Ethylene polymerization catalyzed by a cyclophane-diimine-based Ni(II) complex, a quantum/molecular mechanic study

In work, employing quantum/molecular mechanical calculations, we describe the main steps of ethene polymerization reactions catalyzed by a cationic Ni(II) complex, bearing a cyclophane α-diimine ligand. The combination of Density Functional Theory (DFT) and Molecular Mechanics (MM), within the ONIOM approach, was employed to evaluate the molecular structures and energies involved in ethene polymerization. All intermediate and transition state structures, obtained along these elementary step reactions, were treated as representative molecular arrangements of the polymerization process. The steric environment and the electronic influence imposed by the cyclophane ligand were evaluated for all intermediate and transition state structures, and correlated to that observed with the analogous bulky diimine ligand, bis[N-(2,6-diisopropylphenyl)imino]acenaphthene, present in the Brookhart's catalyst.

Theoretical investigation of ethene polymerization reactions catalyzed by cyclophane cationic α-diimine Ni(II) complex, using DFT and MM (ONIOM approach), was employed to evaluate the molecular structures and energies involved in ethene polymerization. Ground, intermediate, and transition state structures obtained along elementary step reactions were treated as representative molecular arrangements of the polymerization process. Front (a) and top (b) views of the ethene coordination transition state, TS 7, and top view of the resulting out-of-plane π-complex 8, [Ni(η2-ethene)(diimine)(nPr)]+.Figure optionsDownload high-quality image (145 K)Download as PowerPoint slideHighlights
► Computational studies on ethene polymerization catalyzed by cyclophane diimine Ni(II) complex.
► A wide sequence of intermediate and transition state models for olefin polymerization.
► Out-of-plane olefin coordination and agostic structures detected.