Efficient, Regioselective Copolymerization of Ethylene with Cyclopentadiene by the Titanium Complexes Bearing Two β-Enaminoketonato Ligands

Facile, Efficient Copolymerization of Ethylene with Norbornene-Containing Dienes Promoted by Single Site Non-Metallocene Oxovanadium(V) Catalytic System

“…The enchainment of VNB was therefore proven to be exclusively via 2, 3 vinyl-addition of the norbornene ring. The insertion manner was also supported by the 13 C NMR spectra of the copolymers, which presented the signals of pendant vinyl groups at 144.89 (=CH, exo), 142.18 (=CH, endo), 114.85 (=CH2, endo), and 112.09 ppm The incorporations and stereoselectivity of VNB were unambiguously revealed by 1 H, 13 C, and DEPT NMR spectra. All resonances were clearly identified and the data agreed well with the previously reported values [15,16].…”

“…Among these three [ONNO]-type oxovanadium(V) complexes, complex b showed the highest catalytic activities in both homopolymerization of ethylene and copolymerization because of its less steric hindrance originated from the longer bridge between the pendant pyridine donor and the ligand skeleton, and produced copolymers with moderate MWs. Besides the reduction in catalytic activities, the MWs of the resultant polymers were decreased remarkably, and they were further decreased with the increase of VNB concentration in feed (entries 4,[9][10][11][12][13][14]. This result indicated that, during the copolymerization, the continuous coordination-insertion process might be terminated by stable coordination of the pendant vinyl group with the active vanadium center and thus the chain growth was terminated.…”

“…Polymerization conditions: the copolymerizations were carried out in 50 mL of toluene at 50 °C under 4 atm of ethylene pressure, the polymerization time was 10 min, ETA (300 equiv. to vanadium complexes) was employed as reactivating agent; a VNB incorporations were (mol %) calculated from 1 H NMR spectra; b Weight-average molecular weight (Mw) and polydispersity indexes (PDI) of the copolymers were determined by high temperature The incorporations and stereoselectivity of VNB were unambiguously revealed by 1 H, 13 C, and DEPT NMR spectra. All resonances were clearly identified and the data agreed well with the previously reported values [15,16].…”

“…This value is consistent with that of the raw ENB monomer (2A in Figure 4a), and indicates that both the two ENB isomers show the same reactivity toward these vanadium catalysts. The microstructure of copolymer sample 2C (entry 9, Table 2) was also investigated by 13 C NMR spectrum (Figure 4b). Similar to the E/VNB copolymer, the microstructures of the copolymer produced by complex b only possessed isolated ENB inserted units and E/ENB alternating sequence.…”

“…The microstructure of copolymer sample 2C (entry 9, Table 2) was also investigated by 13 C NMR spectrum (Figure 4b). Similar to the E/VNB copolymer, the microstructures of the copolymer produced by complex b only possessed isolated ENB inserted units and E/ENB alternating sequence.…”