A series of novel nickel complexes (
1-
4) bearing anilido-imine ligands, [(Ar
1N=CHC
6H
4NAr
2)NiBr]
2 (Ar
1 = Ar
2 = 2,6-dimethylphenyl,
1; Ar
1 = 2,6-dimethylphenyl, Ar
2 = 2,6-diisopropylphenyl,
2; Ar
1 = Ar
2 = 2,6-diisopropylphenyl,
3; Ar
1 = 2,6-diisopropylphenyl, Ar
2= 2,6-dimethylphenyl,
4), have been synthesized and characterized. The solid-state structuresof the complexes
1,
2, and
4 were confirmed by X-ray single-crystal analyses to be in theform of a dinuclear and bromine-bridged structure. However, there is an equilibrium thatshifts between the monomer and dimer in solution, which has been monitored using
1HNMR and UV-vis spectrophotometry. The themodynamic parameters for the equilibriumswere calculated to be
H = +13.68 kJ/mol and
S = 40.32 J/(mol K) for
1 and
H = +8.35kJ/mol and
S = 15.21 J/(mol K) for
3. All nickel complexes show low activities for ethyleneoligomerization with MAO as cocatalyst but high catalytic activities for norbornenepolymerization in the presence of MAO.