Organic compounds -- part of the class 532-570 series – Organic compounds – Silicon containing
Reexamination Certificate
2001-11-15
2003-07-08
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Silicon containing
Reexamination Certificate
active
06590117
ABSTRACT:
BACKGROUND OF THE INVENTION
In the production of silicon compositions, transition metal catalysts have long been known to promote the hydrosilation reaction. Each transition metal-catalyzed hydrosilation reaction differs dramatically such that it is difficult to predict which transition metal will efficiently catalyze the hydrosilation reaction of a specific hydridosilyl reactant with a particular unsaturated reactant. For example, the effect of substituents on the silicon atom on adduct yield obtained in the platinum (Pt)-catalyzed reactions with 1-alkenes is in the following order of activity (R=Et):
Cl
3
SiH>Cl
2
RSiH>(RO)
3
SiH>(RO)
2
RSiH>R
3
SiH
The general trend for Pt-catalyzed hydrosilation reactions is that chlorosilanes are more reactive than alkoxysilanes (
Comprehensive Handbook on Hydrosilylation
; B. Marciniec, Ed.; Pergamon Press, New York, 1992; Ch.4; J. L. Speier Adv. Organomet. Chem. 1979, 17, 407; E. Lukevics
Russ. Chem. Rev
. 1977, 46, 197). However, if one evaluates a different transition metal or olefin, the above trend may be different. For example, in the hydrosilation reaction of heptene with rhodium (Rh), the above trend is the reversed. Due to the relative importance of the Pt-catalyzed hydrosilation reaction in commercial production of organofunctional silanes, a process that improved both the reactivity and selectivity of alkoxysilanes in the hydrosilation relative to that seen with chlorosilanes would be valuable.
A number of patents in the art have disclosed that various promoters can increase the rates and/or selectivities of hydrosilation reactions. In terms of chemical structures or properties, the various types of promoters differ dramatically, such that it is not possible to predict which chemical structures or properties are important for promotion, or even which hydrosilation reactions may be promoted, since promotion will also depend on the chemical structures and properties of each of the hydridosilyl reactant, the unsaturated reactant, and the hydrosilation catalyst. For example, the reaction of trichlorosilane with allyl chloride is promoted by weak amines such as phenothiazine (V. T. Chuang U.S. Pat. No. 3,925,434), while the reaction of methyldichlorosilane with allyl chloride requires a more basic tertiary amine such as tributylamine (Ger. Patent 1,156,073; C. Hu et al.
Fenzi Cuihua
, 1988, 2, 38-43; see Chem. Abstr. 1989, 111, 78085 m). Both of those reactions can be promoted with a second hydridosilane (U.S. Pat. No. 4,614,812) through a different promotion mechanism. Alkali metal carbonates or bicarbonates promote hydrosilations of allylic amines with hydridoalkoxysilanes (U. S. Pat. No. 4,481,364). Other hydrosilation reactions are promoted by phosphines, oxygen gas (D. L. Kleyer et al. U.S. Pat. No. 5,359,111), oxygen-containing organics including aldehydes, unsaturated ketones (R. Reitmeier et al. U.S. Pat. No. 5,663,400, H. M. Bank et al. U.S. Pat. No. 5,623,083), tertiary alcohols and silylated derivatives thereof, and propargylic alcohols and silylated derivatives thereof (H. M. Bank et al. U.S. Pat. No. 5,756,795), inorganic or organic salts including sodium alkoxides and compounds of tin and cobalt, and other organic compounds, including alcohols, diols, ethers and esters. Carboxylic acids, along with ketones, and esters thereof, appear to promote platinum-catalyzed hydrosilation reactions between hydridoalkoxysilanes and allylamine (U.S. Ser. No. 415,268). The use of acetic acid in promoting hydrosilations involving trimethoxysilane has been coincidental with the use of vinylcyclohexene oxide as the olefin, since acetic acid was discovered to be an impurity derived from early processes to make that epoxyolefin using peracetic acid (U.S. Pat. No. 2,687,406), as well as allyl glycidyl ether
j. Am. Chem. Soc
. 1959, 81, 3350).
Hydrosilation promotion effects are narrowly specific, and an effective promoter may work for a single hydrosilation reaction between a specific hydridosilane and a specific olefin. In addition to increasing reaction rates, yields, or selectivities, a promoter may act by preventing undesirable side reactions, which reduce yields/selectivities, such as undesired polymerization or formation of less desirable isomeric products. For example, added methanol is disclosed as being effective in reducing the undesired beta-isomer content in reaction products from platinum-catalyzed hydrosilations between trimethoxysilane and the epoxyolefins, i.e., vinylcyclohexene monoepoxide and allyl glycidyl ether (H. Takai et al. U.S. Pat. No. 4,966,981).
The use of amines in the hydrosilation of hydridosilane and acrylonitrile has been reported extensively, particularly tertiary amines in the presence of copper (Cu) (B. A. Bluestein U.S. Pat. No. 2,971,970, 1961; Z. V. Belyakova et al. translation from Zhurnal Obshchei Khimii 1964, 34, 1480-1484; A. Rajkumar et al.
Organometallics
1989, 8, 549-550; H. M. Bank U.S. Pat. No. 5,283,348, and U.S. Pat. No. 5,103,033). U.S. Pat. No. 4,292,434 (T. Lindner et al.) describes the preparation of an amine-platinum catalyst and its use in the hydrosilation reaction. K. R. Mehta et al. in U.S. Pat. No. 5,191,103 reported the use of sterically hindered amines, phosphines or their equivalent salts in the presence of a platinum catalyst to promote the hydrosilation reaction.
In addition to promoting the hydrosilation reaction, amines have been reported to be inhibitors for the hydrosilation reaction. For example G. Janik et al. in U.S. Pat. No. 4,584,361 reported that amines inhibited polyorganosiloxane compositions at temperatures below 40° C., but not at 135° C. Also R. P. Eckberg et al. reported the use of tertiary amines in the presence of both Rh and Pt catalysts to inhibit epoxy-polymerization in the production of epoxysilicones.
The hydrosilation reactions of many olefins, particularly amino-functional olefins, are either too slow or do not occur. For those olefins that do undergo hydrosilation, formation of the undesired &bgr;-isomer is a competing side reaction. The type of silane employed also impacts the rate of reaction. Typically, sluggish hydrosilation reactions result in an increase of the competing side-reactions, e.g., olefin isomerization or polymerization. Accordingly, a process which improves the reactivity and selectivity of the transition metal-catalyzed hydrosilation reactions of olefins continues to be a commercially desirable objective.
SUMMARY OF THE INVENTION
In accordance with the invention, a process is provided which comprises reacting (a) hydridoalkoxysilane with (b) olefin in the presence of (c) platinum catalyst and (d) a weakly nucleophilic amine of the formula NZ
1
Z
2
Z
3
, wherein Z
1
is an aryl, alkaryl, or aralkyl group of C
6
to C
20
carbon atoms, or an organosilyl group of the formula SiR
3
, wherein R is alkyl of C
1
to C
20
or aryl of C
6
to C
10
; Z
2
is hydrogen, alkyl of C
1
to C
20
, an aryl, alkaryl, or aralkyl group of C
6
to C
20
, or SiR
3
, wherein R is as previously defined; Z
3
is the same as Z
1
or Z
2
; and optionally two of Z
1
, Z
2
and Z
3
taken together with the nitrogen atom form an aromatic heterocyclic ring. The process of the invention exhibits improved yields and selectivities with respect to the desired reaction products.
DETAILED DESCRIPTION OF THE INVENTION
This invention provides a process for improving the yields and rates of the hydrosilation of alkoxyhydridosilane under relatively mild conditions using a weakly nucleophilic amine in the presence of a hydrosilation catalyst.
AMINES
Weakly nucleophilic amines containing substituents capable of &pgr;-interation with the amine's lone pair of electrons such as aromatic or silicon-substituents can be employed in the practice of this invention. Thus, weakly nucleophilic amine promoters possess the general formulae NZ
1
Z
2
Z
3
wherein Z
1
is an aryl, alkaryl, or aralkyl group of six to twenty carbon atoms, or an organosilyl group of the formula SiR
3
, wherein R is an alkyl of C
1
to C
20
, preferably C
1
to C
4
, or aryl of C
6
Childress R. Shawn
Filipkowski Michelle A.
Hale Melinda B.
Himmeldirk Rodica S.
Westmeyer Mark D.
Barts Samuel
Crompton Corporation
Dilworth Michael P.
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