Nickel Complexes with Functional Zwitterionic N,O-Benzoquinonemonoimine-Type Ligands: Syntheses, Structures, and Catalytic Oligomerization of Ethylene
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- 作者：Qing-Zheng Yang ; Anthony Kermagoret ; Magno Agostinho ; Olivier Siri ; Pierre Braunstein
- 刊名：Organometallics
- 出版年：2006
- 出版时间：November 6, 2006
- 年：2006
- 卷：25
- 期：23
- 页码：5518 - 5527
- 全文大小：628K
- 年卷期：v.25,no.23(November 6, 2006)
- ISSN：1520-6041
文摘
The zwitterionic N,N'-dialkyl-2-amino-5-alcoholate-1,4-benzoquinonemonoiminium derivatives[C6H2(
NHCH2CH2X)2(O)2] (X = NMe2, 9; X = NHEt, 10; X = OMe, 11), previously preparedfrom 4,6-diaminoresorcinol by a transamination reaction, and 12 (X = N(CH2CH2)2O) behave as tridentate ligands when reacted with [Ni(acac)2] to form the corresponding octahedral Ni(II) 2:1 complexes[Ni{C6H2(=NCH2CH2 X) (13-16), respectively. In contrast, ligand 9 reacted
with NiCl2·6H2O in a tandemlike manner to afford the stabilized Ni(II) zwitterionic organometalate 1:1complex [NiCl2{C6H2(=NCH2CH2 NMe2) (17). The bonding parametersof complexes 13·H2O·CH2Cl2 and 17, determined by X-ray diffraction, and the conformation of theligands around the nickel center as well as the supramolecular arrangements are discussed and comparedwith those of their previously reported Zn(II) analogues. Complexes 13-17 were tested in catalytic ethyleneoligomerization with MAO and AlEtCl2 as cocatalysts. Complex 17 yielded the highest turnoverfrequencies, with values up to 20 300 and 48 200 mol of C2H4/((mol of Ni) h), in the presence of 400equiv of MAO and 10 equiv of AlEtCl2, respectively. Selectivities for ethylene dimers were slightlyhigher when using MAO: 94% (14 in the presence of 100 equiv of MAO) and 90% (14 in the presenceof 6 equiv of AlEtCl2). The selectivities for 1-butene within the C4 fraction were much higher whenusing MAO as cocatalyst, with values up to 68% (15 in the presence of 100 equiv of MAO). The factthat 17, which contains only one tridentate ligand per nickel center, leads to higher activities than 13-16underlines the importance of the metal center accessibility in the catalytic process.
NHCH2CH2X)2(O)2] (X = NMe2, 9; X = NHEt, 10; X = OMe, 11), previously preparedfrom 4,6-diaminoresorcinol by a transamination reaction, and 12 (X = N(CH2CH2)2O) behave as tridentate ligands when reacted with [Ni(acac)2] to form the corresponding octahedral Ni(II) 2:1 complexeswith NiCl2·6H2O in a tandemlike manner to afford the stabilized Ni(II) zwitterionic organometalate 1:1complex of complexes 13·H2O·CH2Cl2 and 17, determined by X-ray diffraction, and the conformation of theligands around the nickel center as well as the supramolecular arrangements are discussed and comparedwith those of their previously reported Zn(II) analogues. Complexes 13-17 were tested in catalytic ethyleneoligomerization with MAO and AlEtCl2 as cocatalysts. Complex 17 yielded the highest turnoverfrequencies, with values up to 20 300 and 48 200 mol of C2H4/((mol of Ni) h), in the presence of 400equiv of MAO and 10 equiv of AlEtCl2, respectively. Selectivities for ethylene dimers were slightlyhigher when using MAO: 94% (14 in the presence of 100 equiv of MAO) and 90% (14 in the presenceof 6 equiv of AlEtCl2). The selectivities for 1-butene within the C4 fraction were much higher whenusing MAO as cocatalyst, with values up to 68% (15 in the presence of 100 equiv of MAO). The factthat 17, which contains only one tridentate ligand per nickel center, leads to higher activities than 13-16underlines the importance of the metal center accessibility in the catalytic process.