Notable Effects of Aluminum Alkyls and Solvents for Highly Efficient Ethylene (Co)polymerizations Catalyzed by (Arylimido)- (aryloxo)vanadium Complexes

Abstract

The effects of both Al cocatalyst and solvent on catalytic activity in the ethylene polymerization by the (arylmido)(aryloxo)vanadium

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

“…The reaction products were polyethylene that are insoluble in hot O-dichlorobenzene for measurement of their molecular weight(s) by GPC in the ordinary analysis procedure, suggesting formations of ultrahigh molecular weight polymers as observed previously [8,16,17]. The activity by 2a showed higher than 3a, probably due to a stability of catalytically active species (formed five membered ring around vanadium and L in 2a vs. six membered ring in 3a).…”

“…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. ), exhibited remarkable catalytic activities for ethylene polymerization in the presence of Al cocatalysts [3][4][5][6][7][8][9][10]. The activity by the aryloxo analogue was strongly affected by the Al cocatalyst; the activities in the presence of halogenated Al alkyls ( i Bu 2 AlCl, EtAlCl 2 , Me 2 AlCl, Et 2 AlCl) were higher than those in the presence of methylaluminoxane (MAO) [7,8].…”

“…The activity by the aryloxo analogue was strongly affected by the Al cocatalyst; the activities in the presence of halogenated Al alkyls ( i Bu 2 AlCl, EtAlCl 2 , Me 2 AlCl, Et 2 AlCl) were higher than those in the presence of methylaluminoxane (MAO) [7,8]. Both the activity, and the norbornene incorporation, in the ethylene/norbornene copolymerization were also affected by the Al cocatalyst employed [7,8]. 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].…”

“…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].…”

“…), exhibited remarkable catalytic activities for ethylene polymerization in the presence of Al cocatalysts [3][4][5][6][7][8][9][10]. The activity by the aryloxo analogue was strongly affected by the Al cocatalyst; the activities in the presence of halogenated Al alkyls ( i Bu 2 AlCl, EtAlCl 2 , Me 2 AlCl, Et 2 AlCl) were higher than those in the presence of methylaluminoxane (MAO) [7,8]. Both the activity, and the norbornene incorporation, in the ethylene/norbornene copolymerization were also affected by the Al cocatalyst employed [7,8].…”