The oxidation reaction of tris[(2-methoxy)(5-bromo)phenyl]antimony by tert-butyl hydroperoxide in the presence of 3,4-dioxybenzoic acid

The interaction of tris(5-bromo-2-methoxyphenyl)antimony with 3,4-dioxybenzoic acid, in the presence of tert-butyl hydroperoxide (1:2:1 mol.) in diethyl ether at ambient temperature has given 4-carboxypyrocatecholato-O,O’-tris(5-bromo-2-methoxyphenyl)antimony solvate with cloroform (5-Br-2-MeOC6H3)3Sb[O,O’C6H3-COOH-4] ∙ 2 CHCl3, which has been structurally characterized. According to the X-ray diffraction data obtained on a Bruker D8 QUEST diffractometer, compound 1 has the following crystallographic parameters of the unit cell: space group P21/n, а = 9.302(2), b = 21.166(5), c = 19.517(6) Å, α = 90.00°, β = 96.302(13)°, γ = 90.00°, V = 3819(17) Å3, ρcalc = 1.862 g/cm3, Z = 4. The antimony atom has a distorted trigonal-bipyramidal coordination with one of the oxygen atoms of the pyrocatecholate ligand in the axial position. The Sb-C bond length lies in the range of values 2.107(5)-2.131(5) Å. The CSbC equatorial angles are 95.9(2)-125.7(1)°. The Sb-O bond lengths are not equivalent (2.095(4) and 2.013(3) Å), but are close to the sum of the covalent radii of the antimony and oxygen atoms, 2.05 Å. Crystal 1 contains close contacts of the hydrogen atoms in chloroform with the oxygen atoms of the catecholate ligand (2.40 Å), as well as the hydrogen atoms of the catecholate ligand with the chlorine atoms of chloroform molecules (2.95 Å). Compound 1 in crystals is in the form of dimers, where two molecules are linked by two hydrogen bonds O(6)∙∙∙H(7) (1.864 Å), while the sum of the Van der Waals radii of hydrogen and oxygen is 2.57 Å. Complete tables of atomic coordinates, bond lengths, and bond angles for structure 1 have been deposited at the Cambridge structural data Dank (No. 2144306; deposit@ccdc.cam.ac.uk; https://www.ccdc.cam.ac.uk).