REACTIONS OF ORGANOSTANNANES WITH SILICA, GAMMA-ALUMINA, AND SILICA-ALUMINA

The adsorption of selected organostannanes, Bu4Sn, Bu3SnX (X = H, Cl, OMe), Bu2SnX2 (X = Cl, OMe, OBu(t)), and Sn(OBu(t))4 was achieved on SiO2, gamma-Al2O3, and Al2O3/SiO2 (12.5%) from CH2Cl2 or pentane solution, at 298K. The isotherms were determined for Bu3SnOMe/SiO2 and Al2O3 and Bu2Sn(OMe)2/SiO2 and Al2O3 and show that chemisorption occurs leading to a surface coverage of 0.64, 1.24, 1.75, and 1.11 Sn run-2, respectively. Analysis by FTIR spectroscopy of the adducts pointed out that with SiO2 the isolated OH groups are reacting, whereas with alumina basic oxygen centers are implied. On the four systems studied, one MeO ligand is transformed into methanol, even with Bu2Sn(OMe)2. The determination of the surface coverage on SiO2, gamma-Al2O3, and Al2O3/SiO2 for the remaining organostannanes mentioned, coupled with THF and MeOH extractions, show that the alkoxo compounds are more reactive toward the oxide surfaces. These experiments have led to a more precise picture of the adsorbed species. Monomeric as well as dimeric and trimeric structures are proposed, illustrating how oxide supports can be used to stabilize different organometallic fragments from the same precursor.