Anthony KERMAGORET - THESES ET MEMOIRES DE L'UDS

mass % of 1-butene
100
90
80
70
60
50
40
30
20
10
0
17
18
20
21
22
ref
6
4
2
equivalents
of AlEtCl 2
Figure 6. Selectivity of the complexes 17, 18 and 20-22 for 1-butene using AlEtCl2 as
cocatalyst, Ref: [NiCl2{P(n-Bu)3}2].
3.2 Use of MAO as cocatalyst.
Chapitre IV
Complexes 17, 18 and 20-22 have also been evaluated in the presence of 12.5, 25, 50,
100 and 200 equivalents of MAO as cocatalyst and the catalytic results are given in Tables 5
and 6 and shown in Figures 7-10.
In contrast to analogous Ni(II) complexes with pyridine-phosphine and pyridine-phosphinite
ligands tested under similar conditions, 8 the precatalysts 17, 18 and 20-22 presented high
activities with very small amounts of MAO (Figures 7-9). In particular, 18 showed activities
up to 18400 and 20600 mol C2H4/(mol Ni·h) with only 12.5 and 25 equivalents of MAO,
respectively. The use of fresh MAO under strict conditions could explain these high activities
of 17, 18 and 20-22, respectively, since MAO is known to be very sensitive to air and
moisture and can rapidly evolve to a poor cocatalyst. 71 Increasing the amount of cocatalyst
did not have a major impact on the catalytic results. Precatalysts 17, 18 and 20-22 had similar
activities, between 14100 and 19600 mol C2H4/(mol Ni·h). The precatalyst 16 with a smaller
bite angle ligand than 18-22 presented slightly lower activities but better selectivities for 1-
butene.
16