Mössbauer and infra-red studies of the diffusion and reactivity of (SnO)n species (n 1) initially isolated in solid nitrogen

Abstract

The diffusion and reactivity of the molecules SnO, Sn₂O₂, Sn₃O₃, Sn₄O₄ and higher polymers isolated in solid nitrogen have been investigated using both Mössbauer and i.r. spectroscopy and the changes in the concentrations brought about by annealing at temperatures up to 36 K have been followed quantitatively. The results are compared with three models and indicate that SnO, and probably to a lesser extent Sn₂O₂ are appreciably mobile at 34 K. At this temperature the diffusion coefficient of SnO in α-N₂ is between 10^–20 and 4 × 10^–22 m² s^–1, which is of the same magnitude as the previously determined diffusion coefficient of Sn atoms in α-N₂ at 34 K. The reactions 2SnO → Sn₂O₂ and SnO₂+ Sn₂O₃→ Sn₃ O₃ appear to have a non-zero activation energy sufficient to inhibit their reaction rates compared to the reactions of SnO with higher polymers.

After evaporation of the nitrogen, aggregates of tin(II) oxides remained which were stable to oxidation up to 270 K but were partially oxidised in air to tin(IV) at 295 K. At 4.2 K the isomer shift of the broad tin(II) doublet of the final material is 2.83 mm s^–1 and the quadrupole splitting is 2.0 mm s^–1; these are different from the parameters of both previously known forms of bulk SnO.