Synthesis of Tris(β-Diketonato) Complexes of Cyclopentadienylzirconium

Howe, Jerry J.; Pinnavaia, Thomas J.

doi:10.1080/00945717408070125

Cited by 4 publications

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“…It is noteworthy that both complexes 3 and 4 show two single peaks for their cyclopentadienyl groups in their 1 H NMR spectra. This result may be attributed to two distinct types of stereochemical rearrangement processes of such tris (β-diketonato) cyclopentadienyl Zr complexes in solution [36] . Single-crystal X-ray analyses of complexes 3 and 4 were carried out in order to provide precise structural details of them.…”

Section: Syntheses and Characterization Of The Cyclopenta-mentioning

confidence: 96%

“…The replacement of dienyl β-diketonato Zr complexes both chlorine atoms and one Cp group from zirconocene dichloride by nonfluorinated diketone, acetylaceGenerally, the reaction of Cp′ZrCl 3 (Cp′ = Cp* or Cp) tone, however, readily occurs at room temperature in with two equivalents of lithium acetylacetonate aftriethylamine medium, offering complex 4 [36] (Scheme forded disubstituted bis(β-diketonato) Zr complexes 1 and 2. By the method reported by Pinnavaia [34] , 3).…”

Section: Syntheses and Characterization Of The Cyclopenta-mentioning

confidence: 98%

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Half-sandwich β-diketonato complexes of zirconium and their application as catalysts to ethylene polymerization

2006

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The bis(β-diketonato) Zr complexes CpZr(acac) 2 Cl (acac = acetylacetonato) (1) and Cp*Zr(acac) 2 Cl (2) can be synthesized by the reaction of Cp′ZrCl 3 (Cp′ = Cp or Cp*) with 2 equiv of lithium acetylacetonate. CpZr(acac) 2 Cl (1) can be quantitatively prepared by treatment of Cp 2 ZrCl 2 with excess acetylacetone. The tris(β-diketonato) Zr complex CpZr(tfac) 3 (tfac = trisfluoroacetylacetonato) (3) has been prepared by treatment of CpZrCl 3 with sodium trisfluoroacetylacetonate. The replacement of both chlorine atoms and one Cp group from zirconocene dichloride by nonfluorinated diketone, acetylacetone, readily occurs at room temperature in triethylamine medium, offering the tris(β-diketonato) Zr complex CpZr(acac) 3 (4). The complexes were characterized by 1 H NMR spectroscopic methods. In addition, the molecular structures of complexes 3 and 4 have been determined by X-ray diffraction methods. When activated by excess methylaluminoxane (MAO), these complexes were active for ethylene polymerization, offering polyethylenes with high molecular weights and narrow molecular weight distributions. Complex 4 showed a very high ethylene polymerization activity of up to 7100 kg PE/mol Zr·h at 5 atm. Complexes 1 and 2 were also active for ethylene/1-hexene copolymerization.Since the discovery of homogeneous Ziegler-Natta catalysis by group 4 metallocenes in 1980 [1] , considerable effort has been devoted to catalyst modification in order to improve polymerization activity and control polymer properties such as stereoregularity [2,3] , co-monomer incorporation, and microstructure. Despite the ongoing research on metallocene catalysts, the search for alternatives to the metallocene catalysts that can produce polymers with novel properties has been one of the major goals of transition metal coordination chemistry over the last decade [4][5][6] .Investigation into the use of aryloxide (O-C(sp 2 )) [7-10] and alkoxide (O-C(sp 3 )) [11][12][13][14][15] ligands to replace the ubiquitous cyclopentadienyl type ligands in organo group 4 metal complexes has become popular in recent years. Amongst attractive examples are the monocyclopentadienyl-aryloxy Group 4 metal complexes of the type CpM(OAr)X 2 (M = Ti, Zr). High activities are obtained for these complexes in the homopolymerization of ethylene, 1-hexene, or propylene, as well as for the copolymerization of ethylene with α-olefins, styrene and cyclohexene [16][17][18][19][20][21] .Although binding to a metal using one σ and two π orbits, the alkoxide ligand is normally regarded as a four-electron ligand due to the higher electronegativity of oxygen [22] . This leaves the opportunity to add additional donors, such as O, N donors, to be isonumeral and isolobal with Cp − . With split 2σ and 4π-electrondonor set, the β-diketonato ligand has been viewed as being isoelectronic to Cp, which would result in a cationic 14-electron species [L 2 MR] + (L = diketonato) [4] . Tetrakis-(acetylacetonato)titanium, and acetylacetone itself have been included in the early patent literature for ...

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Section: Syntheses and Characterization Of The Cyclopenta-mentioning

confidence: 96%