SYNTHESIS AND STRUCTURAL CHARACTERIZATION 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 precurso r. 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, disto rted) trigonal bipyramidal geometry, whilst [Sc{N(SiHMe2)(2)}(3)(thf)] has a distorted tetrahedral co-ordination geometry and short Sc ... S i contacts in the solid state. The reaction of [Y{N(SiHMe2)(2)}(3)(thf )(2)] with varying amounts of AlMe3 resulted in desolvation and alkyla tion with formation of AlMe3(thf), {AlMe2[mu-N(SiHMe2](2)}(2) and hete robimetallic (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 desc ribed in detail. Consideration is given to the factors governing the s iloxide formation and silylation reactions, and the thermal stability of the surface species.