Di-μ-hydroxido-bis[dimethyl(thiocyanato-κN)tin(IV)]

The SnIV atom in the centrosymmetric title complex, [Sn2(CH3)4(NCS)2(OH)2], adopts a distorted trigonal–bipyramidal coordination environment defined by two methyl C atoms and one bridging hydroxide group in the equatorial plane while the other bridging hydroxide group and the N atom of the thiocyanate anion are in the apical >positions. The dinuclear species are linked through O—H⋯S and C—H⋯ S hydrogen-bonding interactions into a three-dimensional network.

The Sn IV atom in the centrosymmetric title complex, [Sn 2 (CH 3 ) 4 (NCS) 2 (OH) 2 ], adopts a distorted trigonal-bipyramidal coordination environment defined by two methyl C atoms and one bridging hydroxide group in the equatorial plane while the other bridging hydroxide group and the N atom of the thiocyanate anion are in the apical >positions. The dinuclear species are linked through O-HÁ Á ÁS and C-HÁ Á Á S hydrogen-bonding interactions into a three-dimensional network.
The asymmetric unit of compound (I) is situated close to an inversion centre, which generates a dimer containing a central Sn 2 O 2 ring; the tin(IV) atom is five-coordinated by two methyl groups, two bridging oxygen atoms and one nitrogen atom of the thiocyanate anion, forming a distorted trigonal bipyramid (  (Ng, 1998;Chandrasekhar et al., 2007). The Sn-N and Sn-C bond length are likewise in the range of reported values (Cox & Wardell, 1996;Ng, 1998;Okio et al., 2003;Chandrasekhar et al., 2007). The dinuclear species are linked through O-H···S hydrogen bonds into layers parallel to (001) (Fig. 2); C-H···S hydrogen bonding interactions (Table 1) lead to the formation of a three-dimensional network.

Experimental
All chemicals were purchased from Aldrich (Germany) and used without any further purification. The salt (NH 4 )SCN was obtained by mixing KSCN with NH 4 Cl in ethanol 96%. The title compound (I) was synthesized by reacting Sn(CH 3 ) 2 Cl 2 with (NH 4 )SCN in ethanol (96 wt% ) in a 1:1 ratio. After stirring for two hours a clear solution was obtained that was slowly evaporated, yielding colourless crystals with a melting point of 502 K.

Refinement
Hydrogen atoms bonded to the O atom have been located in difference Fourier maps and have been freely refined. The other hydrogen atoms have been placed onto calculated position and refined using a riding model, with C-H distances of 0.98 Å and U iso (H)= 1.5U eq (C).

Figure 1
The dinuclear complex of compound (I). Displacement ellipsoids are drawn at the 50% probability level.  View of the hydrogen bonding system (dashed lines) between the sulfur atom of the SCNanion and the H atom of the bridging OH group, as well as C-H···S interactions. O atoms are red, S atoms olive, N atoms blue, Sn atoms green, H atoms yellow and C atoms grey.

Di-µ-hydroxido-bis[dimethyl(thiocyanato-κN)tin(IV)]
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.06 e Å −3 Δρ min = −0.64 e Å −3 Extinction correction: SHELXL97 (Sheldrick, 2008), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.0026 (2) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq