•Ni(II) and Pd(II) complexes with P atom in the side arm were successfully synthesized.•All the complexes were highly active for norbornene polymerization.•The side arm of a P donor have a strong influence on catalytic activity.A series of nickel (II) complexes (1a-4a) and palladium (II) complexes (1b-4b) bearing N,N,P tridentate ligands derived from amino-alkyl phosphines and 2-pyridinecarboxaldehyde and 2-quinolinecarboxaldehyde were synthesized and characterized. X-ray diffraction analysis revealed that complexes 1a, 4a, and 2b adopted square-pyramidal geometry, trigonal bipyramid, and distorted square-planar geometry, respectively. Activated by methylaluminoxane (MAO), all the complexes were highly active for norbornene polymerization in a vinyl addition fashion, affording high molecular weight polymers with narrow molecular weight distributions. The activities of palladium complexes are particularly notable; the highest activity reached 2.45 × 108 g PNB (mol of Ni)−1 h−1. The activities of the complexes were affected by the ligand structure as well as the reaction parameters such as polymerization temperature, time, and cocatalyst loading.Download high-res image (114KB)Download full-size image

Cobalt and nickel complexes (1a-1d and 2a-2d, respectively) supported by 2-imidate-pyridine ligands were synthesized and used for 1,3-butadiene polymerization. The complexes were characterized by IR and element analysis, and complex 1a was further characterized by single-crystal X-ray diffraction. The solid state structure of complex 1a displayed a distorted tetrahedral geometry. Upon activation with ethylaluminum sesquichloride (EASC), all the complexes showed high activities toward 1,3-butadiene polymerization. The cobalt complexes produced polymers with high cis-1,4 contents and high molecular weights, while the nickel complexes displayed low cis-1,4 selectivity and the resulting polymers had low molecular weights. The catalytic activities of the complexes highly depended on the ligand structure. With the increment of polymerization temperature, the cis-1,4 content and the molecular weight of the resulting polymer decreased.

trans-1,4-Selective coordination chain transfer polymerization of 1,3-butadiene was achieved by using a Nd(Oi-Pr)3/Mg(n-Bu)2 catalyst, affording polybutadienes having high trans-1,4 contents (ca. 96%), moderate molecular weight (Mn = 1.0–2.3 × 104), and narrow polydispersity (Mw/Mn ∼ 1.7). In the system, Mg(n-Bu)2 acted as both a co-catalyst and a chain transfer agent, and the calculated transfer efficiencies of Mg(n-Bu)2 were 27–34%. The produced living polybutadiene could further initiate the ring-opening polymerization of ε-CL/lactide to give TPB-b-PCL/PLA copolymers in a controlled fashion. The crystalline amphiphilic copolymers (TPB-b-PCL/PLA) were subsequently applied to investigate their self-assembly behavior by adding a selective solvent into a polymer/co-solvent solution. The polymer plates composed of a crystallized TPB core and PCL/PLA brushes were obtained by the crystallization-driven self-assembly. Moreover, the morphology of the polymers underwent change from nano-sized plates to micro-sized plates with increasing addition of the selective solvent.

•Co(II) complexes bearing bidentate oxazoline-containing ligands were synthesized.•The complexes displayed high activity for 1,3-butadiene polymerization.•The addition of PPh3 could switch the selectivity from cis-1,4 to 1,2-manner.A series of cobalt complexes supported by pyridine–oxazoline (Pyox) and quinoline–oxazoline (Quox) were synthesized. Determined by single crystal X-ray crystallography, complexes 6a and 7c adopted distorted octahedron and trigonal bipyramid geometries, respectively, while complex 6b existed as an ion pair comprised of [CoL2]2+ and [CoCl4]2−, in which the cationic and anionic moieties displayed distorted octahedron and tetrahedral geometries, respectively. Upon activation with ethylaluminium sesquichloride (EASC), these cobalt complexes exhibited high catalytic activity and cis-1,4-selectivity toward 1,3-butadiene polymerization. The selectivity of the catalytic system could be switched from cis-1,4 to 1,2-fashion via the addition of PPh3. The effects of ligand environment, polymerization temperature, and [Al]/[Co] ratio on the polymerization were investigated in detail.Cobalt complexes supported by pyridine–oxazoline (Pyox) and quinoline–oxazoline (Quox) were synthesized and polymerized 1,3-butadiene to give polymers with high cis-1,4 contents. The selectivity of the catalytic system could be switched from cis-1,4 to 1,2-fashion via the addition of PPh3.

•Co(II) and Ni(II) complexes performed high activities to butadiene polymerization.•Ligand environment and polymerization conditions influenced catalytic behaviors.•Addition of PPh3 to Co(II) system resulted in 1,2-polybutadiene.A series of 2,6-bis(imidate)pyridine ligated Co(II) and Ni(II) complexes with general formula of [2,6-(2,6-iPr2C6H3N = COR)2C5H3N]MX2 (R = Me, M = Co, X = Cl (1a); R = Me, M = Ni, X = Br (2a); R = Et, M = Co, X = Cl (1b); R = Et, M = Ni, X = Br (2b); R = iPr, M = Co, X = Cl (1c); R = iPr, M = Ni, X = Br (2c); R = CH2CF3, M = Co, X = Cl (1d); R = CH2CF3, M = Ni, X = Br (2d); R = Ph, M = Co, X = Cl (1e); R = Ph, M = Ni, X = Br (2e); R = CH2Ph, M = Co, X = Cl (1f); R = CH2Ph, M = Ni, X = Br (2f)) were synthesized. Determined by single crystal X-ray analysis, complexes 1e and 2c with NNN tridentate ligands adopted approximate distorted square pyramidal configurations whereas complex 1f with tridentate NNO ligand displayed a distorted square pyramidal configuration. Activated by methylaluminoxane (MAO), these complexes exhibited high cis-1,4 selectivity towards 1,3-butadiene polymerization. The structure of substituent and polymerization conditions significantly influenced the catalytic behaviors of the complexes. The addition of PPh3 to the Co(II)-based systems enhanced the catalytic activity and switched the selectivity from cis-1,4 to 1,2 manner.A series of 2,6-bis(imidate)pyridine Co(II) and Ni(II) complexes had been synthesized and performed high activities and high cis-1,4 selectivities towards 1,3-butadiene polymerization. The ligand environment and polymerization conditions significantly influenced the catalytic behaviors of the corresponding complexes. Addition of PPh3 to the Co(II)-based systems increased their catalytic activities and also switched the selectivity from cis-1,4 to 1,2 manner.

•Co(II) complexes bearing pyridine bisoxazoline ligands were successfully synthesized.•The complexes displayed high activity, cis-1,4 selectivity, and thermostability for 1,3-butadiene polymerization.•The addition of PPh3 could switch the selectivity from cis-1,4 to 1,2-manner.A series of ion-pair cobalt complexes bearing pyridine bisoxazoline ligands were successfully synthesized and characterized by IR spectroscopy and elemental analysis. Determined by X-ray crystallographic analysis, complexes 4a, 4b, 4e, and 4f existed as ion pairs comprised of [CoL2]2+ and [CoCl4]2−. In the complex, the cobalt atom was coordinated by six nitrogen atoms from two ligands, and its coordination geometry at the cobalt center of [CoL2]2+ can be described as distorted octahedron. In combination with ethylaluminum sesquichloride, these cobalt complexes displayed high catalytic activity and cis-1,4-selectivity towards 1,3-butadiene polymerization. The selectivity of the catalytic system can be tuned to predominantly 1,2-fashion via addition of PPh3. The effects of reaction parameters and the ligand environment on the polymerization were also investigated.Figure optionsDownload full-size imageDownload as PowerPoint slide

Acetylenic monomers containing salicylidene Schiff-base groups (1a and 1b) as well as Schiff-base and hydroxy groups (1c) were synthesized and polymerized with [(nbd)RhCl]2/Et3N catalyst to afford the corresponding polymers 2a–c with high molecular weights (Mn = 2.6–7.2 × 105) in high yields (75–97%). Polarimetric, circular dichroism (CD), and UV–vis spectroscopic analyses indicated that the polymers formed helical structures with a predominantly one-handed screw sense. The addition of metal ions to salicylidene Schiff-base-containing polymers 2a and 2b produced insoluble polymer/metal complexes through ionic cross-linking as a result of salicylaldimine–metal ion complexation. Polymers 2b and 2c underwent a helix–coil transition upon the addition of HSO4−, whereas these polymers did not exhibit responsiveness to other anions, such as F−, Cl−, and Br−.

Triarylborane-containing polyacetylene derivatives (2a–c) were synthesized by the polymerization of the corresponding monomers with Rh+(nbd)[C6H5B−(C6H5)3] catalyst. The anion sensing ability of 2a–c was examined by using tetra-n-butylammonium salts of a series of halide ions. UV-vis absorption and emission measurements revealed that these polymers could selectively detect F−, while they did not show any response for Cl−, Br−, and I−. The fluoride sensing properties of these polymers are highly dependent on the structure of the spacers between the conjugated main chain and boron atoms. Namely, 2a containing fluorenyl moieties exhibited a “turn on” fluorescence F− sensing ability. 2b having phenyl spacers displayed emission quenching upon addition of F− in solution, and a signal amplification phenomenon was observed compared to the corresponding monomer. Addition of F− changed the color of the biphenyl group-containing 2c in THF from yellow to orange, indicating that 2c can be used as a colorimetric sensor.

•Fe(II), Co(II) and Ni(II) complexes with chlorinated bis(arylimino)pyridine ligands.•Distinctly different catalytic behaviors in ethylene polymerization was observed.•Bimodal PEs with predominately saturated chain ends were obtained for iron complexes.•Unimodal PEs with vinyl and saturated chain ends were obtained for cobalt complexes.A series of late-transition metal complexes supported with chlorinated bis(arylimino)pyridine ligands [2,6-(ArNCCl)2C5H3N]MtCl2 (Ar = 2,4,6-Me3C6H2, Mt = Fe (1a), Co (2a), Ni (3a); Ar = 2,6-iPr2C6H3, Mt = Fe (1b), Co (2b); Ar = 2,6-Et2C6H3, Mt = Co (1c), Ni (3c); Ar = 2,6-Me2C6H3, Mt = Fe (1d), Co (2d); Ar = 4-Cl-2,6-Me2C6H2, Mt = Fe (1e), Co (2e); Ar = 4-Br-2,6-Me2C6H2, Mt = Fe (1f), Co (2f)) were synthesized. At the presence of methylaluminoxane (MAO), Fe(II)- and Co(II)- based complexes were highly active towards ethylene polymerization, affording polymers with bimodal and unimodal molar mass distributions, respectively, while the Ni(II)-based complexes gave no polymer products. Moreover, the obtained polyethylenes were predominately saturated and vinyl-terminated for Fe(II)- and Co(II)-based complexes, respectively. Changing the ligand environment, polymerization parameters also posed a great influence on the catalytic activities and the properties of the resulting polymers.

Acetylenic monomers containing salicylidene Schiff-base groups (1a and 1b) as well as Schiff-base and hydroxy groups (1c) were synthesized and polymerized with [(nbd)RhCl]2/Et3N catalyst to afford the corresponding polymers 2a–c with high molecular weights (Mn = 2.6–7.2 × 105) in high yields (75–97%). Polarimetric, circular dichroism (CD), and UV–vis spectroscopic analyses indicated that the polymers formed helical structures with a predominantly one-handed screw sense. The addition of metal ions to salicylidene Schiff-base-containing polymers 2a and 2b produced insoluble polymer/metal complexes through ionic cross-linking as a result of salicylaldimine–metal ion complexation. Polymers 2b and 2c underwent a helix–coil transition upon the addition of HSO4−, whereas these polymers did not exhibit responsiveness to other anions, such as F−, Cl−, and Br−.