[SnF(bipy)(H2O)]2[SnF6], a mixed-valent inorganic tin(II)–tin(IV) compound

Abstract

In the title compound, bis[aqua(2,2′-bipyridine)fluoridotin(II)] hexafluoridotin(IV), [SnF(C10H8N2)(H2O)]2[SnF6], an ionic mixed-valent tin(II)–tin(IV) compound, the bivalent tin atom is the center atom of the cation and the tetravalent tin atom is the center atom of the anion. With respect to the first coordination sphere, the cation is monomeric, with the tin(II) atom having a fourfold seesaw coordination with a fluorine atom in an equatorial position, a water molecule in an axial position and the two nitrogen atoms of the chelating 2,2′-bipyridine ligand in the remaining axial and equatorial positions. The bond lengths and angles of this hypervalent first coordination sphere are described by 2c–2e and 3c–4e bonds, respectively, all of which are based on the orthogonal 5p orbitals of the tin atom. In the second coordination sphere, which is based on an additional, very long tin–fluorine bond that leads to dimerization of the cation, the tin atom is trapezoidal–pyramidally coordinated. The tetravalent tin atom of the centrosymmetric anion has an octahedral coordination. The differences in its tin–fluorine bond lengths are attributed to hydrogen bonding, as the two of the four fluorine atoms are each involved in two hydrogen bonds, linking anions and cations together to form strands.

Keywords

• mixed-valent
• hyper-valency
• hydrogen bonding
• dimerization
• 3c–4e bonds
• crystal structure