Tris(pyrazolyl)borate Ti(IV) Complexes Containing Phenoxy Ligands: Effective Catalyst Precursors for Ethylene Polymerization That Proceeds via Cationic Ti(IV) Species

Abstract

A series of phenoxy-substituted tris(pyrazolyl)borate titanium complexes, Tp′TiCl 2 (OAr) and Tp*TiMe 2 (OAr) [Tp ) HB(pyrazolyl) 3 , Tp* ) HB(3,5-Me 2 -pyrazolyl) 3 ; Ar ) Ph, 2,6-Me 2 C 6 H 3 , 2,6i Pr 2 C 6 H 3 ], were prepared, and their structures were determined by X-ray crystallography. These complexes exhibited from moderate to remarkable catalytic activities for ethylene polymerization in the presence of MAO; TpTiCl 2 (OPh) exhibited the highest catalytic activity for ethylene polymerization. The cationic Ti(IV)-methyl complex, [Tp*TiMe(O-2,6-Me 2 C 6 H 3 )] + [MeB(C 6 F 5 ) 3 ] -• (THF) 2 , polymerizes ethylene to give polyethylene with a uniform molecular weight distribution, clearly indicating that the cationic Ti(IV) species plays an essential role as the active species.

Synthesis of ethylene/1‐octene copolymers with controlled block structures by semibatch living copolymerization

“…Methylaluminoxane (MAO), purchased from Albemarle as a 10 wt % Al toluene solution, was first evaporated under vacuum at 50 C. It was then washed with distilled n-hexane twice and was finally dried in vacuum and stored as white powder in glovebox (dried MAO, dMAO). 22,23 Scheme 1 shows the structure of the catalyst complex used in this work, bis[N-(3-methylsalicylidene)22,3,4,5,6pentafluoroanilinato] titanium(IV) dichloride. The synthesis was performed following to the literature.…”

Preparation of ultrahigh molecular weight ethylene/1-octene block copolymers using ethylene pressure pulse feeding policies

“…Methylaluminoxane (MAO), 10wt% Al in toluene from Albemarle, was first evaporated under vacuum at 50 °C, then washed twice with distilled n-hexane and finally dried in vacuum and stored as white powder in the glove-box (dried MAO, dMAO). 23,24 The catalyst precursor used in this work was bis[N-(3-methylsalicylidene)-2,3,4,5,6-pentafluoroanilinato] titanium(IV) dichloride, which was synthesized following the literature procedure. 25 The catalyst structure is shown in Scheme 1.…”

Effect of aryloxo substituents in ethylene polymerisation by tris(pyrazolyl)borate titanium(IV) complexes containing aryloxo ligands of type, TpTiCl2(OAr)

“…9 We have recently reported that Tp¢TiCl 2 (OAr) [Tp = HB(pyrazolyl) 3 , Tp* = HB(3,5-Me 2 -pyrazolyl) 3 ; Ar = Ph, 2,6-Me 2 C 6 H 3 , 2,6-i Pr 2 C 6 H 3 ] exhibited moderate to remarkable catalytic activities for ethylene polymerisation in the presence of MAO. 10, 11 The catalytic activity was highly affected by the aryloxo substituents as well as the Tp¢ fragments, and TpTiCl 2 (OPh) (1) showed especially higher activity than TpTiCl 2 (O-2,6-Me 2 C 6 H 3 ) (5), TpTiCl 2 (O-2,6-i Pr 2 C 6 H 3 ) (6), and Tp*TiCl 2 (OAr). 11 It also turned out that the cationic titanium-methyl complex, [Tp*TiMe(O-2,6-Me 2 C 6 H 3 )] + [MeB(C 6 F 5 ) 3 ] -•(THF) 2 , polymerises ethylene with moderate catalytic activity affording polyethylene with uniform distributions.…”

“…10, 11 The catalytic activity was highly affected by the aryloxo substituents as well as the Tp¢ fragments, and TpTiCl 2 (OPh) (1) showed especially higher activity than TpTiCl 2 (O-2,6-Me 2 C 6 H 3 ) (5), TpTiCl 2 (O-2,6-i Pr 2 C 6 H 3 ) (6), and Tp*TiCl 2 (OAr). 11 It also turned out that the cationic titanium-methyl complex, [Tp*TiMe(O-2,6-Me 2 C 6 H 3 )] + [MeB(C 6 F 5 ) 3 ] -•(THF) 2 , polymerises ethylene with moderate catalytic activity affording polyethylene with uniform distributions.…”

“…In particular, we wish to emphasize that a precise modification/tuning of the aryloxo substituent plays an essential key role for exhibiting the remarkable catalytic activity; the mono i Pr analogue (2) showed the highest catalytic activity among TpTiCl 2 (OAr) (1-6). TpTiCl 2 (O-2-i PrC 6 H 4 ) (2), TpTiCl 2 (OC 6 F 5 ) (3), and TpTiCl 2 (O-2,6-Ph 2 C 6 H 3 ) (4) could be prepared according to the analogous procedure for synthesis of TpTiCl 2 (OPh) (1), 11 from TpTiCl 3 by treating with LiOAr in toluene (Scheme 2). 11 The resultant complexes (2-4) were identified on the basis of 1 H-and 13 C-NMR spectra, elemental analyses, and the structures of 3 and 4 were determined by X-ray crystallography.…”