Homogeneous Vanadium‐Based Catalysts for the Ziegler—Natta Polymerization of α‐Olefins

Abstract

Although their activity is often inferior to that of other systems, the use of vanadium-based catalysts in homogeneous Ziegler-Natta polymerizations allows the preparation of high-molecular-weight polymers with narrow molecularweight distributions, ethene/a-olefin copolymers with high a-olefin incorporation, and syndiotactic polypropene. The main reason for the low activity of these catalysts is their deactivation during catalysis by reduction of active vanadium species to low-valent, less active or inactive species. We here present an up-to-date review of this area with particular emphasis on the attempts to improve catalyst performance and stability by the use of additives or ancillary ligands.

Progress in advanced catalyst and their use in ethylene/propylene copolymerization

“…化 合 物 , 例 如 VCl 4 , VOCl 3 , VO(OR) 3 , VOCl(OR) 2 , VOCl 2 (OR)和V(acac) 3 等, 其中R为烷基, acac为乙酰 丙酮 [8] . 中心金属钒具有多个价态, 但并不是所有价 态的钒都具有催化活性, 因此, 选择主催化剂时还要 考虑中心金属钒的价态.…”

Facile, Efficient Copolymerization of Ethylene with Norbornene-Containing Dienes Promoted by Single Site Non-Metallocene Oxovanadium(V) Catalytic System

“…et al reported that either VOCl3/Et3Al2Cl3 or VO(OtBu)3/Et3Al2Cl3 showed high cyclic dienes incorporation ability in the terpolymerization with ethylene and propylene [23]. Since the vanadium catalysts might be deactivated during the polymerization because of the reduction to low-valent, inactive species [27], introduction of bulky and polydentate ancillary ligands to stabilize active vanadium(V) species has been proven to be an effective approach to keep vanadium at high-oxidation and subsequently prolong the catalytic lifetime [28][29][30][31][32][33][34][35][36]. In our previous work, the synthesized [ONNO]-type and [ONN]-type oxovanadium(V) complexes also showed high catalytic activities and promising stabilities in copolymerization of ethylene with norbornene (NBE), and produced E/NBE copolymers with high NBE contents [37,38].…”

Ethylene Polymerization Using (Imino)vanadium(V) Dichloride Complexes Containing (Anilido)methyl-pyridine, -quinoline Ligands–Halogenated Al Alkyls Catalyst Systems

“…and Et 2 AlCl, EtAlCl 2 , n BuLi, etc.] display unique high reactivity toward olefins in olefin coordination/insertion polymerization [1][2][3][4][5]. We previously reported that (arylimido)vanadium(V) complexes, containing anionic donor ligands (L), V(N-2,6-Me 2 C 6 H 3 )Cl 2 (L) (L = aryloxo, ketimide, phenoxyimine etc.…”

“…We thus speculated that a reason for the observed difference would be due to a formation of the different catalytically-active species, catalyst/cocatalyst nuclearity effect (assumed in Scheme 1) [5,[11][12][13]. The activity decreased upon addition of CCl 3 CO 2 Et (for example, [14]), which can be commonly used as effective additives to improve the catalyst stability [8], clearly suggesting that the active species were, thus, different from those prepared from vanadium(III), (IV) complexes [1][2][3][4][5]14]. More recently, we demonstrated that the (adamantylimido)vanadium(V) complexes containing (2-anilidomethyl)pyridine ligand, V(NAd)Cl 2 [2-ArNCH 2 (C 5 H 4 N)] [Ad = 1-adamantyl; Ar = 2,6-Me 2 C 6 H 3 (1a), 2,6-i Pr 2 C 6 H 3 (1b)], efficiently dimerize ethylene with both notable catalytic activities, and high selectivity in the presence of MAO [15,16], whereas the reaction products by 1a,b in the presence of Me 2 AlCl or Et 2 AlCl cocatalyst were ultrahigh molecular weight polyethylene (PE) (runs 1-5, Table 1) [16].…”