A series of highly sterically hindered acenaphthene-based α-diimine nickel complexes with the remote R group in 4-position of diarylmethyl moiety have been synthesized and characterized. Activated with Et 2 AlCl, ethylene polymerization by these nickel complexes is investigated in detail, involving the remote substituent effect and influence of polymerization temperature on catalyst activity, thermal stability, polymer molecular weight, and branching density. These thermostable nickel catalysts are very active (up to 5.1 × 10 6 g•mol −1 •h −1 ) for ethylene polymerization and capable of producing various moderate to highly branched (26−71/1000 C) ultra-high-molecular-weight polyethylenes (UHMWPEs, M w up to 4.5 × 10 6 g•mol −1 ). These polymeric materials with such unique structure show properties characteristic of thermoplastic elastomers, i.e., good elastomeric recovery and high strain at break.

As a promising alternative to thermoset elastomers, thermoplastic elastomers (TPEs) have attracted much attention because of their unique properties, including processability, reusability and recyclability. The synthesis of TPEs based on olefinic building blocks usually requires the use of long chain α-olefins, multiple steps, and/or multiple catalysts. The concept of using only ethylene as feedstock in a single step is fascinating but also very challenging. In this contribution, we report the synthesis of polyethylene-based TPEs through α-diimine nickel-catalyzed ethylene polymerization. The stress-at-break and strain-at-break values of these polyethylene products could be tuned over a very wide range using different nickel catalysts and different polymerization conditions. Most importantly, products with excellent elastic properties could be generated in the screening process.

A series of dinucleating α‐diimine ligands and the corresponding nickel and palladium complexes were synthesized and characterized. The dinucleating α‐diimine ligands are designed to incorporate naphthalene‐, biphenylene‐, and xanthene‐bridged structures, which may lead to different metal–metal distances. The properties of these dinuclear complexes in ethylene polymerization and copolymerization with methyl acrylate are investigated. Higher catalytic activity, higher polyethylene molecular weight, and much lower polyethylene branching density were observed for the dinuclear Ni complexes compared with the mononuclear analogue in ethylene polymerization. For the dinuclear palladium complexes, much more dramatic differences in activity and polyethylene molecular weight were observed. Most interestingly, similar catalytic activities were observed for the dinuclear and mononuclear palladium complexes in ethylene–methyl acrylate copolymerization, whereas only the mononuclear complex was able to incorporate an appreciable amount of the methyl acrylate monomer.

A series of para-phenyl-substituted α-diimine nickel complexes, [(2,6-R 2 -4-PhC 6 H 2 N═C(Me)) 2 ]NiBr 2 (R = i Pr (1); R = Et (2); R = Me (3); R = H (4)), were synthesized and characterized. These complexes with systematically varied ligand sterics were used as precatalysts for ethylene polymerization in combination with methylaluminoxane. The results indicated the possibility of catalytic activity, molecular weight and polymer microstructure control through catalyst structures and polymerization temperature. Interestingly, it is possible to tune the catalytic activities ((0.30-2.56) × 10 6 g (mol Ni·h) −1 ), polymer molecular weights (M n = (2.1-28.6) × 10 4 g mol −1 ) and branching densities (71-143/1000 C) over a very wide range. The polyethylene branching densities decreased with increasing bulkiness of ligand and decreasing polymerization temperature. Specifically, methyl-substituted complex 3 showed high activities and produced highly branched amorphous polyethylene (up to 143 branches per 1000 C).

Bimetallic clusters anchored on thermally stable and high-surface-area supports have gained a wide range of applications in heterogeneous catalysis. Compared to monometallic clusters or large bimetallic nanoparticles, bimetallic clusters show unprecedented catalytic performances due to the modulated electronic and geometric effects arising from the high fraction of surface unsaturated−coordinated metallic atoms and the synergistic effects between two constituting metals. However, even after more than 60 years of efforts, the controlled synthesis of homogeneously distributed bimetallic clusters with well-alloyed structure between two constituting metals remains a tremendous challenge so far. Herein, we present a versatile strategy based on the surface organometallic chemistry concept for synthesizing supported bimetallic cluster catalysts, which is achieved via the hydrogenation of a so-called "double surface organometallic complex". The cooperative decomposition of two surface organometallic fragments in the double surface organometallic complex and their strong interaction with the support enable the formation of well-alloyed bimetallic clusters uniformly dispersed at the surfaces of different supports. This approach can serve as a platform technique for producing a variety of bimetallic clusters with varied compositions on a wide range of supports, such as Al 2 O 3 , TiO 2 , and zeolite. The resulting bimetallic cluster catalysts exhibit remarkably enhanced catalytic performance in benzene hydrogenation as compared to their monometallic counterparts because of highly exposed surface atoms and synergistic effects between constituting metals.

A series of bis(imino)pyridyl iron(II) complexes 1–5 with electron‐donating and ‐withdrawing substituents on the backbone of the ligand have been synthesized and characterized. Activated with methylaluminoxane (MAO), ethylene polymerization by these iron(II) complexes was investigated in detail, involving the electronic effect and influence of reaction conditions on catalyst activity and polymer molecular weight. The electronic perturbations exert great influence on the catalytic activity of ethylene polymerization. Complexes bearing electron‐withdrawing substituents in the 4‐position of the pyridine ring showed the better activity than analogues bearing electron‐donating substituents. However, no clear trend was observed for the dependence of polymer molecular weight on these substituents. In particular, the binuclear iron(III) complex 2′ we obtained by accident displayed a similar catalytic behavior compared to its iron(II) analogue complex 2.

A series of highly active Ir–Sn/SiO2 and Rh–Sn/SiO2 catalysts for ethyl acetate hydrogenolysis to ethanol were prepared from the grafting synthesis based on the surface organometallic chemistry concept.