Asymmetric Cationic [P, O] Type Palladium Complexes in Olefin Homopolymerization and Copolymerization

Abstract

Metal-catalyzed ethylene homopolymerization and ethylene-polar monomer copolymerization to produce new kinds of polyolefins with novel microstructures are of great interest. So far, there are some disadvantages for traditional transition metal catalyst systems. Therefore, it is critical to develop new catalysts or alternative strategies. In recent years, some cationic [P, O] palladium complexes have been demonstrated with the abilities to obtain oligomers and the high molecular weight polymers. Most importantly, these complexes showed high activity and generated polymers with specific microstructures when used for copolymerization of ethylene with industrially relevant polar monomers. This review summarizes several types of high performance cationic [P, O] palladium catalysts in ethylene oligomerization, ethylene homopolymerization and the copolymerization of ethylene with polar monomers. Specially, the regulation of steric and electronic effects at specific sites of the metal complexes was focused.

Synthesis of Various Branched Ultra-High-Molecular-Weight Polyethylenes Using Sterically Hindered Acenaphthene-Based α-Diimine Ni(II) Catalysts

“…A huge amount of late transition metal catalysts have been designed and used for olefin polymerization since Brookhart’s discovery of α-diimine type nickel and palladium catalysts in 1995. − The key to generate the high polymerization activity and high polymer molecular weight using these catalysts is the presence of bulky ortho -aryl substituents in the ligand which could enhance the catalyst stability and retard the chain transfer process. ,, Generally, Brookhart catalysts have a high tendency toward β-hydride elimination and reinsertion, which results in the movement of the metal along the alkyl chain and production of branched polyethylenes. , Moreover, the polymers with various types of branching can also be obtained by tuning the ligand structures and polymerization conditions. − …”

Lysosome-Targeted Phosphine-Imine Half-Sandwich Iridium(III) Anticancer Complexes: Synthesis, Characterization, and Biological Activity

“…Anticancer metallodrugs are continuously developed in the field of bioorganometallic chemistry depending upon the rational design of novel and sophisticated ligand frameworks to obtain effective chemotherapeutic agents with a superior toxicity profile. Among these heavy metal complexes, bidentate chelating ligands bearing phosphorus and/or nitrogen donor atoms have wide applications, such as homogeneous catalysts − and anticancer drugs. − Modifications of the bidentate chelating ligands of anticancer metallodrugs, such as alteration of the steric and electronic properties of the P- or N-bound substituents, are effective strategies to tune the chemical and biological properties of the compounds. Many organometallic anticancer complexes bearing symmetrical phosphorus or nitrogen donor atoms in their bidentate chelating ligands have been reported. − For instance, Quirante et al designed a group of nonplanar cycloplatinated complexes with bidentate phosphine ligand and 2-phenylaniline ligand (Scheme , I ) .…”

Rotation‐restricted strategy to synthesize high molecular weight polyethylene using iminopyridyl nickel and palladium catalyst

“…Particularly, in contrast to early transition metal catalysts, late transition metal catalysts not only could produce branched polyolefins by extensive chain walking process but also generate the functional polyolefins by the copolymerization of olefins with polar monomers due to their low oxophilicity. [2][3][4][5][6][7] In addition to the α-diimine catalysts, some interesting results also have been revealed for [N, N] bidentate iminopyridyl Ni (II) and Pd (II) catalysts. [8][9][10] For example, Laine discovered that the dimeric iminopyridyl Ni (II) catalysts generated low molecular weight polyethylene (Scheme 1, I, M n < 3,500 at temperature above 20 C).…”