Structural Features of Dearylation Reaction Products of Pentarylantimony with Polyfunctional Acids

It has been established that in reactions with pentaphenylantimony, 2,3-dihydroxybenzoic and 5-hydroxypyridine-2-carboxylic acids behave as bifunctional compounds and form binuclear products [Ph4Sb]+[Ph4Sb(O,O′-C6H3COOH-3]− (I) and Ph4SbOC(O)C5H3NOSbPh4-4 (II), respectively. The reaction with 2,3-dihydroxybenzoic acid occurs with the participation of only hydroxy groups, whereas the reaction with 5-hydroxypyridine-2-carboxylic acid occurs with the participation of hydroxy and carboxy groups. 2,6-Dihydroxybenzoic acid reacts with penta(para-tolyl)antimony only at the carboxyl group, giving tetra(para-tolyl)antimony 2,6-dihydroxybenzoate p‑Tol4SbOC(O)C6H3(OH)2-2,6 (III). Structure of compounds I–III was characterized by IR spectroscopy and X-ray diffraction. According to X-ray diffraction data, crystal I contains [Ph4Sb]+ cations with a slightly distorted tetrahedral coordination of the antimony atom (CSbC angles 99.18(14)°−118.07(16)°, Sb−C bonds 2.093(4)−2.119(3) Å) and anions containing a five-membered metallocycle [SbO2C2], in which the antimony atom is hexacoordinated (CSbC cis-angles 91.52(13)°−102.90(13)°; CSbО 85.06(12)°−94.73(13)°, ОSbО 76.22(9)°). The Sb–O distances in the ring are 2.122(2) and 2.215(2) Å. Sb–C bonds vary in the range 2.175(3)–2.187(4) Å. In molecule II, the antimony atoms are structurally nonequivalent. One of the atoms associated with the oxygen atom of the hydroxy group has the coordination of a distorted trigonal bipyramid (axial angle OSbC 174.5(2)°, CSbC angles in the equatorial plane 116.2(3)°−120.9(3)°; distances Sb−O and Sb−C are 2.256(5) Å and 2.108(7)–2.174(7) Å, respectively). The coordination number of the second antimony atom associated with the oxygen of the carboxyl group is increased to six due to the coordination of the nitrogen atom of the pyridine ring located in the ortho position with respect to the carboxyl group (the Sb∙∙∙N distance is 2.402(6) Å). The coordination polyhedron of the atom is a distorted octahedron (cis-angles at the antimony atom vary in the range 72.22(19)°−103.6(3)°). The Sb–O bond length is 2.194(5) Å, the Sb–C distances are 2.165(7)–2.189(7) Å. In molecule III the coordination of the antimony atom is a distorted trigonal bipyramid: axial angle OSbC 170.30(8)°, CSbC angles in the equatorial plane 112.17(9)°−122.09(9)°; Sb−O bonds 2.527(2) Å, Sb−C 2.031(2)–2.258(3) Å.