Preparation of Heterogeneous Constrained-Geometry Catalysts of Group 4 Transition Metals by Amine Elimination Reaction

Abstract

Three heterogeneous constrained-geometry catalysts [(C5H4)SiMe2(N(CH2)3SiMe2−O−)]M(NMe2)2 (M = Hf (catalyst 1), Zr (catalyst 2), and Ti (catalyst 3) were prepared by anchoring of metal amides (M(NMe2)4, M = Hf, Zr, or Ti) to a bifunctional ligand surface on SiO2. Preparation of the bifunctional ligand on silica surface was carried out in two steps. First the silica surface was functionalized with aminopropyldimethylethoxysilane (APDMES) by using saturated gas−solid reactions. Second a reaction of the amino groups on the silica surface with n-BuLi was carried out, producing lithiated amido groups, which were allowed to react further with chlorides of (cyclopentadienyl)dimethylchlorosilane (Me2Si(C5H5)Cl). Anchorage of the metal amides on the prepared surface was carried out by the amine elimination route. The heterogeneous catalysts were comprehensively characterized by 1H, 13C, and 29Si solid state NMR and FTIR spectroscopy.