Synthesis of grouop 4 (Ti, Zr, Hf) homogeneous metallocene catalysts for olefin polymerization

Abstract

A new ligand, cyclopentadienyl-9-fluorene (1), has been prepared from the reaction of NaCp and 9-bromofluorene. The reaction of compound 1 with n-BuLi produces a lithiated ligand, which reacts with 0.5 equiv. of $MCl_4$ to yield [($\eta^5$-cyclopen-tadienyl)-9-fluorenyl]$MCl_2$ [2a(M=Ti), 2b(M=Zr), 2c(M=Hf)]. The reaction of lithiated 1 with $Me_2SiCl_2$ produces a bridged ligand, dimethylbis(cyclopentadienyl-9-fluorenyl))silane(3), which appears to exist as isomers. Dimethylsilanediylbis[($\eta^5$-cyclopenta-dienyl-9-fluorenyl))zirconium dichloride(4), ansa-metallocene catalyst, has been prepared from the reaction of dilithiated 3 and $ZrCl_4$. Complexes ${2a}\sim{2c}$ and 4 have been characterized by spectroscopic methods($^1H$ and $^{13}C$ NMR) and mass spectrometry.