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

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 [LnCl(3)(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[mu-N(SiHMe2](2)}(2) and heterobimetallic (Y/Al) species. The generation of surface-bonded '(=SiO)(x)Y[N(SiHMe2)(2)](y)' and '=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.