Characterisation of the tin(II) hydroxide cation [Sn3(OH)4]2+, and the crystal structure of tritin(II) tetrahydroxide dinitrate

Abstract

The crystal structure of Sn₃(OH)₄(NO₃)₂ has been determined using single-crystal X-ray diffraction and refined by full-matrix least-squares analysis to R₁= 0.0323 and wR₂= 0.1203. The complex crystallises in the monoclinic space group P2₁/n, with a= 7.729(1), b= 9.086(3), c= 14.159(3)Å, β= 90.65(2)° and Z= 4. The tin(II) atoms are contained in discrete polynuclear [Sn₃(OH)₄]²⁺ cluster units in which each tin is bonded pyramidally to three short nearest-neighbour cluster hydroxide oxygen atoms. A distorted octahedron of oxygen atoms around the tin(II) atoms is completed by three longer contacts to nitrate oxygens in the directions in which the tin non-bonding electron pairs point. One of the OH groups in [Sn₃(OH)₄]²⁺ is unique in that it is bonded to all three cluster tin atoms. This cation is considered to be one of the main products of the hydrolysis of tin(II) in aqueous solution. Raman spectroscopic data for Sn₃(OH)₄(NO₃)₂ have also been obtained and the known Mössbauer data are discussed with reference to the structure.