TY - JOUR
T1 - Synthesis, structure, and catalytic ethylene oligomerization of nickel complexes bearing 2-pyrazolyl substituted 1,10-phenanthroline ligands
AU - Yang, Yue
AU - Yang, Peiju
AU - Zhang, Cui
AU - Li, Gang
AU - Yang, Xiao Juan
AU - Wu, Biao
AU - Janiak, Christoph
PY - 2008/12/10
Y1 - 2008/12/10
N2 - A series of nickel(II) halide complexes [NiCl2(L)] (1a-12a) and [NiBr2(L)] (1b-12b) bearing 2-pyrazolyl substituted 1,10-phenanthroline derivatives (L1-L12) have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray diffraction analysis (for 1a′, 10b and 12b). Upon activation with methylaluminoxane (MAO), these complexes display good catalytic activities in ethylene oligomerization (up to 3.01 × 105 g mol(Ni)-1 h-1 at 10 atm of ethylene for 12a with L12 = 2-(3,5-diphenylpyrazol-1-yl)-9-mesityl-1,10-phenanthroline). Complexes with bulkier aryl groups in the 9-position of the phenanthroline ring and the 3- and 5-position of the pyrazolyl ring give higher activities. This is explained with the formation of a more directional environment, a reaction channel around the nickel center which enhances the probability of insertion over dissociation after ethylene coordination to Ni. Also, bulkier aryl substituents can suppress chain-transfer reactions (typically β-H elimination) and therefore increase the activity.
AB - A series of nickel(II) halide complexes [NiCl2(L)] (1a-12a) and [NiBr2(L)] (1b-12b) bearing 2-pyrazolyl substituted 1,10-phenanthroline derivatives (L1-L12) have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray diffraction analysis (for 1a′, 10b and 12b). Upon activation with methylaluminoxane (MAO), these complexes display good catalytic activities in ethylene oligomerization (up to 3.01 × 105 g mol(Ni)-1 h-1 at 10 atm of ethylene for 12a with L12 = 2-(3,5-diphenylpyrazol-1-yl)-9-mesityl-1,10-phenanthroline). Complexes with bulkier aryl groups in the 9-position of the phenanthroline ring and the 3- and 5-position of the pyrazolyl ring give higher activities. This is explained with the formation of a more directional environment, a reaction channel around the nickel center which enhances the probability of insertion over dissociation after ethylene coordination to Ni. Also, bulkier aryl substituents can suppress chain-transfer reactions (typically β-H elimination) and therefore increase the activity.
KW - Ethylene oligomerization
KW - Methylalumoxane
KW - Nickel complexes
KW - Nitrogen ligands
KW - Phenanthroline ligand
UR - http://www.scopus.com/inward/record.url?scp=55549115952&partnerID=8YFLogxK
U2 - 10.1016/j.molcata.2008.08.015
DO - 10.1016/j.molcata.2008.08.015
M3 - Article
AN - SCOPUS:55549115952
SN - 1381-1169
VL - 296
SP - 9
EP - 17
JO - Journal of Molecular Catalysis A: Chemical
JF - Journal of Molecular Catalysis A: Chemical
IS - 1-2
ER -