Hidetsugu Tanaka

Microstructure of Highly Syndiotactic “Living” Poly(propylene)s Produced from a Titanium Complex with Chelating Fluorine-Containing Phenoxyimine Ligands (an FI Catalyst)

Highly syndiotactic “living” poly(propylene)s were synthesized at 25°C using a bis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentafluoroanilinato]titanium (IV) dichloride/MAO catalyst system, and microstructures of the polymer were analyzed by means of 13C NMR spectroscopy. The syndiotactic poly(propylene) contains isobutyl, isopentyl and propyl end groups, suggesting that the living polymerization of propylene was initiated via 1,2-insertion, followed by 2,1-insertion as the principal mode of polymerization. Pentad distribution analysis revealed that the syndiospecific polymerization proceeds under chain-end control.

A new titanium complex having two phenoxy-imine chelate ligands for ethylene polymerization

A new titanium complex having two phenoxy-imine chelate ligands, bis[N-(3-tert-butylsalicylidene)anilinato]titanium(IV)dichloride 1, was synthesized and its structure determined by X-ray analysis. Density functional theory (DFT) calculations and X-ray analysis suggest that complex 1, when activated, possesses two available cis-located sites needed for ethylene polymerization. Complex 1/methylaluminoxane (MAO) in toluene or heptane solvent displayed very high ethylene polymerization activities (2 280-4 150 (kg PE).(mol cat) -1 .h -1 ) with high molecular weight values (M v = 288 000- 881 000) at 25-75 °C under atmospheric pressure. The activity values displayed by complex 1/MAO are some of the highest values exhibited by any titanium complex with no cyclopentadienyl (Cp) ligand(s). Alternatively, complex 1/ i Bu 3 Al/Ph 3 CB(C 6 F 5 ) 4 in toluene solvent displayed high ethylene polymerization activities (190-670 (kg PE).(mol cat) -1 .h -1 ) with exceptionally high molecular weight values (M v = 3 920 000-5 860 000) at 25-75 °C under atmospheric pressure. The molecular weight values displayed by complex 1/ i Bu 3 Al/Ph 3 CB(C 6 F 5 ) 4 are some of the largest values displayed by homogeneous olefin polymerization catalysts including the group 4 metallocenes. The high potential of complex 1 for ethylene polymerization has therefore been demonstrated.

Ethylene and propylene polymerization behavior of a series of bis(phenoxy–imine)titanium complexes

Abstract This contribution reports ethylene and propylene polymerization behavior of a series of Ti complexes bearing a pair of phenoxy–imine chelate ligands. The bis(phenoxy–imine)Ti complexes in conjunction with methylalumoxane (MAO) can be active catalysts for the polymerization of ethylene. Unexpectedly, this C2 symmetric catalyst produces syndiotactic polypropylene. 13 C NMR spectroscopy has revealed that the syndiotacticity arises from a chain-end control mechanism. Substitutions on the phenoxy–imine ligands have substantial effects on both ethylene and propylene polymerization behavior of the complexes. In particular, the steric bulk of the substituent ortho to the phenoxy–oxygen is fundamental to obtaining high activity and high molecular weight for ethylene polymerization and high syndioselectivity for the chain-end controlled propylene polymerization. The highest ethylene polymerization activity, 3240xa0kg/mol-catxa0h, exhibited by a complex having a t-butyl group ortho to the phenoxy–oxygen, represents one of the highest reported to date for Ti-based non-metallocene catalysts. Additionally, the polypropylene produced exhibits a Tm, 140xa0°C, and syndioselectivity, rrrr 83.7% (achieved by a complex bearing a trimethylsilyl group ortho to the phenoxy–oxygen) that are among the highest for polypropylenes produced via a chain-end control mechanism. Hence, the bis(phenoxy–imine)Ti complexes are rare examples of non-metallocene catalysts that are useful for the polymerization of not only ethylene but also propylene.

Catalytic Behavior of Bis(Pyrrolide‐Imine) and Bis(Phenoxy‐Imine) Titanium Complexes for the Copolymerization of Ethylene with Propylene, 1‐Hexene, or Norbornene

This contribution reports the catalytic behavior of bis(pyrrolide-imine)Ti complexes 1 and 2, [2-(RNCH)-C4H3N]2TiCl2 (1, R = Ph; 2, R = cyclohexyl), and bis(phenoxy-imine)Ti complex 3, [2-(Ph-NCH)-3-t Bu-C6H3O]2TiCl2 for the copolymerization of ethylene with propylene, 1-hexene, or norbornene. An inspection of the X-ray structures of complexes 1–3 suggested that complexes 1 and 2 with pyrrolide-imine ligands would provide more space for olefin polymerization than complex 3 with phenoxy-imine ligands. In addition, DFT calculations also showed that active species derived from complexes 1 and 2 possess higher electrophilicity of the Ti center compared to that from complex 3. Complexes 1 and 2 on activation with methylalumoxane (MAO) had higher affinity for propylene and 1-hexene and incorporated higher amounts of propylene (1; 30.5 mol%, 2; 23.4 mol%) and 1-hexene (1; 1.9 mol%, 2; 1.7 mol%) than complex 3 (propylene; 4.5 mol%, 1-hexene; 0.4 mol%). The incorporation levels of propylene and 1-hexene displayed by complexes 1 and 2 were lower than those for Cp2TiCl2 (propylene; 41.6 mol%, 1-hexene; 5.1 mol%) under identical conditions. In contrast, complexes 1 and 2 exhibited higher incorporation ability for norbornene and produced copolymers with much higher norbornene contents (1; 32.0 mol%, 2; 26.5 mol%) than Cp2TiCl2 (1.2 mol%) under the same conditions. Additionally, complex 3 also promoted higher norbornene incorporation (4.3 mol%) than Cp2TiCl2 and provided a copolymer with extremely narrow molecular weight distribution (Mw/Mn 1.14). A correlation exists between electrophilicity of the Ti center in active species and norbornene incorporation.

132 PI catalysts: New titanium complexes having two pyrrolide-imine chelate ligands for olefin polymerization

Publisher Summary This chapter introduces new titanium complexes bearing two pyrrolide–imine chelate ligands, named PI Catalysts. New bis(pyrrolyl-2-aldiminato) titanium complexes, named PI Catalysts, were prepared from the lithium salt of the corresponding ligands and TiCl 4 , and their molecular structures were established by X-ray analyses. Prototype PI Catalyst adopts a distorted octahedral geometry around the Ti center, thus, the two pyrrole nitrogen atoms are situated in trans position, while the two imine nitrogen and the two chlorine atoms are oriented cis to each other at the central titanium. The results of DFT calculations on a methyl cationic complex, an initial active species formed by methylalumoxane (MAO) for olefin polymerization, indicate that the cationic complex has cis -located active sites. These results together with X-ray analysis suggest that a complex has a high potential for olefin polymerization. PI Catalysts displayed high ethylene polymerization activities using MAO as a cocatalyst. The activity increased dramatically by introducing a bulky X substituent. One of the complexes exhibited a very high activity with a very high molecular weight value.

Polyolefin structural control using phenoxy-imine ligated group 4 transition metal complex catalysts

Abstract This paper describes the structural control of polyolefins achieved by using group 4 transition metal complex catalysts featuring a pair of phenoxy-imine chelate ligands (named FI catalysts). FI catalysts can produce very low to ultrahigh molecular weight polymers. For example, a Zr-FI catalyst bearing a cycloalkyl group on the imine-nitrogen with methylaluminoxane (MAO) activation is capable of selectively forming vinyl-terminated low molecular weight polyethylenes (Mw < 5000) whereas a Zr-FI catalyst with a triethylsilyl group ortho to the phenoxyoxygen can generate ethylene/propylene amorphous copolymers with ultra-high molecular weights (Mw > 10 000 000) when treated with iBu3Al / Ph3CB(C6F5)4. In addition, a Ti-FI catalyst, possessing an o-phenoxytrimethylsilyl group, with MAO can form highly syndiotactic polypropylenes ([rrrr] = 84%, Tm = 140°C) via a chainend control mechanism. Conversely, upon activation with iBu3Al / Ph3CB(C6F5)4, a Hf-FI catalyst with a tert-butyl group ortho to the phenoxy-oxygen is able to produce high molecular weight isotactic polypropylenes ([mm] = 69%, Tm = 124°C, Mw = 412 000) via a site control mechanism. Therefore, FI catalysts have shown the ability to create various polyolefin architectures by simple variation of the central metal, the ligand structure and the co-catalyst.