Ni(I) Intermediates Formed Upon Activation of a Ni(II) Α-Diimine Ethylene Polymerization Precatalyst with AlR3 (R = Me, Et, and Ibu), AlR2Cl (R = Me, Et), and MMAO: A Comparative Study

A variety of heterobinuclear Ni(I) complexes of thegeneral formula [LNiI(mu-X1)(mu-X2)AlR2] formed upon the activationof the [LNiIIBr2](1) ethylene polymerization catalyst (L = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with AlR3(R =Me, Et, andiBu), AlR2Cl (R = Me, Et), and MMAO were detectedand characterized in situ by EPR and1H NMR spectroscopy. Thenature of the bridging groups X1and X2(X1,X2= R, Br, or Cl)depends on the nature and excess of the cocatalyst used. The catalystsystems displaying various [LNiI(mu-X1)(mu-X2)AlR2] species werecompared in ethylene polymerization. Possible roles of Ni(I) speciesin the catalytic process are discussed.