmp) was estimated to be about 11 at 70 degrees C.