[ONXO]-Type Amine Bis(phenolate) Zirconium and Hafnium Complexes as Extremely Active 1-Hexene Polymerization Catalysts

• Published in: Organometallics Vol. 21; no. 4; pp. 662 - 670
• Main Authors: Tshuva, Edit Y, Groysman, Stanislav, Goldberg, Israel, Kol, Moshe, Goldschmidt, Zeev
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 18.02.2002; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Physical Sciences; Science & Technology; ALKENE POLYMERIZATION; ALPHA-OLEFIN POLYMERIZATION; GROUP-4 COMPLEXES; LIGANDS; MOLECULAR-STRUCTURE; LIVING POLYMERIZATION; REACTIVITY; CHELATING DIAMIDE COMPLEXES; TITANIUM COMPLEXES; ALKYL COMPLEXES
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om010493w

Several [ONXO]-type zirconium and hafnium dibenzyl complexes of amine bis(phenolate) ligands, where X is a heteroatom donor located on a pendant arm, were synthesized directly from the ligand precursors and the corresponding tetrabenzylmetal complexes in quantitative yields (X = N, O, S). All complexes exhibited remarkable activities in the polymerization of 1-hexene, yielding high-molecular-weight polymers, the highest activity being unprecedented under the conditions employed. An unexpected metal-dependent activity pattern was demonstrated. The high activity of the complexes is derived from the binding of the side-arm donor to the metal and is affected by its nature. The activity order of the zirconium complexes as a function of the side-arm donor was found to be OMe > NMe2 > SMe (5:2:1). The X-ray structures of all zirconium complexes were solved and revealed very similar binding of the [ONO] ligand cores to the metal. The distances between the side-arm donor atoms and the zirconium are relatively long (Zr−O, 2.45 Å; Zr−N, 2.59 Å; Zr−S, 2.86 Å). The X-ray structures of all hafnium complexes were solved as well and found to be closely related to those of the zirconium analogues (Hf−O, 2.45 Å; Hf−N, 2.56 Å; Hf−S, 2.84 Å). However, the activity order was found to be different in the hafnium series, namely SMe > OMe > NMe2 (3.5:1.5:0.2), the [ONSO]-type complex exhibiting the highest activity ever reported for a hafnium complex under the conditions employed. Various NMR experiments supported the notion that the side-arm donor remains attached to the metal in the reactive compounds, which exist as well-separated ion pairs.