Novel routes to bidentate cyclopentadienyl-alkoxide complexes of titanium: Synthesis of (eta(5)-sigma-(C5R4CHRCH2CRRO)-C-1-C-2-R-3-O-4)TiCl2

Reaction of C5R41(SiMe3)(CHRCH2CRROR5)-C-2-R-3-O-4 with titanium tetrachloride gives the bidentate eta(5)-sigma-cyclopentadienyl-alkoxide complexes of titanium (eta(5)-sigma-(C5R4CHRCH2CRR4O)-C-1-C-2-R-3)TiCl2 through elimination of chlorotrimethylsilane and RCl (R = SiMe3, CH2Ph, CMe3). A potentially tridentate system (R-1, R-2, R-3 = H, R-4 = -(CH2)(2)OMe) was synthesized in optically pure form and its structure determined by X-ray diffraction. The pendant ether oxygen does not coordinate to the metal, and hydride transfer reactions catalyzed by the complex gave racemic products. Efficient routes to tetramethylcyclopentadienyl-substituted ligands (R-1 = Me) were developed on the basis of the addition of 2-butenylmagnesium bromide to gamma-lactones to give the dienyl alcohols [C(CH3)=CH(CH3)](2)C(OH)CHR2(CH2)(2)OH, which could be functionalized on the primary alcohol before acid-catalyzed cyclization to afford the 3-alkoxypropyl-substituted tetramethylcyclopentadienes.