Ethylene/Polar Norbornene Copolymerizations by Bimetallic Salicylaldimine−Nickel Catalysts

Ethylene polymerization using heterogeneous multinuclear nickel catalysts supported by a crosslinked alpha diimine ligand network

A crosslinked alpha diimine ligand supporting a nickel metal center polymerizes ethylene to produce polyethylene with controlled microstructures, high activities, and can be removed from the product.

Efficient ethylene copolymerization with polar monomers using palladium anilinonaphthoquinone catalysts

Copolymerizations of ethylene with methyl acrylate (MA) and 5-norbornen-2-yl acetate (NB_AC) were explored using anilinonaphthoquinone-ligated palladium catalysts.

Synthesis of poly(α-olefins) containing rare short-chain branches by dinuclear Ni-based catalysts

Chain walking mechanism with regard to dinuclear Ni-based catalyst stereoisomers in the polymerization of α-olefins: the effects of bridge, backbone and ortho-substituents.

Kinetics, Mechanism and Theoretical Studies of Norbornene-Ethylene Alternating Copolymerization Catalyzed by Organopalladium(II) Complexes Bearing Hemilabile α-Amino-pyridine

Cationic methylpalladium complexes bearing hemilabile bidentate α-amino-pyridines can serve as effective precursors for catalytic alternating copolymerization of norbornene (N) and ethylene (E), under mild conditions. The norbornyl palladium complexes in the formula of {[RHNCH₂(o-C₆H₄N)]Pd(C₇H10Me)(NCMe)}(BF₄) (R = iPr (2a), tBu (2b), Ph (2c), 2,6-Me₂C₆H₃ (2d), 2,6-iPr₂C₆H₃ (2e)) were synthesized via single insertion of norbornene into the corresponding methylpalladium complexes 1a-1e, respectively. Both square planar methyl and norbornyl palladium complexes exhibit facile equilibria of geometrical isomerization, via sterically-controlled amino decoordination-recoordination of amino-pyridine. Kinetic studies of E-insertion, N-insertion of complexes 1 and 2, and the geometric isomerization reactions have been examined by means of VT-NMR, and found in excellent agreement with the results estimated by DFT calculations. The more facile N-insertion in the cis-isomers, and ready geometric isomerization, cooperatively lead to a new mechanism that accounts for the novel catalytic formation of alternating COC.

Modulating polyolefin properties through the incorporation of nitrogen-containing polar monomers

In this work, ethylene copolymerization and terpolymerization reactions with some nitrogen-containing monomers were investigated using α-diimine palladium and phosphine-sulfonate palladium catalysts.

Ethylene polymerization catalyzed by dinickel complexes with a double-decker structure

Double-decker dinickel catalysts, even without any substituent on an ortho-position, afforded high molecular weight polyethylene with high crystallinity and less branching.

Ethylene polymerization by salicylaldimine nickel(ii) complexes containing a dibenzhydryl moiety

The synthesis, characterization and ethylene polymerization properties of a series of salicylaldimine Ni(ii) complexes with a dibenzhydryl moiety are described.

Frustratingly synergic effect of cobalt–nickel heterometallic precatalysts on ethylene reactivity: the cobalt and its heteronickel complexes bearing 2-methyl-2,4-bis(6-aryliminopyridin-2-yl)-1H-1,5-benzodiazepines

The title complexes showed good activities toward ethylene reactivity when obtained oligomers followed a Poisson distribution, but the mononuclear cobalt complexes showed higher activities than the cobalt–nickel analogues.

ON-OFF luminescence signaling of hybrid organic-inorganic switches

The dyads 1OFF and 2OFF were prepared by combining the inorganic luminophores [Ru(phen)2(2-[imidazol-2-yl]pyridine)](2+) and [Re(CO)3Cl(2-[imidazol-2-yl]pyridine)] with 2-(anthracen-9-yl)-4-methylphenol as a second photoactive moiety. In both cases, the inorganic unit operates as the emitter, whereas the organic part acts as a controller. Emission of the inorganic luminophore can be reversibly switched ON and OFF by adjusting the energetic level of the (3)π-π* state of the appended anthracene unit through either dearomatization using a photohydration or aromatization applying a thermal dehydration. Emission of both switches is reversibly recorded and erased multiple times without significant degradation.

Dinickel Bisphenoxyiminato Complexes for the Polymerization of Ethylene and α-Olefins

Dinuclear nickelphenoxyiminato olefin polymerization catalysts based on rigid p-terphenyl frameworks are reported. Permethylation of the central arene of the terphenyl unit and oxygen substitution of the peripheral rings ortho to the aryl-aryl linkages blocks rotation around these linkages allowing atropisomers of the ligand to be isolated. The corresponding syn and anti dinickel complexes (25-s and 25-a) were synthesized and characterized by single crystal X-ray diffraction. These frameworks limit the relative movement of the metal centers restricting the metal-metal distance. Kinetics studies of isomerization of a ligand precursor (7-a) allowed the calculation of the activation parameters for the isomerization process (ΔH(‡) = 28.0 ± 0.4 kcal×mol(-1) and ΔS(‡) = -12.3 ± 0.4 cal×mol(-1)×K(-1)). The reported nickel complexes are active for ethylene polymerization [TOF up to 3700 (mol C(2)H(4))×(mol Ni)(-1)×h(-1)] and ethylene/α-olefin copolymerization. Only methyl branches are observed in the polymerization of ethylene, while α-olefins are incorporated without apparent chain walking. These catalysts are active in the presence of polar additives and in neat tetrahydrofuran. The syn and anti isomers differ in polymerization activity and polymer degree of branching and molecular weight. For comparison, a series of mononuclear nickel complexes (26, 27-s, 27-a, 28, 30) was prepared and studied. The effects of structure and catalyst nuclearity on reactivity are discussed.

Bimetallic effects on ethylene polymerization in the presence of amines: inhibition of the deactivation by Lewis bases

Dinickel complexes supported by terphenyl ligands appended with phenoxy and imine donors were synthesized. Full substitution of the central arene blocks rotation around the aryl-aryl bond and allows for the isolation of atropisomers. The reported complexes perform ethylene polymerization in the presence of amines. The inhibiting effect of polar additives is up to 250 times lower for the syn isomer than the anti isomer. Comparisons with mononuclear systems indicate that the proximity of the metal centers leads to the observed inhibitory effect on the deactivation of the catalysts.