Thermally induced elimination reactions in xerosols derived from (fluoroorgano)tin compounds: A new efficient way to prepare F-doped tin dioxide materials

Trialkynyl(fluoroorgano)tins(IV) (C4H9-C=C)(3)-SnRF (I) (R-F = -(CH2)(2)-CF 3, -o-FC6H4) have been synthesized in three steps from tricyclohexyltin hyd ride or chloride and were characterized by multinuclear H-1, C-13, F-19, an d Sn-119 NMR spectroscopy. Hydrolysis of 1 yielded oxo-hydroxoorganotin oli gomers soluble in acetonitrile and alcohols, where each tin atom bears a fl uorinated organic group. Thermally induced beta- or gamma -elimination reac tions, evidenced by TG/MS measurements, allowed the insertion of fluorine i nto the oxide network and the removal of the undesirable organics. Densific ation at 550 degreesC gave crystalline particles of SnO2 cassiterite contai ning the required amount of doping fluorine (4 at. %) and exhibiting an ele ctronic resistivity (0.3 Omega .cm) lower than that previously reported (2- 10 Omega .cm) for similar tin oxide materials. beta- or gamma -elimination processes in organotin compounds appear to be a suitable method of preparat ion of highly conductive nanocrystalline F-doped SnO2 materials by the sol- gel route with low contaminating carbon content.