Anthony KERMAGORET - THESES ET MEMOIRES DE L'UDS

1. Introduction
Chapitre V
Since the works of Ziegler and Natta, the search for effective olefin polymerization or
oligomerization catalysts with transition metal complexes activated by alkylaluminums
became of high academic and industrial interest. 1-10
Nickel complexes became important for the catalytic ethylene oligomerization after the
discovery of the Shell Higher Olefin Process (SHOP) which involves neutral Ni(II)
complexes bearing a bidentate P,O type ligand (Scheme 1). 11, 12 This system has a remarkable
selectivity for linear α-olefin and presents a Schulz-Flory mass distribution.
Ph
Ph 2
P
O
Ni
1
Ph
PPh 3
Scheme 1. SHOP-type catalyst
Brookhart showed that Ni(II) α-diimine complexes are effective catalysts in polymerization
of ethylene (scheme 2). 6, 7, 13-17 Depending of the steric effect of the substituents of the α-
diimine ligands, the [NiCl2(α−diimine)] precursors form effective catalysts in ethylene
oligomerization with high turnover frequencies (TOF) and a Schulz-Flory mass distribution. 18,
19
N
N
R
R
Ni
R = H, Me, i-Pr
Br
Br
Me
Me
Me
N
N
Me
Scheme 2. α-diimine nickel complexes
Recently we reported the synthesis of nickel complexes bearing P,N-phosphino-pyridine or -
oxazoline ligands which are highly active in the catalytic ethylene oligomerization in the
presence of small amounts of AlEtCl2 or MAO as cocatalyst. 20
Gibson and Brookhart have described highly active olefin polymerization catalysts based on
Fe(II) and Co(II) complexes coordinated by tridentate bis(imino)pyridine ligands and
Ni
Br
Br
4