Mononuclear Aluminum Hydroxide for the Design of Well-Defined Homogeneous Catalysts

An unprecedented aluminum hydroxide LAlMe(OH) (5; L = HC[(CMe)(2,6-iPr2C6H3N)]2) has been
prepared by the hydrolysis of LAlMeCl (4). For the preparation of 5, the reagents of KOH, water, and KH,
as well as the two-phase ammonia/toluene system, were used. Further reactions of 5 with Cp2ZrMe2 (8)
and Cp2ZrHCl in toluene lead to the intermolecular elimination of CH4 and H2 and the formation of μ-O-bridged dinuclear aluminum and zirconium complexes [LAlMe(μ-O)ZrMeCp2] (6) and [LAlMe(μ-O)ZrClCp2]
(7), respectively, in high yields. The crystal structure reveals that 5 is a monomer with terminal OH and Me
groups. The X-ray structure analysis shows that 6 and 7 contain a bent Al−(μ-O)−Zr core with terminal
Al−Me and Zr−Me or Zr−Cl arrangements. The methylalumoxane (MAO)-activated compounds 6 and 7
exhibit high catalytic activity for the polymerization of ethylene. Under comparable polymerization conditions,
the MAO/6 and MAO/7 catalyst systems show considerably higher activity and much lower MAO:catalyst
ratios than that of MAO/8.