[2-(alkylideneamino)benzoato]nickel(II) complexes: Active catalysts for ethylene polymerization

sThe complexes [RR'C=NC6H4C(O)O-kappa(2)N,O]Ni(eta(3)-CH2CMeCH2) (R, R'= -(CH2)(5)-,6; R = Et, R' = Et, 7; R = tBu, R' = H, 8) are prepared by reaction of the corresponding potassium salts with [(eta(3)-CH2CMeCH2)NiCl](2) in CH3CN. Additions of 1 equiv of B(C6F5)(3) afford the zwitterionic complexes [RR'C=NC6H4C{OB(C6F5)(3)}O-kappa(2)N,O]Ni(eta(3)-CH2CMeCH2) (R, R' = -(CH2)(5)-, 9; R = Et, R' = Et, 10; R = tBu, R' = H, 11), which give poly(ethylene) when ethylene gas is added. This result is interesting in that the corresponding 2-(diphenylphosphino)benzoato and 2-(diphenylamino)benzoato complexes give mainly butene. Reactions of the potassium salts with Ni(eta(3)-CH2C6H5)Cl(PMe3) afford benzyl complexes, [RR'C=NC6H4C(O)O-kappa(2)N,O]Ni(eta(1)-CH2C6H5)(PMe3) (R, R'= -(CH2)(5)-,12; R = Et, R'= Et, 13). Additions of 2 equiv of B(C6F5)(3) to 12 and 13 afford the zwitterionic eta(3)-benzyl complexes [RR'C=NC6H4C{OB(C6F5)(3)}O-kappa(2)N,O](2)Ni(eta(3)-CH2C6H5) (R, R'= -(CH2)(5)-,14; R = Et, R'= Et, 15). Complex 14 is rather unstable, and a bis ligand complex, [(CH2)(5)C=NC6H4C{OB(C6F5)(3)}O-kappa(2)N,O](2)Ni (16), is formed during recrystallization. Complexes 14 and 15 are highly active to ethylene polymerization, and activities reach 3000-4000 kg/((mol of Ni) h) at 75 psig pressure. Solid structures of 6, 9, 11, 15, and 16 were determined by X-ray crystallography.