Surface organometallic chemistry of tin: Thermal transformation, in vacuo, of ≡Si-O-SnMe₃ supported on silica; in situ IR, ¹³C CP MAS NMR and TPD experiments

The thermolysis of ≡Si-O-SnMe₃ grafted onto partially dehydroxylated silicas has been studied by in situ IR, ¹³C CP MAS NMR and TPD. The only detected gaseous product was methane, showing that the thermolysis process passes through a simple hydrolysis reaction between the grafted organometallic fragment and silanol groups. This reaction leads to the formation of (≡Si-O)₂SnMe₂, (≡Si-O)₃SnMe, and finally tin compounds without organic ligands. The relative proportions of these surface organometallic fragments have been quantitatively determined by three independent methods which gave concordant results. Due to the higher density of hydroxy groups on SiO₂ 200, the reactions proceed at a lower temperature on this surface. After thermal treatment at 400°C, no more methyl ligands remain on the surface and all tin species are probably present as tin(IV) compounds.