New sol–gel precursors for binary oxides of antimony, Sb2O3 (senarmonite) and α-Sb2O4: synthesis and characterization of some ketoximate modified antimony(III) alkoxides

Hydrolysis of pure Sb(OPri)3 by sol–gel method followed by sintering at 500 °C yields microcrystallites of Sb2O3 (senarmonite phase). Under similar conditions bimetallic alkoxide, [NaSb(OPri)4], yields a mixture of binary oxides Sb2O3 and Sb2O4. Chemical modification of Sb(OPri)3 with oximes forms monomeric products of the type [Sb(OPri)3−n {ON=C(CH3)R} n ] {where R = CH3, n = 1 [1]; n = 2 [2]; n = 3 [3]; R = 2-C5H4N, n = 1 [4]; n = 2 [5]; n = 3 [6]; R = 2-C4H3O, n = 1 [7]; n = 2 [8]; n = 3 [9]; R = 2-C4H3S, n = 1 [10]; n = 2 [11]; n = 3 [12]}. The liquid products [1–3, 7 & 10] were purified by distillation while the solids by recrystallization. All these products were characterized by elemental analyses, IR, NMR (1H and 13C{1H}) and representative derivatives [1], [2] and [3] by FAB mass studies. On the basis of these studies, a distorted pyramidal structure for all the derivatives may be assumed in the solution state containing an end-on coordination of oximes with the metal atom. Hydrolysis of the distilled precursors [1], [2] and [3] under sol–gel conditions yields pure nano-sized α-Sb2O4. All the oxides were characterized by XRD, SEM and EDX analysis exhibiting minimum particle size for the oxide obtained from the precursor [3].