Search

Cationic PdII monophosphine complexes derived from α- and β-cyclodextrins (CDs) promote the homopolymerization of styrene under carbon monoxide pressure. Although reversible CO coordination takes place under catalytic conditions according to 13C NMR studies with 13Cenriched CO, both complexes catalyze the formation of COfree styrene polymers. These macromolecules display optical activity as a result of the presence of stereoregular sequences within the overall atactic polymer. [ABSTRACT FROM AUTHOR]

Dipalladium complexes of a cyclic bis(diimine) ligand with a double-decker structure catalyze polymerization of ethylene and α-olefins and copolymerization of ethylene with 1-hexene. The polymerization of 1-hexene yields a polymer that is mainly composed of the hexamethylene unit formed by 2,1-insertion of the monomer into the palladium-carbon bond, followed by chain-walking (6,1-insertion). The polymerization of 4-methyl-1-pentene proceeds by 2,1-insertion with a selectivity of 92-97 %, and affords the polymer with methyl and 2-methylhexyl branches. 2,1-Insertion occurs selectively in all of the polymerization reactions of α-olefins catalyzed by the dipalladium complexes. Ethylene polymerization with the catalyst at 100 °C lasts over 24 h, whereas the monopalladium-diimine catalyst loses its activity within 8 h at 60 °C. Polyethylene obtained by the dipalladium catalyst is less-branched and has a higher molecular weight compared to that of the monopalladium catalyst under the same conditions. Copolymerization of ethylene with 1-hexene affords solid products with melting points and molecular weights that vary depending on the polymerization time, suggesting formation of a block and/or gradient copolymer. [ABSTRACT FROM AUTHOR]

Chloro(methyl)palladium complexes with 1,2-diimine ligand catalyze the cyclopolymerization of 1,6-heptadienes having two alkoxymethyl substituents at 4-position. The obtained polymers contain a trans-fused five-membered ring in every repeating unit. Molecular weights of the polymers are in the range of M = 3,370-13,000 ( M/ M = 1.28-2.01, by GPC using polystyrene standard), depending on the monomer and the catalyst. The reaction using the Pd complex with a C symmetrical structure forms the polymer with racemo linkage between the monomer units more than meso linkage. The polymerization under ethylene atmosphere produces the copolymer having the diene monomer unit composed of the five-membered ring and the branched oligoethylene block. 1,6,11-Dodecatrienes having four alkoxymethyl groups at the 4- and 9-positions undergo the cyclopolymerization to yield the polymer containing two five-membered rings in every monomer unit. Graphical abstract: Pd-diimine complexes polymerize 1,6-dienes having acyclic substituents and 1,6,11-dodecatrienes having four substituents at 4- and 9-positions to produce the new polymers having trans-five-membered rings along the polymer chain.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A dipalladium complex with a double-decker structure catalyzes ethylene-acrylate copolymerization to produce the branched polymer containing the acrylate units in the polymer chain, not at the branch terminus. The cooperation of the two palladium centers, which are fixed in a rigid framework of the macrocyclic ligand, is proposed to have a significant dinuclear effect on the copolymerization. [ABSTRACT FROM AUTHOR]

Pd and Ni diimine complexes catalyze the isomerization polymerization of alkenylcyclohexanes to afford polymers composed of alternating trans-cyclohexane-1,4-diyl rings and oligomethylene spacers with high selectivity. The melting points of the polymers vary from 130 to 226 °C depending on length of the oligomethylene spacer. [ABSTRACT FROM AUTHOR]

Abstract: This article reviews recent studies on the polymerization of 1,6-heptadienes and 2-aryl- and 2-alkoxy-1-methylenecyclopropanes catalyzed by Co, Fe, and Pd complexes. Co and Fe complexes with bis(imino)pyridine ligands catalyze the cyclopolymerization of 1,6-heptadiene in the presence of MMAO to produce the polymer, which contains five-membered rings in the monomer units. The polymers with cis- or trans-five-membered rings are obtained selectively, depending on the complex used in the polymerization. The catalyst, prepared from the Co complex having a bis(imino)pyridine ligand and MMAO, promotes the polymerization of 2-aryl-1-methylenecyclopropanes without ring-opening. The reaction under ethylene atmosphere produces alternating copolymer of the two monomers to yield the polymers composed of the C4 repeating unit with a 1,1-cyclopropanediyl group. The alternating copolymer of ethylene and 7-methylenebicyclo[4.1.0]heptane undergoes thermal rearrangement to afford the polymer with Cbond in main chain. A radical pathway is proposed. Dinuclear π-allylpalladium complexes with bridging Cl ligands initiate living polymerization of 2-alkoxy-1-methylenecyclopropanes, which accompanies ring-opening of the monomer, to afford the polymers composed of the C3 repeating units having alkoxy and vinylidene groups. A cyclic dinuclear π-allylpalladium complex reacts with 2-alkoxy-1-methylenecyclopropane in the presence of pyridine to produce the living polymer with macrocyclic structures. Block copolymerization of the two monomers that contain OR or O(CH2CH2O)R as the substituents on the three-membered ring, results in the polymers with hydrophobic and hydrophilic segments. [Copyright &y& Elsevier]

Examines the role of copolymerization of palladium-complex-catalyzed on the monomers. Reaction of cyclic olefins with carbon oxychloride; Formation of hydrocarbon polymers; Composition of polyketones.