Preparation and characterization of immobilized constrained-geometry hafnium complexes

Heterogeneous constrained-geometry hafnium complexes were prepared by anchoring Hf(NMe2)4 on a heterogenized ansa-cyclopentadienylamino ligand of type (RN)R′R′′Si(C5R′′′4), surface 1: R=OMe2Si(CH2)3; R′, R′′, R′′′=Me; surface 2: R=OMe2Si(CH2)3; R′, R′′′=Me, R′′=H. Preparation of the constrained-geometry catalyst ligand on silica surface was carried out in two steps: functionalizing of the silica surface with aminopropyldimethylethoxysilane (APDMES) by using saturated gas–solid reactions and immobilizing of (tetramethylcyclopentadienyl)chlorosilanes, Me2Si(C5Me4H)Cl or MeHSi(C5Me4H)Cl, on the functionalized silica by utilizing n-butyllithium (n-BuLi). Hf(NMe2)4 was immobilized on the heterogeneous surfaces by the amine elimination route. The complexes were characterized by 1H, 13C, and 29Si solid state NMR and FTIR spectroscopy.