Synthesis and crystal structure of bis{di-μ-hydroxobis[fac-tribromoaquotin(IV)]} heptahydrate

A product isolated from a reaction mixture of Br2 and Ph3 Sn(CH2)13CH3 (3:1 mole ratio) in CHCl3 solution in air was bis{di-μ-hydroxobis[fac-tribromoaquotin(IV)]} heptahydrate, 2[Br3 (H2O)Sn(μ-OH)2 Sn(O2H)Br3] · 7H2O, 2[fac-(1: X = Br)] · 7H2O. Previous reports had indicated that the tin complexes, [fac-(1: X = Cl or Br)], had been obtained in various solvated forms from hydrolysis or oxidation/hydrolysis of appropriate tin(IV) or tin(II) halides. The crystal structure determination, reported here, provides an improved refinement of the core, i.e., [fac-(1: X = Br)], of 2[fac-(1: X = Br)] · 7H2O compared to previous attempts. The solid state structure consists of a central rhomboidal planar Sn2O2 ring. The tin centres have distorted octahedral geometries, with each Br ligand trans to an O atom. The Br ligands, trans to the aqua ligands, form longer bonds to tin at 2.5556(7) and 2.5544(6) Å, than those trans to the bridging OH ligands, between 2.5021(7) and 2.5127(7) Å. The Br, OH and H2O ligands as well as the solvate water molecules are all involved in an extensive hydrogen bonding system in 2[fac-(1: X = Br)] · 7H2O.