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A high catalyst stability in the aqueous reaction is evidenced by a constant pro-
ductivity over several hours [44-46]. Specially designed water-soluble ligands with
two sulfonated moieties attached to the C
3
-ligand backbone (
2
) [47], or hydroxylated
neutral ligands such as
3
[48] were found to display higher activities than
1
.
The introduction of methoxy substituents at the ortho position of the aryl rings
of diphosphine-modified cationic palladium catalysts results in markedly in-
creased catalyst performance [49]. With the fully
o
-OMe-substituted analogue of li-
gand 1, ethylene-CO copolymers with molecular weights of up to
M
w
1.2
10
5
g
mol
-1
and narrow polydispersitities (
M
w
/
M
n
ca. 2) were obtained in polymeriza-
tions in aqueous suspension. Employing the well-defined complex
4
of this li-
gand, under rather moderate conditions (90
C, 30 bar each of ethylene and CO)
10
4
TO h
-1
have been reported [50].
high activities of 6.1
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