Pentamethylcyclopentadienylrhodium(I) complexes incorporated into porous polysiloxanes prepared by a sol–gel process: catalysts for hydrogenation of crotonic acid in water
✍ Scribed by Jan Čermák; Magdalena Kvíčalová; Vratislav Blechta
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 77 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0268-2605
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✦ Synopsis
Pentamethylcyclopentadiene-functionalized polysiloxanes were prepared by a sol-gel process from tetraethoxysilane and (pentamethylcyclopentadienylmethyl)methyldiethoxysilane without a catalyst. The polysiloxanes are microporous-mesoporous solids, of which the BET surface areas and micropore volumes are inversely proportional to the concentration of the functionalizing agent (5-21 mol%) in the starting mixture of alkoxysilanes. The polysiloxanes were also characterized by CP MAS 13 C NMR spectroscopy, revealing essentially the same structure of organofunctional ligand as that in particulate materials with low surface areas prepared earlier in a sol-gel process catalyzed by dibutyltin diacetate. Novel alkoxysilyl-substituted pentamethylcyclopentadienyl (1,5-cyclo-octadiene)rhodium(I) complexes were synthesized from the corresponding cyclopentadienes by deprotonation followed by reaction with [(cod)RhCl] 2 (cod = cyclo-octadiene). Polysiloxane-bound rhodium complexes were prepared by a sol-gel reaction analogous to the one mentioned above and were found to catalyze the hydrogenation of crotonic acid in water; to the best of our knowledge, this constitutes the first example of catalysis by a well-defined polysiloxane-bound transition metal complex in an aqueous system.