Structual features of the 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), 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 CSbO angles equal 85.06(12)°-94.73(13)°, the OSbO 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.