Synthesis, Characterization, and Polymerization Behavior of Zirconium and Hafnium Complexes that Contain Asymmetric Diamido-N-Donor Ligands
摘要:
Two new "NNN" (diamido-N-donor) ligands have been synthesized that contain ethylene/o-phenylene "arms" and a phenyl-substituted amine donor in the central position, [Mesityl-NH-o-C6H4N(Ph)CH(2)CH(2)NHMesityl] (H(2)1) and [t-Bu-d6-NH-o-C6H4N(Ph)CH(2)CH(2)NHMesityl] (H(2)2). The Zr and Hf complexes that have been isolated include [1]MX2 (M = Zr or Hf, X = NMe2, Cl, or Me) and [2]MX2 (M = Zr or Hf, X = NMe2, Cl, Me). The structures of [1]ZrMe2, [2]ZrMe2, and a dimeric species with the formula [MesitylN-o-C(6)H(4)NCH(2)CH(2)NMesityl]Zr-2(NMe2)(5) have been determined in X-ray crystallographic studies. Abstraction of a methyl kgroup in [1]MMe2 (M = Zr or HO with [Ph3C][B(C6F5)(4)] gives rise to cationic complexes that are active initiators for the polymerization of 1-hexene. Similar activation of [2]MMe2 (M = Zr or Hf) gives rise to dimeric monocations that eventually break up and react further to yield cationic monomethyl species. In all cases the poly[1-hexene] produced in the presence of the monometallic cations was found to be atactic.