1,1-Olefin-bridged bis-(2-indenyl) metallocenes of titanium and zirconium

Tetrasubstituted alkenes bearing geminal 2-indenyl substituents--9-[bis(1H-inden-2-yl)methylidene]-9H-fluorene (6), 2,2'-(2,2-diphenylethene-1,1-diyl)-bis(1H-indene) (7), and 2,2'-(2-propylpent-1-ene-1,1-diyl)-bis(1H-indene) (8) have been synthesized and metallated to form a new class of ansa titanium and zirconium metallocene complexes containing a single sp(2)-hybridized carbon bridge. The synthesis of the tetramethylated bis-indenyl Zr-analog is described. In addition, the 1,1-bis-indenyl ethylene is prepared and the Zr complex is modified by olefin metathesis. X-ray structure analyses reveal strained η(5) sandwich complexes with highly open metal centers. These complexes have proven active in the polymerization of ethylene and its copolymerization with 1-hexene.