NMR and EPR Spectroscopic Identification of Intermediates Formed upon Activation of 8-Mesitylimino-5,6,7-trihydroquinolylnickel Dichloride with AlR2Cl (R = Me, Et)

The intermediates formed upon activation of 8-mesitylimino-5,6,7-trihydroquinolylnickel dichloride [LNiCl2] with AlR2Cl (R = Me, Et) have been studied by 1H NMR and EPR spectroscopy. Activation of LNiCl2 with AlEt2Cl has been shown to afford diamagnetic ion pair [LNiIIEt]+[AlEt3Cl]−, whereas the use of AlMe2Cl as activator yields the paramagnetic ion pair with proposed structure [LNiII(μ-R)2AlMeCl]+[AlMe3Cl]− (R = Cl or Me). With time, both ion pairs convert to bis-ligated Ni(I) complexes with proposed structures [L2NiI]+[A]−, where [A]− = AlEt3Cl– or AlMe3Cl–, respectively. Ethylene reactivity examination reveals that ion pairs [LNiIIEt]+[AlEt3Cl]− and [LNiII(μ-R)2AlMeCl]+[AlMe3Cl]− are the closest precursors of the active species of polymerization.

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