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

Abstract

The synthesis of Group IV metal complexes that contain a tetradentate dianionic [OSSO]-carborane ligand [(HOC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2 (B(10)H(10))] (1a) is described. Reactions of TiCl(4) and Ti(OiPr)(4) with the [OSSO]-type ligand 1a afford six-coordinated titanium complex [Ti(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))Cl(2)] (2a) and four-coordinated titanium complex [Ti(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))(OiPr)(2)] (2b), respectively. ZrCl(4) and HfCl(4) were treated with 1a to give six-coordinated zirconium complex [Zr(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))Cl(2) (thf)(2)] (2c) and six-coordinated hafnium complex [Hf(OC(6)H(2)tBu(2)-4,6)(2)(CH(2))(2)S(2)C(2)(B(10)H(10))Cl(2)] (2d). All the complexes were fully characterized by IR, NMR spectroscopy, and elemental analysis. In addition, X-ray structure analyses were performed on complexes 2a and 2b and reveal the expected different coordination geometry due to steric hindrance effects. Extended X-ray absorption fine structure (EXAFS) spectroscopy was performed on complexes 2c and 2d to describe the coordination chemistry of this ligand around Zr and Hf. Six-coordinated titanium complex 2a 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).

Synthesis and olefin homo- and copolymerization behavior of new vanadium complexes bearing [OSSO]-type ligands

“…Their activities were very high, over 40,000 kg/(mol h). Besides, the activities of the studied vanadium complexes are much higher than those observed in ethylene polymerization for titanium, hafnium and zirconium complexes which contain [OSSO] ligands of different structure [12,19], and for the vanadium(V) complex which contains a trans-1,2-dithiacyclohexane-bridged bis(phenolato) ligand activated with MAO [20]. After the complex amount was reduced to 0.05 lmol, the activity of the catalysts was lowered, which may result from easier reduction of vanadium to inactive oxidation states at a very high Al:V molar ratio amounting to 60,000:1, with a higher loss of activity observed for the complex 2V.…”

“…Enantiomerically pure titanium complexes which contained trans-1,2-cyclohexanediyl-linked [OSSO]-type bis(phenolate) ligand were found to produce low-molecular-weight homochiral isotactic oligostyrenes which showed optical activity [14]. There are also known group 4 metal complexes with o-carborane-bridged [OSSO]-type tetradentate ligands with high activity towards ethylene homo-and copolymerization [19]. In contrast to group 4 elements, the group 5 complexes bearing [OSSO]-type bis(phenolate) ligands are rare [20,21].…”

Multi-Alkenylsilsesquioxanes as Comonomers and Active Species Modifiers of Metallocene Catalyst in Copolymerization with Ethylene

“…ethylene/POSS copolymerization [3][4][5][6]17]. However, a positive effect of comonomers was observed earlier for other organometallic systems, i.e., for both metallocene [28,29] and post-metallocene [30] catalysts, in the case of ethylene copolymerization with α-olefins.…”

Ethylene/1-olefin copolymerization behaviour of vanadium and titanium complexes bearing salen-type ligand

“…and 10 min as reported in the quoted papers. Indeed, the amount of comonomer in copolymer decreased for longer reaction times, with other polymerization conditions kept constant 13,14,16,17,8). Comonomer content in the polymer was equal 5.5 mol% after 10 min and dropped down to about 3.7 mol% if the reaction was continued over 1 h. The obtained results showed also that the copolymer yield increased for the increasing polymerization time, but the catalyst activity reached its peak value, 1,332 kg/(mol V 0.5 h), at the shortest polymerization time (run 17) and then it gradually decreased for longer reaction times.…”

“…They are not only highly active but they also give copolymers with high comonomer contents, up to 19.1 mol% [12]. Considerable copolymerization potential is also exhibited by other titanium complexes, and namely those which contain the o-carborane-bridged [OSSO]-type tetradentate ligand [13]. Their catalytic activity for ethylene/1-hexene copolymerization is higher than for homopolymerization (positive ''comonomer effect'').…”