Vinyl polymerization of norbornene with bis(imino)pyridyl nickel(II) complexes

Abstract

A series of different steric hindrance nickel(II) complexes 1-6 bearing 2,6-bis(imino)pyridine ligands have been synthesized and characterized. The molecular structures of the complexes 3-5 were determined by X-ray diffraction analysis. The coordination geometry around the nickel center of the complexes is either square pyramid for complexes 3 and 4 or trigonal bipyramid for complex 5. All of the nickel complexes exhibit high catalytic activity for norbornene polymerization in the presence of MAO, although low activity for ethylene oligomerization and polymerization. The effects of the Al/Ni ratio, halogen, monomer concentration, temperature, and reaction time on activity of catalyst for norbornene polymerization and polymer microstructure were investigated.

[Pd(acac)(MeCN)2]BF4: air-tolerant, activator-free catalyst for alkene dimerization and polymerization

“…c In units of g of PNB mol À1 of Pd h À1 . d M v  10 5 , obtained by capillary viscosimetry using the Mark-Houwink coefficients a ¼ 0.56, and K ¼ 7.78  10 À4 dL g À1 64. 65 e Polymers obtained were insoluble.…”

Ni(ii) and Fe(ii) complexes based on bis(imino)aryl pincer ligands: synthesis, structural characterization and catalytic activities

“…In conclusion, a series of Ni(II) and Fe(II) complexes based on bis(imino)aryl [NCN] − ligands were synthesized and characterized. With MAO as a cocatalyst, the nickel complexes (1-3) and iron complex (6) show moderate activities towards the vinyl polymerization of norbornene, while the iron complexes with less bulky substituents show very low activities. Under the activation of alkylaluminium, the Fe(II) complexes show moderate activities in butadiene polymerization, affording a cis-1,4 enriched polymer.…”

“…[Bis(N-2,6-diisopropylphenyl)isophthalaldimin-2-yl]Fe(μ-Cl) 2 Li-(THF) 2 (6). The same procedure described for the preparation of 4 was used in the treatment of bis(N- 1434m, 1384m, 1361m, 1326m, 1253w, 1226w, 1180m, 1160w, 1103w, 1045m, 933w, 883w, 844w, 798w, 775m, 755m, 613w, 520m, 512w.…”

“…2 Three years later, Brookhart and Gibson reported Fe(II) and Co(II) complexes supported by bis(imine)pyridine ligands, respectively, which show high activities in ethylene polymerization. 3 The bis(imino)pyridine Ni(II) complexes show moderate to low activities in ethylene oligomerization/polymerization, 4,5 but exhibit high activities in norbornene vinyl polymerization 6 and butadiene polymerization. 5 In these bis(imino) pyridine-based complexes, the metal centers were firmly chelated by the tridentate ligands.…”

Highly active and easily accessible catalysts for vinyl polymerization of norbornene obtained by oxidative addition of salicylaldimine ligands to bis(1,5‐cyclooctadiene)nickel(0) and methylaluminoxane

“…Over the past decade, there has been an increasing interest in the use of late transition metal complexes, and in particular, nickel‐based catalysts, for the vinyl polymerization of NB 4–12. Among the nickel‐based precursors, neutral mono‐ and/or bis‐salicylaldiminate Ni(II) complexes bearing bulky substituents on the imino group were found to be active in the presence of a cocatalyst 13–15.…”