Tetrakis(μ2-5-methylpyrazine-2-carboxylato)-1:2κ3 N 1,O:O;2:3κ3 O:N 1,O;1:2κ2 O:O′;3:4κ2 O:O′-octaoctyl-1κ2 C,2κ2 C,3κ2 C,4κ2 C-di-μ3-oxido-1:2:3κ3 O;1:3:4κ3 O-tetratin(IV)

The title compound, [Sn4(C8H17)8O2(C6H5N2O2)4], is a tetranuclear SnIV complex, built up by inversion symmetry around the central Sn2O2 ring. The SnIV coordination geometries are distorted SnO3C2 trigonal-bipyramidal and distorted SnO4C2 octahedral. The three-coordinate μ3-oxido bridging O atom in the Sn2O2 ring is attached to three Sn atoms. All non-H atoms, with the exception of the Sn-bonded octyl groups, lie approximately on a non-crystallographic mirror plane.

The title compound, [Sn 4 (C 8 H 17 ) 8 O 2 (C 6 H 5 N 2 O 2 ) 4 ], is a tetranuclear Sn IV complex, built up by inversion symmetry around the central Sn 2 O 2 ring. The Sn IV coordination geometries are distorted SnO 3 C 2 trigonal-bipyramidal and distorted SnO 4 C 2 octahedral. The three-coordinate 3 -oxido bridging O atom in the Sn 2 O 2 ring is attached to three Sn atoms. All non-H atoms, with the exception of the Sn-bonded octyl groups, lie approximately on a non-crystallographic mirror plane.
The title compound, (Fig. 1), is a tetranuclear tin(IV) complex containing a total of 110 non-H atoms. The molecule is centrosymmetric with a central core Sn 2 O 2 ; the structure is similar to those seen previously in resemble compounds (Yin et al., 2003). The µ 3 -bridging O5 atom in the Sn 2 O 2 ring is also attached to a capryl 2 SnO 2 unit (capryl is the trivial name of the octyl group). In addition, the carboxylate group coordinates to two Sn atoms in a bridging mode. Sn-O and Sn-C bond lenghts are shown in Table 1.
The geometries of both the exocyclic Sn atoms are distorted trigonal-bipyramidal. For the Sn1, atoms O1 and O7 are in axial positions [O1-Sn1-O4 = 168.0 (3)°] and the C atoms of the two capryl groups and O5 are in equatorial positions.
The sum of the equatorial C-Sn-C and O-Sn-C angles is 339°, indicating a significant distortion from coplanarity for these atoms.
The geometry around the endocyclic atom Sn2 is different from that of Sn1 and is a distorted octahedron. Here, O3 and O5 are in axial positions [O3-Sn2-O5 =158.9 (3)°] and the C atoms of the two capryl groups, O5 i [symmetry code: -x + 1, -y + 2, -z + 2] and O1 are in equatorial positions. The sum of the equatorial C-Sn-C and O-Sn-C angles is 353.7°, indicating a significant distortion from coplanarity for these atoms. This distortion may arise because of a short Sn2···N1 contact of 2.829 (6)Å (sum of the van der Waals radii = 3.81 Å). Related µ 3 oxo-bridhed tin(IV) ladder structures were reported by Vollano et al., 1984) (Fig. 2).

Experimental
A mixture of dicapryltin oxide (2.0 mmol,0.722 g) and 2-methylpyrazine-5-carboxylic acid (2.0 mmol, 0.276 g) in methanol (80 ml) was heated under reflux for 8 h. The obtained clear solution was evaporated under vacuum. The product was crystallized from a mixture of dichloromethane/ethanol (1:1) to yield blocks of (I  Fig. 1. The molecular structure of (I) with 30% displacement ellipsoids (H atoms omitted for clarity) and the short Sn···N contacts indicated by dashed lines. Symmetry codes as in Table 1. Crystal data [Sn 4 (C 8