Europaisches Patentamt (19) European Patent Office Office europeen des brevets (11) EP 0 785 203 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) IntCI.6: C07F7/14 23.07.1997 Bulletin 1997/30 (21) Application number: 97100533.5 (22) Date of filing : 1 5.01 .1 997 (84) Designated Contracting States: (72) Inventor: Roy, Aroop Kumar DE FRGBITNL Midland, Michigan 48642 (US) (30) Priority: 17.01.1996 US 583730 (74) Representative: Spott, Gottfried, Dr. et al Patentanwalte (71) Applicant: DOW CORNING CORPORATION Spott, Weinmiller & Partner Midland, Michigan 48686-0994 (US) Sendlinger-Tor-Platz 11 80336 Munchen (DE) (54) Process for alkyne hydrosilation using cycloalkene as catalyst modifier (57) A process is described for hydrosilating alkynes with organodihalosilanes and trihalosilanes in the presence of a platinum catalyst, selected from plati- num halides or the reaction product of platinum halides with organosilicon compounds having terminal aliphatic unsaturation. The process uses a cycloalkene compris- ing 6 to 20 carbon atoms as a catalyst modifier to reduce formation of the bis-silated adduct of the alkynes. < CO o CM LO CO o Q_ LU Printed by Rank Xerox (UK) Business Services 2.14.11/3.4 EP 0 785 203 A1 Description The present invention is a process for hydrosilating alkynes with organodihalosilanes or trihalosilanes in the pres- ence of a platinum catalyst, selected from platinum halides or the reaction product of platinum halides with organosili- 5 con compounds having terminal aliphatic unsaturation. This process uses a cycloalkene comprising 6 to 20 carbon atoms as a catalyst modifier to reduce formation of the bis-silated adduct of the alkynes. Virtually any compound which contains a =SiH group is reacted with compounds containing aliphatic unsaturation in the presence of a platinum compound, such as chloroplatinic acid, to effect a reaction typically referred to as hydrosi- lation or hydrosilylation. U.S. Patent 2,823,218 discusses such hydrosilation reactions in greater detail. 10 U.S. Patent 3,419,593 describes a group of catalysts that are the reaction product of chloroplatinic acid with orga- nosilicon compounds having terminal unsaturation that are particularly useful in hydrosilation processes. U.S. Patent 4,292,434 discloses a hydrosilation catalytic mixture obtained by dissolving a platinum halide in at least 20 parts by weight of olefin, for each part by weight of platinum halide, and subsequently heating and mixing the solu- tion obtained with from 0.5 to one mole of a primary or secondary amine for each gram atom of platinum. 15 A common problem associated with the hydrosilation of an alkyne with a hydridosilane, in the presence of a plati- num halide or platinum olefin complex as catalyst, is the formation of the bis-silated adduct of the alkyne as a by-prod- uct. Typically, such hydrosilation processes are run under high pressure to increase the concentration of alkyne in the reaction mixture, relative to the alkenyl substituted product, thereby minimizing the formation of the bis-silated adduct of the alkyne. However, alkynes such as acetylene are explosive at high pressures, thereby making those processes 20 dangerous. We have surprisingly found that in processes where an alkyne is silated with either a trihalosilane or orga- nodihalosilane in the presence of a platinum catalyst, selected from platinum halides or the reaction product of platinum halides with organosilicon compounds having terminal aliphatic unsaturation, the presence of a cycloalkene comprising 6 to 20 carbon atoms will reduce the amount formed of the bis-silated adduct of the alkyne. This reduction allows such processes to be run at near normal atmospheric pressure while still providing an acceptable ratio of alkenyl substituted 25 product to bis-silated adduct of the alkyne. The present invention is a process for hydrosilation of an alkyne. The process comprises contacting at a tempera- ture within a range of 40 to 150°C. an alkyne described by formula R1C=CH (1) where R1 is selected from hydrogen atom or alkyl groups comprising one to ten carbon atoms; with a hydridosilane described by formula R2nHSiX3.n (2) where R2 is selected from alkyl groups comprising one to 20 carbon atoms or aryl groups, each X is an independently 30 selected halogen atom and n has a value of zero or one; in the presence of a platinum catalyst selected from platinum halides or the reaction product of platinum halides with organosilicon compounds having terminal aliphatic unsaturation and a cycloalkene comprising 6 to 20 carbon atoms in an amount sufficient to reduce formation of a bis-hydrosilated adduct of the alkyne. The alkyne is contacted with the hydridosilane in standard low-pressure reactors suitable for reacting such com- 35 pounds. The pressure at which our process is conducted is not critical and is varied within a wide range. However, the present process is unexpectedly advantageous in that it is conducted at near normal atmospheric pressure while still providing an acceptable ratio of alkenyl-substituted product to bis-silated by-product. Therefore, it is preferred that the process is conducted at a pressure within a range of 10.1 to 303.9 kPa (0.1 to 3 atmospheres). More preferred is when the process is conducted at 101 .3 to 303.9 kPa (1 to 3 atmospheres). 40 The present process can be conducted in either a gas or liquid phase. However, it is preferred that the process is conducted in a liquid phase using a liquid hydrocarbon solvent in which the alkyne and hydridosilane are soluble. It is preferred that the liquid hydrocarbon solvent having a boiling point greater than the boiling point of the alkenyl substi- tuted product of our process to facilitate separation of the product from the solvent. The solvent is, for example, an aro- matic hydrocarbon such as xylene or a mixture of the isomers of xylene, toluene or benzene. A demonstration of such 45 a liquid phase process is provided in the examples herein. The present process is conducted at a temperature within a range of 40 to 1 50°C. A preferred temperature is 60 to 100°C. The optimal temperature for conducting our process will depend upon such factors as the alkyne and hydridosi- lane to be reacted. For example, when acetylene is reacted with methyldichlorosilane a preferred temperature for con- ducting the process is within a range of 70 to 80°C. so Alkynes useful in the present process are described by formula (1), where R1 is selected from hydrogen atoms or alkyl groups comprising one to ten carbon atoms. R1 is methyl, ethyl, propyl, tert-butyl and decyl. Preferred is when R1 is hydrogen atom, thereby making the alkyne acetylene. Hydridosilanes useful in our process are described by formula (2), where R2 is selected from alkyl groups compris- ing one to 20 carbon atoms or aryl groups, each X is an independently selected halogen atom and n has a value of zero 55 or one. R2 is, for example, alkyl groups such as methyl, ethyl, propyl and tert-butyl; halogen substituted alkyl groups such as chloromethyl or 3,3,3-trifluoropropyl; aryl groups such as phenyl, tolyl and xylyl; and halogen substituted aryl groups such as chlorophenyl. Preferred is when R2 is methyl. Also preferred is when X is a chlorine atom. The preferred hydridosilane is selected from trichlorosilane or methyldichlorosilane. The most preferred hydridosilane is methyldichlo- rosilane. 2 EP 0 785 203 A1 In the present process, it is preferred that the mole ratio of the alkyne to the hydridosilane fed to the process is within a range of 0.5:1 to 3:1 . Preferred is when the mole ratio of alkyne to hydridosilane is within a range of 1 :1 to 1 .3:1 . The present process is conducted in the presence of a platinum catalyst selected from platinum halides or the reac- tion product of platinum halides with organosilicon compounds having terminal aliphatic unsaturation. Platinum halides 5 useful in the present invention include platinum dichloride, platinum dibromide, platinum tetrachloride, dipotassium tet- rachloroplatinate (K2PtCI4) and chloroplatinic acid (H2PtCI6.6H20). The preferred platinum halide is chloroplatinic acid. Platinum catalysts useful in the present invention also include the reaction product of a platinum halide with an organo- silicon compound having terminal aliphatic unsaturation. Such catalysts are more fully described in U.S. Patent 3,419,593 which teaches platinum catalysts useful in the present process. A preferred catalyst for the present process 10 is the reaction product of a solution of chloroplatinic acid in 2-propanol with methylvinyldichlorosilane as shown in our examples herein. Other preferred catalysts are the reaction products of platinum dichloride or chloroplatinic acid with 1 ,3-divinyl-1 ,1 ,3,3- tetramethyldisiloxane. The concentrations of platinum catalyst used in the present process are varied within wide limits. In general, when our process is run as a batch process in the liquid phase the catalyst concentration in the liquid phase is that providing 15 one to 20,000 parts per million (ppm) of platinum. Preferred is 100 to 10,000 ppm of platinum in the liquid phase. The present process requires the presence of a cycloalkene comprising 6 to 20 carbon atoms in an amount suffi- cient to reduce the formation of a bis-hydrosilated adduct of the alkyne. Preferred are those cycloalkenes which do not undergo hydrosilation under our process conditions to create unwanted by-products. Preferred is when the cycloalkene comprises 7 to 1 0 carbon atoms. The cycloalkenes are, for example, cyclohexene, cycloheptene, cyclooctene, nor- 20 bornene and cyclodecene. The preferred cycloalkene is cyclooctene. In general, an amount of cycloalkene sufficient to reduce the formation of a bis-hydrosilated adduct of the alkyne is 200 to 5,000 moles of cycloalkene per each g • atom of platinum provided by the platinum catalyst to the process.