Hexacoordinated nickel catalysts containing salicylaldbenzhydrylimine ligand and tetrahydrofuran heterocycle: High catalytic activity and high 1-hexene insert ratios for norbornene (Co)polymerization

Norbornene Copolymerization with Polar Monomers Catalyzed by Palladium Catalysts Containing Imidazolidin-2-imine/Guanidine Ligands

“…Moreover, the Pd displacement was found to have a further variation from 0.046 to 0.543 Å, and the dihedral angle θ changed from 2.24 to 24.25°in the complexes Pd3−Pd7, which can be explained by the different steric conflicts between the N-aryl substituents and the imidazolidin-2-imine/guanidine moiety in Pd complexes (Figure 3). 62,63 The Pd−CH 3 group of the PdMeCl complexes was confirmed by the presence of proton signals at δ 0.98 (Pd8), 1.52 (Pd9), and 1.60 ppm (Pd10) in the 1 H NMR spectra and carbon signals at δ 0.76 (Pd8), 2.70 (Pd9), and 2.44 ppm (Pd10) in the 13 C NMR spectra, respectively. The structures in Figure 1 revealed that these PdMeCl complexes also adopted a square-planar coordination geometry with N1, N2, C, and Cl atoms, in which the Me group is trans to the N2 atom of the imidazolidin-2-imine/guanidine donor and the Cl is trans to the N1 atom of the N-aryl donor, respectively.…”

“…Norbornene (NB) can be polymerized through three different catalytic approaches: ring-opening metathesis polymerization, cationic/radical polymerization, and vinyl-type addition polymerization. − Among them, the vinyl-type polynorbornene (PNB) obtained by the transition-metal-catalyzed coordination polymerization of NB exhibits unique properties, such as high thermal stability, good chemical resistance, and excellent transparency, owing to its rigid structure. The development of NB-based copolymers through the copolymerization of NB with substituted NB derivatives, ethylene, − propylene, , higher α-olefins, − styrenes, − and dienes , achieved further improvements to the polymer properties, such as toughness, solubility, and surface properties. Moreover, the structure and properties of these copolymers can be further tailored by the appropriate choice of catalyst together with a variation of the comonomer contents, structures, and sequence distributions.…”