A Strategy for the Preparation of Thioantimonates Based on the Concept of Weak Acids and Corresponding Strong Bases

Rapid synthesis process and characterization for high purity sodium thioantimoniate nonahydrate

For the first time, Na₃SbS₄·9H₂O, also known as Schlippe's salt, has been synthesized through high-energy ball milling. This innovative synthesis way allows for obtaining high purity thioantimonate nonahydrate with around 90% yield in only approximately four hours. To validate the synthesis route described herein, the crystal structure has been refined, at room temperature, through high-resolution X-ray diffraction, pair distribution function analysis and energy dispersive spectrometry. Dehydration and rehydration of the compound have also been studied by thermogravimetric analysis and differential scanning calorimetry.

Synthesis and crystal structure of poly[[di-μ3-tetra-thio-anti-monato-tris-[(cyclam)cobalt(II)]] aceto-nitrile disolvate dihydrate] (cyclam = 1,4,8,11-tetra-aza-cyclo-tetra-deca-ne)

Reaction of Co(ClO4)2·6H2O with cyclam (cyclam = 1,4,8,11-tetra-aza-cyclo-tetra-deca-ne) and Na3SbS4·9H2O (Schlippesches salt) in a mixture of aceto-nitrile and water leads to the formation of crystals of the title compound with the composition {[Co3(SbS4)2(C10H24N4)3]·2CH3CN·2H2O} n or {[(Co-cyclam)3(SbS4)2]·2(aceto-nitrile)·2H2O} n . The crystal structure of the title compound consists of three crystallographically independent [Co-cyclam]2+ cations, which are located on centers of inversion, one [SbS4]3- anion, one water and one aceto-nitrile mol-ecule that occupy general positions. The aceto-nitrile mol-ecule is disordered over two orientations and was refined using a split model. The CoII cations are coordinated by four N atoms of the cyclam ligand and two trans-S atoms of the tetra-thio-anti-monate anion within slightly distorted octa-hedra. The unique [SbS4]3- anion is coordinated to all three crystallographically independent CoII cations and this unit, with its symmetry-related counterparts, forms rings composed of six Co-cyclam cations and six tetra-thio-anti-monate anions that are further condensed into layers. These layers are perfectly stacked onto each other so that channels are formed in which acetontrile solvate mol-ecules that are hydrogen bonded to the anions are embedded. The water solvate mol-ecules are located between the layers and are connected to the cyclam ligands and the [SbS4]3- anions via inter-molecular N-H⋯O and O-H⋯S hydrogen bonding.

The cation and anion bonding modes make a difference: an unprecedented layered structure and a tri(hetero)nuclear moiety in thioantimonates(V)

Mixing solutions of M²⁺ (M = Cu²⁺ or Zn²⁺) salts containing cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) as the ligand and an aqueous solution of Na₃SbS₄·9H₂O at room temperature led to the crystallization of two new compounds within minutes: {[Cu(cyclam)]₃[SbS₄]₂}_n·20nH₂O (I) and {[Zn(cyclam)]₃[SbS₄]₂}·8H₂O (II). In the structure of I [SbS₄]^3- anions acting as a tridentate ligand join CuN₄S₂ octahedra generating twelve-membered rings by corner-sharing of SbS₄ and CuN₄S₂ units. The rings are condensed into layers, which are stacked onto each other in a 6R polytype manner. The layers contain large pores with the water molecules located between the layers above and below the pores. In contrast, the structure of II comprises a discrete molecular tri(hetero)nuclear moiety with a bidentate [SbS₄]^3- anion connecting two rectangular pyramidal ZnN₄S polyhedra. The crystal water molecules of I and II can be thermally removed, and I and II are recovered by treatment under a humid atmosphere. The EPR spectrum of I indicates the presence of Cu²⁺ cations, which is unusual in the environment of S^2- anions. The different bonding situations and the preferences for the coordination geometries of Cu²⁺ and Zn²⁺ cations are rationalized by DFT based calculations, demonstrating that Cu²⁺ prefers an octahedral environment while Zn²⁺ adopts the square-pyramidal coordination. The pronounced differences in the vibrational spectra are also analyzed with DFT, showing how the different modes are influenced by the differing bond strengths.

Synthesis and crystal structure of (1,4,7,10-tetra-aza-cyclo-dodecane-κ4 N)(tetra-sulfido-κ2 S 1,S 4)manganese(II)

The title compound, [Mn(S4)(C8H20N4)], was accidentally obtained by the hydro-thermal reaction of Mn(ClO4)2·6H2O, cyclen (cyclen = 1,4,7,10-tetra-aza-cyclo-dodeca-ne) and Na3SbS4·9H2O in water at 413 K, indicating that polysulfide anions might represent inter-mediates in the synthesis of thio-metallate compounds using Na3SbS4·9H2O as a reactant. X-ray powder diffraction proves that the sample is slightly contaminated with NaSb(OH)6 and an unknown crystalline phase. The crystal investigated was twinned with a twofold rotation axis as the twin element, and therefore a twin refinement using data in HKLF-5 format was performed. The asymmetric unit of the title compound consists of one MnII cation, one [S4]2- anion and one cyclen ligand in general positions. The MnII cation is sixfold coordinated by two cis-S atoms of the [S4]2- anions, as well as four N atoms of the cyclen ligand within an irregular coordination. The complexes are linked via pairs of N-H⋯S hydrogen bonds into chains, which are further linked into layers by additional N-H⋯S hydrogen bonding. These layers are connected into a three-dimensional network by inter-molecular N-H⋯S and C-H⋯S hydrogen bonding. It is noted that only one similar complex with MnII is reported in the literature.

Tris-chelated complexes of nickel(II) with bipyridine derivatives: DNA binding and cleavage, BSA binding, molecular docking, and cytotoxicity

Two nickel(II) complexes with substituted bipyridine ligand of the type [Ni(NN)₃](ClO₄)₂, where NN is 4,4'-dimethyl-2,2'-bipyridine (dimethylbpy) (1) and 4,4'-dimethoxy-2,2'-bipyridine (dimethoxybpy) (2), have been synthesized, characterized, and their interaction with DNA and bovine serum albumin (BSA) studied by different physical methods. X-ray crystal structure of 1 shows a six-coordinate complex in a distorted octahedral geometry. DNA-binding studies of 1 and 2 reveal that both complexes sit in DNA groove and then interact with neighboring nucleotides differently; 2 undergoes a partial intercalation. This is supported by molecular-docking studies, where hydrophobic interactions are apparent between 1 and DNA as compared to hydrogen bonding, hydrophobic, and π-π interactions between 2 and DNA minor groove. Moreover, the two complexes exhibit oxidative cleavage of supercoiled plasmid DNA in the presence of hydrogen peroxide as an activator in the order of 1 > 2. In terms of interaction with BSA, the results of spectroscopic methods and molecular docking show that 1 binds with BSA only via hydrophobic contacts while 2 interacts through hydrophobic and hydrogen bonding. It has been extensively demonstrated that the nature of the methyl- and methoxy-groups in ligands is a strong determinant of the bioactivity of nickel(II) complexes. This may justify the above differences in biomolecular interactions. In addition, the in vitro cytotoxicity of the complexes on human carcinoma cells lines (MCF-7, HT-29, and U-87) has been examined by MTT assay. According to our observations, 1 and 2 display cytotoxicity activity against selected cell lines. Communicated by Ramaswamy H. Sarma.

Room-Temperature Synthesis of Thiostannates from {[Ni(tren)]2[Sn2S6]}n

The compound {[Ni(tren)]2[Sn2S6]}n (1) (tren = tris(2-aminoethyl)amine, C6H18N4) was successfully applied as source for the room-temperature synthesis of the new thiostannates [Ni(tren)(ma)(H2O)]2[Sn2S6]·4H2O (2) (ma = methylamine, CH5N) and [Ni(tren)(1,2-dap)]2[Sn2S6]·2H2O (3) (1,2-dap = 1,2-diaminopropane, C3H10N2). The Ni-S bonds in the Ni2S2N8 bioctahedron in the structure of 1 are analyzed with density functional theory calculations demonstrating significantly differing Ni-S bond strengths. Because of this asymmetry they are easily broken in the presence of an excess of ma or 1,2-dap immediately followed by Ni-N bond formation to N donor atoms of the amine ligands thus generating [Ni(tren)(amine)](2+) complexes. The chemical reactions are fast, and compounds 2 and 3 are formed within 1 h. The synthesis concept presented here opens hitherto unknown possibilities for preparation of new thiostannates.

Room temperature synthesis, crystal structure and selected properties of the new compound [Mn2(bipy)4SbS4](ClO4)

The new compound [Mn2(bipy)4SbS4](ClO4) was prepared by a new synthetic route for the preparation of thioantimonates(V) that can be used even at room temperature. Mixing aqueous solutions of [Mn(bipy)3](ClO4)2 and Na3SbS4 · 9H2O leads to immediate crystallization of the pure compound. In the structure an SbS4 3– anion acts as a tetradentate bridge connecting two Mn2+ cations of [Mn(bipy)3]2+ complexes (bipy = 2,2′-bipyridine). The compound features a hitherto unknown [Mn2(bipy)4SbS4]+ cation. Bipy ligands of adjacent cations are arranged parallel to each other leading to weak off-center parallel π-π interactions stabilizing the crystals. Magnetic measurements indicate weak antiferromagnetic exchange interactions between the Mn2+ centers.

Formation and Reactivity of Organo-Functionalized Tin Selenide Clusters

Reactions of R(1) SnCl3 (R(1) =CMe2 CH2 C(O)Me) with (SiMe3 )2 Se yield a series of organo-functionalized tin selenide clusters, [(SnR(1) )2 SeCl4 ] (1), [(SnR(1) )2 Se2 Cl2 ] (2), [(SnR(1) )3 Se4 Cl] (3), and [(SnR(1) )4 Se6 ] (4), depending on the solvent and ratio of the reactants used. NMR experiments clearly suggest a stepwise formation of 1 through 4 by subsequent condensation steps with the concomitant release of Me3 SiCl. Furthermore, addition of hydrazines to the keto-functionalized clusters leads to the formation of hydrazone derivatives, [(Sn2 (μ-R(3) )(μ-Se)Cl4 ] (5, R(3) =[CMe2 CH2 CMe(NH)]2 ), [(SnR(2) )3 Se4 Cl] (6, R(2) =CMe2 CH2 C(NNH2 )Me), [(SnR(4) )3 Se4 ][SnCl3 ] (7, R(4) =CMe2 CH2 C(NNHPh)Me), [(SnR(2) )4 Se6 ] (8), and [(SnR(4) )4 Se6 ] (9). Upon treatment of 4 with [Cu(PPh3 )3 Cl] and excess (SiMe3 )2 Se, the cluster fragments to form [(R(1) Sn)2 Se2 (CuPPh3 )2 Se2 ] (10), the first discrete Sn/Se/Cu cluster compound reported in the literature. The derivatization reactions indicate fundamental differences between organotin sulfide and organotin selenide chemistry.

Utilization of mixtures of aromatic N-donor ligands of different coordination ability for the solvothermal synthesis of thiostannate containing molecules

Utilization of mixtures of differently coordinating aromatic N-donor ligands leads to the formation of the two new compounds {[Ni(phen)2]2Sn2S6}·4,4'-bipy·½H2O I and {[Ni(phen)2]2Sn2S6}·2,2'-bipy II that could be prepared under solvothermal conditions (4,4'-bipy = 4,4'-bipyridine, C10H8N2; phen = 1,10-phenanthroline, C12H8N2; 2,2'-bipy = 2,2'-bipyridine, C10H8N2). In the structures of both compounds Ni-S bond formation is observed which is highly unusual when only bidentate N-donor ligands are applied in the reaction mixture. The detailed analysis of the crystal structure indicates that the presence of 4,4'-bipy and 2,2'-bipy molecules are essential for the stabilization of the arrangement of the constituents. The main structural motif {[Ni(phen)2]2Sn2S6} is arranged generating off center parallel stacking of the phen ligands. The empty spaces between the {[Ni(phen)2]2Sn2S6} moieties are occupied by either 2,2'-bipy (I) or 4,4'-bipy (II) molecules which are oriented towards the phen ligands to form intermolecular π-π interactions.