A Valence Force Field for Zirconocene Dichlorides

Hoeweler, U.; Mohr, Rolf; Knickmeier, Markus; Erker, Gerhard

doi:10.1021/om00018a033

Cited by 22 publications

(11 citation statements)

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“…The zirconium-chlorine bond lengths are almost identical at 2.4406(5) and 2.4462(5) Å. 26 There is only a marginal structural shielding (C 2 -symmetric) of the sectors above Cl1 and below Cl2. The respective methyl-substituentcarbon-chloride distances are 3.661 (Cl1-C121) and 3.409 Å (Cl2-C42), respectively.…”

Section: Characterization Of the Ansa-metallocenementioning

confidence: 92%

Diastereoselective Synthesis of a Bis(tetrahydroindenyl)zirconocene Dichloride with “Ansa-Fused” Annulated Six-Membered Ring Systems: A Specific Solution of the Synthetic rac-/meso-Group 4 Bent Metallocene Problem

et al. 1997

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1-Phenyl-1,4-pentanedione (3) is selectively converted to the corresponding fulvene-ketone (4) by treatment with cyclopentadiene in the presence of pyrrolidine. Treatment with lithium dimethylcuprate results in selective CH 3 -addition at the fulvene carbon and subsequent ringclosure reaction to give 7, which in the presence of lithium diisopropylamide is rapidly dehydrated to yield the bicyclic fulvene 8. Its treatment with amalgamated calcium metal leads to reductive fulvene coupling and formation of the calcocene complex (10) of the substituted 7,7′-bi(tetrahydroindenyl) ligand. Only the respective rac-isomer is obtained. Hydrolysis of 10 followed by double deprotonation with butyllithium yields the corresponding 7,7′-bi(tetrahydroindenyl) dianion equivalent 16. In tetrahydrofuran, 16 is cleaved at the 7,7′-linkage with formation of the "monomeric" disproportionation products 11-Li and 12-Li, and treatment of 16 with zirconium tetrachloride in THF leads back to the formation of the fulvene 8. Transmetalation to zirconium is, however, cleanly achieved when 16 is treated with donor-ligand-free ZrCl 4 suspended in toluene. The corresponding diastereomerically pure rac-ansa-zirconocene dichloride 17 containing the ansa-bridge as part of the R-fused bi(tetrahydroindenyl) ligand system is obtained under these specific conditions. Complex 17 was characterized by X-ray diffraction, and the outcome of the preliminary propene polymerization experiments is reported.

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Section: Characterization Of the Ansa-metallocenementioning

confidence: 92%

Diastereoselective Synthesis of a Bis(tetrahydroindenyl)zirconocene Dichloride with “Ansa-Fused” Annulated Six-Membered Ring Systems: A Specific Solution of the Synthetic rac-/meso-Group 4 Bent Metallocene Problem

et al. 1997

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“…[27] The parameters for the description of zirconium and its ligands in the [Zr]Cl 2 complexes were used as previously described by us. [9] A new set of parameters was deduced for the ZrϪ(sp 3 -C) bond (carbon atom type MC) using 12 representative metallocene structures from the Cambridge Structural Database (details are provided with the Supporting Information). The following force-field data for the ''new'' carbon atom type MC were used (force constant in kcal mol Ϫ1 , reference values in Å or°): ZRϪMC (110/2.275), HCϪMC (330/1.09), MCϪZRϪMC (80/95.5), MPϪZRϪMC (80/104.2), XCϪMCϪZR (5/109.5), HCϪMCϪZR (40/109.5), ϪZRϪMCϪ (0/180.0, threefold) [MP denotes the artificial Cp(centroid) atom used in the metallocene force-field calculation and XC is the sp 2 -carbon atom that is common to both the five-and six-membered ring of the indenyl ligand].…”

Section: Methodsmentioning

confidence: 99%

“…[9] Relative energies of the located conformers were determined. These geometries were then used in the DFT calculation to give the respective single-point energies on the B3LYP level [10] for comparative purposes.…”

Section: Computational Studiesmentioning

confidence: 99%

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Conformational Features of Group-4ansa-Metallocenes with Long −(CH2)n− Chains Connecting Their Cyclopentadienyl Ligands

Jödicke¹,

Menges²,

Kehr³

et al. 2001

Eur. J. Inorg. Chem.

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Treatment of 1,9-bis(lithiocyclopentadienyl)nonane (8b) with ZrCl 4 (THF) 2 , in dilute solution, gave the crystalline mononuclear ''large'' ansa-metallocene 3b (7% isolated). The X-ray crystal structure analysis of 3b revealed a metallocene conformation where the nonamethylene bridge is oriented toward the lateral sector of the bent metallocene wedge. An analogous structure of 3b is probable in solution, as shown by dynamic 1 H NMR spectroscopy. The activation barrier for the metallocene conformational equilibration process of 3b

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“…[46] The description of the bisindenyldimethylzirconium moiety has been taken from the force field developed by Erker and co-workers. [47] Some new atom types have been introduced to describe the carbon atoms of the indenyl moiety and the methyl group bridging the boron and the zirconium atoms. The force field has been parameterized in order to reproduce the molecular geometry of a set of seven ion pairs; [48] the coordinates have been obtained from the Cambridge Crystallographic Data Centre.…”

Section: Dynamic Behavior Of 2 B: a 2dmentioning

confidence: 99%

Solution Conformation and Dynamics of the Ion Pairs Originating from the Reaction of B(C₆F₅)₃ with Bisindenyl Dimethyl Zirconium Complexes

Beringhelli¹,

D’Alfonso²,

Maggioni³

et al. 2004

Chemistry A European J

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The two ion pairs [(4,7‐Me2indenyl)2ZrMe]+[MeB(C6F5)3]− (1 b) and [(indenyl)2ZrMe]+ [MeB(C6F5)3]− (2 b) have been generated in situ by reaction of stoichiometric B(C6F5)3 with the corresponding dimethyl zirconocenes. It has been shown that molecular mechanics computations, guided by experimental 1H/1H NOE correlations, can provide information on the conformers present in solution. The dynamics of the ion pairs has also been investigated, showing the occurrence of both the processes previously characterized for this class of compounds, namely the B(C6F5)3 migration between the two methyl groups and dissociation–recombination of the whole [MeB(C6F5)3]− anion, the latter process being much faster than the first one (about three order of magnitude). Moreover, it has been shown that in certain conditions intermolecular processes can occur, which mimic the above‐mentioned dissociative exchanges. In particular, the presence of species containing loosely bound [MeB(C6F5)3]− anion fastens the exchange of this anion, while the presence of free B(C6F5)3 accelerates its exchange between the two methyl sites.

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A Valence Force Field for Zirconocene Dichlorides

Cited by 22 publications

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Diastereoselective Synthesis of a Bis(tetrahydroindenyl)zirconocene Dichloride with “Ansa-Fused” Annulated Six-Membered Ring Systems: A Specific Solution of the Synthetic rac-/meso-Group 4 Bent Metallocene Problem

Diastereoselective Synthesis of a Bis(tetrahydroindenyl)zirconocene Dichloride with “Ansa-Fused” Annulated Six-Membered Ring Systems: A Specific Solution of the Synthetic rac-/meso-Group 4 Bent Metallocene Problem

Conformational Features of Group-4ansa-Metallocenes with Long −(CH2)n− Chains Connecting Their Cyclopentadienyl Ligands

Solution Conformation and Dynamics of the Ion Pairs Originating from the Reaction of B(C₆F₅)₃ with Bisindenyl Dimethyl Zirconium Complexes

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A Valence Force Field for Zirconocene Dichlorides

Cited by 22 publications

References 0 publications

Diastereoselective Synthesis of a Bis(tetrahydroindenyl)zirconocene Dichloride with “Ansa-Fused” Annulated Six-Membered Ring Systems: A Specific Solution of the Synthetic rac-/meso-Group 4 Bent Metallocene Problem

Diastereoselective Synthesis of a Bis(tetrahydroindenyl)zirconocene Dichloride with “Ansa-Fused” Annulated Six-Membered Ring Systems: A Specific Solution of the Synthetic rac-/meso-Group 4 Bent Metallocene Problem

Conformational Features of Group-4ansa-Metallocenes with Long −(CH2)n− Chains Connecting Their Cyclopentadienyl Ligands

Solution Conformation and Dynamics of the Ion Pairs Originating from the Reaction of B(C6F5)3 with Bisindenyl Dimethyl Zirconium Complexes

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Solution Conformation and Dynamics of the Ion Pairs Originating from the Reaction of B(C₆F₅)₃ with Bisindenyl Dimethyl Zirconium Complexes