Catalysts for hydrosilylation reactions

Details Catalysts for hydrosilylation reactions Catalysts for hydrosilylation reactions

2002-09-13

2004-10-12

Peng, Kuo-Liang (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

C528S015000, C528S021000, C528S032000, C528S031000, C502S325000

Reexamination Certificate

active

06803440

ABSTRACT:

The invention relates to a catalyst which is appropriate for catalyzing hydrosilylation reactions.
The addition of an organosilylated compound having an Si—H unit to an olefin or to an acetylene derivative through the formation of a carbon-silicon bond (hydrosilylation reaction) is conventionally carried out in the presence of a metal catalyst. The hydrosilylation reaction is schematically represented in the following manner in the case of olefins:
As an example of a catalyst, platinum catalysts have been recommended by numerous authors. Thus, U.S. Pat. No. 2,823,218 describes a chloroplatinic acid as catalyst. U.S. Pat. No. 2,970,150 proposes the use of metallic platinum on a finely divided support. The hydrosilylation methods described in these patents are however, not very attractive from an economic point of view since they require the use of large quantities of platinum catalyst.
Thus, up until now, most industrial hydrosilylation reactions are catalyzed by the Karstedt solution which consists of complexes of platinum having the oxidation number 0. The general formula of the Karstedt complex is Pt
2
(tetramethyldivinylsiloxane)
3
:
where Me represents methyl.
One of the disadvantages of this catalyst lies in the possible instability of the catalyst during the course of a reaction: it has been possible to observe the precipitation of metallic platinum and the formation of insoluble colloids in the reaction medium: this instability of the catalyst in the reaction medium has the effect of reducing the catalytic activity. Furthermore, it results in cloudy and highly colored solutions which are not much liked by the user since they lead to the formation of highly colored hydrosilylation products.
Another major disadvantage of the Karstedt catalyst is the concomitant formation of by-products of the hydrosilylation reaction: alongside the hydrosilylation products, the products resulting from olefin double bond isomerization reactions and/or hydrogenation reactions are isolated.
One of the objectives of the present invention is therefore to provide a stable catalyst complex which makes it possible to limit the side reactions.
Because of its excellent stability, the complex of the invention moreover makes it possible to operate at higher reaction temperatures.
The other advantages of the invention will appear to a person skilled in the art on reading the preferred embodiments of the invention.
The invention relates more particularly to a metal complex of formula I:
in which:
M represents a metal having an oxidation number 0 chosen from the group 8 metals in the Periodic Table as published in the Handbook of Chemistry and Physics, 65
th
edition, 1984-1985;
X represents O, NR
a
or CR
f
R
g
;
Y
1
and Y
2
represent, independently of each other, CR
b
R
c
or SiR
d
R
e
;
R
1
, R
2
, R
5
and R
6
, which are identical or different, are chosen from a hydrogen atom, an alkyl group and an aryl group optionally substituted with alkyl;
R
3
, R
4
, R
a
, R
b
, R
c
, are independently chosen from a hydrogen atom; an alkyl group; an acyl group; an aryl group optionally substituted with alkyl; a cycloalkyl group optionally substituted with alkyl; and an arylalkyl group in which the aryl portion is optionally substituted with alkyl;
R
d
and R
e
are independently chosen from alkenyl; alkynyl; alkyl; alkoxy; acyl; aryl optionally substituted with alkyl; cycloalkyl optionally substituted with alkyl; and arylalkyl in which the aryl portion is optionally substituted with alkyl; or alternatively
when Y
1
and Y
2
independently represent SiR
d
R
e
, two R
d
groups linked to two separate silicon atoms together form a chain of formula:
in which n is an integer from 1 to 3; X is as defined above; R and R′, which are identical or different, take any one of the meanings given above for R
e
, it being understood that when n is 2 or 3, a single silicon atom of said chain may be substituted with one or two alkenyl or alkynyl groups;
or alternatively when Y
1
and Y
2
independently represent SiR
d
R
e
, two R
d
groups linked to separate silicon atoms together form a saturated hydrocarbon chain, the two R
b
groups together with said silicon atoms and X forming a 6- to 10-membered ring; or alternatively
when Y
1
and Y
2
independently represent CR
b
R
c
, two R
b
groups linked to separate carbon atoms together form a saturated hydrocarbon chain, the two R
b
groups together with the carbon atoms carrying them and X form a 6- to 10-membered ring;
R
f
and R
g
represent, independently of each other, a hydrogen atom; an alkyl group; an acyl group; an aryl group optionally substituted with alkyl; a cycloalkyl group optionally substituted with alkyl; an arylalkyl group in which the aryl portion is optionally substituted with alkyl; a halogen atom; an alkenyl group; an alkynyl group; or a group SiG
1
G
2
G
3
where G
1
, G
2
and G
3
are, independently of each other, alkyl; alkoxy; aryl optionally substituted with alkyl or alkoxy; or arylalkyl in which the aryl portion is optionally substituted with alkyl or alkoxy;
L represents a carbene of formula II.1 or II.2:
in which:
A and B independently represent C or N, it being understood that when A represents N, then T
4
represents nothing and when B represents N, then T
3
represents nothing;
T
3
and T
4
independently represent a hydrogen atom; an alkyl group; a cycloalkyl group optionally substituted with alkyl or alkoxy; an aryl group optionally substituted with alkyl or alkoxy; an alkenyl group; an alkynyl group; or an arylalkyl group in which the aryl portion is optionally substituted with alkyl or alkoxy;
T
1
and T
2
independently represent an alkyl group; an alkyl group which is perfluorinated or optionally substituted with a perfluoroalkyl group; a cycloalkyl group optionally substituted with alkyl or alkoxy; an aryl group optionally substituted with alkyl or alkoxy; an alkenyl group; an alkynyl group; or an arylalkyl group in which the aryl portion is optionally substituted with alkyl or alkoxy; or alternatively
the substituents T
1
, T
2
, T
3
and T
4
, may form in pairs, when they are located on two adjacent summits in the formulae II.1 and II.2, a saturated or unsaturated hydrocarbon chain.
According to the invention, the oxidation number 0 of the metal M is an essential characteristic of the invention.
Preferably, the group 8 metals which M represents are palladium, platinum or nickel. According to a more preferred embodiment of the invention, M represents platinum having the oxidation number 0.
The expression alkyl is understood to mean, according to the invention, a linear or branched, saturated hydrocarbon chain, preferably having from 1 to 10 carbon atoms, for example from 1 to 8 carbon atoms, even better from 1 to 7 carbon atoms.
Examples of alkyl groups are in particular methyl, ethyl, isopropyl, n-propyl, tert-butyl, isobutyl, n-butyl, n-pentyl, isoamyl and 1,1-dimethylpropyl.
According to the invention, the alkyl portion of the alkoxy radical is as defined above.
The alkyl radical which is perfluorinated or optionally substituted with a perfluoroalkyl group preferably has the formula:
—(CH
2
)
p
—C
q
F
2q+1
in which p represents 0, 1, 2, 3 or 4; q is an integer from 1 to 10; and C
q
F
2q+1
is linear or branched. Preferred examples of this radical are: —(CH
2
)
2
—(CF
2
)
5
—CF
3
and —(CF
2
)
7
—CF
3
.
The expression aryl denotes an aromatic hydrocarbon group having from 6 to 18 carbon atoms, which is monocyclic or polycyclic, and preferably monocyclic or bicyclic. It should be understood that in the context of the invention, the expression polycyclic aromatic radical is understood to mean a radical having two or more aromatic rings, condensed to each other, that is to say having, in pairs, at least two carbons in common. By way of example, there may be mentioned the phenyl, naphthyl, anthryl and phenanthryl radicals.
The expression arylalkyl denotes an alkyl group as defined above, substituted with one or more aryl groups on its hydrocarbon chain, the aryl group being as defined above. Examples thereof are benz

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