Anthony KERMAGORET - THESES ET MEMOIRES DE L'UDS

Ph
O
toluene
PR2R' + Ni(COD) 2 + C5H5N room temp.
3, 8-11
R R'
Ph
P
O
Ni
Ph
Py
18 R = R' = Ph
19 R = Ph, R' = t-Bu
20 R = R' = n-Bu
21 R = Ph, R' = n-Bu
22 R = Me, R' = Ph
(5)
Chapitre VI
However, the reactions were not quantitative and unreacted [Ni(COD)2] and β-keto
phosphorus ylids were detected in the 1 H and 31 P{ 1 H} NMR spectra. Moreover 7, remained
unreactive toward [Ni(COD)2] and an excess of pyridine, in contrast to 11. Here too, an
increase of the reaction temperature to 60 °C led to decomposition of the products and
formation of nickel metal.
3 Catalytic oligomerization of ethylene
The catalytic tests have been performed with in situ-prepared catalysts by stirring equimolar
amounts of the β-keto phosphorus ylids, [Ni(COD)2] and PPh3 under ethylene pressure (30 or
60 bar) and the results are given in Table 3.
Ylids 3, 8, 10 and 12 formed active species for ethylene oligomerization whereas catalytic
tests with 7 and 9 were unsuccessful. The catalytic results with the mass distributions for the
C4-C8 olefins are given in Table 3. Catalytic tests with 8 and 10 showed low activities, with
TON of 1500 and 800 mol C2H4/(mol Ni) after consumption of 8.4 g and 4.5 g of ethylene in
24 h, respectively, but very high selectivities for 1-hexene, 99% with 10 and 99% with 8
(Table 3). The β-keto phosphorus ylids 3 and 12 formed more active catalysts than 8 and 10
with TON of 11000 and 12700 mol C2H4/(mol Ni), respectively, and both showed a similar
selectivity of 98% for 1-hexene.
Catalysis with 3 and 12 have also been performed under an ethylene pressure of 60 bar
during a period of 1.5 and 2 h and at 50 and 82 °C, respectively. Under these conditions, 3
and 12 consumed 15.9 g of ethylene (TON of 5700) in 1.5 h and 12.9 g (TON of 4600) in 2 h,
respectively. 56 Comparing the results obtained under similar catalytic conditions between
isolated complexes 12 and 14 shows that the former presents higher activities and K values. 56
Catalytic polymerization conditions were applied to 8 by using three equiv. of
[Ni(COD)2] for one equiv. of β-keto phosphorus ylid and of PPh3 under an ethylene pressure
10