The product pattern of the aforementioned reactions implies that single-electron redox reactions between the Pd(I) aryl complex and these organic halides might have occurred. It can be proposed that the single-electron transfer reactions between 2 and the organic halides R-X might form the Pd(II) species (IPr)Pd(Ar Trip -CF3-p)(X) (A) and the organic radical R • (Figure ). The relatively long lifetimes of alkyl and benzylic radicals as compared to aryl radicals might allow them to combine with intermediate A, yielding the Pd(III) species (IPr)Pd(Ar Trip -CF3-p)(X)(R) (B). Further reductive elimination reactions from B can yield the crosscoupling products R-Ar Trip -CF3-p (5-R) and the Pd(I) species (IPr)PdX. Proposals on radical combination with Pd(II) species to form Pd(III) species and C-X bond-forming reductive elimination from Pd(III) species have been known. There is also report on C-X bond-forming reductive elimination from isolable mononuclear Pd(III) species. Alternatively, B might undergo Pd-C(aryl) bond homolysis reaction to form the aryl radical [p-CF3-Ar Trip ] • and the Pd(II) species (IPr)Pd(R)(X). The aryl radical can then transform into 3-CF3 and 4 upon hydrogen-atom abstraction reactions. When R is an alkyl group containing β-hydrogen, (IPr)Pd(R)(I) might undergo β-hydride elimination to yield ). As to the reaction with 3,5-dimethylphenyl iodide, the resulting aryl radical [3,5-Me2C6H3] • is highly reactive and might quickly perform hydrogen-atom-abstraction reaction with the benzylic C-H bonds of the Trip groups on A, giving 1,3-dimethylbenzene and the Pd(II) aryl intermediate C that could decompose into 3-CF3 and 4. Indeed, our studies showed that the Pd(II) aryl species [(IPr)Pd(Ar Trip - CF3-p)] 1+ , which was generated by single-electron-oxidation of 2 with AgBF4, is unstable at ambient temperature and can convert into a complex mixture containing 3-CF3 and 4 (Figures and). The high lability of low-coordinate Pd(II) hydrocarbyl species with NHC ligation has been well documented in literature. The aryl homo-coupling product bis(3,5-dimethylphenyl) might come from the interaction of in-situ formed Pd(0) species with 3,5-dimethylphenyl iodide.