Platinum-styrene complexes which promote hydrosilation reactions

Platinum-styrene complexes are prepared by reacting a platinum halide with styrene or substituted styrenes in the presence of a basic material for a sufficient amount of time to form a complex having more than one and less than four gram atoms of halogen per gram atom of platinum. These platinum-styrene complexes may be used to promote the addition of organosilicon compounds having at least one .tbd.SiH group per molecule to a compound containing aliphatic unsaturation.

The present invention relates to platinum complexes and more particularly 
to platinum-styrene complexes having improved stability which promote 
hydrosilation reactions. 
BACKGROUND OF THE INVENTION 
Various platinum compounds and complexes have been used heretofore to 
promote hydrosilation reactions. The platinum compounds and complexes 
which have been used to promote hydrosilation reactions such as the 
addition of organosilicon compounds containing .tbd.SiH groups to 
compounds containing aliphatic unsaturation are compounds such as 
chloroplatinic acid, platinum chloride-olefin complexes, platinum 
chloride-cyclopropane and complexes derived from the reaction of alcohols, 
ethers, aldehydes, ketones and vinyl siloxanes with chloroplatinic acid. 
While chloroplatinic acid and elemental platinum may be used as catalysts 
for hydrosilation reactions, they have certain disadvantages. For example, 
chloroplatinic acid is insoluble in many organic solvents and is not 
always effective at low concentrations. Moreover, these catalysts are 
subject to poisoning in the presence of a number of common materials. The 
disadvantages of elemental platinum and chloroplatinic acid with respect 
to poisoning and speed of reaction have been overcome by the use of the 
platinum compounds described above, such as the platinum-olefin complexes 
described in U.S. Pat. Nos. 3,159,601 and 3,159,662 to Ashby. Faster and 
more active catalysts are described in U.S. Pat. Nos. 3,715,334; 
3,775,452; and 3,814,730 to Karstedt, in which platinum vinyl siloxane 
complexes are treated with a base material to form a catalyst in which the 
halogen to platinum ratio is about 1:1 or less than 1:1. 
It has been found that a platinum-styrene complex which is formed in the 
presence of a basic material and has a halogen to platinum ratio of more 
than one, but less than four gram atoms of halogen per gram atom of 
platinum, is substantially more stable than other platinum complexes and 
maintains its level of activity for longer periods of time. 
Therefore, it is an object of this invention to provide a novel platinum 
catalyst. Another object of this invention is to provide a platinum 
catalyst for effecting the addition of SiH-containing organosilicon 
compounds to unsaturated organic compounds. Still another object of this 
invention is to provide a catalyst which is highly reactive at room 
temperature and is more effective at lower concentrations. A further 
object of this invention is to provide a catalyst which is more stable and 
maintains its level of activity for longer periods of time. 
SUMMARY OF THE INVENTION 
The foregoing objects and others which will become apparent from the 
following description are accomplished in accordance with this invention, 
generally speaking, by providing a process for preparing a platinum 
complex which comprises reacting a platinum halide with styrene or 
substituted styrenes in the presence of a basic material to form a 
platinum complex which contains more than one and less than four gram 
atoms of halogen per gram atom of platinum. The resultant complex may be 
used to promote the addition of organosilicon compounds containing 
silicon-bonded hydrogen to unsaturated organic compounds. 
DETAILED DESCRIPTION OF THE INVENTION 
Platinum complexes are known in the art and their preparation and 
properties are described, for example, in "Coordination Compounds of 
Olefins with Metallic Salts," R. N. Keller, Chemical Reviews, 1940-41, 
27-28, pages 229-267; and Joy and Orchin, Journal of the American Chemical 
Society, 81, pages 305-311 (1959). The olefin portion of the platinum 
complexes of this invention is styrene and ring substituted styrenes. 
Examples of substituted styrenes are alkyl ring substituted styrenes such 
as m-methylstyrene, p-ethylstyrene, p-ethoxystyrene and the like. The 
platinum complexes of this invention are prepared by reacting a platinum 
halide with styrene or substituted styrenes in the presence of a basic 
material. Examples of suitable basic materials are alkali metal 
carbonates, such as sodium carbonate, potassium carbonate and sodium 
bicarbonate. 
Although, the amount of base employed is not critical, a sufficient amount 
of base should be present to neutralize at least some of the available 
halogen. Even though less than a stoichiometric amount can be employed, it 
is preferred that a stoichiometric amount or even a slight excess be 
employed in order to neutralize enough of the available halogen to form a 
complex containing more than one and less than four gram atoms of halogen 
per gram atom of platinum. 
The platinum-styrene complex of this invention is prepared by reacting a 
platinum halide, such as chloroplatinic acid, with styrene in the presence 
of a base and preferably an alcohol at a temperature of from 0.degree. to 
150.degree. C., preferably at a temperature from 25.degree. to 100.degree. 
C. and more preferably at a temperature of from 40.degree. to 60.degree. 
C. Also, it is possible to form a platinum-styrene complex in the absence 
of the base and thereafter react the platinum complex with the basic 
material to substantially reduce the halogen content of the resultant 
catalyst. 
The reaction between the platinum halide, styrene and base is dependent on 
the amount of base present and the temperature. Thus, the reaction time 
varies inversely with the temperature, i.e., the higher the temperature, 
the shorter the reaction time and conversely, the lower the temperature, 
the longer the reaction time. When the reaction temperature is in the 
preferred range, i.e., from 40.degree. to 60.degree. C., the reaction time 
varies from about one hour to about 0.25 hours. 
The reaction may be conducted at atmospheric pressure or below or above 
atmospheric pressure. Preferably, the reaction is conducted at atmospheric 
pressure. 
The platinum halide such as chloroplatinic acid which is employed in the 
reaction with the olefin is commercially available in the form of 
chloroplatinic acid hexahydrate, 
EQU H.sub.2 PtCl.sub.6.6H.sub.2 O, 
however, the material can be used in the anhydrous form or it can be used 
as the hexahydrate. 
Suitable solvents which may be employed in the preparation of the 
platinum-styrene complexes of this invention are alcohols having from 1 to 
6 carbon atoms such as methanol, ethanol, propanol, butanol and hexanol 
and aromatic hydrocarbon solvents such as benzene, toluene and xylene. It 
is preferred that the solvent be an alcohol and more preferably ethanol. 
Mixtures of alcohols or alcohols and aromatic hyrocarbons may be used. The 
amount of solvent is not critical and may range from about 1 to 100 parts 
and more preferably from about 10 to 50 parts per part of platinum halide. 
The platinum-styrene complexes of this invention are effective for the 
addition of organosilicon compounds containing silicon-bonded hydrogen to 
organic compounds having carbon-carbon unsaturation. The catalysts of this 
invention are effective for the addition reactions described in U.S. Pat. 
Nos. 2,823,218 to Speir et al, 2,970,150 to Bailey and 3,220,970 to 
Lamoreaux. 
Suitable monomeric silicon compounds and organosilicon compounds containing 
silicon-bonded hydrogen which may be used in the present invention are 
those represented by the formula 
##STR1## 
in which R is an alkyl, cycloalkyl, alkaryl, aralkyl, haloalkyl or 
haloaryl radicals, X is a hydrolyzable radical, such as halogen, alkoxy 
radicals, aryloxy radicals and acyloxy (OOCR) radicals; c is a number of 
from 0 to 3, d is a number of from 1 to 3; and the sum of c and d is from 
1 to 4. When more than one R radical is present in the compound the 
various R radicals may be the same or different. 
Among the radicals represented by R are alkyl radicals, e.g., methyl, 
ethyl, propyl, octyl and octadecyl radicals; cycloalkyl radicals such as 
the cyclohexyl and cycloheptyl radicals; aryl radicals such as the phenyl, 
biphenyl, alkaryl radicals such as tolyl and xylyl radicals; aralkyl 
radicals such as the benzyl and phenylethyl radicals; haloaryl radicals 
and haloalkyl radicals such as the chlorophenyl, chloromethyl and the 
dibromophenyl radicals. Preferably, R is a methyl or a mixture of methyl 
and phenyl radicals. 
Examples of suitable silicon compounds represented by the above formula 
which can be employed in the present invention are: methyldichlorosilane, 
phenyldichlorosilane, diethylchlorosilane, dimethylethoxysilane, 
diphenylchlorosilane, dichlorosilane, dibromosilane, pentachlorodisiloxane 
and the like. 
Suitable silicon-bonded hydrogen containing which may may be used in the 
present invention are those in which each molecule contains at least one 
silicon-bonded hydrogen. Suitable examples of such compounds are 
organopolysiloxanes and various polysilalkylene compounds containing, for 
example, an --Si--Y--Si-- linkage in which Y is a divalent hydrocarbon 
radical having from 1 to 8 carbon atoms or a nitrogen atom, such as 
organosilazanes, having the --Si--N--Si-- linkage in the polymer. 
Suitable examples of organopolysiloxanes are polymers and copolymers 
containing up to one or more of the units having the formulae: R.sub.3 
SiO.sub.0.5, R.sub.2 SiO, RSiO.sub.1.5 or SiO.sub.2 along with at least 
one unit per molecule having the formulae: RHSiO, R.sub.2 HSiO.sub.0.5, 
HSiO.sub.1.5, H.sub.2 SiO, RH.sub.2 SiO.sub.0.5 wherein R is the same as 
above. Any of the silicon hydrogen compounds described above, are 
operative in the practice of the present invention, however, it is 
preferred that the silicon hydrogen compound be an organopolysiloxane such 
as an organopolysiloxane (RHSiO).sub.n or an organopolysiloxane polymer or 
copolymer having the formula R.sub.y SiH.sub.z O.sub.4-y-z where R is the 
same as above, n is a number of from 1 to 20,000, y is a number of from 
about 0.5 to 2.49 and z is a number of from 0.001 to 1 and the sum of y 
and z is a number equal to from 1 to 25. 
Compounds containing carbon-to-carbon unsaturation, particularly 
unsaturated compounds containing olefinic or acetylenic unsaturation which 
can react with the organic compounds described above containing the 
silicon-bonded hydrogen are monomeric and polymeric compounds containing 
aliphatic unsaturation. These compounds can contain only carbon and 
hydrogen or they may also contain another element or elements. Where the 
aliphatically unsaturated compounds contain an element other than carbon 
and hydrogen, it is preferred that the other element by oxygen, halogen, 
nitrogen, silicon or mixtures thereof. Aliphatically unsaturated compounds 
which may be employed that have a single pair of carbon atoms linked by 
multiple bonds are for example, ethylene, propylene, butylene, octylene, 
styrene, butadiene, pentadiene, 2-pentene, 2-divinylbenzene, vinyl 
acetylene and the like. Preferably the unsaturated compound does not 
contain more than about 24 carbon atoms in the chain. 
Included in the oxygen containing unsaturated compounds which may be 
employed in the practice of the invention are methylvinylether, 
divinylether and the like; the monoalkylethers of ethylene glycol, allyl 
aldehyde, methylvinyl ketone, phenylvinyl ketone, acrylic acid, 
methylmethacrylate, phenylmethacrylate, vinylacetic acid, vinyl octoate, 
vinyl acetate, maleic acid, linoleic acid and the like. Other unsaturated 
compounds which may be employed are cyclic and heterocyclic materials 
containing aliphatic unsaturation in the ring, such as, cyclohexene, 
cycloheptene, cyclopentadiene, dihydrofuran, dihydropyrene and the like. 
The sulfur analogues of the unsaturated oxygen containing materials may 
also be employed in the practice of this invention. In addition to 
compounds containing carbon, hydrogen, oxygen and sulfur, compounds 
containing other elements may also be employed. Thus, halogenated 
derivatives of any of the materials described above can be employed 
including the acryl chlorides as well as compounds containing a halogen 
substituent on a carbon atom. Thus, halogen containing materials include, 
for example, vinyl chloride, the vinyl chlorophenyl esters, the allyl 
esters of trichloroacetic acid and the like. 
Other types of unsaturated materials which are useful in the practice of 
this invention include compounds containing nitrogen substituents such as 
acrylonitrile, allylcyanide, nitroethylene and the like. Unsaturated 
polymeric materials containing aliphatic unsaturation such as polyester 
resins prepared from polybasic saturated or unsaturated acids and 
polyhydric unsaturated alcohols may also be used in the practice of this 
invention. 
Other unsaturated compounds which may be used in the practice of this 
invention are those compounds containing silicon such as the material 
commonly referred to as organosilicon monomers or polymers. The scope of 
the organosilicon compounds which are applicable to the process is 
identical to the scope of the silicon-bonded hydrogen compounds useful in 
the practice of this invention. For example, the unsaturated organosilicon 
compounds are identical to the silicon-bonded hydrogen compounds, except 
that the silicon-bonded hydrogen is replaced by silicon-bonded organic 
radicals containing at least one pair of aliphatic carbon atoms having 
aliphatic unsaturation. Although it is preferred that the organosilicon 
compounds be free of silicon-bonded hydrogen atoms, organosilicon 
compounds containing both silicon-bonded hydrogen atoms and silicon-bonded 
unsaturated radicals may be used. The only requirement of these 
unsaturated silicon compounds is that there be at least one unsaturated 
organic radical attached to a silicon atom per molecule. Thus, the 
unsaturated organosilicon compounds include silanes, siloxanes, silazanes, 
as well as monomeric or polymeric materials having silicon atoms joined 
together by methylene or polymethylene groups or by phenylene groups. 
Examples of suitable unsaturated silicon compounds which may be used are 
methylvinyldichlorosilane, vinyltrichlorosilane, allyltrichlorosilane, 
methylphenylvinylchlorosilane, phenylvinyldichlorosilane, 
diallyldichlorosilane, vinylcyanoethyldichlorosilane, cyclic polysiloxanes 
such as the cyclic trimer of methylvinylsiloxane, cyclic tetramer of 
methylvinylsiloxane, cyclic pentamer or methylvinylsiloxane, cyclic 
tetramer of vinylphenylsiloxane, linear or branched vinyl terminated 
diemthylpolysiloxanes, trimethylsiloxy terminated 
vinylmethylpolysiloxanes, ethylphenylpolysiloxanes and copolymers thereof. 
The ratio of the silicon-bonded hydrogen compound and the unsaturated 
compound employed can vary over a wide range. Generally, one 
silicon-bonded hydrogen is equivalent to one olefinic double bond or 
one-half acetylenic triple bond so that this equivalency establishes the 
general order of magnitude of the two reactants employed. However, for 
many purposes it may be desirable to employ an excess of one of the 
reactants to facilitate the completion of the reaction or to insure that 
the reaction contains one or more pairs of carbon atoms linked by multiple 
bonds. In general, however, the ratio of the reactants is selected so that 
there are present from about 0.5 to 20 silicon-bonded hydrogen linkages 
available for each unsaturated carbon-carbon double bond and from about 
1.0 to 15 silicon-bonded hydrogen linkages for each carbon-carbon triple 
bond. 
To effect the addition reactions of the organosilicon compositions in the 
presence of the platinum-styrene complexes of this invention, the 
reactants and catalyst are thoroughly mixed and allowed to react at 
temperatures of from 10.degree. to 200.degree. C. The time required for 
the addition reaction is a function of temperature. At a temperature of 
from about 15.degree. to 175.degree. C. and more preferably from 
20.degree. to 150.degree. C., the reaction times can vary from a few 
seconds up to about 10 minutes or more depending upon the amount of 
catalyst complex employed. 
In some cases, it is desirable to employ a solvent for one or both 
reactants. The amount of solvent employed is not critical and can vary 
over a wide range. Obviously, the same material may in some cases serve 
both as the reactant and as the solvent. 
The amount of catalyst employed can vary over a wide range. It is preferred 
that enough catalyst be employed to provide from about 0.5 to 500 ppm by 
weight and more preferably from 2 to 500 ppm by weight calculated at 
platinum and based on the weight of the total composition, including 
silicon compounds, platinum catalyst and any additional materials. 
One of the advantages of the novel catalysts of this invention is that a 
very small amount of the catalyst will effect the desired reaction between 
the silicon-bonded hydrogen compound and the unsaturated organic compound. 
In addition, it has been found that the catalyst retains its level of 
activity even after storing for prolonged periods of time at elevated 
temperatures. Furthermore, the activity of the catalyst is such that 
silicon-bonded hydrogen containing organopolysiloxanes and vinyl 
containing organopolysiloxanes can be cured very rapidly and therefore 
used as potting or encapsulating compositions for electrical components on 
assembly lines. 
These organopolysiloxane compositions may contain in addition to the 
silicon-bonded hydrogen containing organopolysiloxanes, and vinyl 
containing organopolysiloxanes, other additives such as fillers, i.e., 
silica, hydrogels, aerogels; treated fillers such as silicas which have 
been treated with, for example trimethylchlorosilane or 
hexamethyldisilozane to impart hydrophobic properties thereto, quartz, 
alumina, glass fibers, diatomaceous earth, organosilicon plasticizers, 
Ultraviolet stabilizers, heat stabilizers and the like. Other additives 
which may be included in the compositions are those which retard or 
inhibit the addition of Si-bonded hydrogen to an aliphatic multiple bond 
at room temperature. Examples of such additives are benzotriazole, 
1,3-divinyl-1, 1,3,3-tetramethydisiloxane and/or 2-methyl-3-butyn-2-ol. 
The catalysts of this invention are combined with .tbd.SiH containing 
compounds and organic compounds containing olefinic unsaturation to form 
elastomeric compositions. These compositions may be used as potting 
compounds, sealants, coatings and particularly as dental impression 
materials. 
When the compositions of this invention are to be stored for a period of 
time prior to use, it is preferred that the catalyst be mixed with a 
portion of the organosilicon compound containing olefinic unsaturation and 
stored in one package. The remainder of the organosilicon compound 
containing olefinic unsaturation is preferably mixed with the 
organosilicon compound containing silicon-bonded hydrogen and stored as a 
second package. The two packages can then be mixed together at the 
appropriate time of their use and molded. If other materials are to be 
added to the composition, they should be incorporated in the individual 
packages during their preparation rather than adding those materials 
during the final mixing of the whole composition. 
In preparing dental impression compositions, it is preferred that the 
organosilicon compound containing olefinic unsaturation be a 
diorganopolysiloxane containing terminal triorganosiloxy groups in which 
at least one vinyl group is present in each of the triorganosiloxy groups 
be mixed at room temperature with an organopolysiloxane containing at 
least three silicon-bonded hydrogen atoms per molecule and the 
platinum-styrene complex of this invention. Other materials which may be 
added are additives such as the fillers described above, pigments, 
flavoring substances and plasticizers. The dental impression compositions 
of this invention can be used in accordance with the conventional methods 
of working when using dental impression compositions and employing the 
devices customarily used for such purposes. 
Various embodiments of the invention are illustrated in the following 
examples in which all parts are by weight unless otherwise specified.

PREATION OF PLATINUM-STYRENE COMPLEX 
EXAMPLE 1 
A platinum-styrene complex is prepared by adding 6 parts of sodium 
bicarbonate to a mixture containing 3 parts of chloroplatinic acid 
(H.sub.2 PtCl.sub.6.6H.sub.2 O), 6 parts of styrene and 50 parts of 
ethanol. The mixture is heated to reflux temperature, (about 55.degree. 
C.) and refluxed for about 35 minutes with agitation, and then cooled to 
room temperature. The resultant mixture which contains orange crystals is 
filtered and the crystals washed with about 30 parts of acetone. About 30 
parts of xylene are added to the filtrate which results in the formation 
of crystals. This mixture is filtered and the orange crystals are 
recovered and dried. Analysis of these crystals indicates that a 
platinum-styrene complex is formed having a platinum to chloride ratio of 
1:3.1 
EXAMPLE 2 
The procedure of Example 1 is repeated except that the mixture is heated at 
60.degree. C. for 38 minutes. The resultant product has a platinum to 
chloride ratio of 1:1.9. 
COMISON EXAMPLE 3 
The procedure of Example 1 is repeated except that the mixture is heated at 
70.degree. C. for 55 minutes. The resultant product has a platinum to 
chloride ratio of 1:0.9. 
COMISON EXAMPLE 4 
The procedure of Example 1 is repeated except that 6 parts of 1-dodecene 
are substituted for the styrene. 
A catalyst is obtained having a platinum to chloride ratio of 1:2.8. 
COMISON EXAMPLE 5 
The procedure of Example 1 is repeated except that the sodium bicarbonate 
is omitted. The resultant catalyst contains a platinum to chloride ratio 
of 1:4.0. 
PREATION OF CROSSLINKED COMPOSITION 
EXAMPLE 6 
(a) A mixture is prepared by adding 3 parts of fumed silica and 100 parts 
of quartz powder to 7 parts of a methylhydrogenpolysiloxane having a 
viscosity of 50 cs. at 25.degree. C. and 100 parts of vinyl terminated 
dimethylpolysiloxane having a viscosity of 500 cs. at 25.degree. C. 
(b) The platinum-styrene complexes prepared in the above examples are each 
dissolved in isopropanol to form a solution containing 0.75 percent by 
weight of elemental platinum. About 1.6 parts of the platinum-styrene 
complex solutions are added to 100 parts of vinyl terminated 
dimethylpolysiloxane having a viscosity of 500 cs. at 25.degree. C. The 
isopropanol is removed at reduced pressure and then 100 parts of quartz 
powder and 3 parts of fumed silica are added to the vinyl terminated 
dimethylpolysiloxane catalyzed mixture. The resultant mixture containing 
about 60 ppm of platinum, calculated as elemental platinum, is stored for 
three days at room temperature. 
A portion of each mixture is heated at 60.degree. C. for various periods of 
time, cooled to room temperature and then combined with composition (a) 
above in equal parts and the time required for crosslinking "working time" 
is observed. A portion of each mixture is also stored at room temperature 
and combined with equal parts of (a) above. The stability of the catalyst 
is illustrated in the following table by changes in the "working times". 
TABLE 
______________________________________ 
Heat Aging Stability Data 
Heat Aging 
Example Ratio Time Temperature 
Working Time 
No. Pt:Cl (Hrs.) (.degree.C.) 
(Seconds) 
______________________________________ 
1 1:3.1 24 60.degree. 
50 
72 25.degree. 
50 
72 60.degree. 
50 
120 25.degree. 
50 
120 60 35 
240 25.degree. 
40 
240 60.degree. 
40 
2 1:1.9 24 60.degree. 
47 
72 25.degree. 
49 
72 60.degree. 
50 
120 25.degree. 
53 
120 60.degree. 
45 
240 25.degree. 
48 
240 60.degree. 
45 
3 1:0.9 24 60.degree. 
&gt;600 
72 25.degree. 
&gt;600 
72 60.degree. 
&gt;600 
4 1:2.8 24 60.degree. 
&gt;600 
72 25.degree. 
50 
72 60.degree. 
&gt;600 
5 1:4.0 8 60.degree. 
&gt;600 
24 60.degree. 
&gt;600 
______________________________________ 
The heat aging tests in the above table show that a catalyst composition 
having a platinum to chloride ratio of less than 1 and 4 or more gram 
atoms of chloride per gram atom of platinum does not maintain its level of 
activity over a long period of time.