- Nickel(II) complexes with imino-imidazole chelating ligands bearing pendant donor groups (SR, OR, NR2, PR2) as precatalysts in ethylene oligomerization
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New imino-imidazole ligands bearing a pendant donor function L were synthesized in excellent yields. The corresponding nickel(II) complexes [NiCl2(imino-imidazole-L)]n (L = (CH2) 2SMe (2a), (CH2)2OMe (2b), (CH 2)2NEt2 (2c), (CH2) 2PPh2 (2d), (C6H4)-p-OMe (2e), (CH2)3OMe (2f), (CH2)3CH3 (2g); n = 1, 2) were prepared and characterized by FT-IR spectroscopy and elemental analysis. Furthermore, the coordination geometry around the metal center in the dinuclear complex 2a and the mononuclear complexes 2c and 2e was unambiguously established by single crystal X-ray diffraction. All complexes have been evaluated for the oligomerization of ethylene in the presence of EtAlCl2 or MAO (methylaluminoxane) as cocatalyst, and mostly dimers and trimers were produced. Better activities were observed with EtAlCl 2 as cocatalyst than with MAO.
- Boudier, Adrien,Breuil, Pierre-Alain R.,Magna, Lionel,Olivier-Bourbigou, Helene,Braunstein, Pierre
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p. 31 - 37,7
(2020/08/20)
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- Mono- and dinuclear nickel complexes with phosphino-, phosphinito-, and phosphonitopyridine ligands: Synthesis, structures, and catalytic oligomerization of ethylene
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The P,N-type ligands 2-[(diphenylphosphino)methyl]pyridine (12), 2-[2-(diphenylphosphino)ethyl]pyridine (13), 2-methyloxy(diphenylphosphino) pyridine (14), 2-methyloxy(dibenzyl-1,2-oxaphosphorino)pyridine (15), and 2-methyloxy(di-tert-butylphosphino)pyridine (16) have been prepared in good yields, and 12 and 13 have been used to synthesize Ni(II) complexes of formula [Ni(P,N)Cl2], 17 (P,N = 12) and 18 (P,N = 13), by reaction with NiCl2 in methanol. The crystal structure of 18 has been determined by X-ray diffraction to be dinuclear with a distorted square-base pyramidal geometry around the Ni(II) centers. To examine the possible influence of the nature of the spacer link between the P and N donor atoms, we compared ligand 13, with a CH2CH2 spacer, with 14 and 16, which have a isosteric CH2-O spacer. Reactions of the phosphinitopyridine ligands 14 and 16 and of the phosphonitopyridine 15 with [NiX2(DME)] (X = Cl or Br) afforded the complexes [Ni(P,N)Cl2] 20 (X = Cl; P,N = 14), 21 (X = Br; P,N = 14), 22 (X = Cl; P,N = 16), and 23 (X = Cl; P,N = 15), respectively. The mononuclear structure of complex 22 has been established by X-ray diffraction and showed a distorted tetrahedral geometry around the metal center. Complexes 17, 18, and 20-22 have been tested as precatalysts in the oligomerization of ethylene, with AlEtCl2 or MAO as cocatalyst, in order to evaluate the influence of the stereoelectronic properties of the phosphorus substituents. With only 6 equiv of AlEtCl2 as cocatalyst and 4 × 10-5 mol precatalyst, complex 18 was the most active, with turnover frequencies (TOF) up to 91 200 C2H4/(mol Ni·h), and 20 with 2 equiv of AlEtCl2 showed the highest selectivities for ethylene dimers (up to 97%) and in 1-butene (up to 72%). When only 10-5 mol precatalyst was used, the TOF values went up to 207 600 for 18 and 150 100 for 20. With only 25 equiv of MAO as cocatalyst, complex 18 was again the most active, with TOF values up to 20 600 C2H 4/(mpl Ni·h). Despite the high selectivity for C4 olefins of 17, 18, 20, and 21 (up to 93% for 20), 22 presented the best selectivities for 1-butene (up to 73%) with MAO as cocatalyst, and its high reactivity for the reinsertion of 1-butene resulted in 2-ethyl- 1-butene being the main product of the catalytic reaction (up to 91%).
- Kermagoret, Anthony,Braunstein, Pierre
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- Method for the production of nickel(0)-phosphorous ligand complexes
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The present invention provides a process for preparing nickel(0)-phosphorus ligand complexes starting from nickel(II)-ether adducts.
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Page/Page column 11
(2008/06/13)
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- DIMERISATION DE MONOOLEFINES CATALYSEE PAR DES COMPLEXES DU NICKEL ET DU COBALT GENERES ELECTROCHIMIQUEMENT
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Dimerization of olefins was performed with NiL2X2 and CoL2X2 complexes by an electrochemical reduction process under controlled cathodic potential.The influence of several parameters (choice of anode, supporting electrolyte, ligand, temperature and pressure) was studied in order to increase the dimer production and selectivity.In case of ethylene, with nickel-based catalysts, 2-butenes are formed selectively with a turn-over number of 12 000 within 50 h.With propylene as substrate methylpentenes are the main products, in which case the reaction rate appears to be two orders of magnitude lower than with ethylene under identical conditions.Although less active, cobalt based catalysts show an unusual behaviour, as they are particularly selective for 1-butene production (>90percent).
- Masotti, H.,Wallet, J. C.,Pfeiffer, G.
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p. 241 - 252
(2007/10/02)
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