Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis

Abstract

The synthesis and characterization of new zirconium permethylpentalene (form)­amidinate complexes are described: Pn*Zr­{N­(Dipp)2CH}Cl (1), Pn* = η8-C8Me6 and Dipp = 2,6- i Pr-C6H3; [Pn*Zr­{N­(p-tol)2CH}­Cl]2 (2), p-tol = 4-Me-C6H4; [Pn*Zr­{N­( i Pr)2CMe}­Cl]2 (3); Pn*Zr­{N­( i Pr)2CPh}Cl (4); Pn*Zr­{N­(4-Me-C6H4)2CH}2 (5); [Pn*Zr­{N­( i Pr)2CCH2}]2 (6); and Pn*Zr­{N­( i Pr)2CPh}­(O-2,6,-Me-C6H3) (7). The monohalide derivatives 1–4 demonstrate considerable structural diversity as the nature of the (form)­amidinate-supporting ligand is changed. While complexes with acidic backbone protons proved susceptible to deprotonation using mild bases, those without underwent straightforward salt metathesis reactions with alkali metal salts, leading to complexes [Pn*Zr­{N­( i Pr)2CCH2}]2 (6) and Pn*Zr­{N­( i Pr)2CPh}­(O-2,6-Me-C6H3) (7). Preliminary slurry-phase ethylene polymerization studies are also reported using complexes 2, 4, 5, and 7 to gain a direct comparison to the highly active, yet electronically saturated, Pn*Zr­(CpR)Cl catalyst family.

Catalytic Behavior of Half‐Metallocene Non‐Cp‐Type Group 4 Metal Complexes (M=Zr, Hf) with a Cyclooctatetraenyl Dianion during Olefin Polymerization

“…Conversely, several complexes bearing similar aromatic anionic ligands have been reported, although they deviate from this Cp‐type half‐metallocene complex. For example, O'Hare's group reported the synthesis of group 4 metal complexes containing pentalenyl (Pn) ligand and their olefin‐polymerization activities (Figure 1, D) [30–33] . Particularly, the Pn‐titanium complex exhibited high activity for ethylene polymerization when combined with solid polymethylaluminoxane (sMAO), which has been synthesized by the controlled hydrolysis of trimethylaluminum with benzoic acid, followed by thermolysis.…”