Synthesis and structural characterisation of rare-earth bis(dimethylsilyl)amides and their surface organometallic chemistry on mesoporous MCM-41 †

Abstract

Rare-earth silylamides of type [Ln{N(SiHMe₂)₂}₃(thf )_x] (Ln = Sc, Y, La, Nd, Er or Lu) have been prepared in high yield by reaction of 2.9 equivalents of Li[N(SiHMe₂)₂] with [LnCl₃(thf )_x] in n-hexane or thf, depending on the solubility of the rare-earth halide precursor. The complexes [Ln{N(SiHMe₂)₂}₃(thf )₂] (Ln = Y, La to Lu) are isostructural in the solid state, adopting the preferred (3 + 2, distorted) trigonal bipyramidal geometry, whilst [Sc{N(SiHMe₂)₂}₃(thf )] has a distorted tetrahedral co-ordination geometry and short Sc  · · ·  Si contacts in the solid state. The reaction of [Y{N(SiHMe₂)₂}₃(thf )₂] with varying amounts of AlMe₃ resulted in desolvation and alkylation with formation of AlMe₃(thf ), {AlMe₂[µ-N(SiHMe₂]₂}₂ and heterobimetallic (Y/Al) species. The generation of surface-bonded ‘([triple bond, length half m-dash]SiO)_xY[N(SiHMe₂)₂]_y’ and ‘[triple bond, length half m-dash]SiOSiHMe₂’ moieties via the grafting of [Y{N(SiHMe₂)₂}₃(thf )₂] onto the mesoporous silicate MCM-41 is described in detail. Consideration is given to the factors governing the siloxide formation and silylation reactions, and the thermal stability of the surface species.

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