Group 4 complexes derived from o-carborane: synthesis, structures and ethylene polymerization properties

Nine thermally stable complexes (η⁵-Cp*)η⁵-(C₅H₄)CMe₂CB₁₀H₁₀CR]MCl₂ (R=H and Me) and (η⁵-Cp*)η⁵; η¹-(C₅H₄)CMe₂(CB₁₀H₁₀C)]MCl have been prepared via metathesis reactions of Cp*MCl₃ (M=Ti, Zr and Hf, Cp*=pentamethylcyclopentadienyl) with monolithium salts of (C₅H₅)CMe₂(CB₁₀H₁₀CR) (R=H and Me) and with dilithium salt of (C₅H₅)CMe₂(CB₁₀H₁₀CH), respectively. These compounds have been fully characterized by various spectroscopic methods and elemental analyses. All of the compounds except (η⁵-Cp*)η⁵-(C₅H₄)CMe₂CB₁₀H₁₀CMe]HfCl₂ were additionally characterized by a single crystal X-ray diffraction study, establishing their monomeric bent metallocene structural feature with carborane acting as a substituent or an ancillary ligand. The titanium and zirconium complexes produce high-density polyethylenes with the activity range of about 10³-10⁴ g PE per mol of M bar h in the presence of modified methylaluminoxane cocatalyst.