No abstract

Catalyzed by the (pyridylamido)hafnium/organoboron system, a series of halogen-functionalized isotactic polypropylenes were synthesized via the stereospecific copolymerization of propylene with ω-halo-α-alkenes. The (pyridylamido)hafnium/organoboron system has been proved to be a potent catalyst for propylene/ω-iodo-α-alkenes copolymerization, producing well-defined poly(propylene-coω-iodo-α-undecene)s with outstanding properties. The high molecular weight (M w > 100 kg mol −1 ) functional iPPs possessing abundant iodoalkene units (up to 11.7 mol %) and unimodal molecular weight distributions (M w /M n ≈ 2) could be easily obtained under mild conditions with excellent catalytic activity. High isotactic selectivity of monomers, including propylene and polar comonomer, was unexpectedly observed ([mmmm] > 99%). Moreover, based on the unique copolymerization process and the highly reactive sites on the copolymers, the halogen groups of the resultant copolymers could be easily transformed into other polar groups via click chemistry, and the new functional iPPs with high molecular weights and abundant polar groups could be efficiently obtained.

No abstract

No abstract

No abstract

The synthesis, characterization, and ethylene polymerization behavior of a novel macrocycle trinuclear 2,6-bis(imino)pyridyliron precatalyst 2 are reported. The molecular model of 2 was predicted using the Insight II software package. The molecular simulation indicates that the center iron atoms of complex 2 are located inside the macrocycle ligand. This new precatalyst could restrain active iron center from deactivation and effectively control chain transfer reaction, such as β-H transfer to the metal or the monomer. Compared with its mononuclear analogue 1, precatalyst 2 shows higher activity and longer lifetime for ethylene polymerization in the presence of modified methylalumoxane as a cocatalyst and produces much higher molecular weight polyethylenes with higher melting temperatures. Furthermore, higher molecular weight polymers with unimodel molecular weight distribution can be easily obtained using triisobutylaluminum as a cocatalyst.

No abstract

A series of (imido)vanadium(V) dichloride complexes containing 8-(2,6-dimethylanilide)-5,6,7-trihydroquinoline ligands of the type V(NR)Cl2[8-(2,6-Me2C6H3)N(C9H10N)] (R = Ad (3), 2-MeC6H4 (4), 2,6-Me2C6H3 (Ar, 5)) have been prepared and identified, and their structures have been determined by X-ray crystallographic analysis. The ethylene dimerization catalyst generated from complex 3 upon treatment with an excess amount of MAO exhibited remarkable catalytic activities (e.g. TOF = 9600000 h–1 (2670 s–1), Al/V = 4000 (molar ratio)), affording 1-butene as the major product (95.0–99.4%). The activities of 3 and 4 were higher than those exhibited by the corresponding 2-(anilide)methylpyridine analogues; 3 showed higher 1-butene selectivity than the others and the activity did not decrease remarkably at 50 °C. Complex 5 afforded a mixture of polymer and oligomers with low activities, suggesting that a fine tuning of both the imido and the anionic donor ligands plays an essential role in this catalysis.