Anthony KERMAGORET - THESES ET MEMOIRES DE L'UDS

1. Introduction
Chapitre IV
The catalytic production of linear α−olefins (LAO) has enjoyed major industrial
developments since the seminal works of Ziegler and Natta on the oligomerization and
polymerization of ethylene with metal catalysts activated by alkylaluminiums. 1-4 By favoring
chain transfer over propagation during the catalytic cycle, late transition metals such as Ni,
Pd, Co and Fe are good candidates for the formation of oligomerization catalysts. 5-9 The
discovery of the “nickel effect” by Ziegler in 1953 proved the preference of this metal for the
oligomerization of ethylene 10 and many systems based on nickel complexes with P,O, 11-18
N,N, 19-21 N,O, 22-27 P,P, 28 and P,N 8 chelating ligands have provided very interesting catalytic
results. The SHOP process which is based on neutral phenyl nickel complexes of type 1 and
does not require any cocatalyst, remains a reference in oligomerization of ethylene with its
remarkable selectivity for LAO and Schulz-Flory distribution. 11,12 The α-diimine Ni(II)
complexes 2 and 3 also form very active and selective catalysts for LAO when activated by a
cocatalyst like methylalumoxane (MAO). 20,21
Ph
Ph 2
P
O
Ni
1
Ph
PPh 3
R = H, Me, i-Pr
N
N
R
Ni
Br
Br
Me
Me
Me
N
N
Ni
R
Me
2 3
In combinaison with divalent nickel or palladium, P,N-type ligands, such as phosphinoimines
in 4 and 5, 29,30 phosphinonicotine-methyl-esters in 6, 31 phosphinosulfonamides in 7, 32
phosphinidine-imines in 8, 33 phosphinooxazolines in 9, 34,35 phosphinopyrazole in 10, 36 or
derived from α-iminoazatriphenylphosphoranes in 11, 37 result in active catalysts for ethylene
oligomerization or polymerization (Scheme 1).
Br
Br
3