Fluorinated Bis(phenoxyketimine)titanium Complexes for the Living, Isoselective Polymerization of Propylene:  Multiblock Isotactic Polypropylene Copolymers via Sequential Monomer Addition

Abstract

A series of bis(phenoxyketimine)titanium dichloride complexes were synthesized and evaluated as catalysts for living, isoselective propylene polymerization upon activation with methylaluminoxane (MAO). Catalysts bearing phenoxyketimine ligands with different substituents at the ortho and para positions of the phenolate ring and substituents at the ketimine carbon were investigated. The identity of the ketimine substituent had the largest effect on the activity and isoselectivity of propylene polymerization. Complex 12/MAO promoted the living, isoselective polymerization of propylene ([m4] = 0.73, alpha = 0.94). This catalyst system was used for the synthesis of a number of block copolymers featuring isotactic polypropylene semicrystalline blocks and poly(ethylene-co-propylene) amorphous blocks. Several triblock samples with varying block lengths, a pentablock, and a heptablock copolymer were synthesized. Mechanical testing has revealed that each is elastomeric with elongations at break between approximately 790-1000%.

Synthesis of N-aryl trifluoromethylarylketoimines by palladium-catalyzed Suzuki coupling reaction of N-aryltrifluoroacetimidoyl chlorides with aryl boronic acids

“…The results indicated that the coupling reaction could be catalyzed by either Pd(0) or Pd(II) catalyst, and Pd(PPh 3 ) 4 provided the highest yield of target product 3 (87% entry 4). Subsequently, a series of bases were investigated, the results suggested that bases have dramatic effects on the yields of cross-coupling product (entries [4][5][6][7][8]. We were delighted to observe the reaction provided target product 3 in 97% yield in the presence of 3 equiv.…”

“…As listed in Table 2, a series of N-aryltrifluoroacetimidoyl chlorides and aryl boronic acids were investigated under the optimized conditions. Initially, a series of aryl boronic acids bearing different substitutes were tested by their reaction with substrate 1a or 1b (entries [1][2][3][4][5][6][7][8]. The results revealed that both electron-rich and electron-deficient phenyl boronic acids are suitable substrates for the coupling reaction and provided the corresponding trifluoromethyl arylketoimines in good to excellent yields (entries [1][2][3][4].…”

“…The CF 3 -containing chiral amines could also be synthesized from trifluoromethyl arylketoimines by an asymmetric alkylation reaction [4]. Fluorinated bis(phenoxyketimine)titanium complexes, the catalysts for polymerization of propylene, were also prepared from CF 3 -containing arylketoimines [5]. Usually, trifluoromethyl arylketoimines were synthesized via condensation reaction of trifluoromethyl ketones with amines under high temperature conditions [6].…”

“…However, some substituted-aryl trifluoromethylketoimines are unavailable because of the scarcity of 1-(substituted-aryl)-2,2,2-trifluoroethanones. Friedel-Crafts reaction of N-aryltrifluoroacetimidoyl chlorides with aromatic compounds provides another access for trifluoromethyl arylketoimines [5,7], but aromatic compounds were limited to electronrich phenols. Therefore, the discovery of new readily available fluorine sources for efficient and concise synthesis route to trifluoromethyl arylketoimines remains a challenging area for exploration.…”

FI Catalysts: Unique Olefin Polymerization Catalysis for Formation of Value-added Olefin-based Materials

“…In addition, another research group has revealed that Ti _ FI catalyst 32 bearing a phenyl group on the imine-C can induce isoselective living propylene polymerization and form moderately isotactic and nearly monodisperse PPs (0 polymerization; Mw/Mn 1.11, Mn 27,900, mmmm 53%, Tm 69.5 ), probably because of the suppression of the site-inversion process by the steric congestion provided by the phenyl group on the imine-C 108), 109) . The corresponding Ti _ FI catalysts bearing a sterically encumbered group at the R 2 position (which may produce higher tacticity PPs) exhibit virtually no reactivity toward propylene.…”