SYNTHESIS, STRUCTURE DETERMINATION, AND REACTIVITY OF C-2-SYMMETRICALETHYLENE-BRIDGED ANSA-BIS(DIMEBCOCP)TITANIUM DICHLORIDES

The bridging of C-2-symmetric ,10-dimethyltricyclo[5.2.2.0(2,6)]-2,5-u ndecadiene (DMeBCOCpH) by silicon, methylene, and ethylene was investi gated. The dimethylsilyl-bridged bis(BCOCp) ligand was accessible but could not be converted to its titanium, zirconium, or niobium chloride complexes. -4-(1-methylethylidene)tricyclo[5.2.2.0(2,6)]-2,5- undecad iene (DMeBCOCp-dimethylfulvene) was formed, but did not react with cyc lepentadienyl anions. A regioisomeric mixture of 1,2-bis[(1R,7R,8R,10R )-8,10-dimethyltricyclo [5.2.2.0(2,6)]-2,5-undecadienyl]ethane [en(DMe BCOCpH)] ligands could be formed and metalated to form ricylo[5.2.2.0( 2,6)]-2,5-undecadien-4-yl]]titanium dichloride [(+)-beta,beta-en(DMeBC OCp)(2)TiCl2, (+)-11] along with its alpha,alpha- and alpha,beta-bridg ed regioisomeric titanocene dichlorides. (+)-11 is unique in that it i s a chiral ethylene-bridged ansa-metallocene which contains only homot opic cyclopentadienyl faces. (+)-11 was characterized by X-ray crystal lography and was applied as a catalyst for the enantioselective isomer ization of alkenes. (+)-11 was less active and less enantioselective t han a known chiral ansa-bis(indenyl)titanium catalyst for the enantios elective alkene isomerization.