Octabutylbis(μ2-2-chloro-5-nitrobenzoato)bis(2-chloro-5-nitrobenzoato)di-μ3-oxido-tetratin(IV)

The title complex, [Sn4(C4H9)8(C7H3ClNO4)4O2], is a cluster formed by a crystallographic inversion center around the central Sn2O2 ring. Both of the two independent Sn atoms are five-coordinated, with distorted trigonal–bipyramidal SnC2O3 geometries. One Sn atom is coordinated by two butyl groups, one O atom of the benzoate anion and two bridging O atoms, whereas the other Sn atom is coordinated by two butyl groups, two O atoms of the benzoate anions and a bridging O atom. The O atoms of the bridging benzoate anion are disordered over two sites with an occupancy ratio of 0.862 (12):0.138 (12). One of the butyl groups coordinated to the Sn2O2 ring is disordered over two sites with an occupancy ratio of 0.780 (8):0.220 (8), whereas both of the two butyl groups coordinated to the other Sn atom are disordered over two sites with occupancy ratios of 0.788 (5):0.212 (5) and 0.827 (10):0.173 (10). All the butyl groups are equatorial with respect to the SnO3 trigonal plane. In the crystal, complex molecules are stacked down [010] with weak intermolecular C—H⋯π interactions stabilizing the crystal structure.

The title complex, [Sn 4 (C 4 H 9 ) 8 (C 7 H 3 ClNO 4 ) 4 O 2 ], is a cluster formed by a crystallographic inversion center around the central Sn 2 O 2 ring. Both of the two independent Sn atoms are five-coordinated, with distorted trigonal-bipyramidal SnC 2 O 3 geometries. One Sn atom is coordinated by two butyl groups, one O atom of the benzoate anion and two bridging O atoms, whereas the other Sn atom is coordinated by two butyl groups, two O atoms of the benzoate anions and a bridging O atom. The O atoms of the bridging benzoate anion are disordered over two sites with an occupancy ratio of 0.862 (12):0.138 (12). One of the butyl groups coordinated to the Sn 2 O 2 ring is disordered over two sites with an occupancy ratio of 0.780 (8):0.220 (8), whereas both of the two butyl groups coordinated to the other Sn atom are disordered over two sites with occupancy ratios of 0.788 (5):0.212 (5) and 0.827 (10):0.173 (10). All the butyl groups are equatorial with respect to the SnO 3 trigonal plane. In the crystal, complex molecules are stacked down [010] with weak intermolecular C-HÁ Á Á interactions stabilizing the crystal structure.

Related literature
For general background to and applications of the title complex, see: Li et al. (2006); Win et al. (2008aWin et al. ( ,b, 2010. For closely related structures, see: Li et al. (2006); Win et al. (2008a,b;2010). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).
Cg1 is the centroid of the C16-C21 ring. Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009). molecule, with the other half of the molecule is generated by symmetry code -x+1, -y, -z+1. Both Sn atoms are five-coordinated in distorted trigonal bipiramidal geometries but the coordination environment is different. The Sn1 atom is coordinated by two butyl groups in equatorial position, an O atom of the monodentate benzoate anion, an O atom of the bridging benzoate anion and a bridging O atom whereas the Sn2 atom is coordinated by two butyl groups in equatorial position, an O atom of the bridging benzoate anion and two bridging O atoms. Atoms O7 and O8 of the bridging benzoate anion are disordered over two sites with occupancy ratio of 0.862 (12):0.138 (12). The two butyl groups (C8-C11 and C12-C15) bonded to the Sn1 atom are disordered over two sites with occupancy ratios of 0.780 (8):0.220 (8) and 0.827 (10):0.173 (10), respectively.
There is no significant intermolecular hydrogen bond observed and the complex are stacked down the [010] axis (Fig. 2).

Refinement
All H atoms were placed in their calculated positions, with C-H = 0.93 -0.97 Å, and refined using a riding model with U iso = 1.2 or 1.5 U eq (C). Atoms O7 and O8 were disordered over two sites with a refined occupancy ratio of 0.862 (12):0.138 (12).
The butyl groups (C8-C11, C12-C15 and C23-C26) were disordered over two sites with refined occupancy ratios of 0.780 isotropically. Similarity, simulation and rigid restraints were applied to the disordered components. The C-C distances involving the minor disordered butyl groups were restrained to 1.50 (1) Å. The Sn1-C12X and Sn2-C23X distances were restrained to 2.10 (1) Å. The highest residual electron density peak and the deepest hole were located at 1.02 and 0.71 Å, respectively, from atom Sn1. Fig. 1. The molecular structure of the title complex, showing the atom-numbering scheme. The suffix A corresponds to symmetry code [-x, -y+1, -z] and minor disordered components are labelled as suffixes X and Y. All H atoms have been omitted for clarity.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.