Transition-metal ligands bound onto the micelle-templated silica surface

This paper reviews recent works on the design of immobilized transition-met al ligands on solid supports. After an overview of some results concerning ligand anchorage on polymeric supports and encapsulation of transition-meta l complexes inside layered or zeolitic minerals, the grafting of ligands on to the silicic wall surface of micelle-templated silicas (MTS) is reported. MTS silicas featuring a regular mesoporous system of pore-monodispersed si ze and exhibiting larger pores than zeolites, provide a new opportunity to allow anchorage of organic moieties through the silanation procedure. Mn(II I) Salpr and tSalpr complexes bound onto the MTS surface are active in epox idation reaction using PhIO as oxygen donor. Anchorage of (1R,2S)-ephedrine has been also investigated with the aim to obtain benefit from the MTS str ucture effect. These new supported chiral catalysts are active in alkylatio n of benzaldehyde with diethylzinc although less enantioselective than the corresponding homogeneous catalyst. The effect of dispersion of active site s and of surface passivation has been investigated and discussed in terms o f the nature of the support surface. (C) 1998 Elsevier Science S.A. All rig hts reserved.