Shaofeng Liu

University of Strasbourg, Strasburg, Alsace, France

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Publications (3)12.45 Total impact

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    ABSTRACT: To gain a deeper knowledge of the nature of the species formed in situ by reaction of a catalyst precursor complex and typical cocatalysts used for ethylene oligomerization or polymerization, the Cr(III) complex fac-[Cr(NPN)Cl3] (1; NPN = bis(2-picolyl)phenylphosphine) was reacted with MAO and partial methylation to give the mononuclear complex fac-[Cr(NPN)Cl2.23Me0.77] (2) was observed, whereas reaction with AlMe3 in toluene led to partial halide abstraction and produced the dinuclear, chloride-bridged dicationic complex [{fac-Cr(NPN)Me(μ-Cl)}2][AlMexCl4–x]2 (3·[AlMexCl4–x]2), in which the metal centers are bridged by two chloride ligands. The complex fac-[Cr(NPN)Cl2Et] (4) was isolated in high yield from the reaction of 1 with AlEt3 and contains a rare example of CrIII–Et function. Upon treatment of 1 with EtAlCl2, the dinuclear Cr(III) complex [{fac-Cr(NPN)}2(μ-Cl)3][AlCl4]3 (5·[AlCl4]3) was obtained, which contains three bridging chlorides. Thus, under the conditions investigated, MAO and AlEt3 behaved as alkylation agents, whereas AlMe3 and EtAlCl2 reacted as cationization agents. On activation with MAO and under comparable conditions, 1–5 exhibited similar catalytic properties, with activities between 2700 and 2800 g of C2H4/((g of Cr) h), but the major oligomer produced using the 4/MAO system was 1-decene. The neutral alkyl complexes 2 and 4 and the cationic complexes 3 and 5 did not exhibit catalytic activity for ethylene oligomerization in the absence of MAO. The structures of the complexes 2, 3·[AlMexCl4–x]2, 4, and 5·[AlCl4]3 have been determined by single-crystal X-ray diffraction.
    Organometallics 06/2011; 30(13):3549–3558. · 4.25 Impact Factor
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    ABSTRACT: Reaction of TlPF(6) with the Cr(III) complex fac-[CrCl(3)(NPN)] (NPN = bis(2-picolyl)phenyl phosphine) did not lead to precipitation of TlCl but rather to addition of the Tl(+) cation to the CrCl(3) moiety, which resulted in a pseudo-dimeric adduct which has an unusual tetranuclear centrosymmetric structure in the solid state.
    Dalton Transactions 09/2010; 39(34):7881-3. · 4.10 Impact Factor
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    ABSTRACT: A variety of Pd(II) complexes containing the neutral N,P,N-ligand bis(2-picolyl)phenylphosphine (N(py)PN(py)) have been synthesised and characterized by IR and NMR spectroscopy and X-ray diffraction. The neutral complex [PdCl(2)(N(py)PN(py)-N,P)] (1) has been selectively obtained in high yield by reaction of [PdCl(2)(NCPh)(2)] with the ligand in dichloromethane. The cationic complexes [PdCl(N(py)PN(py)-N,P,N)]PF(6) (2) and [Pd(N(py)PN(py)-N,P,N)(NCMe)](PF(6))(2) (5) have been prepared from the same reagents by addition to the reaction mixture of one or two equivalents of TlPF(6), respectively. It was found that dynamic exchange of the pyridine rings of 1 occurs on the NMR time-scale and possible mechanisms are discussed. As a by-product of the synthesis of 2, the unexpected dinuclear complex [Pd(2)Cl(2)(mu-N(py)PN(py))(2)](PF(6))(2) (3) has been isolated in 10% yield. Its molecular structure in the solid state reveals the presence of two N(py)PN(py) chelating/bridging ligands. The cationic complex [Pd(2)Cl(2)(mu-N(py)PN(py))(2)](2+) was then selectively obtained by reaction of cis-[Pd(N(py)PN(py)-N,P)(2)](BF(4))(2) (4) with [PdCl(2)(cod)]. (1)H- and (31)P{(1)H} NMR studies have demonstrated that 3 converts slowly into 2 in DMSO solution. The Ir(I) complexes [IrCl(cod)(N(py)PN(py))] (6) and [Ir(cod)(N(py)PN(py)-N,P,N)]BAr(F) (7) have also been prepared, the latter exhibits a trigonal bipyramidal structure with the ligand displaying a facial coordination mode. Compound 7 represents a rare example of an Ir(I) complex bearing a N,P,N-chelating ligand.
    Dalton Transactions 03/2010; 39(10):2563-72. · 4.10 Impact Factor