Preparation, Structure, and Ethylene (Co)Polymerization Behavior of Group IV Metal Complexes with an [OSSO]‐Carborane Ligand

The synthesis of Group IV metal complexes that contain a tetradentate dianionic [OSSO]‐carborane ligand [(HOC 6 H 2 t Bu 2 ‐4,6) 2 (CH 2 ) 2 S 2 C 2 (B 10 H 10 )] ( 1 a ) is described. Reactions of TiCl 4 and Ti(O i Pr) 4 with the [OSSO]‐type ligand 1 a afford six‐coordinated titanium complex [Ti(OC 6 H 2 t Bu 2 ‐4,6) 2 (CH 2 ) 2 S 2 C 2 (B 10 H 10 )Cl 2 ] ( 2 a ) and four‐coordinated titanium complex [Ti(OC 6 H 2 t Bu 2 ‐4,6) 2 (CH 2 ) 2 S 2 C 2 (B 10 H 10 )(O i Pr) 2 ] ( 2 b ), respectively. ZrCl 4 and HfCl 4 were treated with 1 a to give six‐coordinated zirconium complex [Zr(OC 6 H 2 t Bu 2 ‐4,6) 2 (CH 2 ) 2 S 2 C 2 (B 10 H 10 )Cl 2 (thf) 2 ] ( 2 c ) and six‐coordinated hafnium complex [Hf(OC 6 H 2 t Bu 2 ‐4,6) 2 (CH 2 ) 2 S 2 C 2 (B 10 H 10 )Cl 2 ] ( 2 d ). All the complexes were fully characterized by IR, NMR spectroscopy, and elemental analysis. In addition, X‐ray structure analyses were performed on complexes 2 a and 2 b and reveal the expected different coordination geometry due to steric hindrance effects. Extended X‐ray absorption fine structure (EXAFS) spectroscopy was performed on complexes 2 c and 2 d to describe the coordination chemistry of this ligand around Zr and Hf. Six‐coordinated titanium complex 2 a showed good activity toward ethylene polymerization as well as toward copolymerization of ethylene with 1‐hexene in the presence of methylaluminoxane (MAO) as cocatalyst (up to 1060 kg [mol (Ti)] −1  h −1 in the case of 10 atm of ethylene pressure).