Tetraalkyltin complexes, SnR4 (R = Me, Et, i-Pr, Bu), and tributylhydridotin were reacted with the surface of partially dehydroxylated silica. Interaction between the complexes and the silica surface was followed by IR and 13C and 119Sn MAS NMR spectroscopies and analysis of the evolved gases. At room temperature, all the studied complexes are physisorbed: a hydrogen-type bonding between the terminal methyl group of the alkyl ligands and/or the hydride ligand and the surface silanol groups is evidenced. Above 100 °C, with silica dehydroxylated at 500 °C (SiO2(500)), a reaction occurs, leading to the formation at 200 °C of essentially one surface complex, ⪫SiO-SnR3 (1) with evolution of 1 mol of alkane per mol of surface tin. 1 is already formed at room temperature by reaction of silica with Bu3SnH; the reaction is slow and liberates 1 mol of H2/mol of surface Sn. At low surface coverage, and for R ≠ Me, the alkyl ligands of 1 are folded toward the surface, interacting with it via hydrogen-type bonding. The same interaction and reaction are observed when the surface of silica is less dehydroxylated, SiO2(200): nevertheless 1 is less stable, probably due to the availability of surface silanol groups in the neighborhood of 1.
ASJC Scopus subject areas
- Colloid and Surface Chemistry