The synthesis, characterization, and ethylene reactivity of a nickel-activated alpha-cyano-beta-ketoiminate complex with B(C6F5)(3) is reported. The X-ray diffraction studies of the Ni complex 1 revealed that a weak interaction between the distal aryl rings of the N-terphenyl moiety could be responsible for the low molecular weights and highly branched microstructure of the polyethylene compounds. In addition, a supported single-site Lewis acid based on reduced graphene oxide, rGO-O-B(C6F5)(2), was used, and we studied its ability to activate complex 1 for the generation of polyethylene/reduced graphene oxide nanocomposites. The supported catalyst rGO-B(C6F5)(2)-Ni-CN exhibited an ethylene polymerization activity that was approximately 2 times greater than that of the unsupported system. Meanwhile, the microstructure of the polyethylene nanocomposites was analyzed by C-13 NMR, revealing the presence of a low molecular weight and hyperbranched motif due to the presence of sec-butyl groups. These results indicated that the graphene support actively participated in the polymerization process. The morphological examinations of the nanocomposites by TEM revealed the effective exfoliation and good dispersion of rGO in the polymer matrix at the nanoscale level.