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Synthesis of end-functionalized poly(norbornenes) (PNBs) and poly(ethylidenenorbornenes) (PENBs) were prepared using the palladium catalyst tBu3PPdMeCl/NaBArfin combination with the chain transfer agents (CTAs) 4-penten-1-ol and 10-undecenal. These CTAs produce polymers end-capped with −OH and −CHO groups, respectively, in high yields with Mnvalues in the range of 6–17K, depending on the CTA:monomer molar ratio. End-functionalized PNBs and PENBs with precisely controlled Mnvalues and very narrow molecular weight distributions were accessed by using 4-penten-1-ol and 10-undecenal as chain-terminating agents following living polymerizations in which the monomer is completely consumed. The utility of the aldehyde-functionalized polymers is illustrated via coupling to a dye molecule and by the synthesis of ambiphilic diblock copolymers, PNB-b-PEG and PENB-b-PEG.

The scope of palladium-catalyzed, auxiliary-assisted direct arylation and alkylation of sp2and sp3C–H bonds of amine and carboxylic acid derivatives has been investigated. The method employs a palladium acetate catalyst, substrate, aryl, alkyl, benzyl, or allyl halide, and inorganic base in tert-amyl alcohol or water solvent at 100–140 °C. Aryl and alkyl iodides as well as benzyl and allyl bromides are competent reagents in this transformation. The picolinic acid auxiliary is used for amine γ-functionalization, and the 8-aminoquinoline auxiliary is used for carboxylic acid β-functionalization. Some optimization of base, additives, and solvent is required for achieving best results.

A general method for synthesis of 1,2-bis-trifluoromethylthioarenes has been developed. Arynes generated from silyl aryl triflates or halides react with bis(trifluoromethyl)disulfide to afford 1,2-bis-trifluoromethylthioarenes. Aryl, alkyl, ester, halide, and methoxy functionalities are compatible with reaction conditions. Use of bis(perfluoroaryl)disulfides gave moderate yields of aryne disulfenylation or cyclization to fluorinated dibenzothiophenes.

The palladium diphosphine complex 4converts ethylene to hyperbranched unsaturated oligomers (Mn≈ 330 g/mol) at 22 °C. In addition to the high stability of this catalyst observed at temperatures up to 75 °C, an increase of the reaction temperature leads to a decrease in branching densities of the oligomers, in sharp contrast to the palladium and nickel diimine catalyst systems. One-pot oligomerizations/hydrogenations were carried out to form hyperbranched saturated oligomers.

Nickel α-diimine catalysts have been previously shown to perform the chain straightening polymerization of α-olefins to produce materials with melting temperatures (Tm) similar to linear low density polyethylene (Tm= 100–113 °C). Branching defects due to mechanistic errors during the polymerization currently hinder access to high density polyethylene (Tm= 135 °C) from α-olefins. Understanding the intricacies of nickel α-diimine catalyzed α-olefin polymerization can lead to improved ligand designs that should allow production of chain-straightened polymers. We report a 13C NMR study of poly(α-olefins) produced from monomers with 13C-labeled carbonsspecifically 1-decene with a 13C-label in the 2-position and 1-dodecene with a 13C-label in the ω-positionusing a series of α-diimine nickel catalysts. Furthermore, we developed a mathematical model capable of quantifying the resulting 13C NMR data into eight unique insertion pathways: 2,1- or 1,2- insertion from the primary chain end position (1°), the penultimate chain end position (2p°), secondary positions on the polymer backbone (2°), and previously installed methyl groups (1m°). With this model, we accurately determined overall regiochemistry of insertion and overall preference for primary versus secondary insertion pathways using nickel catalysts under various conditions. Beyond this, our model provides the tools necessary for determining how ligand structure and polymerization conditions affect catalyst behavior for α-olefin polymerizations.

Nickel(II) α-diimine dibromide complexes incorporating 8-p-tolylnaphthylimino groups have been prepared and used for ethylene polymerization by activation with modified methylalumoxane (MMAO). These catalysts possess increased axial bulk relative to standard diimine-nickel complexes, resulting in lower rates of chain transfer relative to chain propagation rates and thus higher polymer molecular weights and narrower PDIs. They yield the most highly branched PE produced by Ni catalysts seen to date. The easy synthesis of 8-aryl-1-naphthylamines provides ready access to a new class of α-diimine-based nickel catalysts in which the 8-substituent is ideally positioned to provide steric bulk at the axial sites.