Synthesis And Catalytic Properties Of Novel Three-dimensional Geometry α-diimine Nickel, Palladium Complexes On Polymerization Of Cycloolefin And Its Derivatives

In this paper, a series of novel three-dimensional geometry9,10-dihydro-9,10-ethanoanthracene-11,12-diimine nickel complexes with different aryl substituentsC1-C4(Aryl: C1,2,6-dimethylphenyl; C2,2,6-diisopropylphenyl; C3,2,4,6-trimethylphenyl; C4,2,6-dimethyl-4-bromophenyl) were synthesized. The solid-statestructures of all complexes had been determined by single crystal X ray diffractions.In these complexes, the coordination geometries of the complexes C1, C3and C4were demonstrated to be very similar in the solid state. They were both mononuclearand four-coordinate. However, the crystal structure of C2showed a binuclearcomplex, where each nickel atom is five-coordinate. The two nickel atoms togetherwith two bromine atoms form planar four-membered ring.The nickel complexes C1-C4, with three-dimensional geometry, exhibited veryhigh activities for norbornene (NB) homopolymerization with only B(C6F5)3ascocatalyst(107gpolymer/molNi·h). To investigate whether they also had high activitiestoward copolymerization of NB and5-norbornene-2-yl acetate(NB-OCOCH3),complexes C2and C3were selected for copolymerization of NB and NB-OCOCH3inrelatively high activities. Comparing the activities with structures of catalysts, it couldbe found that the activities were following the law: C2>C3>C1>C4. The activitieswere affected remarkably by bulky effect and electronic effect, larger steric hindranceand stronger electron-donating effect of substituents around the aryl in the ligandcould increase the activities. The reactivity ratios of the NB and NB-OCOCH3monomers for C2/B(C6F5)3system by the Kelen-Tüd s method were determined toberNB OCOCH3=0.05and rNB=6.72, respectively. Moreover, the mechanism ofpolymerization catalyzed by the novel three-dimensional geometry nickel(II)complexes was presented and supported by the end group analysis of the polymer anddensity functional theory (DFT) calculation of the reaction. The substituent effect ofthe catalysts and the interaction between Ni2+and NB were discussed, and the resultsshowed that α-diimine nickel complexes with smaller HOMO–LUMO gap couldachieve higher reactivity. Six three-dimensional geometry9,10-dihydro-9,10-ethanoanthracene-11,12-diimine methyl palladium chloride complexes C5-C10with different aryl substituents(Aryl: C5,2,6-dimethylphenyl; C6,2,6-diisopropylphenyl; C7,2,4,6-trimethylphenyl; C8,2,6-dimethyl-4-bromophenyl; C9,4-chlorophenyl; C10,4-trifluoromethylphenyl) were synthesized and characterized. The solid-state structuresof palladium complexes C5, C7and C9had been determined by single crystal X raydiffractions. They featured a square-planar coordination of the central metal. Thebond angles and distances in the palladium coordination plane were within thestandard range for these types of complexes. Two aniline moieties of C5, C7and C9were nearly perpendicular to the five-membered coordination plane, showing noobviously repulsive interactions between the aniline moiety and backbonesubstituents.The catalytic system C5-C10/B(C6F5)3exhibited high activities(105gpolymer/molPd·h) in the homopolymeization of norbornene and copolymerization ofnorbornene with5-norbornene-2-carboxylic acid methyl ester. Introduction ofthree-dimensional geometry on the backbone of palladium complexes couldeffectively improve their thermal stability and afford high incorporation of polarmonomer. The α-diimine palladium complexes with big steric hindrance or stronglyelectron-donating on the aryl ring of ligand could achieve higher reactivities.Moreover, The13C NMR and1H NMR analysis of polymer revealed that the bond ofpalladium-halogen of complexes could be effectively activated by B(C6F5)3.Supported catalyst was an effective method that increased the catalysts’ stabilityand prepared polyolefin nanocomposite materials. The covalently immobilizedmultiwalled carbon nanotubes(MWNTs) supported three-dimensional geometryα-diimine nickel, palladium catalysts(C11/Me3Al/MWNTs and C12/Me3Al/MWNTs)were prepared by corresponding α-diimine nickel(C11), palladium(C12) complexesand Me3Al activated MWNTs(Me3Al/MWNTs). Compared with C11, C12andphysical mixing of nickel, palladium catalysts with MWNTs(C11@MWNTs andC12@MWNTs), C11/Me3Al/MWNTs and C12/Me3Al/MWNTs showed improvedactivity and productivity in norbornene homopolymerization and copolymerizationwith polar monomer. The morphology of the resulting polymers obtained from C11/Me3Al/MWNTs revealed that the MWNTs were dispersed uniformly in polymerand wrapped by polymers to squeeze out of spherical particles, leading to theenhanced processability and mechanical properties.The functionalization of polynorbornene was proved to be an effective strategyto expand its application prospect. Two novel benzonorbornadiene derivatives(OAc)2BenzoNBD and (OCH2PhBr)2BenzoNBD monomers were synthesized andused to copolymerization with2-butoxymethylene norbornene(BN) by the catalyticsystem of C2/B(C6F5)3in toluene, respectively. The (OCH2PhBr)2BenzoNBD or(OAc)2BenzoNBD content in the copolymers could be controlled up to9.1-26.7%or9.7-30.4%by varying the comonomer feed ratios (OCH2PhBr)2BenzoNBD or(OAc)2BenzoNBD from10%to50%. The BN/(OCH2PhBr)2BenzoNBD copolymersand BN/(OAc)2BenzoNBD copolymers exhibited high thermal stability and highglass transition temperature, together with excellent optical transparency. Copolymerswere processed into films and fibers by solution casting method and electrospinning.The films showed good transparency in the visible region, the fibers were uniformand their surfaces were reasonably smooth, with the average diameters of fibersranging from700to1200nm.