N,O-chelating bidentate Ni (II) and Pd (II) complexes for copolymerization of norbornene and norbornene ester

Synthesis and characterisation of κ2-N,O-oxazoline-enolate complexes of nickel(ii): explorations in coordination chemistry and metal-mediated polymerisation

The synthesis and characterisation (UV-Vis, IR, X-ray diffraction, etc.) of a series of Ni(ii) complexes derived from both known and novel 2-acylmethyl-2-oxazolines (2a-g: i.e., (Z)-1-R-2-(4,4'-dimethyl-2'-oxazolin-2'-yl)eth-1-en-1-ol; R = -Ph, -2-furanyl, -p-NO2-Ph, -t-Bu, -2-thiofuranyl, p-NC-Ph, -CF3) is reported. These Ni materials (3a-g) represent the first group 10 metal complexes of this ligand class. All derivatives reported are paramagnetic (S = 1) compounds of formulae Ni(κ2-N,O-L)2 where L represents an enolate of structure (Z)-1-R-2-(4',4'-dimethyl-2'-oxazolin-2'-yl)eth-1-en-1-ate formed via proton loss from 2. The air- and moisture-stable metal complexes feature a less typical distorted seesaw-shaped disposition of binding atoms around the metal centre for six structurally characterised (X-ray) examples. Preliminary investigations indicate that 3a (R = -Ph) is a useful catalysts for olefin polymerisation in the presence of alkylaluminum reagents.

Bis-(salicylaldehyde-benzhydrylimino)nickel complexes with different electron groups: crystal structure and their catalytic properties toward (co)polymerization of norbornene and 1-hexene

Eight bis-(salicylaldehyde-benzhydrylimino)nickel complexes with different electron groups (Ni1–Ni8), Ni{(3-R₁)(5-R₂)C₆H₂(O)CHNCH(C₆H₅)₂}₂, (R₁ = H, R₂ = H, Ni1; R₁ = H, R₂ = CH₃, Ni2; R₁ = H, R₂ = OCH₃, Ni3; R₁ = H, R₂ = Br, Ni4; R₁ = CH₃, R₂ = H, Ni5; R₁ = OCH₃, R₂ = H, Ni6; R₁ = Br, R₂ = Br, Ni7; R₁ = Cl, R₂ = Cl, Ni8), were synthesized and their crystal structures were characterized using single crystal X-ray diffraction. The results revealed that Ni1–Ni6 belong to the monoclinic system (space group P2(1)/n), Ni7 belongs to the monoclinic system (space group C2/c) and Ni8 belongs to the triclinic system (space group P1̄). All nickel complexes exhibited high activities (0.46–2.07 × 10⁶ g_polymer mol_Ni⁻¹ h⁻¹) toward norbornene homopolymerization, and a strong electron-withdrawing group on the salicylaldimino aromatic ring can enhance the catalytic activity and favor polymerization. Ni1 and Ni2 exhibited high activities (0.55–2.40 × 10⁵ g_polymer mol_Ni⁻¹ h⁻¹) toward copolymerization of norbornene and 1-hexene in the presence of B(C₆F₅)₃. The 1-hexene content in the copolymers could be controlled up to 7.98–12.50% by varying the comonomer feed ratio of 1-hexene from 10 to 50%. It is observed that when the 5-position of the salicylaldimino aromatic ring has a substituent (–CH₃), the 1-hexene insertion rate is lower than that without a substituent. In addition, the polymers showed high molecular weights (1.5–2.4 × 10⁵ g mol⁻¹) and narrow molecular weight distributions (1.62–1.89). The obtained polymers were also verified to be amorphous copolymers and had high thermal stability, good solubility and optical transparency.

Ni(ii) complexes were successfully synthesized and characterized, and were highly active toward (co)polymerization of norbornene, and the 1-hexene content could be controlled.

Synthesis of bis-(benzocyclohexan-ketoimino) Ni(ii) with different electron groups and their catalytic copolymerization of norbornene and polar norbornene

Several N,O-chelating type bidentate ligand nickel complexes were synthesized, characterized and applied to catalyze copolymerization of norbornene and polar norbornene.

Synthesis of well defined C–C bridged Ni(ii) complexes bearing β-ketoiminato-fluorene ligands by bifluorenyl in situ coupling and application for norbornene (co)polymerization

9-Substituted fluorene C–C bridged constrained geometry configuration (CGC) Ni(ii) complexes Ni1 and Ni2 were synthesized by coordination reaction and in situ coupling reaction in the presence of (DME)NiBr₂.