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Issue 33, 2013
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Direct synthesis of cis-dihalido-bis(NHC) complex of nickel(II) and catalytic application in olefin addition polymerization: Effect of halogen co-ligands and density functional theory study

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Abstract

Two novel amine-containing N-heterocyclic carbene ligand precursors [H(1a–b)]Br have been prepared in good yield and fully characterized. Direct syntheses of cis- and trans-dihalido-bis(NHC) nickel complexes [Ni(NHC)2X2] (X = Cl, Br) are reported. The solid structures of trans-[Ni(1a–b)2Br2] (2a–b) and cis-[Ni(1a)2Cl2] (3) were determined by single-crystal X-ray analysis and 3 was found to be the first example of cis-configuration coordination of monodentate NHC ligands to a metal center for dihalido-bis(NHC) nickel complexes. DFT calculations were conducted to determine the energy difference between cis- and trans-isomers of complexes 2a and 3 bearing bromide and chloride co-ligands. The cis-[Ni(1a)2Cl2] (cis-3) is 1.77–1.55 kcal mol−1 lower in energy than its trans-isomer in polar solvents including CH2Cl2 and THF, while the trans-[Ni(1a)2Br2] (trans-2a) is more stable than the cis-isomer similarly in the gas phase. The cis nickel complex 3 with two coordinated monodentate NHCs was tested for olefin addition polymerization at standard conditions. It was found that cis-3 was inactive in ethylene polymerization but showed moderate catalytic activities (0.5–3.0 × 106 g of PNB (mol of Ni)−1 h−1) in the addition polymerization of norbornene in the presence of methylaluminoxane (MAO) as cocatalyst.

Graphical abstract: Direct synthesis of cis-dihalido-bis(NHC) complex of nickel(ii) and catalytic application in olefin addition polymerization: Effect of halogen co-ligands and density functional theory study

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Publication details

The article was received on 11 Apr 2013, accepted on 15 May 2013 and first published on 22 May 2013


Article type: Paper
DOI: 10.1039/C3DT50957E
Citation: Dalton Trans., 2013,42, 12020-12030
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    Direct synthesis of cis-dihalido-bis(NHC) complex of nickel(II) and catalytic application in olefin addition polymerization: Effect of halogen co-ligands and density functional theory study

    D. Zhang, S. Zhou, Z. Li, Q. Wang and L. Weng, Dalton Trans., 2013, 42, 12020
    DOI: 10.1039/C3DT50957E

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