SYNTHESIS AND STRUCTURE OF TRI(META-TOLYL)ANTIMONY BIS(BENZENESULFONATE)

Tri(meta-tolyl)antimony bis(benzenesulfonate) m-Tol3Sb(OSO2C6H5)2 (1) has been synthesized by interaction of tri(meta-tolyl)antimony with benzenesulfonic acid in the presence of tert-butyl hydroperoxide (mole ratio 1:2:1) in ether solution. Antimony atoms in 1 have trigonal-bipyramidal coordination with arenesulfonate substituents in axial positions (OSbO 171.05(11), CSbC 116.21(19), 117.38(18), 126.40(15)). The SbC and SbO distances equal 2.091(4), 2.098(4), 2.115(4) и 2.105(2), 2.116(3) Å. Intermolecular contact (Sb···O 3.421(3) Å) occurs between the central atom and the oxygen atom of sulfonate group.


Introduction
In the course of research on the synthesis and structure of quinqevalent antimony arenesulfonates [1][2][3][4] we have studied the reaction of tri(meta-tolyl)antimony with benzenesulfonic acid in the presence of tert-butyl hydroperoxide in ether. The structure of the obtained product has been established by X-ray diffraction analysis.
IR spectra were recorded on the Fourier-transform spectrometer Bruker Tensor 27 in KBr pellets. The X-ray diffraction analyses of crystal 1 were performed on the Bruker D8 Quest diffractometer (Mo K  -emission,  = 0.71073 Å, graphite monochromator). The data were collected and analyzed, the unit cell parameters were refined, and the absorption correction was applied using the SMART and SAINT-Plus programs [5]. All calculations for structure determination and refinement were performed using the SHELXL/PC [6] and OLEX2 programs [7]. The structures were determined by the direct method and refined by the least-squares method in the anisotropic approximation for non-hydrogen atoms. The main crystallographic data and refinement results for the structures are listed in Table 1, the selected bond lengths and bond angles are given in Table 2.

Results and Discussion
It is known that oxidation of tri(meta-tolyl)antimony by hydrogen peroxide in the presence of benzenesulfonic acid leads to formation of tri(meta-tolyl)antimony bis(benzenesulfonate) with 72% yield [4].
We have established that the oxidative addition reaction with the use of tri(meta-tolyl) antimony, benzenesulfonic acid and tert-butyl hydroperoxide leads to formation of the target product with 86% yeild: Note that compound 1, obtained by this reaction, has higher melting point (152 С), than that according to the procedure with the use of hydrogen peroxide (145 С [4]).
As viewed from the maximal equatorial angle CSbC the close intermolecular contact between the central atom and the oxygen atom O(6) of the sulfonate group is observed (Sb···O 3.421(3) Å), which is less than the sum of Van der Waals radii of antimony and oxygen atoms (3.7 Å [8]). The structural organization of the crystal is formed with the participation of weak hydrogen bonds of the type O···H (2.525, 2.650 Å).