Synthesis, structural characterization, and biological studies of new antimony(III) complexes with thiones. The influence of the solvent on the geometry of the complexes

Five new antimony(III) complexes with the heterocyclic thiones 2-mercapto-benzimidazole (MBZIM), 5-ethoxy-2-mercapto-benzimidazole ((EtMBZIM)), and 2-mercapto-thiazolidine (MTZD) of formulas {[SbCl2(MBZIM)(4)](+)center dot Cl-center dot 2H(2)O(CH3OH)} (1), {[SbCl2(MBZIM)(4)](+)center dot Cl-center dot 3H(2)O center dot CH3CN)} (2), [SbCl3(MBZIM)(2)] (3), [SbCl3(EtMBZIM)(2)] (4), and [SbCl3(MTZD)(2)] (5) have been synthesized and characterized by elemental analysis, FT-IR, far-FT-IR, differential thermal analysis-thermogravimetry, X-ray diffraction, and conductivity measurements. Complex {[SbCl2(tHPMT)(2)]Cl-+(-)}, (tHPMT = 2-mercapto-3,4,5,6-tetrahydro-pyrimidine), already known, was also prepared, and its X-ray crystal structure was solved. It is shown that the complex is better described as {[SbCl3(tHPMT)(2)]} (6). Crystal structures of all other complexes (1-5) have also been determined by X-ray diffraction at ambient conditions. The crystal structure of the hydrated ligand, EtMBZIM center dot H2O is also reported. Compound [C28H24Cl2N8S4Sb center dot 2H(2)O center dot Cl center dot(CH3OH)] (1) crystallizes in space group P2(1), with a = 7.7398(8) angstrom, b = 16.724(3) angstrom, c = 13.717(2) angstrom, beta = 98.632(11)degrees and Z = 2. Complex [C28H24Cl2N8S4Sb center dot Cl center dot 3H(2)O center dot(CH3CN)] (2) corresponds to space group P21, with a = 7.8216(8) angstrom, b = 16.7426(17) angstrom, c = 13.9375(16) angstrom, beta = 99.218(10)degrees, and Z = 2. In both 1 and 2 complexes, four sulfur atoms from thione ligands and two chloride ions form an octahedral (Oh) cationic [SbS4Cl2]+ complex ion, where chlorides lie at axial positions. A third chloride counteranion neutralizes it. Complexes 1 and 2 are the first examples of antimony(III) compounds with positively charged Oh geometries. Compound [C(14)Hl(2)Cl(3)N(4)S(2)Sb] (3) crystallizes in space group P (1) over bar, with a = 7.3034(5) angstrom, b = 11.2277(7) angstrom, c = 12.0172(8) angstrom, alpha = 76.772(5)degrees, beta = 77.101(6)degrees, gamma = 87.450(5)degrees, and Z = 2. Complex [C18H20Cl3N4O2S2Sb] (4) crystallizes in space group P (1) over bar, with a = 8.6682(6) angstrom, b = 10.6005(7) angstrom, c = 13.0177(9) angstrom, alpha = 84.181(6)degrees, beta = 79.358(6)degrees, gamma = 84.882(6)degrees, and Z = 2, while complex [C6H10Cl3N2S4Sb] (5) in space group P2(1/c) shows a = 8.3659(10) angstrom, b = 14.8323(19) angstrom, c = 12.0218(13) angstrom, beta = 99.660(12)degrees, and Z = 4 and complex [C8H16Cl3N4S2Sb] (6) in space group F shows a = 7.4975(6) angstrom, b = 10.3220(7) angstrom, c = 12.1094(11) angstrom, alpha = 71.411(7)degrees, beta = 84.244(7)degrees, gamma = 73.588(6)degrees, and Z = 2. Crystals of complexes 3-6 grown from acetonitrile solutions adopt a square-pyramidal (SP) geometry, with two sulfur atoms from thione ligands and three chloride anions around Sb(III). The equatorial plane is formed by two sulfur and two chloride atoms in complexes 3-5, in a cis-S, cis-Cl arrangement in 3 and 5 and a trns-S, trans-Cl arrangement in 4. Finally, in the case of 6, the equatorial plane is formed by three chloride ions and one sulfur from the thione ligand while the second sulfur atom takes an axial position leading to a unique SP conformation. The complexes showed a moderate cytostatic activity against tumor cell lines.