Phenoxide-Modified Half-Titanocenes Supported on Star-Shaped ROMP Polymers as Catalyst Precursors for Ethylene Copolymerization

Abstract

The synthesis and identification of half-titanocenes containing an aryloxide ligand supported at the chain end (surface) of soluble star-shaped polymers, by adopting sequential one-pot living ring-opening metathesis polymerizations (ROMP) of norbornene (NBE) and a cross-linking reagent using a molybdenum alkylidene catalyst, have been explored. The Ti Kedge XANES spectra (in toluene at 25 °C) indicate that the basic geometry and electronic nature of the original complex, Cp*TiMe 2 (O-i Pr 2 C 6 H 3 ) (1), were preserved in the supported catalyst on the star-shaped ROMP polymers. The supported catalyst showed high catalytic activities for ethylene polymerization, which are lower than that by 1 but higher than that by the supported catalyst at the linear ROMP polymer chain end; efficient 1-hexene incorporation in the ethylene/1-hexene copolymerization has also been demonstrated in this star-shaped supported catalyst.

Star-Shaped ROMP Polymers Coated with Oligothiophenes That Exhibit Unique Emission

“…The resultant polymers were highly soluble in ordinary organic solvents, such as toluene, tetrahydrofuran, chloroform, or dichloromethane. It turned out that, as reported previously, 33 − 35 an increase in CL (10 → 15 equiv to Mo) resulted in affording the polymers with large M n values [ e.g. M n = 1.14 × 10 5 (run 1) vs 1.51 × 10 5 (run 2); 1.00 × 10 5 (run 7) vs 1.52 × 10 5 (run 8)], suggesting the formation of a star-shaped polymer with increased arm numbers (more branching).…”

“…According to the established procedure, 29 − 35 various star-shaped polymers modified with oligo(thiophene) were prepared through the core-first (in and out) approach in the living ROMP ( Scheme 2 ), consisting of 4 key steps by sequential addition of a cross-linker (CL, 1,4,4a,5,8,8a-hexahydro-1,4,5,8- exo - endo -dimethanonaphtalene, exo / endo = 0.15:1.00), 44 NBE, and aldehyde for the termination [ArCHO, Ar = 2,2′-bithiophene-5-carboxaldehyde ( 2T-CHO ), 2,2′:5′,2″-terthiophene-5-carboxaldehyde ( 3T-CHO ), 5″-(3,4,5-trimethoxyphenyl)-2,2′:5′,2″-terthiophene-5-carboxaldehyde ( MP3T-CHO ), a 5″-phenyl-2,2′:5′,2″-terthiophene-5-carboxaldehyde ( 3TPh-CHO ), a and 2,2′:5′,2″:5″,2‴-quaterthiophene-5-carboxaldehyde ( 4T-CHO )]. 31 Mo cat has been chosen as the initiator because of its promising ability for the preparation of the multiblock ring-opened copolymers in a precise manner and the ability for the quantitative introduction of functionality into the polymer chain end via a Wittig-like reaction (a cleavage of the ROMP polymer–metal double bonds with aldehyde; excess amount for achieving the complete conversion).…”

“… 31 Mo cat has been chosen as the initiator because of its promising ability for the preparation of the multiblock ring-opened copolymers in a precise manner and the ability for the quantitative introduction of functionality into the polymer chain end via a Wittig-like reaction (a cleavage of the ROMP polymer–metal double bonds with aldehyde; excess amount for achieving the complete conversion). 12 , 15 , 29 − 35 , 41 − 43 These oligothiophenes were chosen because an interaction between terthiophene and the phenyl group in the initiation fragment was assumed through the previous communication, 31 and this should be affected by the thiophene repeat unit and the substituent; this effect was also observed as the end-group effect in poly(fluorene-2,7-vinylene)s on emission properties. a , 45 The selected polymerization results are summarized in Table 1 .…”

“… 1 − 7 Among them, the one-pot synthesis by adopting living ring-opening metathesis polymerization (ROMP), 8 − 15 conducted by the sequential addition of monomers and cross-linkers (CLs), 12 , 16 − 37 attracts considerable attention. Two major approaches ( Scheme 1 ), such as arm- (brush) first approach using a ruthenium-carbene catalyst (so-called third-generation Grubbs catalyst) 17 − 28 and core-first (in and out) approach using a molybdenum-alkylidene catalyst, 29 − 35 have been known. Moreover, the preparation of cross-linked ROMP polymers applied as monolith materials that are insoluble in common organic solvents was also reported.…”

Polymerization of norbornene and alkenyl-norbornenes catalyzed by palladium-benzyl or nickel-aryl complexes: Effects in polymer structure and application as catalyst support

“…171,172 Derivatives of polystyrenes such as Merrifield resin™ and JandaJel resin™ are the most common polymers for heteregeneous catalysis with supported copper complexes. 173 Other supports such as biodegradable polymers 174 or ROMP polymers 175 Even though polystyrene supports are extensively used, some uncontrolled side reactions can occur in their skeleton as, for example the reaction of benzylic positions in the polystyrenes in radical processes (Figure 4.1). The double bonds in the ROMP polymers are also reactive centers that may interfere and limit their applicability.…”