New C-2v- and chiral C-2-symmetric olefin polymerization catalysts based on nickel(II) and palladium(II) diimine complexes bearing 2,6-diphenyl aniline moieties: Synthesis, structural characterization, and first insight intopolymerization properties

Four new 1,4-diaza-2,3-dimethylbutadiene ligands (Ar-N=C(CH3)-(H3C)C=NAr; A r: 3a = 2,6-diphenylphenyl; 3b = 2,6-di(4-OCH3-phenyl)phenyl; 3c = 2,6-di(4 -tert-butyl-phenyl)-phenyl; 3d = 2,6-di(3,5-dimethylphenyl)phenyl) as well as the palladium dichloride complexes 4a-c and methyl monochloride derivati ves 5a-c,were prepared, and their polymerization behavior was investigated. The corresponding nickel species 6a-c were tested for the insertion polyme rization of ethene by in situ reactions of 3a-c with (DME)NiBr2. The ligand s are accessible by a three-step procedure. Aryl boronic acids were prepare d by Grignard reactions of substituted aryl bromides and were coupled,with 2,6-dibromo aniline according to a Suzuki cross-coupling protocol to give t he corresponding terphenyl anilines 2a-d. Condensation of 2,3-butanedione w ith the corresponding aniline afforded the formation of the diimines 3a-d; The corresponding palladium dichloride complexes 4a-e are-accessible by rea ction with (PhCN)(2)PdCl2. The structures of 4a-e could be determined by X- ray analysis. While the terphenyl complex 4a adopts a C-2v-symmetry, 4c exi sts in a chiral C-2-symmetric coordination geometry, due: to the repulsive interactions of the sterically demanding tert-butylphenyl substituents of t he aniline moieties. All palladium and nickel complexes are catalysts for t he polymerization of ethene. However, the chiral NI(II) complex ww6c shows by far the highest polymerization activity up to 2 x 10(4) kg(PE) [mol (Ni) h](-1). The polyethenes obtained with the palladium methyl monochloro cata lysts activated with Na[(3,5-(CF3)(2)C6H3)(4)B] and the nickel dibromo comp lexes activated with MAO are linear and show in the case of the Ni(II)deriv atives molecular weights up to 4.5 x 10(6) g mol(-1) (M-w/M-n approximate t o 2), which can be controlled by addition of hydrogen.