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Zirconium(IV) Complexes Having a Rigid 1,8-Naphthalene Diamide versus a Flexible 1,3-Propylene Diamide for Olefin Polymerization

2000; American Chemical Society; Volume: 19; Issue: 3 Linguagem: Inglês

10.1021/om990360z

1520-6041

Choong Hoon Lee, Young‐Hye La, Joon Won Park,

Synthetic Organic Chemistry Methods

Structure and chemical properties of zirconium(IV) complexes containing a rigid naphthalene diamide ligand ([1,8-C10H6(NSiMe3)2]2-) or flexible propylene diamide ligands ([1,3-C3H6(NR)2]2-, R = SiMe3, Si(i-Pr)3) are described. The reaction of 1,8-C10H6(NHSiMe3)2 with Zr(NMe2)4 in refluxing toluene yields [1,8-C10H6(NSiMe3)2]Zr(NMe2)2 (1), and the product 1 is converted to [1,8-C10H6(NSiMe3)2]ZrCl2 (2) in a moderate isolation yield by the treatment with excess ClSiMe3. X-ray crystallographic analysis establishes that 2 forms a dimer associated through two chloride bridges in the solid state and has a highly puckered six-membered ring with a small N−Zr−N bite angle (91.05°). The reaction of 1,3-C3H6(NHR)2 (R = SiMe3, Si(i-Pr)3) with Zr(NMe2)4 also affords [1,3-C3H6(NR)2]Zr(NMe2)2. Treatment of the amide complex with excess ClSiMe3 results in [1,3-C3H6(NR)2]ZrCl2 (4, R = SiMe3; 5, R = Si(i-Pr)3) in a facile manner. The crystal structure of 5 shows that the molecule is monomeric, featuring a mirror plane that passes the zirconium atom and two chloride atoms, and the chelate and the metal form a boatlike six-membered ring with a large N−Zr−N angle (104.31°). While these zirconium(IV) diamide complexes (2, 4, and 5) exhibit moderate ethylene polymerization activity (10−90 kg of PE/(molcat·atm·h)) in the presence of methylalumoxane, the diamide dimethyl compound [1,3-C3C6(NSi(i-Pr)3)2]ZrMe2 (6) shows a high activity (300 kg of PE/(molcat·atm·h)) for the ethylene polymerization when it is activated with Ph3CB(C6F5)4.