reference for GC analysis. The appropriate amount of catalyst
was added at time zero corresponding to the desired silane–Pt
molar ratio of 1 : 1 × 10Ϫ3. A 5% w/w H2PtCl6ؒH2O in isopro-
panol catalyst was used. The vial was then shaken using a
Stuart Scientific shaker and the mixture was left to react under
ambient conditions. The reaction was followed by gas
chromatography.
Impact 400D instrument using 10 scans at a resolution of
4 cmϪ1 1H and 13C NMR analyses were recorded using a
400 MHz Bruker DPX-400 spectrometer.
.
GC analysis of each hydrosilylation reaction was carried out
using initially a Fisons DP 1701 (30 × 0.32 × 0.25) silica capil-
lary column and later a Chrompack CP-SIL 19CB (30 × 0.32 ×
0.25) silica capillary column. These were mounted on a Carlo
Erba HRGC 5300 Mega Series instrument fitted with a flame
ionisation detector. Hydrogen was used as the mobile phase and
n-nonane was used as an internal reference standard. Samples
were prepared for injection by dripping one drop of the
appropriate reaction mixture into 1 cm3 of cyclohexane and
0.2 µl of this mixture was injected and analysis run using a two
Heterogeneous hydrosilylation reactions
These were carried out essentially as described for the homo-
geneous reactions although in this case the appropriate amount
of the resin catalyst corresponding to a molar ratio of silane–Pt
of 1 : 1 × 10Ϫ3 was weighed initially into the vial. The reaction
mixture was then added at time zero and the above procedure
followed.
minute temperature program [60 ЊC (1 min)
100 ЊC (at 40 ЊC
minϪ1)]. It was necessary to calibrate the GC instrument at
regular intervals to maintain accuracy.
Confirmation of the identity of the hydrosilylation product
was also carried out via GC analysis. Samples were prepared for
injection by dripping one drop of the appropriate spent reac-
tion mixture into 1 cm3 of cyclohexane; 0.5 µm of this mixture
was then injected and analyses run using a ten minute temper-
Catalyst recycling reactions
In these experiments the performance of a sample of each
catalyst C1–C10 was evaluated in up to 10 back-to-back
catalytic reactions. After each run was complete the super-
natant liquid phase was carefully decanted from the reaction
vial, taking care that all of the resin catalyst beads remained
behind in the vial. The sample of catalyst was then recycled by
adding a fresh reaction mixture. The quantities of materials
were standardised as described above and each reaction was
monitored by GC.
ature program [50 ЊC (1 min)
maintained for 3 min)].
200 ЊC (at 25 ЊC minϪ1
;
Acknowledgements
S. J. T. acknowledges the receipt of a studentship from
Dow Corning. The gift of vinylbenzyl chloride from the Dow
Chemical Co. is appreciated. We also thank Dr G Wiltshire,
University of Paisley, UK for the supply of ICP AAS data.
Catalyst leaching reactions
Initially, a fresh reaction mixture and catalyst resin were added
to a reaction vial (as detailed above) and then shaken for a
previously decided length of time, this being long enough for an
intermediate conversion to be achieved. At this point the reac-
tion mixture was sampled for analysis in order to assess the
progress of the reaction. The supernatant (liquid phase) was
then decanted into a second vial, taking care that no resin
catalyst beads were also removed. The second vial was then
shaken for 24 h before being analysed to check whether further
conversion had occurred. Simultaneously, over the same 24 h
period, the original vial containing the heterogeneous catalyst
(along with a fresh reaction mixture) was also put through
another catalysis cycle. This whole procedure was then repeated
until each catalyst sample had catalysed either eight or ten
different hydrosilylations.
References
1 B. Marciniec, J. Gulinski, W. Urbaniak and Z. W. Kornetka,
Comprehensive Handbook on Hydrosilylation, ed. B. Marciniec,
Pergamon Press, Oxford, UK, 1992, ch. 2, p. 8.
2 J. L. Speier, J. A. Webster and C. H. Barnes, J. Am. Chem. Soc., 1957,
79, 974.
3 For a summary of work published prior to 1985 see: F. R. Hartley,
Supported Metal Complexes – A New Generation of Catalysts,
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10 Z. M. Michalska, B. Ostaszewski and K. Strzelec, J. Organomet.
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Control reactions
In those recycling experiments using crushed resin catalysts
it was necessary to centrifuge reaction mixtures (3000 rpm,
30 min) to effect separation of the catalyst particles.
In those recycling experiments where the catalyst resin beads
were washed between successive runs two procedures were
employed. In the first, recovered catalyst from decantation of
the previous reaction mixture was washed successively with
three oct-1-ene–nonane mixtures of the same composition and
volume as those used in a reaction. The wash solutions were left
in contact with catalyst for 20, 10 and 13 hours respectively.
Again separation was by decantation. In the second method
recovered catalyst was washed successively with ten oct-1-ene–
nonane mixtures as above each for 5 min only.
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79, 974.
Analytical methods and instrumentation
Elemental microanalyses were carried out by the Microanalysis
Laboratory at the University of Strathclyde. ICP AAS was
carried out by the Centre for Particle Characterisation and
Analysis (CPCA) at the University of Paisley, Scotland. N2
BET analyses were performed using a Micromeritics ASAP
2000 instrument. FTIR spectra were collected using a Nicolet
22 J. C. Saam and J. L. Speier, J. Am. Chem. Soc., 1958, 80, 4104.
23 P. M. van Berkel and D. C. Sherrington, Polymer, 1996, 37, 1431.
1534
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