SYNTHESIS, STRUCTURE, AND PROPERTIES OF CHIRAL TITANIUM AND ZIRCONIUM COMPLEXES BEARING BIARYL STRAPPED SUBSTITUTED CYCLOPENTADIENYL LIGANDS

The synthesis and characterization of 2,2'-bis(2-tetrahydroindenyl)biaryl metallocenes of titanium and zirconium which alleviate many of the stereochemical problems associated with previous ligand systems are described. Such systems give only a single chiral isomer of the complex, the biaryl link determines the chirality of the complex, and the tetrahydroindenyl ligands project their C2 chirality directly to the site of reaction. The reaction of the di-Grignard of o-bis(chloromethyl)benzene with the 2,2'-dimethyl esters of biphenyl, 6,6'-dimethylbiphenyl, and binaphthyl gave the corresponding bis(carbinols) in good yields. Acid catalyzed dehydrations of these diols gave the bis(2-indene) compounds in high yield. Both the racemic and the homochiral forms of the bis(2-indene) of the 6,6'-dimethylbiphenyl compound were prepared. Reaction of the dilithio anions of these indene compounds with TiCl3 and ZrCl4 gave the corresponding bis(indenyl) complexes which are sensitive to protic media and decomposed, in some cases rapidly, to the indene ligands. The protic sensitivity has been studied. The in situ prepared bis(2-indenyl) complexes are readily reduced with H-2 and Adam's catalyst to the tetrahydroindenyl complexes. The Ti(IV) and Zr(IV) tetrahydroindenyl complexes are stable in protic media. The yields of the complexes are generally good. X-ray diffraction structures for a bis(tetrahydroindenyl).0.5(hexane) and a bis(indenyl)metal complex (Ti(IV)) have been determined and confirm the expected structures.