The structure of trimethyltin fluoride

Abstract

The solid-state structure of (CH₃)₃SnF was reinvestigated by X-ray diffraction techniques as well as by multi-nuclear solid-state NMR spectroscopy. Trimethyltin fluoride crystallizes from hot ethanol in the orthorhombic space group Pnma at room temperature and changes to a low-temperature orthorhombic phase (space group: Cmcm) below −70 °C. In both modifications, trimethyltin fluoride adopts a linear chain structure with symmetric fluorine bridges, in contrast to previous reports. During its synthesis, (CH₃)₃SnF precipitates in another, poorly crystalline modification, as shown by powder X-ray diffraction. Solid-state MAS NMR experiments of both room-temperature phases of (CH₃)₃SnF (non-recrystallized and recrystallized) were carried out for the ¹H, ¹³C, ¹⁹F, and ¹¹⁹Sn nuclei. The ¹¹⁹Sn{¹⁹F, ¹H} and ¹⁹F{¹H} NMR spectra offer unambiguous determination for the ¹⁹F and ¹¹⁹Sn shielding tensors. The ¹¹⁹Sn{¹H} solid-state NMR spectra are in agreement with pentacoordination of Sn in this compound for the non-recrystallized and the recrystallized modifications. Based on the solid-state NMR results, the non-recrystallized modification of (CH₃)₃SnF also consists of linear, symmetrically fluorine-bridged chains, and differs from the recrystallized orthorhombic phase only in packing of the chains.