Note: Descriptions are shown in the official language in which they were submitted.
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PLATINUM (O) ALKY,`JE COI~PL~XES
AND A ~lETHOD FOR T~E:IR PREPARATION
This invention relates to certain novel platinum (O)
alkyne complexes and to a novel method of preparing them. By
platinum (O) alkyne complexes, it is rneant hPrein organo-
metallie platinum complexes with acetylene derivatives as
ligands, wherein the platinum atom has a formal oxidation
state of zero, as measured by cyclic voltammetry.
Platinum (O) alkyne complexes in general are useful
as hydrosilylation catalysts, hydrogenation catalysts, and
isomerization catalysts for olefins and alkynes.
Platinum (O) alkyne comple~es have a number of
advantages over the well known platinum catalyst
H2PtCl6 (H20~x, hereinafter referred to as hexachloroplatinic
acid. For example, platinum (O) alkyne complexes tend to be
more compatible with the reactants they are called upon to
catalyze. The platinum (O) alkyne complexes are thus more
effective, since it is not necessary to provide excess amounts
to make up for losses due to precipitation.
Additionally, platinum (O) alkyne complexes are
inherently more chemically stable than hexachloroplatinic
acid, especially in the presence of moisture.
The synthesis of platinum (O) alkyne complexes is
known. For example, F. Gordon A. Stone, Ligand-Free Platinum
Compounds, Acc. Chem. Res. 1981, 14, 317-327, describes the
synthesis of platinum (O) alkyne complexes using platinum bis
(cyclooctadiene) complexes. Unfortunately, the cyclooctadiene
complex itself is difficult to make~ involving sensitive
intermediates which require special handling. These platinum.
~is (cyclooctadiene) complexes are much more suitable for
laboratory preparations than industrial processes.
l~d
3i~3~
N. Boag et al., J.C.S. Dalton (1980) pg. 2170 et
seq. describe a number of platinum (O) alkyne complexes
synthesized via platinum bis (cyclooctadiene) complexes, and
platinum tris (ethylene) complexes.
None of the above references describes a method ~or
the synthesis of platinum (O) alkyne complexes that can be
practiced without special handling precautions for the
intermediates. Moreover, none of the above references
disclose the complexes:
Pt(HC-CC(CH3)2OH)2 or
Pt(C6~5C-CC(C~3)(C6H5)(OH))2
C6H5 is to be taken throughout this specification and the
ap ~ ded claims as representing the phenyl radical, i.e.
_~.
It is an object of this invention to provide a
simple method for making platinum (O) alkyne complexes. It is
a further object to provide new hydrosilylation and hydrogen-
ation catalysts.
These objects and others are attained by the me~h^d
and compositions of the present invention. The method of the
present invention comprises contacting an alkyne with a
platinum-vinylsiloxane complex to provide a platinum (O)
alkyne complex. In other aspects, the present invention
relates to certain specific platinum (O) alkyne complexes and
their use.
The present invention, in one aspect, resides
in the compound having the formula Pt(HC~CC(CH3)2OH)2.
The present invention, in another aspect, resides in
the compound having the formula Pt(C6H5C-CCCH3~C6H5)OH)2.
The present invention in a further aspect, resides in a
method for making platinum IO) alkyne complexes, said
method comprising contacting an alkyne with a platinum-
vinylsiloxane complex.
~3--
In the method of one aspect of the present invention,
an alkyne is contacted with a platinum-vinylsiloxane complex.
The platinum-vinylsiloxane complex is the reaction product of
hexachloroplatinic acid and a vinylsiloxane having the general
XaRnSi(4_a_n)/2 I wherein X is a hydrolyzable
radical; R is a monovalent hydrocarbon radical; each a has a
value of 0 or 1; each n has a value of 1, 2, or 3; the sum of
the values of a and n has a maximum value of 3; and the~e is
at least one R unit in said vinylsiloxane having the formula
CH2=CH-.
These aspects of the invention are also disclosed,
and are claimed, in Canadian Application No. 483,871 filed
June 13, 1985, of which the present application is a
divisional.
Platinum-vinylsiloxane compounds have been described
in U.S. Pa~ent No. 3,419,593, issued December 31, 1968 to
David N. Willing, to furth~r teach a method for making
suitable platinum-vinylsiloxane complexes. U.S. Patent No.
3,775,452, issued Novem~er 27, 1973 to Karstedt also disclose
methods for making suitable platinum-vinylsiloxane complexes.
In general, platinum-vinylsiloxane complexes are
made by contacting a vinylsiloxane as described above with a
suitable platinum compound such as hexachloroplatinic acid.
Hexachloroplatinic acid is well known and widely available
commercially.
R in the above general unit form~la for the vinyl-
siloxane is a monovalent hydrocarbon radical. Thus, R can be
an alkyl radical, such a5 methyl, ethyl, propyl or butyl; an
aryl radical such as phenyl or naphthyl; a cycloalkyl radical,
such as cyclohexyl, cycloheptyl, and the like; an alkenyl
radical, such as vinyl or allyl; or a cycloalkenyl radical,
such as cyclohexenyl, cycloheptenyl and the like. ~t least
one R of each vin~lsiloxane, on average, must be a vinyl
radical.
X in the above general formula is a hydrolyzable
radical. For example, X can be a halogen atom, such as F, Cl,
Br, or I; an alkoxy or aryloxy radical, such as -OCH3, -OC2H5,
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-OC3H7, -OC6H5, and the like; a carboxy radical, such as
acetyl, propionyl, benzoyl, cyclohexanoyl, and the like;
and other hydrolyzable groups known in organosilicon
chemistry.
The vinylsiloxane can be linear, branched, or cyclic
in structure. Examples of appropriate vinylsiloxanes include
the following. The term Vi in the following examples of
vinylsiloxanes represents the CH2=CH- radical; the term Me
represents the CH3- radical. ViMe2SiOSiMe2Vi;
ViMe2SiO~SiMeViO)75iMe2Vi;ViMe2SiO(SiMeO~3SiMe3;
OSiMe3
(MeViSiO)3; (MeViSiO)4, the last two formulae representing
cyclosiloxanes; and other structures.
Briefly, platinum-vinylsiloxane complexes can be
made by contacting the vinylsiloxane with hexachloroplatinic
acid. Heatins can accelerate the formation of the platinum-
vinylsiloxane complex.
Alkynes suitable for reacting with the platinu~-
vinylsiloxane complex are well known and readily available.
Suitable alkynes are described by the general formula
R'C-CR', wherei~ each R' independently represents a monovalent
hydrocarbon radical, a hydride radical, with the proviso that
only one R' can be a hydride radical, or a monovalent
hydrocarbon radical substituted with a hydroxyl radical. More
preferably, each R' is selected from the group consisting of
H; -C(CH3)2(OH); -C(CH3)(C2H5)(OH); -C(C2H5)2(08);
-C(CH3)(~3H7)(OH); C(C5Hll)~ 3
( 2 5)( 3H7)(0H); ~ ; -C(CH3)3; -Si(CH3)3; ~C6H4 3
and -C( ~ )(CH3)(OH).
~ any suitable alkynes are commercially available.
Alternatively, suitable alkynes can be made by dehydrohalogen-
ation of appropriately substituted vicinal dialkvl halides; by
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reaction of sodium acetylide with appropriate alkyl halides;
and by other known methods of synthesizing alkynes.
The method of the present invention is carried ou
by contacting an alkyne, as defined above, with a platinum-
vlnylsiloxane complex, also defined above~
The contacting referred to is done by simply
exposing the two reactants to one another as by simply mixing.
Mixing can be accomplished manually, by placing the two
reactants in a single vessel and swirling or shaking. More
preferably, mixing is accomplished with a mechanical stirrer
or mixer.
The contacting can be done with the two reactants
neat, or it can be done in a suitable solvent. The solvent
can be polar or non-polar. Solvents which are known to
complex with platinum, or that are discovered to complex with
platinum, should be avoided.
If a solvent is used, it is highly preferred to
select a solvent in which the reactants are soluble and in
which the product, the platinum (O) alkyne complex, is
insoluble. If such a solvent is used, the product will
precipitate, thus facilitating isolation of the product.
Preferably, 2 moles of the al}cyne are provided for
each mole of platinum present. However, it may be beneficial
in some circumstances to provide partial complexes, such as
platinum-alkyne-vinylsiloxane complexes. The method of
providing such complexes by furnishing less than 2 moles of
alkyne for each mole of platinum is encompassed by the method
~f the present invention.
Similarly, mixed complexes may be formed by
providing two or more di~erent alkynes conjointly. Thus, for
example, reacting one mole of platinum with one mole of
HC-CC(CH3)20H and simultaneously with one mole of
C6H5C-CC(CH3)(C6H5)(0H) will result in a distribution of
products including Pt(HC-CC(CH3)20H)2, Pt(C6H5C-CC(CH3)-
(C6~5)(0H))2 , and also the mixed complex,
Pt(HC-CC(CH3)20H)((C6H5)C-CC(CH3)(C6H5)(OH)~.
The production of mixed complexes with two or more
different alkynes is also encompassed by the method of the
present invention.
The platinum tO) alkyne complexes resulting from the
method of the present invention are useful as catalysts for
hydrosilylation reactions; as catalysts for hydrogenation of
unsaturated organic compounds or polymers; as catalysts for
the isomerization of olefins; as catalysts for the
oligomerization of acetylene and other alkynes; as flame
retardancy additives for silicone rubber; and in many other
applications which require a compatible form of platinum.
The platinum ~O) alkyne complexes resulting from the
method of the present invention are especially useful as
curing catalysts for curable silicone compositions comprising
1) a silicone polymer having at least one unit selected from
the group consisting of CH2=CH-Si- units and -SiOH units;
2) a silicone polymer having at least one -SiH unit; and
3) a platinum (O) alkyne complex formed by contacting an
alkyne with a platinum-vinylsiloxane complex. Such
compositions represent a further aspect of the present
invention and are claimed herein.
A curable silicone composition as described above i5
made by simply mixing the appropriate polymers and platinum
(O) alkyne complex together. Simple mixing is accomplished by
mixers, such as Myers mixers, sigmoid blade mixers,
three-roll mills, two-roll mills, Baker Perkins type mixPrs,
and other known mixers.
Generally from 1 to 99 parts by weight of Component
1), from 1 to 99 parts by weight of Component 2), and a
eatalytieally effective amount of the platinum (O) alkyne
complex are used. By catalytically effective amount, it is
mean~ herein an amount sufficient ~o allow the curable
composition to be cured in a reasonable amount of time, such
as an hour or less, at a reasonable elevated temperature, such
as 35C or higher.
Catalytically effective amounts of the platinum ~O)
alkyne complex of the present invention vary from 1 part per
million by weight to 0.1% by weight.
More preferably, the amounts of Components 1) and 2)
are selected 50 that approximately equimolar amounts of -SiH
on the one hand and -SiCH=CH2 or -SiOH on the other hand are
used.
A curable composition as described above is a useful
coating material, such as a paper release coating. If a
reinforcing filler, such as amorphous silica, is added to the
curable composition, a useful elastomer will result upon cure.
The platinum (O) alkyne complexes produced by the
method are useful catalysts for both filled and unfilled
curable silicone compositions.
The following examples are here presented to further
teach the method of the present invention and the use of the
products of the present invention. All parts and percentages
in the examples are by weight unless otherwise specified.
The term Me in the examples represents the methyl
radical. The term Vi in the examples represents the vinvl
radical.
Characterization Methods
The products of the method of the present invention
were characterized by the following methods:
Yield: Yields were determined by dividing the weight of the
product actually obtained by the weight of produc-t which would
result from complete reaction and recovery of product, and
multiplying the result of this division by 100%.
Elemental Analxsis: Carbon and hydrogen percentages were
determined by the combustion method. The complexes being
--8--
analyzed were quantitatively burned in oxygen, and the
resulting weights of CO2 and H2O were determined. These
weights were used to calculate the percentages of carbon anà
hydrogen originally present in the complex.
Infared and Nuclear Ma~netic Resonance SE~ E~ Infared
and nuclear magnetic resonance spectra were obtained for each
complex in the Examples to help identify the product. The
spectra determined were consistent with the reported
structures in all cases. The infared vibrational frequency of
the acetylene bond is often used in characterizing
metal-alkyne complexes. The vibrational frequency of the
acetylene bond i5 reported for each complex in the examples.
A platinum-vinylsiloxane complex was first formed by
reacting hexachloroplatinic acid with IViMe2Si32O. The
resulting product was neutralized with NaHCO3 and filtered.
The filtra~e was 4.02% platinum.
5.4 g of this platinum-vinylsiloxane complex ~1.1
mmole of platinum) was added to 14 ml of a toluene solution of
C6H5C-CC(Me)(C6H5)(OH). The 14 ml of solution constituted 2.3
mmoles of the alkyne.
This mixture was stirred for 5 hours, after which
time the toluene was removed by distillation at a temperature
of 20C and under reduced pressure. The resulting product was
a white solid. The product was washed with pentane and dried
under vacuum. The product was identified as Pt(C6H5C-CC(Me)-
(C6H5)(OH))2. This product had a melting range of 99C-101~C.
Other characterization data are found in Table 1.
Exam~le 2-4
The procedures of Exa~ple l were follow~d for each
of the following alkynes:
(Me)2(OH)CC-CC(2~e)2(OH),
C6H5c-cc6H5~ ard
- 9 -
HC-CC(~5e2)(OH).
Characterization data are found in Table 1.
This example illustrates the use of a product of the
method of the present invention in a hydrosilylation reaction.
11.2 g of 1-octene were heated with .0009 g of the
platinum (O) alkyne complex of Example 1, at 65C, for 1
minute; A clear solution resulted. This clear solution was
cooled to a temperature of 30C. MeHSiC12 was added to the
cooled solution in a dropwise mannerO A vigorously exothermic
reaction resulted. The temperature of the reac~ion mixture
rose to 110C, and external cooling was applied. After 30
minutes, the stoichiometric amount of MeHSiCl2, 11.5 g, had
been added, and the reaction appeared ~o have stopped.
Gas chromatographic analysis of the product
indicated that the major species (84~) of the reaction mixture
was n-octyl SiMeCl2.
Example 6
50 grams of a 30% toluene solution of a silicone gum
containing 2 mole percent vinyl substituted groups was mixed
with 0.18 g of the platinum (O) alkyne complex produced in
Example 3, and 0.15 g of methylvinylcyclosiloxanes.
10 g of the above mixture was subsequently mixed
with 40 g of heptane, and 0.04 g of a silicone polymer having
the average formula Me3SiO~MeHSiO)40SiMe3.
The resulting mixture was a curable silicone
composition of the present invention. This curable silicone
composition was coated in a thin layer on a sheet of paper and
was exposed for 40 seconds in a 77C air-circulating oven.
The coating on the paper was cured. Th~ cured
coating did not rub off when rubbed by a finger; it did not
smear when rubbed by a finger; and the subsequent adhesion of
a piece of adhesive tape pressed upon the coating and removed
--10--
was not noticeably diminished. The above results are
charackeriskic of a well-cured paper coating.
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