Grafting of lanthanide complexes on silica surfaces dehydroxylated at 200 °C: a theoretical investigation

Abstract

Cluster models of SiO_2-200 are proposed and compared with spectroscopic (IR and NMR) experimental data. Five models describing the variety of surface silanols (isolated, vicinal and germinal) at the SiO_2-200 surface have then been derived and used to study the grafting reaction of homoleptic silylamide lanthanum(III) complexes. Three different grafting modes have been obtained (mono-, bi- and tri-grafted) in line with the experimental knowledge. In terms of energetic stability as well as spectroscopic properties of coordinated OPPh₃ (as a probe), all modes could coexist at the surface. The analysis of the δ(³¹P) chemical shifts for the coordinated OPPh₃ indicates some possible important differences in Lewis acidity of the lanthanide centre, which may impact the catalysis.