Concerted steric and electronic effects on α-diimine nickel- and palladium-catalyzed ethylene polymerization and copolymerization

For transition metal-based olefin polymerization catalysts, ligand steric and electronic effects can strongly influence important catalytic properties. However, the simultaneous tuning of both steric and electronic effects has not been explored in most of the previous studies. In this contribution, a strategy to tune the ligand electronic and steric effects in a concerted fashion is reported. In such a system, both dibenzhydryl groups and multiple methoxy/fluoro groups were installed in α-diimine ligands. In addition to strongly influencing ligand electronics, the methoxy/fluoro groups can interact with the dibenzhydryl groups and efficiently increase ligand sterics. In ethylene polymerization, this concurrent tuning of electronic and steric effects can lead to simultaneous enhancement of several parameters (activity, stability, polymer molecular weight, melting point, branching density) for both the nickel and palladium catalysts. The effectiveness of this strategy is highly attractive for future studies in other catalytic systems.

Comprehensive studies of the ligand electronic effect on unsymmetrical α-diimine nickel(ii) promoted ethylene (co)polymerizations

The ligand electronic effects on the horizontal axis and vertical axis are systematically disclosed in unsymmetrical α-diimine Ni(ii)-promoted ethylene polymerization and copolymerization reactions.

A continuing legend: the Brookhart-type α-diimine nickel and palladium catalysts

Here we will summarize some of the recent advances in α-diimine ligand developments, as well as some new and challenging monomers that this class of catalysts can address through these ligand improvements.

Synthesis and characterization of aminopyridine iron(ii) chloride catalysts for isoprene polymerization: sterically controlled monomer enchainment

Aminopyridine iron(ii) chloride complexes coordinating a type of flexible ligand are reported as precursors for controlled polymerization of isoprenes.

Preparation and in situ chain-end-functionalization of branched ethylene oligomers by monosubstituted α-diimine nickel catalysts

Chain-end-functionalization of (highly) branched ethylene oligomers was achieved in situ with the most/least bulky α-diimine nickel catalysts for the first time.

Synthesis of poly(α-olefins) containing rare short-chain branches by dinuclear Ni-based catalysts

Chain walking mechanism with regard to dinuclear Ni-based catalyst stereoisomers in the polymerization of α-olefins: the effects of bridge, backbone and ortho-substituents.