New Group IV Metallocene Systems Active in the Copolymerization of α‐Olefins and Conjugated Dienes

Abstract

Summary: Rac‐[CH2(2,4‐di‐tert‐butyl‐cyclopentadienyl)2]ZrCl2 (1), rac‐[CH2(3‐tert‐butyl‐4,5,6,7‐tetrahydroindenyl)2]ZrCl2 (2), rac‐[CH2(3‐isopropyl‐4,5,6,7‐tetrahydroindenyl)2]ZrCl2 (3), and rac‐[CH2(3‐methyl‐4,5,6,7‐tetrahydroindenyl)2]ZrCl2 (4) were synthesized and characterized by 1H NMR analysis. These C2 symmetric ansa‐zirconocenes, activated with methylaluminoxane (MAO), were able to promote copolymerization of ethene and 1,3‐butadiene. The structures of the copolymers are strongly influenced by zirconocene utilized as catalytic precursor. Depending on the reaction conditions polyethenes containing cyclopropane and cyclopentane rings, or 1,1‐ 1,3‐butadiene inserted constitutional units, were obtained.Structures of the synthesized catalytic precursors.magnified imageStructures of the synthesized catalytic precursors.

Ethylene/1,3-butadiene cyclocopolymerization catalyzed by zirconocene systems

“…Cross-linked materials are, instead, obtained by using a,x-nonconjugated dienes with double bonds, that are connected by more than four carbon atoms [10,11]. In the last decade, several articles focused on COCs obtained by copolymerization of a-olefins and conjugated dienes in the presence of group IV metal [12][13][14][15][16][17][18][19][20][21] or rare earth [22][23][24] based catalysts, were reported. In particular, Longo et al recorded an unprecedented cyclopropanation reaction by copolymerization of 1,3-butadiene with a-olefins (ethylene and propylene) [12][13][14][15], catalyzed by the highly sterically hindered metallocene rac-[CH 2 (3-tertbutyl-1-indenyl) 2 ]ZrCl 2 [25], activated by methylalumoxane (MAO).…”

Synthesis and Deconstruction of Polyethylene-type Materials

“…Most commonly, lanthanide catalysts based on Nd ,,− or Sc ,, are used for copolymerization of ethylene and butadiene. But also group IV catalysts based on titanocenes, , zirconocenes, − ,, or hafnium , are suitable. Even cobalt-based late transition-metal catalysts were reported .…”

Synthesis of Ethylene/Isoprene Copolymers Containing Cyclopentane/Cyclohexane Units as Unique Elastomers by Half-Titanocene Catalysts

“…Unique properties observed in the copolymers would be due to their microstructure containing cyclopentane units formed by cyclization after 2,1- or 1,4- My insertion followed by ethylene insertion (Scheme ). The results thus suggest a possibility of the synthesis of ethylene/IP copolymers, although, as described below, the reported examples for ethylene copolymerization with conjugated diene, especially using group 4 transition-metal catalysts, have been limited. − …”

“…In transition-metal-catalyzed coordination polymerization, reported examples in ethylene (propylene, α-olefin) copolymerization with linear conjugated dienes [butadiene (BD), IP, 1,3-pentadiene, and My] still have been limited to neodymium, − scandium, ,− samarium, , zirconium, − titanium, ,− hafnium, and cobalt catalysts. In particular, the reports with IP have been limited, ,,,,,,, and there was only one report in the titanium-catalyzed synthesis of the ethylene/IP copolymers in the presence of a 1,4-dithabutanediyl-linked bis­(phenolato) titanium complex catalyst .…”