Search

Novel nickel complexes bearing different electron groups on substituted salicylaldnaphthylmethyleneimine ligands, bis‐(salicylaldnaphthylmethyleneimino)Ni(II) (Ni{(3‐R1)(5‐R2)C6H2(O)CH[N (naphthyl‐CH2)]}2Ni1: R1 = H, R2 = H; Ni2: R1 = H, R2 = CH3; Ni3: R1 = H, R2 = Br; Ni4: R1 = H, R2 = OCH3; Ni5: R1 = CH3, R2 = H; Ni6: R1 = Br, R2 = H), were synthesized. Ni2, Ni3, Ni5, and Ni6 are clearly characterized by single‐crystal X‐ray diffraction. Co‐polymerization of norbornene (NB) with 5‐norbornene‐2‐methylene butyl ether (BN) was carried out in toluene with the aforesaid complexes as catalyst precursors and B(C6F5)3 as the co‐catalyst. Catalyst activity, molecular weight, thermal stability, solubility, regularity, and optical transparency were investigated, and the mechanism of the electron groups changing catalyst performance is explained. All catalysts show high activity toward co‐polymerization (up to 3.53 × 105 gpolymer molNi−1 h−1). Ni3 shows the highest activity and Ni5 shows the highest insertion rate (up to 37.6%). The obtained poly(NB‐co‐BN)s are confirmed to be vinyl‐addition‐type co‐polymers, and they are noncrystalline. The co‐polymers exhibited excellent thermal stability and processability (Td ≥ 400 °C, Tg < 240 °C), optical transparency (up to 90%), and good solubility. [ABSTRACT FROM AUTHOR]

Three novel hexacoordinated nickel catalysts containing salicylaldbenzhydrylimine ligand and tetrahydrofuran heterocycle, Ni{(THF) (3-R 1) (5-R 2)C 6 H 2 (O)CHNCH(C 6 H 5) 2 } 2 , (R 1 = Br, R 2 = H, Ni1 ; R 1 = Br, R 2 = Br, Ni2 ; R 1 = Cl, R 2 = Cl, Ni3.), were synthesized and their molecular structures were confirmed by X-ray crystallography. Ni1–Ni3 catalysts exhibited high activities (0.53–2.11 × 106 g polymer /mol Ni ·h) toward norbornene homopolymerization and high activity (0.29–2.62 × 105 g polymer /mol Ni ·h) to copolymerization of norbornene and 1-hexene. When the 1-hexene feed ratio was changed from 10 to 70%, the 1-hexene content in the obtained copolymers could be controlled to 8.23–26.58%. The Ni3 with R 1 and R 2 were both electron withdrawing groups (-Cl) on the aromatic ring of salicylaldehyde, showed the highest activity as well as the highest 1-hexene insert ratios. At the same time, only a small amount of B(C 6 F 5) 3 cocatalyst (5 × 10−5 mol) need to be consumed in the copolymerization process. In addition, the obtained copolymers had a high thermal decomposition temperature (T d > 386 °C) and a low glass transition temperature (T g = 208.67–237.42 °C), which showed that the processability of these polymers was improved while the high thermal decomposition temperature was kept. The copolymers also exhibited good solubility in general organic solvents and high optical transparency in the visible region. Image 1 • Three novel hexacoordinated nickel catalysts containing salicylaldbenzhydrylimine ligand and tetrahydrofuran heterocycle were prepared. • These nickel catalysts exhibited high catalytic activity and high insert ratios in the copolymerization of norbornene and 1-hexene. • All copolymers displayed low T g (208.67–237.42 °C). • A small amount of cocatalyst was consumed in the copolymerization. [ABSTRACT FROM AUTHOR]

Two C–C bridged Ni(II) complexes bearing β‐keto‐9‐fluorenyliminato ligands with electron‐withdrawing groups (─CF3), Ni{PhC(O)CHC[N(9‐fluorenyl)]CF2}2 (Ni1) and Ni{CF3C(O)CHC[N(9‐fluorenyl)]Ph}2 (Ni2), were synthesized by metal coordination reaction and different in situ bonding mechanisms. The C–C bridged bonds of Ni1 were formed by in situ intramolecular trifluoromethyl and 9‐fluorenyl carbon–carbon cross‐coupling reaction and those of Ni2 were formed by in situ intramolecular 9‐fluorenyl carbon–carbon radical coupling reaction mechanism. The obtained complexes were characterized using 1H NMR spectroscopy and elemental analyses. The crystal and molecular structures of Ni1 and Ni2 with C–C bridged configuration were determined using X‐ray diffraction. Ni1 and Ni2 were used as catalysts for norbornene (NB) polymerization after activation with B(C6F5)3 and the catalytic activities reached 106 gpolymer molNi−1 h−1. The copolymerization of NB and styrene catalyzed by the Ni1/B(C6F5)3 system showed high activity (105 gpolymer molNi−1 h−1) and the catalytic activities decreased with increasing feed content of styrene. All vinyl‐type copolymers exhibited high molecular weight (104 g mol−1), narrow molecular weight distribution (Mw/Mn = 1.71–2.80), high styrene insertion ratios (11.13–50.81%) and high thermal stability (Td > 380°C) and could be made into thin films with high transparency in the visible region (400–800 nm). Novel C–C bridged Ni(II) complexes bearing β‐keto‐9‐fluorenyliminato ligands with electron‐withdrawing groups were synthesized by metal coordination and different in situ intramolecular bonding mechanisms, and applied in the (co)polymerization of norbornene and styrene. The copolymers were obtained with high styrene monomer content, and exhibited high thermal stability, narrow molecular weight distribution and high transparency in the visible region. [ABSTRACT FROM AUTHOR]