Ethylene Polymerization at High Temperatures Catalyzed by Double-Decker-Type Dinuclear Iron and Cobalt Complexes: Dimer Effect on Stability of the Catalyst and Polydispersity of the Product

Dinuclear Fe and Co complexes with a double-decker structure were synthesized by using macrocyclic ligands having two bis­(imino)­pyridine groups. X-ray crystallography of the dinuclear Co complex revealed that the two bis­(imino)­pyridine Co moieties stack in an antiparallel manner with a distance of 7.74 Å. A dinuclear Fe complex catalyzes ethylene polymerization at 80–120 °C (5 atm ethylene) to produce polymers with a relatively narrow molecular weight distribution (<i>M</i>_w/<i>M</i>_n = 1.75–2.77); its highest activity is 975 g (mmol Fe)⁻¹ h^–1 atm^–1 at 100 °C. Ethylene polymerization at room temperature under 1 atm ethylene catalyzed by the dinuclear Co and Fe complexes produces polymers with much higher molecular weight (<i>M</i>_n up to 15.5-fold increase) than the corresponding mononuclear complexes

Alkyl chain self ordering, induction and suppression of mesophase by Cu(II) containing [1,2,3]-triazole-based bidentate salicylaldimine ligands: synthesis, characterisation and X-ray diffraction studies

<div><p>Some new Cu(II) complexes containing [1,2,3]-triazole-based bidentate salicylaldimine and its analogues with terminal substituent (F, Cl, Br and I) have been synthesieed. All the target complexes and their uncoordinated ligands were elucidated by elemental analysis and spectroscopic techniques (UV-visible, FT-IR, 1D, 2D ¹H and ¹³C-NMR). The polarising optical microscope and differential scanning calorimetry (DSC) have disclosed all complexes and ligands are mesomorphic except the complex without any terminal substituent. The fluoro-substituted complexes with even parity C₁₄H₂₉ and C₁₆H₃₃ exhibit new enantiotropic nematic phase which was absent in their corresponding ligands, whereas the suppression of SmC phase occurred for all complexes with longer C₁₆H₃₃ and C₁₈H₃₇. X-ray diffraction confirmed the existence of SmA, SmC and N phases for complexes and ligands. The other notable feature is that the self-ordering of terminal alkyl chain occurred in SmA and SmC phases of complexes with even terminal alkyl chain ranging from C₁₄H₂₉ to C₁₈H₃₃. Their corresponding ligands exhibit intercalated structure of SmA and SmC phases. The thermal behaviour studies show that the fluoro-substituted triazole-based complexes possess lowest phase transition temperature and more stable as compared to other substituent which decomposed during the isotropisation.</p></div