18 research outputs found

    First-row transition metal bis(amidinate) complexes; Planar four-coordination of Fe-II enforced by sterically demanding aryl substituents

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    The sterically hindered benzamidinate ligand [PhC(NAr)(2)](-) (Ar = 2,6-iPr(2)C(6)H(3)) has been employed to prepare bis(amidinate) complexes [{PhC(NAr)(2)}(2)M] of the divalent first-row transition metals Cr-Ni (1-5). For Cr (planar), Mn and Co (tetrahedral) the observed structures follow the electronic preference for the metal ion in its highest spin multiplicity, as determined by DFT calculations. Remarkably, the Fe derivative adopts a distorted planar structure while retaining the high-spin (S = 2) configuration. This rare combination due to reduced interligand steric interactions in the planar vs. the tetrahedral structure, combined with a relatively small electronic preference of Fen for the tetrahedral environment. Thus, the simple bidentate ligand N,N '-diarylbenzamidinate provides a convenient means to make this unusual species accessible for further study. (c) Wiley-VCH Verlag GmbH & Co

    Reactivity of cationic decamethylmetallocene complexes towards ketones

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    Reaction of decamethylmetallocene cations [Cp*2M]+ (M = Sc, Ti, V) with acetone and benzophenone resulted in the formation of the corresponding acetone adducts [Cp*2M(OCMe2)n]+ (M = Sc, n = 2; M = Ti, n = 1; M = V, n = 1) and benzophenone adducts [Cp*2M(OCPh)]+. The stoichiometry of these adducts is determined by both the electronic configuration of the metal center as well as steric pressure imparted by the large Cp*-ligands. In addition, the M-O-C angle is controlled by the number of free valence orbitals of the Cp*2M unit.

    Structure and dynamics in solution of bis(phenoxy-amine)zirconium catalysts for olefin polymerization

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    The activity of two bis(phenoxy-amine)ZrR2 precatalysts (bis(phenoxy-amine) = N,N'-(3-tBu-5-OMe-2-C6H 2OCH2)2-N,N'-Me2-(NCH 2CH2N); R = Me (1), Bn (2, benzyl)) toward propene polymerization has been evaluated using different activators and cocatalysts: MAO, MAO/TBP, B(C6F5)3/TIBA, and [CPh 3][B(C6F5)4]/TIBA (MAO = methylalumoxane, TBP = 2,6-di-tert-butylphenol, TIBA = triisobutylaluminum). It was found that the nature of the activator affects the activity only to a small extent. NMR studies in solution and DFT calculations on the 3a-c and 4a-c(a, MeB(C6F5)3-; b, BnB(C 6F5)3-; c, B(C6F 5)4-) ion pairs deriving from the activation processes of 1 and 2, respectively, showed that three isomers can form. All of them have the anion in the second coordination sphere, whereas the binding modality of the ligand leads to the mer-mer most stable isomer, fac-mer isomer of intermediate stability, and fac-fac least stable isomer. Notably, the energy of the fac-fac isomer, which is supposed to be the active species in the polymerization process, depends more on the R group and not much on X-, in agreement with the small influence of the activators on the polymerization activity. © 2011 American Chemical Society

    Structure and dynamics in solution of bis(phenoxy-amine)zirconium catalysts for olefin polymerization

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    The activity of two bis(phenoxy-amine)ZrR2 precatalysts (bis(phenoxy-amine) = N,N'-(3-tBu-5-OMe-2-C6H 2OCH2)2-N,N'-Me2-(NCH 2CH2N); R = Me (1), Bn (2, benzyl)) toward propene polymerization has been evaluated using different activators and cocatalysts: MAO, MAO/TBP, B(C6F5)3/TIBA, and [CPh 3][B(C6F5)4]/TIBA (MAO = methylalumoxane, TBP = 2,6-di-tert-butylphenol, TIBA = triisobutylaluminum). It was found that the nature of the activator affects the activity only to a small extent. NMR studies in solution and DFT calculations on the 3a-c and 4a-c(a, MeB(C6F5)3-; b, BnB(C 6F5)3-; c, B(C6F 5)4-) ion pairs deriving from the activation processes of 1 and 2, respectively, showed that three isomers can form. All of them have the anion in the second coordination sphere, whereas the binding modality of the ligand leads to the mer-mer most stable isomer, fac-mer isomer of intermediate stability, and fac-fac least stable isomer. Notably, the energy of the fac-fac isomer, which is supposed to be the active species in the polymerization process, depends more on the R group and not much on X-, in agreement with the small influence of the activators on the polymerization activity. © 2011 American Chemical Society

    CCDC 775894: Experimental Crystal Structure Determination

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    Related Article: M.W.Bouwkamp, P.H.M.Budzelaar, A.Meetsma, B.Hessen|2011|J.Organomet.Chem.|696|1920|doi:10.1016/j.jorganchem.2011.02.023,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

    CCDC 775893: Experimental Crystal Structure Determination

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    Related Article: M.W.Bouwkamp, P.H.M.Budzelaar, A.Meetsma, B.Hessen|2011|J.Organomet.Chem.|696|1920|doi:10.1016/j.jorganchem.2011.02.023,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

    CCDC 775896: Experimental Crystal Structure Determination

    No full text
    Related Article: M.W.Bouwkamp, P.H.M.Budzelaar, A.Meetsma, B.Hessen|2011|J.Organomet.Chem.|696|1920|doi:10.1016/j.jorganchem.2011.02.023,An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
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