EPR Spectroscopy of catalytic systems based on nickel complexes of 1,4-diaza-1,3-butadiene (α-diimine) ligands in hydrogenation and polymerization reactions

EPR spectroscopy is used to study catalytic hydration and polymerization reaction systems based on α-diimine complexes of Ni(0) and Ni(II) with the general formula NiBr2(DAD–R) (R = –C3H7 or –CH3) or Ni(DAD–CH3)2 (DAD(–C3H7) = 1,4-bis(2,6-diiso-propylphenyl)-2,3-(dimethyl-1,4-diazabuta-1,3-diene, DAD(–CH3) = 1,4-bis(2,6-dimethylphenyl)-2,3-dimethyl-1,4-diazabuta-1,3-diene)), in combination with Lewis acids (AlEt3, AlEt2Cl, AlEtCl2, B(F5C6)3, BF3·OEt2). Ni(I) complexes of the form (DAD–R)NiX2AlX′y(C2H5)3–y composition (an aluminum atom can be replaced by a boron atom) were identified, where R = –CH3 or –C3H7, X = Br, and X′ = Cl or –C2H5 and α-diimine anion radicals are included in derivatives of aluminum or boron. Oxidation reactions of the Ni(DAD–CH3)2 complex with aluminum alkyl halides and boron derivatives with formation of paramagnetic nickel complexes are observed. It is found that there is no direct relationship between the polymerization activity of ethylene or hydration of the alkenes and the concentration of paramagnetic particles.