New substituted 5-aryl-2-(N-2,6-diisopropylphenylformimino)-1H-pyrrole ligand precursors reacted with the complex trans-[Ni(o-C 6 H 4 Cl)(PPh 3 ) 2 Cl] to give rise to new mono(2-iminopyrrolyl) nickel(II) complexes with general formula [Ni{κ 2The pyrrole 5-aryl substituent is a phenyl or a bulky anthracen-9-yl ring, the first being also modified by para-substituents with electron-releasing (methoxy) or electron-withdrawing (fluorine) characteristics. The new compounds were fully characterized by NMR spectroscopy, elemental analysis, and two of them by single crystal Xray diffraction. The complexes were tested as aluminum-free catalysts for the oligo-/polymerization of ethylene, at different reaction conditions, revealing catalytic activity even when tested as single-component catalysts. The addition of a phosphine scavenger, such as [Ni(COD) 2 ], enhances significantly the catalytic activity. The polyethylene products obtained are hyperbranched low-molecular-weight oligomers with M n 's in the range 570−3200 g/mol (GPC-based values) and very high branching degrees (80−130 branches/1000 C atoms).

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New mono(5-aryl-2-(N-arylformimino)pyrrolyl) Ni(ii) complexes were synthesised and tested as aluminium-free catalysts for the polymerisation of ethylene, yielding hyperbranched oligo-/polyethylenes.

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The influence of sodium chloride and hydrochloric acid on the diffusion of aqueous nickel chloride has been investigated by using Taylor dispersion to measure ternary mutual diffusion coefficients for aqueous solutions of NiCl2 + NaCl and NiCl2 + HCl at 298.15 K and carrier concentrations from (0.000 to 0.050) mol·dm–3 for each solute. Mutual diffusion coefficients estimated from limiting ionic conductivities using Nernst equations are used to discuss the composition dependence of the diffusion coefficients and the electrostatic mechanism for the strongly coupled diffusion of the solutes.