The use of pyridine-functionalised polydimethylsiloxane polymers as a supercritical carbon dioxide solubilising support for copper compounds

Pyridine-terminated polydimethylsiloxane (PDMS) was synthesised by hydrosilylation of 4-vinylpyridine with hydride terminated PDMS. The product obtained was a mixture of both the Markovnikoff and anti-Markovnikoff products. Reaction with [Cu(AcO)2(H2O)]2 in ethanol, yielded 1, isolated as a green oil. Compound 1 contained 4–6% copper by weight indicating that some terminal pyridines remained uncoordinated. Solubility studies of 1 in supercritical carbon dioxide (scCO2) demonstrated the effectiveness of PDMS chains as solubilising groups. Whilst 1 showed a solubility ca. 1.7 mM in scCO2, related copper derivatives were observed to be insoluble.