Syntheses of rac/meso-{PhP(3-t-Bu-C5H3)2}-Zr{RN(CH2)3NR}, structural analyses of rac-{PhP(3-t-Bu-C5H3)2}Zr{RN(CH2)3NR} (where R is SiMe3 or Ph), and meso to rac isomerization

Axtell, Jonathan C.; Thai, Susan D.; Morton, Laurel A.; Kassel, W. Scott; Dougherty, William G.; Zubris, Deanna L.

doi:10.1016/j.jorganchem.2008.09.018

Cited by 4 publications

(6 citation statements)

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“…The rac/meso isomerization of metallocenes has been reported in the literature, [11][12][13] together with that of ansabridged species. [14][15][16][17][18][19] In order for isomerizations to occur, one of the Cp moieties must dissociate from the metal and recoordinate by the other face.…”

Section: Resultsmentioning

confidence: 81%

“…The rac / meso isomerization of metallocenes has been reported in the literature, − together with that of ansa -bridged species. − In order for isomerizations to occur, one of the Cp moieties must dissociate from the metal and recoordinate by the other face. Interchange is promoted by coordinating solvents and LiCl, and mechanisms have been proposed involving the coordination of anions and/or donor solvents to the metal center with cation assistance to encourage the M−Cp bond heterolysis .…”

Section: Resultsmentioning

confidence: 90%

“…Both isomers of 2 have been characterized by 1 H and 13 C NMR spectroscopy, high-resolution mass spectrometry, elemental analysis, single-crystal X-ray diffraction, and electrochemical studies. Single crystals of rac-2 suitable for X-ray diffraction were grown as pale orange plates by the layering of a sample in CD 2 Cl 2 with Et 2 O.…”

Section: Resultsmentioning

confidence: 99%

“…Both isomers of 3 were characterized by 1 H and 13 C NMR spectroscopy, mass spectrometry, elemental analysis, single-crystal X-ray diffraction, and electrochemical studies. The 1 H NMR spectral data of racand meso-3 were similar to those observed with racand meso-2, in a number of different solvents.…”

Section: Resultsmentioning

confidence: 99%

“…Deuterated solvents for NMR spectroscopy of oxygen-or moisture-sensitive materials were treated as follows: C 6 D 6 was freeze-pumpthaw degassed and dried over a K mirror; d 5 -pyridine and CDCl 3 were dried by reflux over calcium hydride and purified by trap-to-trap distillation; and CD 2 Cl 2 was dried over 3 A molecular sieves. 1 H and 13 C NMR spectroscopy were performed using a Varian 300 MHz spectrometer and recorded at 300 K unless stated otherwise. 1 H and 13 C NMR spectra were referenced via the residual protio solvent peak.…”

Section: Methodsmentioning

confidence: 99%

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Synthesis, Characterization, and Polymerization Studies of Ethylenebis(hexamethylindenyl) Complexes of Zirconium and Hafnium

et al. 2011

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The chemistry of a series of ansa-bridged ethylene-bis(hexamethylindenyl)zirconium and hafnium complexes has been explored. Treatment of EBI*Li 2 3 THF 0.38 with MCl 4 3 THF 2 (M = Zr, Hf) gives rac-EBI*MCl 2 (rac-2, rac-3) and meso-EBI*MCl 2 (meso-2, meso-3) (M=Zr and Hf), respectively. The rac-and meso-isomers can be separated by fractional crystallization. meso-EBI*ZrMe 2 (meso-4) can be prepared by alkylation of meso-2 with MeLi 3 LiBr. The molecular structures of racand meso-2 and racand meso-3 have been determined by single-crystal X-ray crystallography. A comprehensive structural comparison between these compounds and related ansa metallocenes has been carried out. racand meso-2 and racand meso-3 in the presence of modified methylaluminoxane (MMAO) are very active catalyst precursors for the polymerization of ethene to give high-density polyethene (HDPE) with molecular weights (M w ) in the range 100 000-220 000 and polydispersities (M w /M n ) of ca. 2.6. The activities of both catalyst precursors racand meso-2 are some of the highest reported in the literature, at 61 800 and 38 200 kg PE /mol met/h/bar, respectively.

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