Metallaoxirane-Supported Hydrido Group 4 Metallocene Cations

The (η2-diaryl ketone)zirconocene dimers 17a and 17b (aryl = phenyl or p-tolyl) react with the group 4 metallocene dihydride complexes [RCp2MH2] (RCp2M = Cp2Zr, (MeCp)2Zr, or Cp2Hf) to yield the dimetallic compounds [(μ-η1-O:η2-C,O-Ar2CO)ZrCp2/H2MRCp2] 18a−f. These systems contain a dimetallabicyclic framework in which the two metal centers are bridged by the η2-diaryl ketone ligand oxygen atom and a μ-hydride ligand. The remaining hydride ligand is trans-oriented to the μ-H moiety at the MRCp2 unit. The complexes 18a−c were characterized by X-ray diffraction. Treatment of the complexes 18 with B(C6F5)3 results in the selective abstraction of the terminal hydride ligand to form the dimetallic cation complexes [(μ-η1-O:η2-C,O-Ar2CO)ZrCp2(μ-H)MRCp2]+ 19a−f (with HB(C6F5)3 - anion). The complexes 19 contain the intact (η2-diaryl ketone)ZrCp2 unit to which a (H−MRCp2)+ cation is formally attached. They exhibit a planar dimetallabicyclic framework, in which the two group 4 metal centers are connected by means of the η2-ketone oxygen atom and the μ-hydride ligand. The complexes 19a,b and e were characterized by X-ray crystal structure analyses. The complexes 19 behave chemically as adducts of the highly reactive (RCp2M−H)+ cations with a metallaoxirane matrix. Ethene is polymerized by the systems 19 with high catalyst activities.