Scope and Limitations of Auxiliary-Assisted, Palladium-Catalyzed Arylation and Alkylation of sp<sup>2</sup> and sp<sup>3</sup> C–H Bonds
作者:Enrico T. Nadres、Gerson Ivan Franco Santos、Dmitry Shabashov、Olafs Daugulis
DOI:10.1021/jo4013628
日期:2013.10.4
auxiliary-assisted direct arylation and alkylation of sp2 and sp3 C–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
Synthesis of Highly Branched Polyethylene Using “Sandwich” (8-<i>p</i>-Tolyl naphthyl α-diimine)nickel(II) Catalysts
作者:Danfeng Zhang、Enrico T. Nadres、Maurice Brookhart、Olafs Daugulis
DOI:10.1021/om400704h
日期:2013.9.23
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
Facile access to ultra-highly branched polyethylenes using hybrid “sandwich” Ni(II) and Pd(II) catalysts
作者:Weiqing Lu、Yudan Liao、Shengyu Dai
DOI:10.1016/j.jcat.2022.05.003
日期:2022.7
59–130 kg/mol) than the corresponding “semi-sandwich” Pd(II) catalysts. Moreover, the hybrid “sandwich” Pd(II) catalyst generated E-MA copolymers with the highest branching densities and incorporation ratios among the catalysts. Overall, the hybrid sandwich structure facilitates the synthesis of higher branched polyethylene in the Ni(II) and Pd(II) catalyzed ethylene (co)polymerization reactions.
Chain-Straightening Polymerization of Olefins to Form Polar Functionalized Semicrystalline Polyethylene
作者:James M. Eagan、Omar Padilla-Vélez、Kyle S. O’Connor、Samantha N. MacMillan、Anne M. LaPointe、Geoffrey W. Coates
DOI:10.1021/acs.organomet.2c00366
日期:2022.11.28
We report the design and synthesis of an α-diimine PdII catalyst that copolymerizes functionalized and long chain α-olefins to produce semicrystalline polyethylene materials. Through a chain-straightening polymerization mechanism, the catalyst afforded high-melting point polymers with Tm values of up to 120 °C. The chain-straightening polymerization operates with high [ω,1]-insertion selectivity at
Synthesis of Branched Polyethylene with “Half-Sandwich” Pyridine-Imine Nickel Complexes
作者:Zhou Chen、Kate E. Allen、Peter S. White、Olafs Daugulis、Maurice Brookhart
DOI:10.1021/acs.organomet.6b00165
日期:2016.6.13
Traditional cationic Pd(II) and Ni(II) ethylene polymerization catalysts are supported by ortho-disubstituted aryl diimine ligands. These catalysts are capable of producing high-molecular-weight polyethylene due to positioning of bulk in the two axial sites of the square coordination plane which retards chain transfer. Similar pyridine-imine complexes bearing a single ortho-disubstituted aryl imine moiety were reported to yield very low M-n polyethylene. In earlier studies, "sandwich" diimine nickel catalysts incorporating two 8-arylnaphthylimino groups which provide exceptional shielding of the two axial sites were shown to yield ultrahigh-molecular weight polyethylene. Here we demonstrate that 8-arylnaphthyl groups incorporated into pyridine-imine nickel catalysts that block only a single axial site are highly effective in retarding chain transfer. These catalysts produce branched polyethylene (ca. 30-90 branches per 1000 carbons) with M-n, values up to 2.6 x 10(4) g/mol. Effects on the catalyst lifetimes and polymerization behavior as a function of substituent variations at the imine carbon and the aryl group are reported.