The synthesis methods of dicarboxylic and hydroxylic acids organoantimony derivatives. Molecular structure of bis(tetraphenylantimony) bicinchoninate

The reaction between pentaphenylantimony and bicinchoninic acid (2:1 mol, toluene) proceeds with the substitution of the hydrogen atom for the Ph4Sb fragment with the formation of bis (tetraphenylantimony) bicinchoninate (1). According to the X-ray analysis, carried out on a D8 QUEST Bruker diffractometer, the compound unit cells parameters are: C2/c group of symmetry, а = 25.332(16), b = 18.361(13), c = 15.250(14) Å, α = 90.00°, β = 104.17(4), γ = 90.00°, V = 6877(9) Å3, ρcalc = 1.162 g/сm3, Z = 8. Molecule 1 is centrosymmetrical, the antimony atoms have a distorted trigonal bipyramidal coordination. The OSbC axial angle equals 176.49(12)°, the sum of СSbC angles in the equatorial plane equal 356.7(15)°. The Sb-Cax axial bond is longer than equatorial one (2.166(3)Å), the Sb-Ceqv equatorial bonds equal 2.105(4) - 2.125(4) Å. The Sb-O bond length equals 2.269(2) Å, the intramolecular Sb∙∙∙O=С distance is 3.116(3) Å. Tetraphenylantimony 2,6-dihydroxybanzoate (2) was obtained by the interaction of 1 mol pentaphenylantimony and 1 mol triphenylantimony bis (2,6-dihydroxybenzoate) in benzene solution at the room temperature according to the reaction of the ligand re-arrangement. Compound 2 was isolated with 85 % yield in the form of brown crystals with m. p. 215 °С. The absorption band of the carbonyl group with the frequency 1616 cm-1 is presents in the IR-spectra, obtained in the 4000-400 сm-1 range on Shimadzu IRAffinity-1S IR-Fourier spectrometer with the use of KBr pellets. The band is displaced into the low-frequency area compared with the corresponding acid spectrum (1705 cm-1) and corresponds to the analogous band in the spectra of compound 2 synthesized by the reaction between pentaphenylantimony and 2,6-dihydroxybenzoic acid .