Synthesis and Molecular Structures of Neutral Nickel Complexes. Catalytic Activity of (Benzamidinato)(acetylacetonato)nickel for the Addition Polymerization of Norbornene, the Oligomerization of Ethylene, and the Dimerization of Propylene

The new neutral nickel complexes PhC(NSiMe3)2Ni(acac) (3), PhC(NSiMe3)2Ni(acac)(TMEDA) (4), [PhC(NSiMe3)2]2Ni2 (5), [PhC(NSiMe3)2]2Ni·Li2Br2(TMEDA)2 (6), (TMEDA)2Ni
(7), p-MePhC(NSiMe3)2Ni(acac) (8), p-MePhC(NSiMe3)2Ni(acac)(TMEDA) (9), [p-MePhC(NSiMe3)2]2Ni (10), NiMe2Py2 (11) and [p-MePhC(NSiMe3)]2Ni(Py) (14) have been synthesized
and characterized. The solid-state molecular structures of all complexes have been confirmed
by low-temperature X-ray diffraction analysis. The methyl complex p-MePhC(NSiMe3)2Ni(Me)(Py) (13) is not stable and rapidly decomposes, forming the complex [p-MePhC(NSiMe3)]2Ni(Py) (14). Complex 3 activated with MAO has been shown to be an efficient catalytic system
for the norbornene vinyl-type polymerization. The activity of the catalyst and the molecular
weights of the resulting polynorbornenes were found to be dependent on the reaction time,
the MAO/precatalyst ratio, and the reaction temperature. In addition, this catalytic system
has been found to dimerize propylene to a mixture of hexenes with a high turnover frequency
of η = 9040 h-1 and oligomerize ethylene to either a mixture of C4−C6 or/and C4−C14 products,
depending on the temperature and the solvent, extremely rapidly (η = 83 500 h-1).