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.

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The copper(I)-catalyzed alkylation of electron-deficient polyfluoroarenes with N-tosylhydrazones and diazo compounds has been developed. This reaction uses readily available starting materials and is operationally simple, thus representing a practical method for the construction of C(sp(2) )-C(sp(3) ) bonds with polyfluoroarenes through direct C-H bond functionalization. Mechanistically, copper(I) carbene formation and subsequent migratory insertion are proposed as the key steps in the reaction pathway.

A highly efficient and operationally simple palladium-catalyzed formal [4 + 1] annulation reaction has been developed. The reaction is featured by the formation of two different C−C bonds on a carbenic center. It represents a concise method for the synthesis of a wide range of polycyclic aromatic hydrocarbons (PAHs) and 1H-indenes with easily available (trimethylsilyl)diazomethane as the carbene source. Metal carbene migratory insertion and C(sp 2 )−H bond activation are proposed as the key steps in this transformation. The reaction further demonstrates the versatility of the carbene-based coupling in combination with various transition-metal-catalyzed transformations.

A Cu(I)-catalyzed cross-coupling reaction of bis(trimethylsilyl)diazomethane and benzoxazoles/oxazoles is reported. A wide range of functional groups can be tolerated in this transformation. This reaction provides a new method to directly introduce a 1,1-bis(trimethylsilyl)methyl group into heteroaromatic C−H bonds. Subsequent transformations of 1,1-bis(trimethylsilyl)-methylated heteroaromatic compounds are also presented.

An efficient method for the synthesis of organophosphonates through palladium-catalyzed coupling of α-diazo phosphonates with benzyl or allyl halides has been developed. Trisubstituted alkenylphosphonates bearing versatile functional groups can be easily accessed in good yields and with excellent stereoselectivity through this method. Moreover, with similar strategy α-substituted vinylphosphonates can also be attained by the palladium-catalyzed coupling reaction of N-tosylhydrazones and aryl bromides. Migratory insertion of palladium carbene is proposed as the key step in this reaction.

With palladium catalysis, allyl bromides or chlorides react with α-diazocarbonyl compounds or N-mesylhydrazones to afford 1,3-diene derivatives. The reaction represents a novel and efficient method for the synthesis of 1,3-butadiene derivatives. Mechanistically, the reaction is proposed to follow a pathway involving the formation of a π-allylic palladium carbene complex and subsequent migratory insertion.

The Cu(I)-catalyzed olefination of N-sulfonylhydrazones with sulfones via metal carbene intermediates is reported. This reaction uses readily available starting materials and is operationally simple, thus representing a practical method for the construction of carbon-carbon double bonds. Mechanistically, Cu(I) carbene formation and subsequent carbene migratory insertion are proposed as the key steps.