Abstract
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), Ph4SbOC(O)C5H3NOSbPh4-4 (II), respectively. The reaction with 2,3-dihydroxybenzoic acid occurs with the participation of just hydroxy groups, while the interaction with 5-hydroxypyridine-2-carboxylic acid proceeds 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). The structures of compounds I–III have been characterized by IR spectroscopy and X-ray diffraction. According to the X-ray diffraction data, crystal I contains [Ph4Sb]+ cations with a slightly distorted tetrahedral coordination of the antimony atom (the CSbC angles are 99.18(14)°-118.07(16)°, the Sb-C bonds are 2.093(4)-2.119(3) Å) and anions containing a five-membered metallocycle [SbO2C2], in which the antimony atom is hexacoordinated (the CSbC cis-angles are 91.52(13)°-102.90(13)°; the CSbО angles equal 85.06(12)°-94.73(13)°, the ОSbО angle is 76.22(9)°). The Sb–O distances in the ring are 2.122(2) and 2,215(2) Å. The 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 (the OSbC axial angle equals 174.5(2)°, the CSbC angles in the equatorial plane are 116.2(3)°-120.9(3)°; the Sb-O and Sb-C distances 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 6 due to 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: the OSbC axial angle equals 170.30(8)°, the CSbC angles in the equatorial plane are 112.17(9)°-122.09(9)°; the Sb-O bond is 2.527(2) Å, and the Sb-C bond equals 2.031(2)–2.258(3) Å.
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