Grafting of Zr(NMe 2) 4 on mesoporous silica SBA-15 afforded selec-tively well-defined surface species R R RSiOZr(NMe 2)(g 2 NMeCH 2). 2D solid-state NMR (1 H– 13 C HETCOR, Multiple Quantum) experiments have shown a unique structural rearrangement occurring on the immobilised zirconium bis methylamido ligand. Supporting complexes onto silica, within the framework developed by Surface Organometallic Chemistry (SOMC), can allow the isolation of species on surface otherwise elusive to observe in solution. Their presence can lead to the discovery of new modes of activation or new catalytic reactions. 1–5 In that context, solid-state NMR, specifically when combined with advanced experiments, has proven to be instrumental in determining the coordination sphere of supported metal centers. We report herein the first surface azazirconacyclo-propane, RSiOZr(NMe 2)(NMeCH 2), obtained by the reaction of Zr(NMe 2) 4 with the isolated silanols present at the surface of highly dehydroxylated mesoporous silica (SBA-15 pretreated at 700 1C). This structure was evidenced using SS NMR, IR spectroscopy and elemental analysis. Mesoporous silica SBA-15 was dehydroxylated using the traditional protocol to afford supports with expected textural parameters (see Fig. S2 (ESI) for the nitrogen adsorption– desorption isotherm and Fig. S3 for XRD). 6 SBA-15 (700) (0.260 g, 1.07 mmol silanols per gram) was treated with Zr(NMe 2) 4 in slight excess (0.107 g, 1.4 mol equivalent) with respect to the amount of surface accessible silanols in pentane at room tem-perature for 1 h (see Scheme 1). After filtration and four washing cycles, all volatiles were evaporated and the solid was dried for 1 h in vacuo (o10 À5 mbar). Comparison of the IR spectra before and after treatment with Zr(NMe 2) 4 indicates the consumption of all the silanols avail-able at the surface. New bands related to the alkyl vibrations are observed: intense bands at 2967–2776 cm À1 – CH stretching – and weak bands in the 1500–1400 cm À1 – C–H band (see Fig. 1). It is noteworthy that a broad and weak signal is observed at around 3292 cm À1 , ascribed to the N–H band, consistentl with the presence of physisorbed dimethyalmine. Elemental analysis gave 10.1% Zr, 10.1% C and 5.58% N. The metal content of the solid, ca. 1.03 zirconium per silanol, confirms a total reaction of the silanols. The ratios of nitrogen and carbon against the zirconium content, respectively (3.61 N/Zr (expd 3) and 7.60 C/Zr (expd 6)), were higher than that expected for trisamido monopodal surface complex 1. It was then postulated that a significant amount of dimethylamine released by proto-lysis by the silanol on the amido ligand may remain adsorbed on the surface. Longer drying time of the powder did not reveal any decrease in the 3292 cm À1 signal, thus suggesting that dimethylamine strongly physisorbed onto the silica support. 7 Additional experiments using a pellet of SBA-15 contacted by Zr(NMe 2) 4 in the gas phase confirmed the evolu-tion of dimethylamine with concomitant physisorption on silica (see ESI). Scheme 1 Reagents and conditions: SBA-15 was dehydroxylated at 700 1C (i) Zr(NMe 2) 4 , pentane, room temperature, 1 h.