Aquadi-n-butyl(5-methylpyrazine-2-carboxylato)tin(IV) methanol solvate

In the monomeric title compound, [Sn(C4H9)2(C6H5N2O2)2(H2O)]·CH3OH, the Sn atom is seven-coordinate, displaying a distorted pentagonal bipyramidal SnC2N2O3 geometry with the two C atoms in the axial sites. In the crystal structure, intermolecular O—H⋯O hydrogen bonds link the complex and solvent molecules into infinite chains.

The title compound, (I), consists of two butyl, two N,O-bidentate 2-methylpyrazine-5-carboxylate groups and a water molecule bonded to the Sn atom and has a monomeric structure. The Sn atom is seven-coordinate with a distorted pentagonal bipyramidal SnC 2 N 2 O 3 geometry (Table 1, Fig. 1). Around the central Sn atom, atoms C13 and C17 of the two butyl groups occupy the axial position, while O and N atoms lie in equatorial positions. The sum of the angles between the tin atom and the equatorial atoms is 360.4°. The axial bond angle C17-Sn1-C13 [161.6 (3)°] deviates from linearity by over 18°, which shows that these atoms have significant deviations from ideal pentagonal bipyramidal geometry. Otherwise, the bond lenghts and angles in (I) are similar to those in related structures (Ma et al., 2004).
In the crystal, strong intermolecular O-H···O hydrogen bonds (Table 2) between O atoms of the carboxyl groups, methanol and coordinate water molecules result in the formation of one-dimensional polymeric chains (Fig. 2).

Refinement
The H atoms were positioned geometrically (C-H = 0.93-0.97 Å, O-H = 0.82-0.85 Å) and refined as riding with U iso (H) Fig. 1. The molecular structure of (I), with displacement ellipsoids for the non-hydrogen atoms drawn at the 30% probability level. The hydrogen bond is indicated by a double-dashed line.

Special details
Geometry. All e.s. 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 Rfactors(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 Sn1 0.256428 (17