Grafting of a new bis-silylamido aluminum species on silica: insight from solid-state NMR into interactions with the surface

Abstract

The new bisamido aluminum species [AlCl{N(SiMe₃)₂}₂(THF)] (1) was prepared and fully characterized by ²⁷Al and ³⁵Cl solid-state NMR, along with X-ray diffraction studies. 1 was grafted on silica partially dehydroxylated at 700 °C, affording silica-supported Al species. The resulting material (2) was characterized by IR, elemental analysis and ¹H, ¹³C and ²⁷Al solid-state MAS NMR. The 1D and 2D ²⁷Al MAS NMR studies showed the occurrence of two types of species, where the Al center adopts a tetracoordinated coordination sphere, with as an additional coordinated Lewis base, either a THF ligand or a silica-surface siloxane moiety. DFT calculations allowed understanding the grafting mechanism and the spectroscopic properties of the material.