The synthesis, characterization, and ethylene reactivity of a nickel-activated α-cyano-β-ketoiminate complex with B(C 6 F 5 ) 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(C 6 F 5 ) 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(C 6 F 5 ) 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 13 C 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.
The photophysics of the mono- and homobimetallic complexes of tungsten benzylidyne has been examined by using absorption and emission. Theoretical calculations were carried out to gain further understanding of these novel molecular systems.
Two α‐iminocarboxamidato‐nickel(II) complexes containing ligands with several CF3 groups were synthesized and characterized by NMR spectroscopy, elemental analysis, and density functional theory (DFT) calculations. Surprisingly, the prepared complexes were inactive toward ethylene oligo/polymerization reactions upon activation attempts with common lewis acid co‐catalysts such as B(C6F5)3 and BF3. Quantum chemistry calculations were employed to reveal that adduct formation is thermodynamically favored for small Lewis acids such as BF3 due to the sterically demanding ligand environment of the complex, confirming the experimental findings. DFT results associate the lack of polymerization activity with a highly unfavorable steric environment, undesirable London dispersion interactions between the ligands, and a strong electrostatic stabilization caused by the employed ligands. Our findings should help future researchers to identify necessary electronic and steric requirements for the compounds to generate active Ni(II) catalysts for ethylene oligo/polymerization activated by suitable boron Lewis acids.
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