Central Tin Research Articles

Organotin(IV) complexes derived from N-ethyl-N-phenyldithiocarbamate: Synthesis, characterization and thermal studies

Organotin(IV) dithiocarbamate complexes, RSnClL2 and R2SnL2 (R=Me, Bu, Ph, and L=N-ethyl-N-phenyldithiocarbamate), have been synthesized by the reaction of mono- and disubstituted organotin(IV) with ammonium dithiocarbamate. The complexes were characterized by elemental analyses, and spectroscopic techniques (1H, 13C NMR and FTIR). The structures of Me2SnL2 and Bu2SnL2 were further established by single crystal X-ray diffraction technique. The crystal structure analysis showed that both complexes (Me2SnL2 and Bu2SnL2) exist as monomers. One of the dithiocarbamate ligands formed a chelate, while the other dithiocarbamate bonded to the central tin atom through one of the sulfur atoms and the second sulfur atom existed as a pendant to form distorted trigonal bipyramidal geometry. The thermal stability of all the complexes was studied using simultaneous thermogravimetry (TG) and differential scanning calorimetry (DSC). The TG-DSC results showed that Me2SnL2, BuSnClL2, Bu2SnL2, and PhSnClL2 displayed similar decomposition pathway via isothiocyanate intermediate, while MeSnClL2 and Ph2SnL2 showed decomposition pathways different from the rest of the complexes. All the complexes resulted in SnS as the final product of the thermal decomposition process.

Schiff base Sn(IV) complexes as cytotoxic agents: Synthesis, structure, isosteric and bioisosteric replacement

The preparation and characterization of two series of organotin(IV) complexes are reported, each series differing in the nature of the substituent bonded to the tin atom (cyclohexyl or bis(trimethyl)silylmethyl). The isosteric and bioisosteric approach was used as the strategy of molecular design. The ligand was 5-hydroxymethyl-4-[(2-hydroxyphenyl)iminomethyl]-2-methylpyridin-3-ol substituted at position 4 by methyl, halogeno (F, Cl), methoxy, nitro and tert-butyl; the synthesis of the organotin(IV) complexes was performed by a multi-component strategy in reasonable to high yields depending on the nature of the ligand. All new complexes were fully characterized by IR, MS, X-ray determinations and NMR (1H, 13C, 119Sn). Crystallographic data of complexes showed the geometries adopted around the metal tin center varied between square pyramidal in 2c and a trigonal bipyramidal in 3b-3d with the alkyl groups in the trigonal plane and the two oxygen atoms in the equatorial plane. Additionally, the in vitro cytotoxicity tests of the complexes towards six types of human cancerous cell lines U-251 (glioblastoma), K-562 (chronic myelogenous leukemia), HCT-15 (human colorectal), MCF-7 (human breast), MDA-MB-231(human breast) and SKLU-1 (non-small cell lung) showed the superior activity of the organotin complexes compared to the corresponding cisplatin used as positive control. The complexes containing fluorine exhibited excellent IC50 data indicating that both the bioisosteric replacement and the cyclohexyl ring bonded to the tin atom increased the potency of the cytotoxic activity towards the cancer cell lines tested.

Magnesium Reagents Featuring a 1,1′‐Bis(o‐carborane) Ligand Platform

The synthesis of two bis(carboranyl) (bc) magnesium reagents is described. Treatment of 1,1′‐bis(o‐carborane) (H2‐bc) or 8,8′,9,9′,10,10′,12,12′‐octamethyl‐1,1′‐bis(o‐carborane) (H2‐Mebc) with Mg(nBu)2 in 1,2‐dimethoxyethane (DME) affords (bc)Mg(DME)2 (1a,b) as crystalline solids. The magnesium compounds, which have been characterized by NMR spectroscopy and single‐crystal X‐ray crystallography in the case of 1a, serve as competent Grignard‐type reagents to generate bc‐containing species of tin from Me2SnCl2 (2a,b). The type of substitution of the bis(o‐carboranyl) ligand framework is found to strongly affect the electronic character of the tin center, as judged by 119Sn NMR spectroscopy. The disclosed compounds, which are stable solids under an atmosphere of dry nitrogen gas at room temperature, provide a new class of bc‐transfer reagents.

Hydrogen activation using a novel tribenzyltin Lewis acid.

Over the last decade there has been an explosion in the reactivity and applications of frustrated Lewis pair (FLP) chemistry. Despite this, the Lewis acids (LAs) in these transformations are often boranes, with heavier p-block elements receiving surprisingly little attention. The novel LA Bn3SnOTf (1) has been synthesized from simple, inexpensive starting materials and has been spectroscopically and structurally characterized. Subtle modulation of the electronics at the tin centre has led to an increase in its Lewis acidity in comparison with previously reported R3SnOTf LAs, and has facilitated low temperature hydrogen activation and imine hydrogenation. Deactivation pathways of the R3Sn+ LA core have also been investigated.This article is part of the themed issue ‘Frustrated Lewis pair chemistry’.

Synthesis, thermoanalytical and spectroscopic characterization of newly synthesized macrocyclic complexes of thallium(III) and tin(IV)

Spectroscopic, thermal and fluorescence properties of various thallium and tin complexes, X-Tl(III)t(4-Y)PP and X-Sn(IV)t(4-Y)PP where X = 5-SO3H-2-OHOC6H4,(5-SSA); 5-Cl-2-OHOC6H4,(5-CSA); and 5-NH2-2-OHOC6H4,(5-NSA) and Y = –Cl, –OCH3, are investigated in detail. Analysis of the spectral data [IR, UV–Vis and NMR (1H and 119Sn)] of complexes suggests that the two trans-axial ligands are strongly bound in a symmetric manner at the tin center in these complexes. Whereas the absorption and emission studies of thallium complexes characterized the sitting-Atop (SAT) feature of the complexes, the fluorescence lifetime of the tin complexes is found to be higher than thallium complexes. The structure and morphology of complexes were studied by X-ray powdered diffraction analysis. From the X-ray diffractograms, it could be revealed that the complexes are crystallized in mixed crystalline forms. Thermal studies of these porphyrins were carried out in an argon atmosphere from room temperature to 800 °C using thermal analyzer. Evaluation of the thermal analysis of the two metal complexes reveals that the tin(IV) porphyrin complexes are more stable than thallium(III) complexes. Some of the synthesized complexes of thallium and tin have been screened for biological activity against B. subtilis, M. luteus, S. aureus, P. florescens and E. coli by agar well diffusion methods that were found to be inactive against bacterial strains.

NEW SELENATO TRIPHENYLTIN (IV) AND TRIMETHYLTIN (IV) DERIVATIVES: SYNTHESIS, INFRARED AND NMR STUDIES

Five derivatives of general formulae [cation] [SeO4SnR3] (R = Ph, Me) have been studied by infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. The suggested structures are infinite chains or oligomers, the environment around the tin centre being trans trigonal bipyramidal, the phenyl and methyl substituants occupying equatorial positions, the selenate anion behaving as a bridging bidentate ligand and occupying the apical positions. When cations are involved, supramolecular architectures may be obtained.

Synthesis, characterization, antimicrobial evaluation and QSAR studies of organotin(IV) complexes of Schiff base ligands of 2-amino-6-substituted benzothiazole derivatives

A series of organotin(IV) complexes of type R2SnLCl [R = Ph, Bu, Et, Me] were prepared by reaction of diorganotindichloride(IV) with Schiff base ligands, L1 = (1-[(6-ethoxy-benzothiazol-2-ylimino)-methyl]-naphthalen-2-ol), L2 = (1-[(6-nitro-benzothiazol-2-ylimino)-methyl]-naphthalen-2-ol), L3 = (1-[(6-methoxy-benzothiazol-2-ylimino)-methyl]-naphthalen-2-ol) and L4 = (1-[(6-methyl-benzothiazol-2-ylimino)-methyl]-naphthalen-2-ol) obtained from 2-amino-6-substituted benzothiazole derivatives with 2-hydroxy-1-naphthaldehyde in 1:1 molar ratio. These organotin(IV) complexes were characterized by various spectroscopic techniques (1H, 13C and 119Sn NMR, FT-IR), and physical techniques (X-ray powder diffraction analysis and elemental analysis). The coordination of the prepared complexes has been planned as pentacoordinated around the central tin atom during which ligands coordinated to tin atom in bidentate manner acted as N, O donor system. The ligands and their complexes were screened for antibacterial and antifungal activities against Gram-positive bacteria Bacillus cereus (MTCC 10072), Staphylococcus aureus (NCIM 2901), Gram-negative bacteria Escherichia coli (MTCC 732), Pseudomonas aeruginosa (MTCC 424) and fungi Aspergillus niger (MTCC 9933) and Aspergillus flavus (ATCC 76801). The output of QSAR analysis indicated that topological parameters (molecular connectivity indices) were responsible for controlling the antimicrobial activity of the synthesized compounds.

Synthesis and characterization of tin, tin/aluminum, and tin/boron containing MFI zeolites

The synthesis and characterization of tin, tin/aluminum, and tin/boron containing MFI zeolites are reported. It is shown that tin uptake is high (near 100%) but decreases with the introduction of a second heteroatom. Additionally, the zeolite crystal size decreases and morphology changes with the introduction of a second heteroatom as evidenced by FE-SEM and XRD. UV-Vis confirms the tetrahedral framework coordination of tin within the zeolite and the absence of tin oxide clusters. Studies of methanol adsorption using in-situ IR spectroscopy indicate that tin-MFI sample with low tin contents possess lower acidity, and that tin/aluminum samples confirm aluminum within the zeolite through the presence of a Brönsted acid site. Comparison of spectra of adsorbed d-acetonitrile on the surface of these catalysts with the silicalite-1 is consistent with the tin centers in the framework possessing Lewis acidity.

Molecular structure, supramolecular association and anion sensing by chlorodiorganotin(IV) methylferrocenyldithiocarbamates

Three new chlorodiorganotin(IV) methylferrocenyl dithiocarbamate complexes viz. [(FcCH2)(CH2CH2OH)NCS2SnMe2(Cl)] (1), [(FcCH2)(CH2CH2OH)NCS2SnnBu2(Cl)] (2) and [(FcCH2)(CH2CH2OH)NCS2SnPh2(Cl)] (3) have been synthesized and characterized by elemental analysis, IR, UV-Vis, 1H, 13C and 119Sn NMR spectroscopy and X-ray crystallography. The crystal structure of 1 indicates that the coordination geometries around the tin(IV) center is intermediate between ideal trigonal-bipyramidal and square pyramidal coordination polyhedra bonded through two sulfur atoms of the dithiocarbamate ligand in an isobidentate mode, two CH3 groups and one chlorine atom. Since, in 2 and 3 only alkyl and aryl fragments have been changed we infer that both 2 and 3 would also have the same behaviors in the solution state as observed in 1. Ionic interactions abilities of 1–3 are examined in acetonitrile through UV-vis absorption spectroscopy which offers reasonably good selectivity and sensitivity towards the detection of the acetate ion. Compounds 1–3 exhibit a bathochromic shift with the acetate ion with a moderate association constant.

Organotin(IV) complexes derived from hydrazone Schiff base: Synthesis, crystal structure, in vitro cytotoxicity and DNA/BSA interactions

Four new organotin(IV) complexes Me2SnL1, Ph2SnL1, Me2SnL2 and Ph2SnL2 (H2L1=5-chlorosalicylaldehyde isonicotinoyl hydrazone and H2L2=2-hydroxy-4-methoxybenzaldehyde isonicotinoyl hydrazone) have been synthesized and characterized by elemental analyses, FT-IR, NMR (1H, 13C and 119Sn) and single crystal X-ray diffraction techniques. The crystal structure analysis shows that complexes 1 and 2 are trinuclear compounds, of which the enolic hydrazone Schiff base ligand chelate to tin center in the ONO tridentate mode. In contrast, the complexes 3 and 4 are uninuclear compounds with the central Sn atoms adopting five-coordinated distorted trigonal bipyramid geometry. Cytotoxicity of the four complexes was studied against two human cancer cell lines (A549 and HeLa) by the MTT assay method. The results demonstrate that the four complexes exhibited good anticancer activity, and mononuclear complex 4 was found to be more effective towards HeLa cancerous cells. The interactions between all complexes with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) were investigated using various spectroscopic techniques. The viscosity measurements, thermal temperature (Tm) and UV–Vis spectra data suggested intercalative binding between DNA and the four organotin (IV) complexes. In addition, all complexes could quench the intrinsic fluorescence of BSA in a static quenching process, which was also confirmed by the docking study.

NITRATO ADDUCTS AND DERIVATIVES: SYNTHESIS AND INFRARED STUDY

Five new nitrato adducts and derivatives have been synthesized and studied by infrared spectroscopy. The suggested structures are discrete or of infinite chain type, the nitrate behaving as a bidentate or a monodentate ligand, the environment around the tin (IV) centres being octahedral or trigonal bipyramidal. When extra hydrogen bonds are considered supramolecular architectures may be obtained.

Employing a C,N-chelate makes organotin(IV) nitrates and nitrites exceptionally stable

A series of tri- and diorganotin(IV) nitrates and nitrites bearing the 2-(N,N-dimethylaminomethyl)phenyl-as a C,N-chelating ligand (LCN) has been prepared and structurally characterized. Air-stable triorganotin(IV) nitrates and nitrites of the type LCNR2SnX (for X = NO3: R = n-Bu (1), R = Ph (2); for X = NO2: R = n-Bu (7), R = Ph (8)) and (LCN)2(n-Bu)SnX (X = NO3 (3), NO2 (9)) are monomeric both in solution and solid state with distorted trigonal bipyramidal geometry around the central tin atom. These species were prepared in biphasic systems (water/organic solvent) using AgNO3 and NaNO2, respectively. Diorganotin(IV) dinitrates (i.e. LCN(n-Bu)Sn(NO3)2 (4), LCNPhSn(NO3)2 (5) and (LCN)2Sn(NO3)2 (6)) and dinitrites (i.e. LCN(n-Bu)Sn(NO2)2 (10), LCNPhSn(NO2)2 (11) and (LCN)2Sn(NO2)2 (12)) are monomeric species due to the bidentate bonding fashion of the nitrato, nitrito and/or LCN substituents. Compounds 4–6 and 10–12 were prepared under an inert atmosphere using AgNO3 in acetonitrile and KNO2 in THF/benzene mixture of solvents, respectively. All these extraordinary stable compounds have been characterized by IR and NMR spectroscopy. In addition, solid-state structures of 2, 4, 5, 6, 8, 11, 12 and one decomposition product of 10 (i.e. [LCN(n-Bu)Sn(NO3)(μ-OH)]2; 4a) were determined by the SC-XRD techniques.

Homobimetallic organotin(IV) complexes with succinohydrazide Schiff base: Synthesis, spectroscopic characterization, and biological screening

Six new bis-diorganotin(IV) complexes, [(Me2Sn)2L] (1), [(Et2Sn)2L] (2), [(n-Bu2Sn)2L] (3), [(Ph2Sn)2L] (4), [(n-Oct2Sn)2L] (5), and [(tert-C4H9)2Sn)2L] (6), where L = N 1',N 4'-bis(2-oxidobenzylidene)-succinohydrazide, were synthesized and characterized by elemental analysis, FT-IR, NMR (1H, 13C, and 119Sn) and Mass spectra. Spectroscopic data authenticated the existence of two pentacoordinated tin centers in all complexes, formed via coordination of bis-ONO donor sites with dialkyltin(IV) moieties. Biological screening against selected pathogenic strains of bacteria and fungi revealed high activity of compound 3 against Bacillus subtilis and Aspergillus flavis, it also exhibited highest cytotoxicity against Artemia salina.

Blue-emitting phosphate glasses synthesized via reduction of tin(IV) by silicon

The Si-reductant route to produce blue-emitting tin-doped phosphate glasses is proposed. SnO2/Si co-doped glasses were prepared in a P2O5:BaO matrix by a simple melt-quench method in ambient atmosphere. This lead to the silicon-driven reduction of tin(IV) to tin(II) resulting in the production of the luminescent glasses. While the as-prepared SnO2-doped glass appeared non-luminescent, the addition of increasing amounts of silicon powder up to 6 mol% to batch materials facilitated developing the blue-emitting character of the glasses under excitation in the ultraviolet (UV). Reductant-induced luminescent defects became readily noticeable upon addition of the highest amount of silicon. Time-resolved UV-excited emission spectra appeared consistent with the different contributors to the exhibited luminescence being the twofold-coordinated tin centers alongside silicon-related defects. Emission from the latter appeared to be analogous to that of carbon-related defects recently reported, thus supporting that the corresponding luminescence results from the presence of oxygen radicals created by the highly reductive environment irrespective of the element (C or Si).

Tetrel bonds, penta‐ and hexa‐coordinated tin and lead centres

A tetrel bond – an interaction between a Group 14 element acting as Lewis acid centre and an electron‐donating moiety – is analysed for ZF4 (Z = Sn, Pb) complexes with NH3 and HCN species. MP2/aug‐cc‐pVTZ calculations were performed and supported by results of the quantum theory of atoms in molecules. The results of calculations show that the tetrel centre may be considered as a pentavalent one if ZF4 interacts with one NH3 or HCN ligand or even as a hexavalent centre if it interacts with two ligands; thus the hypervalency phenomenon is discussed for the complexes analysed here. The theoretical analysis is supported by a discussion of the crystal structures containing the SnF4 fragment; these structures are characterized by a hexa‐coordinated tin centre.

Two-electron exchange between impurity centers of tin in PbS z Se1–z solid solutions

Using emission Mossbauer spectroscopy on 119mmSn(119mSn) and 119Sb(119mSn) isotopes, the electron exchange process between neutral and doubly ionized U – tin centers is studied in partially compensated PbS z Se1–z solid solutions. The activation energy of this process for compositions with z ≈ 1 is comparable to the deposition depth of the tin energy levels in the band gap of PbS (~0.11(1) eV, and for compositions with z ≈ 1, it is comparable with the correlation energy of donor U – tin centers in PbSe (~0.05(1) eV). For all compositions of solid solutions, the exchange is realized by the simultaneous transfer of two electrons with the use of the delocalized states of the valence band.

Crystal structure of bis-{μ-(E)-2-[(2-oxido-phenyl-imino)-meth-yl]quinolin-8-olato-κ4O,N,N',O'}bis-[di-butyl-tin(IV)

Condensation of 8-hy-droxy-quinoline-2-carbaldehyde with 2-amino-phenol gave the (E)-2-[(2-hy-droxy-phenyl-imino)-meth-yl]quinolin-8-ol derivative that reacted with di-n-butyl-tin oxide with release of H2O to yield the chelate title complex, [Sn2(C4H9)4(C16H10N2O2)2]. The compound crystallizes in the triclinic space group P-1, with two independent centrosymmetric dimers in the unit cell. Each features a typical pincer-type structure where the dianionic ligand is tetra-dentate, coordinating to the central tin atom through both phenolate oxygen atoms, as well as through the quinoline and imine N atoms. Each metal atom adopts a distorted penta-gonal-bipyramidal SnC2N2O3 coordination arising from the N,N',O,O'-tetra-dentate deprotonated Schiff base, one bridging phenolate O atom of the neighbouring ligand and two butyl groups in the axial sites.

Luminescent tin-doped phosphate glasses activated by carbon

This paper reports on the use of carbon powder together with tin(IV) oxide to produce rare earth-free blue-emitting phosphate glasses by melting in ambient atmosphere. While the as-prepared SnO2-doped glass was lacking in luminescent features, increasing amounts of graphite added to batch materials lead to developing the blue-emitting character of the glasses under excitation in the ultraviolet (UV). Upon addition of the highest amount of graphite at 2.0wt%, the luminescence of carbon-induced defects became noticeable. Time-resolved UV-excited emission spectra appeared consistent with the different contributors to the exhibited luminescence being the twofold-coordinated tin centers alongside carbon-induced defects.

Oxidative halogenation of Sn(II)heteroaryl alkenolates: Formation of unusual trans-dihalo Sn(IV) complexes

A series of novel tin(IV)-heteroaryl alkenolates of the general formula [Sn(DMOTFP)2X2] (3–6, X=F, Cl, Br, I) were prepared by direct oxidative halogenation of the corresponding tin(II) derivative [SnII(DMOTFP)2] (2) and by cleavage of the carbon-tin bonds in diphenyltin dichloride [Ph2SnCl2] by (4,5-dimethyloxazolyl)-1,1,1-trifluoropropen-2-ol, (H-DMOTFP, 1) with a subsequent halide exchange reaction. The molecular structures elucidated in solution (multi-nuclear NMR spectroscopy) and by single crystal X-ray diffraction confirmed the sixfold coordination of the tin(IV) center with a distorted octahedral arrangement of ligands. An unusual centrosymmetric octahedral trans-dihalo configuration was found for the compounds [SnIV(DMOTFP)2X2] (X=Cl, Br, I), while the compound [Sn(DMOTFP)2F2] adopted a cis-dihalide configuration.

Synthesis, characterization and antimicrobial activity of triorganotin(IV) derivatives of some bioactive Schiff base ligands

Triorganotin(IV) complexes of the type Me3Sn[OC(R1):CH(CH3)C:NR2OH] and Ph3Sn[OC(R′):CH(CH3)C:NR″OH] (R′ = ─CH3, ─C6H5; R″ = ─(CH2)2─, ─(CH2)3─) have been synthesized by the reactions of trimethyl/phenyltin(IV) chloride with the sodium salt of corresponding Schiff base ligands in unimolar ratio in refluxing tetrahydrofuran. All these compounds have been characterized using elemental analyses and their probable structures have been proposed on the basis of infrared, 1H NMR, 13C NMR, 119Sn NMR and mass spectroscopic studies. In the trimethyltin(IV) derivatives the central tin atom is tetracoordinated, whereas in the analogous triphenyltin(IV)derivatives the central tin atom is pentacoordinated. All these ligands, metal precursors and corresponding triorganotin(IV) complexes have been screened for antimicrobial activities. A comparison of activities of the ligands and their corresponding triorganotin(IV) derivatives has been made. Attempts have also been made to relate the activity to the structure of these compounds.