Metal Mediated Reactions on Porous Silicon Surfaces

Reactions that efficiently form Si–C bonds between silanes and unsaturated carbon–carbon bonds are widely known in molecular, solution phase chemistry. The possibility of covalent functionalization of porous silicon surfaces, which have similar chemical moieties to certain classes of molecular silanes, is intriguing. In this paper we describe approaches toward hydrosilylation of alkynes and alkenes and bis-silylation of alkynes utilizing known solution phase Lewis acid and late transition metal catalysts on silicon hydride terminated porous silicon surfaces. Both EtAlCl2 and Wilkinsonʹs catalyst, RhCl (PPh3)3, effectively induce hydrosilylation of alkynes and alkenes. Bissilylation using palladium-based complexes, however, did not occur and thermally induced hydrosilylation took place in its stead. The Lewis acid mediated hydrosilylation is extremely efficient and yields highly stabilized surfaces. When Wilkinsonʹs catalyst and palladium complexes are utilized, on the other hand, extensive oxidation upon exposure to air is observed.