Hydrogen bonding in substitutionally disordered di-μ-hydroxido-bis{aquatri[bromido/chlorido(1/2)]tin(IV)} acetone disolvate

The structure of the title compound, [Sn2Br1.97Cl4.03(OH)2(H2O)2]·2C3H6O, contains two hexacoordinated Sn atoms bridged symmetrically by two hydroxide groups, with an inversion center in the middle of the planar Sn2O2 ring, half of the molecule being generated by inversion symmetry. The other sites of the distorted octahedral coordination geometry are occupied by halide atoms and water molecules. The structure exhibits substitutional disorder of the halide atoms bonded to the Sn atom, with 0.672 (4) occupancy for Cl and 0.328 (4) for Br for each halide position. The compound crystallizes with two acetone molecules, which are involved in intra- and intermolecular O—H⋯O contacts. The water molecules coordinated to the Sn atoms are also involved in O—H⋯O and O—H⋯X contacts, leading to a polymeric array along the a axis.

The structure of the title compound, [Sn 2 Br 1.97 Cl 4.03 (OH) 2 -(H 2 O) 2 ]Á2C 3 H 6 O, contains two hexacoordinated Sn atoms bridged symmetrically by two hydroxide groups, with an inversion center in the middle of the planar Sn 2 O 2 ring, half of the molecule being generated by inversion symmetry. The other sites of the distorted octahedral coordination geometry are occupied by halide atoms and water molecules. The structure exhibits substitutional disorder of the halide atoms bonded to the Sn atom, with 0.672 (4) occupancy for Cl and 0.328 (4) for Br for each halide position. The compound crystallizes with two acetone molecules, which are involved in intra-and intermolecular O-HÁ Á ÁO contacts. The water molecules coordinated to the Sn atoms are also involved in O-HÁ Á ÁO and O-HÁ Á ÁX contacts, leading to a polymeric array along the a axis.
The tin atoms are hexacoordinated with the two hydroxo, three halides and one water molecule occupying the distorted octahedral positions around the metal centre. The tin atoms are out of the best plane described by O1/O1 i /X1/X2 (X = Cl/Br) with 0.174 Å towards X3.
The compound exhibits substitutional disorder of the halide atoms bonded to the Sn with 0.672 occupancy for Cl and 0.328 for Br for each halide position.
The compound crystallizes with two acetone molecules, which establish two strong hydrogen bonds, one with the hydroxo group and one with the water from a neighboring dimer (Table 1). The water molecules are also involved in hydrogen bond type interactions with halide atoms, a strong one inside the dimeric unit and one intermolecular with a halide from another dimer ( Table 1). The intramolecular interactions strengthen the dimeric unit and the intermolecular ones give rise to a polymer-like supramolecular arrangement along the a axis ( Figure 2), with no further interactions between different chains ( Figure 3).

S2. Experimental
The title compound was obtained as a by-product after the work up of the crude reaction mixture obtained by reacting [2,6-(Me) 2 C 6 H 3 ]MgBr and SnCl 4 .

S3. Refinement
The hydrogen atoms of the methyl groups were placed in calculated positions and were allowed to rotate but not to tip, View of the title compound showing the atom-numbering scheme at 30% probability thermal ellipsoids [symmetry code: (i) = -x + 1, -y + 1, -z + 1].

Figure 2
Intra-and intermolecular interactions in the title compound (