(41c) Hybrid Organic-Inorganic Materials for Heterogeneous Catalysis: Development of Highly Structured Multifunctional Silicon Surfaces

Functionalization of single-crystal silicon surfaces is an area of intense research due to the potential use of hybrid organo-silicon materials as the basis for integrating various functionalities, such as molecular recognition devices and biomolecules, including proteins, DNA and carbohydrates. For instance, a wide variety of methods was developed to prepare organic monolayers of 1-alkenes and 1-alkynes on hydrogen-terminated silicon (H-Si).^1,2 Taking advantage of the strong Si-C bond, this kind of functionalization can also be used for the covalent immobilization of organometallic complexes onto silicon, thus leading to a powerful approach for the preparation of catalytically active materials, which can be repeatedly recycled.

We recently reported the covalent immobilization of a tethered ethylenebis(indenyl) (=EBI) ligand,³ tethered EBI-zirconocenes⁴ and of biomolecules⁵ on H-terminated Si(111)-surfaces.

In this contribution we present the design of hybrid organic-inorganic silicon surfaces that include different kinds of organometallic catalysts in a highly structured arrangement.

The preparation of these multifunctional surfaces included in the first step the immobilization of an organic bis(oxazoline)-ligand on a H-terminated Si(111)-surface. The immobilization reaction was carried out via a UV-mediated hydrosilylation of the terminal double bond of the ligand and the Si-H group of the Si-wafer. In addition to being a clean and straightforward approach, this method lends itself to the sub-micron structuring of catalytic surfaces via photopatterning and photolithography. The immobilized ligand was then metalated with Pd(OAc)₂ to give a highly potential heterogeneous Pd-catalyst. On the same Si-wafer tethered titanocenes were attached to the surface applying again a hydrosilylation reaction. The resulting multifunctional surfaces were tested for the heterogeneous synthesis of active pharmaceutical ingredients, such as amines and substituted biphenyls.

(1) Buriak, J. M. Chem.Rev. 2002, 102, 1271-1308 and references therein.

(2) Scheres, L.; Giesbers, M.; Zuilhof, H. Langmuir 2010, 26, 4790-4795 and references therein

(3) Langner, A.; Panarello, A.; Rivillon, S.; Vassylyev, O.; Khinast, J.; Chabal, Y. J. J.Am.Chem.Soc. 2005, 127, 12798-12799.

(4) Gruber-Woelfler, Rivillon, S.; Chabal, Y. J.; Schitter, G.; Polo, E.; Ringwald, M.; Khinast, J. G.. Chem.Comm. (Hot Paper) 2008, 1329-1331

(5) Jeanquartier, C.; Schider, G.; Feichtenhofer, S.; Schwab, H.; Schennach, R.; Stettner, J.; Winkler, A.; Gruber-Woelfler, H.; Schitter, G.; Eder, R. J. P.; Khinast, J. G.. Langmuir 2008, 24, 13957-13961