Synthesis of new homogeneous olefin polymerization catalysts

Abstract

Nine thermally stable complexes $(η^5-Cp^*)[η^5-(C_5H_4)CMe_2CB_{10}H_{10}CR]MCl_2$ (R = H; a and Me; b) (M = Ti; 1, Zr; 2 and Hf; 3) and $(η^5-Cp^*)[η^5; η^1-(C_5H_4)CMe_2(CB_{10}H_{10}C)]MCl$ (M = Ti; 4, Zr; 5 and Hf; 6) have been prepared via metathesis reactions of $Cp^*MCl_3 (M = Ti, Zr and Hf, Cp^* = pentamethylcyclopentadienyl)$ with monolithium salts of $(C_5H_5)CMe_2(CB_{10}H_{10}CR)$ (R = H; a and Me; b) and with dilithium salt of $(C_5H_5)CMe_2(CB_{10}H_{10}CH)$, respectively. These compounds have been fully characterized by various spectroscopic methods and elemental analyses. All of the compounds except $(η^5-Cp^*)[η^5-(C_5H_4)CMe_2CB_{10}H_{10}CMe]HfCl_2$ 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 $10^3-10^4$ g PE/(mol of M?bar?h) in the presence of MMAO cocatalyst. Reactions of the dilithium salt of aminosilylene-bridged ligands with $(Me_2N)_2ZrCl_2(THF)_2$ followed by the treatment of TMSCl are found to be the efficient method to synthesize aminosilylene-bridged ansa-zirconocenes, $R_2N(Me)Si(η^5-C_5H_4)_2ZrCl_2$ (R = Me (1), Et (2)), $R_2N(Me)Si(η^5-C_5H_4)(η^5-C_5Me_4)ZrCl_2$ (X = Me (3), Et (4)). These complexes were completely characterized and the complex 3 was also characterized by X-ray crystallography. The complex 3 and its prototype complex, $Me_2Si(η^5-C_5H_4)(η^5-C_5Me_4)ZrCl_2$ (9) have very similar steric environment around the metal center comparing their geometrical parameters. Even the similar steric environment, the aminosilylene-brigded ansa-zirconocenes generate branched polyethylenes with broad molecular weight distribution caused by the interaction the amine groups introduced and methylalumoxane (MAO) in ethylene homopolymerization. The branched polyethylene can...