Diorganotin Dichlorides Research Articles

Efficacy of Radical‐Scavenging Activity in Novel Diorganotin(IV) Complexes of Schiff Bases of Salicylaldehyde

AbstractBiopotent hybrid diorganotin(IV) complexes, derived from salicylaldehyde Schiff bases having general formula R2SnL, where LH = (OH)C6H4HC: NCR′(R″)CHR‴OH] [where R = Me or Bu], were logically designed, generated, and characterized using spectroscopic techniques, single‐crystal X‐ray investigations, and DFT studies. Different diorganotin(IV) complexes were synthesized because of interaction between diorganotin(IV) dichloride and sodium salts of Schiff bases of salicylaldehyde ligand in anhydrous refluxing THF at 1:1 and 1:2 molar ratio (Product A and B). The chelating property of Schiff bases replaces organo group from diorganotin(IV) dichloride. It creates an O2SnL type of complex when diorganotin(IV) dichloride and ligand interact in 1:2 ratio, which is this study's most fascinating aspect. The characterization of these complexes is aided by physicochemical and spectroscopic investigations, including IR and NMR (1H, 13C, and 119Sn). Single‐crystal X‐ray investigations, mass spectrum studies, and DFT investigations suggest the dimeric structure of these compounds. These diorganotin(IV) complexes have a dimeric structure containing hexacoordinated central tin atom. Two µ2─O atoms bridge the gap between two Sn(IV) atoms in the dimeric dimethyltin(IV) complexes. The DPPH assay results for radical scavenging activity and IC50 values demonstrate the antioxidative potential of diorganotin(IV).

Exploring the Microbial Inhibition Ability of Newly Synthesized Diorganotin(IV) Complexes of Hydrazone Ligands: Structural Elucidation, Crystal Structure, and DFT Studies

ABSTRACTIn our work, we have successfully synthesized twelve diorganotin(IV) complexes (4–15) from different hydrazone ligands and diorganotin(IV) dichlorides. The complexes have a general formula [R2SnL1–3], where R = Et, Me, Bu, and Ph groups. The hydrazone ligands (1–3) were synthesized through a condensation reaction involving 3‐ethoxysalicylaldehyde with different benzhydrazide derivatives. All the synthesized hydrazone ligands and their complexes underwent screening by employing numerous spectroscopic and physicochemical techniques, such as molar conductance measurements, mass spectrometry, (1H, 119Sn, and 13C) NMR, SEM‐EDAX, and FT‐IR. Spectroscopic analysis revealed that the hydrazone ligands were attached to tin atoms in a tridentate fashion via ONO donor atoms, suggesting a pentacoordinated geometry for the complexes. Furthermore, the X‐ray crystallography analysis for Complex 6 revealed the distorted square pyramidal geometry around the tin atom. Moreover, a DFT study was also carried out for Ligand 3 and its complexes (12–15) by employing B3LYP/LanL2DZ theory level (Gaussian 9 software package) to obtain the optimized geometry and global reactivity descriptors, structural behavior, and their efficacy against different microbes. To assess the biological efficacy of synthesized compounds, an in vitro antimicrobial assay was conducted against different fungal (Aspergillus niger and Candida albicans) and bacterial (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa) strains. The results of the antimicrobial assay demonstrated that Complexes 7, 11, and 15 depicted better results against E. coli strain and C. albicans strain, implying that the higher lipophilic character of these complexes facilitates their easy passage through the cell membrane of microbes. Furthermore, an ADMET study was carried out to evaluate the toxicity score of synthesized compounds.

Synthesis, characterization, and biological evaluation of eight new organotin(IV) complexes derived from (1R, 2S) ephedrinedithiocarbamate ligand

The synthesis of eight new organotin derivatives containing ephedrine-substituted dithiocarbamate ligands [R3Sn(ephedtc)] 2–5. 2: R = Me; 3: R = Bu; 4: R = Cy; 5: R = Ph and [R2Sn(ephdtc)2] 6–9. 6: R = Me; 7: R = Bu; 8: R = t-Bu; 9: R = Ph is reported. The complexes were obtained from sodium ephedrinedithiocarbamate [Na(ephedtc)] 1 and the corresponding tri-organotin(IV) chlorides, R3SnCl 2–5 or di-organotin(IV) dichlorides, R2SnCl26–9. They were characterized by elemental analysis, IR, and NMR spectroscopy (1H, 13C, and 119Sn). The infrared spectra (solid-state) suggest that the Sn(IV) is coordinated to the ligand ephedtc, through the two sulfur atoms in an anisobidentate coordination mode. In solution, the 119Sn NMR indicates the coordination numbers: tetracoordinated for 2–4, pentacoordinate for 5, and hexacoordinated for 6–9. The single-crystal X-ray diffraction analysis of 4 reveals an anisobidentate coordination mode with a trigonal bipyramid distorted geometry around the Sn(IV). All compounds except 2, show inhibition in at least one bacterial strain, and 7 and 9 have the best antibacterial activity, mainly in the clinically isolated strains.

Pentacoordinated diorganotin(IV) complexes resulting from tridentate (NOO) donor Schiff bases: Synthesis, characterization, in vitro antioxidant, antimicrobial activities, and QSAR studies

A series of diorganotin(IV) complexes of type R2SnL, (where R = Me, Et, Bu and Ph) were prepared by the reaction of tridentate (NOO) donor Schiff base ligands with diorganotin(IV) dichloride in an equimolar ratio. The products were characterized by various spectroscopic techniques and physical and analytical methods (UV–vis, FTIR, NMR, fluorescence, elemental analysis). Spectroscopic data suggest that the Schiff base acts as a tridentate ligand (NOO) coordinated with a central tin atom via two oxygen and one imine nitrogen atom in a pentacoordinated fashion. The synthesized compounds were assayed for their in vitro antimicrobial activity against bacterial and fungal strains. All the compounds displayed promising results with the complexes being more potent than free ligands. The antioxidant activity of the compounds was determined by interaction with 2,2-diphenyl-1-picrylhydrazyl free radical. Complex Ph2SnL3 (16) was found to have the most potential antimicrobial activity against all tested strains and also exhibited excellent antioxidant activity. Quantitative structure–activity relationship of compounds was studied for antimicrobial activity with molar refractivity indices as significant statistical parameter.

Synthesis, structural characterization, and antibacterial activity of diorganotin complexes of Schiff base derived from 4-(diethylamino)salicylaldehyde and L-tyrosine

Four new diorganotin complexes of Schiff base derived from 4-(diethylamino)salicylaldehyde and L-tyrosine, R2Sn[2-O-4-Et2NC6H3CH=NCH(CH2C6H4OH-4)COO] (R = Me (1), Et (2), Cy (3), Ph (4)), were synthesized by the one-pot reaction of L-tyrosine, 4-(diethylamino)salicylaldehyde and diorganotin dichloride in the presence of triethylamine and characterized by means of elemental analysis, IR, 1H and 13C NMR spectra, and the X-ray single-crystal diffraction. X-Ray analyses of 1–4 revealed that the tin atoms of the complexes exhibit seriously distorted trigonal-bipyramidal geometries with a monodentate carboxylate oxygen atom and a phenolic oxygen atom occupying the axial positions. The intermolecular O─H⋅⋅⋅O hydrogen bonds and Sn⋅⋅⋅O weak interactions connected the molecules into one-dimensional supramolecular chain. Bioassay results indicated that 1–4 had moderate antibacterial activity against Escherichia coli and the fluorescence determinations show the complexes may be explored for potential luminescent materials.

Hypercoordinated organotin(IV) compounds containing C,O- and C,N- chelating ligands: Synthesis, characterisation, DFT studies and polymerization behaviour

A series of 2-methoxymethyl tetraorganotins [2-(MeOCH2)C6H4]SnR3 (21: R = Ph; 22: R = n-Bu; 23: R = Me), diorganotin chlorides [2-(MeOCH2)C6H4]R2SnCl (24: R = Ph; 25a, 25b: R = n-Bu), monoorganotin dichlorides [2-(MeOCH2)C6H4]RSnCl2 (26: R = Ph; 27: R = n-Bu; 28: R = Me) and the tin trichloride [2-(MeOCH2)C6H4]SnCl3 (29) were successfully prepared from the reaction of the organolithium, [2-(MeOCH2)C6H4]Li, and the appropriate chlorostannane. Similarly, a series of dimethylamino stannanes including the tetraorganotin [2-(Me2NCH2)C6H4]SnPh3 (30), the diorganotin halides [2-(Me2NCH2)C6H4]Ph2SnX (34: X = Cl; 35: X = Br), dichlorides [2-(Me2NCH2)C6H4]RSnCl2 (38: R = Ph; 39: R = n-Bu; 40: R = Me) and the tribromide [2-(Me2NCH2)C6H4]SnBr3 (37) were prepared by reaction of the appropriate organochlorostannane and the organolithium [2-(Me2NCH2)C6H4]Li followed by selective halogenations in the case of 34–37. 2-Methoxymethyl and dimethylamino diorganotin dichlorides (27, 28 and 39, 40) were hydrogenated with LiAlH4 to produce new 2-methoxymethyl [2-(MeOCH2)C6H4]RSnH2 (41: R = n-Bu; 42: R = Me) and dimethylamino [2-(Me2NCH2)C6H4]RSnH2 (44: R = n-Bu; 45: R = Me) dihydrides. X-ray structure determination of 30 revealed a nearly tetrahedral stannane, while structural analysis of 24, 29 and 40 display distorted trigonal bipyramidal geometry at Sn with Cl trans to the datively coordinated heteroatom. A selection of DFT methods were assessed for accuracy in predicting the solid-state geometries of the hypercoordinate Sn complexes. Catalytic dehydrocoupling of C,O- (41) and C,N- (44) diorganotin dihydrides was explored using Wilkinson's catalyst at RT leading to the recovery of modest molecular weight polymers (52: Mw = 3.03 × 104 Da, PDI = 1.4, 53: Mw = 3.1 × 104 Da, PDI = 1.86). The new rigid polymers were isolated in moderate (52: 65%) and low yields (53: 18%) and were found to be amorphous by DSC.

New insight into the reactions of organoplatinum(II) complexes with diorganotin dichloride and diisothiocyanate: Oxidative addition, reductive elimination and α-elimination

The reaction of electron rich [PtMe2(NN)] with SnMe2Cl2 in a 1:3/Pt:Sn mole ratio resulted in formation of Pt(IV) complexes [PtMe2(SnMe2Cl)Cl(NN)] {NN = 4,4′-Me2bpy (4,4′-dimethyl-2,2′-bipyridine) (7); 5,5′-Me2bpy (5,5′-dimethyl-2,2′-bipyridine) (8); bphen (4,7-diphenyl-1,10-phenanthroline) (9)}. NMR data show that the resulting complexes exist as the sole product corresponding to that of trans oxidative addition of SnMe2Cl2. The yellow polymorph of complex [PtCl2(5,5′-Me2bpy)] (10) was characterized by X-ray crystallography from the reaction of [PtMe2(5,5′-Me2bpy)] and excess of SnMe2Cl2 due to the reductive elimination of 8. On the other hand, the reaction of [PtMe2(NN)] with SnEt2Cl2 in a 1:3/Pt:Sn mole ratio resulted in formation of new complexes [PtMe2(SnEt2Cl)Cl(4,4′-Me2bpy)] (11), [PtMe2(SnEt2Cl)Cl(5,5′-Me2bpy)].SnEt2Cl2 (12) and [PtMe2(SnEt2Cl)Cl(bu2bpy)].SnEt2Cl2 (bu2bpy = 4,4′-di-tert-butyl-2,2′-dipyridine) (13). NMR data indicate that the PtSnEt2Cl bond is weaker than the PtSnMe2Cl bond. The X-ray crystal structure of 13 reveals that organoplatinum(IV) complex acts as a donor to the SnEt2Cl2 to form an adduct in a distorted trigonal bipyramid with the axial Cl⋯SnCl and equatorial SnEt2Cl units. Moreover, the X-ray crystal structure of the new yellow form of [PtClMe(4,4′-Me2bpy)] (14), which has been formed by the crystallization of a mixture of [PtMe2(4,4′-Me2bpy)] and excess of SnEt2Cl2, is described. The reaction of dimethylplatinum(II) complexes with dimethyltin diisothiocanate are reported for the first time which occur via Sn-NCS bond cleavage to afford the organoplatinum(IV) complexes [PtMe2(SnMe2NCS)(SCN)(NN)] {NN = bpy (17); phen (18); 5,5′-Me2bpy (19); bu2bpy (20); bphen (21)}. The crystal structures of the novel thiocyanatoplatinum(IV) complexes [PtMe2(SCN)2(bpy)] (22) and [PtMe2(SCN)2(5,5′-Me2bpy)]. H2O (23) are discussed which have been obtained due to the α-elimination of SnMe2. The crystal structures of 22–23 show that platinum adopts a slightly distorted octahedral geometry with trans- Pt(SCN)2 configuration in which SCN is bonded through sulfur atom while the nitrogen atom is coordinated to tin. NMR data indicate that the products dissociate via α-elimination of SnMe2 or reductive elimination of organotin(IV) compound and the stability of the organoplatinum(IV) compounds varies according to the trends [PtMe2(SnMe2Cl)Cl(NN)]>[PtMe2(SnMe2NCS)(SCN)(NN)]>[PtMe2(SnEt2Cl)Cl(NN)].

Organoselenium compounds containing pyrazole or phenylthiazole groups: Synthesis, structure, tin(IV) complexes and antiproliferative activity

The diorganodiselenides (pzCH2CH2)2Se2 (1) and (PhtzCH2)2Se2 (2) were prepared by reacting Na2Se2 with 1‐(2‐bromoethyl)‐1H‐pyrazole and 4‐(chloromethyl)‐2‐phenylthiazole, respectively, while the reactions between 1‐(2‐bromoethyl)‐1H‐pyrazole or 4‐(chloromethyl)‐2‐phenylthiazole and the lithium organoselenolates [2‐(Et2NCH2)C6H4]SeLi and [2‐{O(CH2CH2)2NCH2}C6H4]SeLi in a 1:1 molar ratio resulted in the heteroleptic diorganoselenium(II) compounds [2‐(Et2NCH2)C6H4](R)Se (R = pzCH2CH2 (3) or PhtzCH2 (5)) and [2‐{O(CH2CH2)2NCH2}C6H4](R)Se (R = pzCH2CH2 (4) or PhtzCH2 (6)). The diorganotin(IV) bis(organoselenolato) derivatives of type R2Sn(SeCH2CH2pz)2 (R = 2‐(Me2NCH2)C6H4 (7) or Me (8)) were obtained by reacting (pzCH2CH2)SeNa with the appropriate diorganotin(IV)dichloride in a 2:1 molar ratio. All compounds were investigated using NMR spectroscopy (1H, 13C, 77Se, 119Sn as appropriate) and ESI+ mass spectrometry. The molecular structures of 2 and 6 were determined using single‐crystal X‐ray diffraction. The formation of a 10–Se–3 hypercoordinated species was evidenced for 6 in the solid state, as a consequence of the C,N coordination behaviour of the 2‐{O(CH2CH2)2NCH2}C6H4 group. Compounds 1, 7 and 8 were investigated for their antiproliferative activity towards the mouse colon carcinoma C26 cell line with the preliminary results showing a better activity than 5‐fluorouracil.

Organotin(IV) 4-(benzo[d][1,3]dioxol-5-ylmethyl)piperazine-1-carbodithioates: Synthesis, characterization and biological activities

A series of organotin(IV) derivatives R3SnL (1–3), R2SnLCl (4–6) and R2SnL2 (7–9) (where R = Me, Bu, Ph and L = 4-(benzo[d][1,3]dioxol-5-ylmethyl)piperazine-1-carbodithioate) were prepared from the reaction of 4-(benzo[d][1,3]dioxol-5-ylmethyl)piperazine-1-carbodithioate (L-salt) with the corresponding triorganotin(IV) chlorides and diorganotin(IV) dichlorides. All compounds were characterized by FT-IR, 1H, 13C and 119Sn NMR spectroscopy. Dimethylstannyl bis(4-(benzo[d][1,3]dioxol-5-ylmethyl)piperazine-1-carbodithioate) (7) was also characterized in the solid state by single crystal x-ray diffraction, showing a distorted octahedral geometry. The diorganotin(IV) derivatives have shown significant antibacterial and antifungal activity and good cytotoxic activity against ovarian cancer cells with IC50 values greater or comparable to that of cisplatin.

Schiff base supported mononuclear organotin(IV) complexes: Syntheses, structures and fluorescence cell imaging

Three mononuclear organotin(IV) complexes supported by Schiff bases have been synthesized. The complexes [(C6H5)2Sn(L)] (1), [(t‐Bu)2Sn(L)] (2) and [(t‐Bu)2Sn(L')] (3) (L, L' = deprotonated Schiff bases) were obtained in good yield by the reaction of Schiff bases H2L or H2L′ with corresponding diorganotin dichlorides respectively. All newly synthesized complexes were characterized by means of FT‐IR spectroscopy, elemental analysis and multinuclear (1H, 13C and 119Sn) NMR spectroscopy. In addition, single crystal X‐ray diffraction analyses were employed to establish the solid state molecular structures of these complexes. The structures of 1–3 reveal that all complexes are mononuclear with a five‐coordinated tin(IV) centre in it. The absorption and emission properties of all complexes have been investigated. Moreover, cytotoxicity and fluorescence cell imaging studies of theses complexes have been performed.

Variation of the Molecular Conformation, Shape, and Cavity Size in Dinuclear Metalla-Macrocycles Containing Hetero-Ditopic Dithiocarbamate-Carboxylate Ligands from a Homologous Series of N-Substituted Amino Acids.

A homologous series of dithiocarbamate ligands derived from N-substituted amino acids was reacted with different diorganotin dichlorides to give 18 diorganotin complexes. Spectroscopic and mass spectrometric analysis evidenced the formation of assemblies with six-coordinate tin atoms embedded in skewed-trapezoidal bipyramidal coordination environments of composition C2SnS2O2. Single-crystal X-ray diffraction analysis for three of the compounds revealed a one-dimensional polymeric structure for the complex with the ligand derived from 5-aminopentanoic acid, which through further intermolecular Sn···O interactions generated an overall two-dimensional coordination polymer containing 40-membered hexanuclear tin macrocycles. On the contrary, the ligands derived from 6-aminohexanoic and 8-aminooctanoic acid provided the expected 22- and 26-membered dinuclear macrocyclic structures. Density functional theory calculations for a representative series of macrocyclic complexes of composition [Me2SnLx]2 with Lx = ¯S2CN(Me)-(CH2)x-COO¯ (x = 3-12) enabled a detailed analysis of the variations in the molecular conformation, shape, and cavity size of the macrocycles in dependence of the aliphatic spacer. Because of odd-even effects, the difunctional ligands can adopt either a curved or a twisted-pincer shape, while the SnSxO4-x (x = 0-4) moieties can act either as linear or angular tectons with varying connectivity angles.

Synthesis, structural characterization and antimicrobial activities of diorganotin(IV) complexes with azo-imino carboxylic acid ligand: Crystal structure and topological study of a doubly phenoxide-bridged dimeric dimethyltin(IV) complex appended with free carboxylic acid groups

Diorganotin(IV) complexes appended with free carboxylic acids were synthesized by reacting diorganotin(IV) dichlorides [R2SnCl2; R = Me (1), Bu (2) and Ph (3)] with an azo-imino carboxylic acid ligand i.e. 2-{4-hydroxy-3-[(2-hydroxyphenylimino)methyl]phenylazo}benzoic acid in presence of triethylamine. The complexes were characterized by elemental analysis, IR and multinuclear NMR (1H, 13C and 119Sn) spectroscopy. The structure of 1 in solid state has been determined by X-ray crystallography. Crystal structure of 1 reveals that the compound crystallizes in monoclinic space group P21/c and is a dimeric dimethyltin(IV) complex appended with free carboxylic acid groups. In the structure of 1, the Sn(IV) atoms are hexacoordinated and have a distorted octahedral coordination geometry in which two phenoxy oxygen atoms and the azomethine nitrogen atom of the ligand coordinate to each tin atom. One of the phenoxy oxygen atom bridges the two tin centers resulting in a planar Sn2O2 core. Topological analysis is used for the description of molecular packing in 1. Tin NMR spectroscopy study indicates that the complexes have five coordinate geometry around tin atom in solution state. Since the complexes have free carboxylic acids, these compounds could be further used as potential metallo-ligands for the synthesis of other complexes. The synthesized diorganotin(IV) complexes were also screened for their antimicrobial activities and compound 2 showed effective antimicrobial activities.

Synthesis and characterization of organotin(IV) semicarbazones: potential precursors for nanosized tin oxide

A series of organotin(IV) semicarbazone adducts of the type R2SnCl2� nLH (1-6) were synthesized by the reactions of R2SnCl2 with newly synthesized car- vone semicarbazone (LH) in anhydrous ethanol (where R = CH3, n = 1( 1), 2 (2); R = C4H9, n = 1( 3), 2 (4); and R = C6H5, n = 1( 5), 2 (6)). All the compounds have been characterized by elemental analyses, FT-IR, NMR ( 1 H, 13 C, 119 Sn) and FAB mass spectral studies. 119 Sn NMR studies suggest monodentate mode of attachment of the ligand with central tin atom in the solution state. Thermogravimetric study of (6) shows large thermal events. Transformations of (4) and (6) to pure tin oxides (i and ii, respectively) have been carried out using sol-gel technique. Powder XRD patterns of the formed tin oxides indicate the formation of tetragonal cassiterite structure. SEM images of (i) and (ii) show wire- and grain-like morphologies of the crystallites, respectively. Graphical Abstract A series of organotin(IV) semicar- bazone adducts were synthesized by the reactions of diorganotin dichloride with newly synthesized carvone semicarbazone. Transformations of some of the newly synthesized adducts to pure tin oxides have been carried out using sol-gel technique. Powder XRD patterns of the formed tin oxides indicate the formation of tetragonal cassiterite structure, while SEM images show wire- and grain-like morphologies.

Potentiometric Study of Speciation and Thermodynamics of Complex Formation Equilibria of Diorganotin(IV) Dichloride with 1-(2-Aminoethyl)piperazine

The interaction of DET (diethyltin(IV)) and DVT (divinyltin(IV)) with 1-(2-aminoethyl)piperazine (AEP) was investigated potentiometrically at different temperatures in 0.1 mol·dm−3 NaNO3. The hydrolysis constants of diethyltin(IV) and divinyltin(IV) cations and the stepwise formation constants of the complexes formed in solution were calculated at different temperatures and in solutions of dioxane–water solutions of different compositions. The stoichiometries and stability constants for the complexes formed are reported. The results show formation of 1:1 complexes and the corresponding hydroxide complexes. The concentration distributions of the various complex species were evaluated as a function of pH. The thermodynamic parameters ΔH° and ΔS° calculated from the temperature dependence of the equilibrium constants were investigated for DET and DVT complexes with AEP.

Synthesis, structural, and spectral studies of diorganotin(IV) complexes with 2–hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone

Three new diorganotin(IV) complexes, [Me2Sn(L)] (2), [Bu2Sn(L)] (3), and [Ph2Sn(L)] (4) [where H2L (1) = 2-hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone] have been synthesized by reacting the corresponding diorganotin(IV) dichloride with H2L (1) in absolute methanol in the presence of potassium hydroxide. All the compounds have been characterized by CHN analyses, UV–vis, FT-IR, 1H, 13C, and 119Sn NMR spectroscopy. The molecular structures of H2L (1) and 2 have been confirmed by single crystal X-ray diffraction analysis. H2L (1) is found to be in the thiol tautomeric form. The X-ray structure of 2 showed that H2L is a tridentate ligand and binds to the tin(IV) atom via the phenolic oxygen, azomethine nitrogen, and thiolate sulfur. Complex 2 has a triclinic structure and the coordination geometry of tin(IV) is distorted trigonal bipyramidal. The sulfur and oxygen are in axial positions while the azomethine nitrogen of 1 and two methyl groups occupy the equatorial positions. The C-Sn-C angles determined from 1J(119Sn, 13C) for 2, 3, and 4 are 124.35°, 123.11°, and 123.82°, respectively. The values of δ(119Sn) for 2, 3, and 4 are −153.4, −180.59, and −158.3 ppm, respectively, indicating five-coordinate tin(IV). From NMR data a distorted trigonal-bipyramidal configuration at each tin is proposed.

Synthesis, structural, and spectral studies of diorganotin(IV) complexes with 2–hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone

AbstractThree new diorganotin(IV) complexes, [Me2Sn(L)] (2), [Bu2Sn(L)] (3), and [Ph2Sn(L)] (4) [where H2L (1) = 2-hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone] have been synthesized by reacting the corresponding diorganotin(IV) dichloride with H2L (1) in absolute methanol in the presence of potassium hydroxide. All the compounds have been characterized by CHN analyses, UV–vis, FT-IR, 1H, 13C, and 119Sn NMR spectroscopy. The molecular structures of H2L (1) and 2 have been confirmed by single crystal X-ray diffraction analysis. H2L (1) is found to be in the thiol tautomeric form. The X-ray structure of 2 showed that H2L is a tridentate ligand and binds to the tin(IV) atom via the phenolic oxygen, azomethine nitrogen, and thiolate sulfur. Complex 2 has a triclinic structure and the coordination geometry of tin(IV) is distorted trigonal bipyramidal. The sulfur and oxygen are in axial positions while the azomethine nitrogen of 1 and two methyl groups occupy the equatorial positions. The C-Sn-...

Structural studies and bioactivity of diorganotin(IV) complexes of pyridin-2-thionato derivatives

A series of diorganotin(IV) derivatives containing the potentially chelating S,N-ligands, 3-trifluoromethyl-pyridine-2-thione (3-CF3-pySH) and 5-trifluoromethyl-pyridine-2-thione (5-CF3-pySH), were prepared by direct reaction between the ligand and the corresponding diorganotin(IV) dichloride R2SnCl2 (R = Me, nBu, Ph) in the presence of triethylamine. The compounds have been characterized by microanalysis, mass spectrometry, IR spectroscopy and by 1H, 13C and 119Sn NMR spectroscopies. The crystal structures of compounds [Ph2Sn(3-CF3-pyS)2] (1) and [nBu2Sn(5-CF3-pyS)2] (2) were analyzed by X-ray diffraction. In both cases, the metal is in a bicapped tetrahedron environment, bound to two carbon atoms of the alkyl or aryl substituents and to the sulfur atoms and the heterocyclic nitrogen atoms of two pyridine-2-thionato ligands, which act as κ2-N,S chelating ligands. The supramolecular structure of 1 consists of chains of complexes parallel to the crystallographic b axis, built up by F⋯F, π-stacking and C–H⋯π intermolecular interactions. In the case of compound 2, the supramolecular structure is mainly determined by CH⋯F(CF3) intermolecular interactions that propagate along the crystallographic b axis. The antimicrobial activities of all complexes against S. aureus (MSSA and MRSA), A. baumanni, Aspergillus fumigates, Bacillus subtilis, E coli and Pseudomonas aeruginosa were also evaluated and in general the complexes derived from 5-trifluoromethylpyridine-2-thionate were found to be more active than the complex derived from 3-trifluoromethylpyridine-2-thionate.

Ladder-like diorganotin(IV) complexes containing cyclohexanecarboxylates: Synthesis, characterization and biological activities

Reactions of the diorganotin(IV) dichlorides with cyclohexanecarboxylate ligands yielded four new dimeric ladder-like tetraorganostannoxanes formulated as [R4Sn2(C6H11COO)(μ3-O)(μ-OH)]2[R=Et (1), nBu (2), nOct (3) and Ph (4)]. All these complexes were characterized by elemental analysis, IR, NMR (1H, 13C, 119Sn) spectra and in one case by X-ray diffraction analysis. The crystal structure of 1 reveals the formation of the tetranuclear species contains a planar Sn4O4 core, consisting of three adjacent rhombs with bridging oxo and hydroxyl ligands. The central tin atoms are five-coordinated to assume a distorted trigonal bipyramidal configuration and the OH ligands act as monodentate O-bound planar. 2 exhibits good antitumor activity against KB cells (IC50=0.90μM) and 4 shows significant antibacterial activity against Gram-positive bacteria Staphylococcus aureus (MIC=0.147μg/ml), both being even higher than those of clinically used drugs.

Synthesis, characterization and biological studies of diorganotin(IV) complexes with tris[(hydroxymethyl)aminomethane] Schiff bases

Several Schiff base ligands derived from tris(hydroxymethyl)aminomethane were synthesized and a series of diorganotin(IV) complexes were obtained from the reaction of diorganotin dichlorides or oxides with Schiff base ligands. The ligands and complexes have been characterized by elemental analysis, IR, 1H, 13C and 119Sn NMR spectroscopies. Single-crystal X-ray diffraction analysis reveals that bis[(2-{[1,1-bis(hydroxymethyl)-2-oxidoethyl]iminomethyl}phenolato)]dimethyltin(IV), 1 and bis[(2-{[1,1-bis(hydroxymethyl)-2-oxidoethyl]iminomethyl}-4-bromophenolato)]dimethyltin(IV), 7 are dimeric structures, in which the central tin atom is rendered six-coordinate while (2-{[1,1-bis(hydroxymethyl)-2-oxidoethyl]iminomethyl}-4-bromophenolato)diphenyltin(IV), 9, (2-{[1,1-bis(hydroxymethyl)-2-oxidoethyl]iminomethyl}-4-chlorophenolato)dimethyltin(IV), 13, (2-{[1,1-bis(hydroxymethyl)-2-oxidoethyl]iminomethyl}-4-chlorophenolato)diphenyltin(IV), 15 and (2-{[1,1-bis(hydroxymethyl)-2-oxidoethyl]iminomethyl}-4-chlorophenolato)dicyclohexyltin(IV), 16 are monomeric structures, whereby the tin atom is in a distorted trigonal–bipyramidal configuration. The Schiff bases and their corresponding diorganotin(IV) complexes have been evaluated against three human carcinoma cell lines, namely HT29 (human colon carcinoma cell line), SKOV-3 (human ovarian cancer cell line) and MCF-7 (hormone-dependent breast carcinoma cell line), for its in vitro cytotoxic activities. The dibutyltin and dicyclohexyltin derivatives of the Schiff base ligands display good cytotoxic activities against the tested cell lines.

Syntheses and characterization of organostannoxanes derived from 2-chloroisonicotinic acid: Tetranuclear and hexanuclear

Three types of ladder-like organostannoxanes, [(Me2Sn)2(μ3-O)L2]2 (1), [(n-Bu2Sn)2(μ3-O) (μ-OH)L]2 (2), [(Ph2Sn)2(μ3-O) (μ-OH)L]2 (3), [(Bz2Sn)2(μ3-O) (μ-OH)L]2 (4) and [(Me2Sn)2(μ3-O) (μ-OSnMe3)L]2 (5) (LH=2-chloroisonicotinic acid), have been synthesized by the treatment of 2-chloroisonicotinic acid and the corresponding diorganotin(IV) dichloride or trimethyltin(IV) chloride with sodium ethoxide in methanol. All of the complexes have been fully characterized by elemental analysis and FT-IR, NMR (1H, 13C, and 119Sn) spectroscopy, and particularly for 1, 2, 4 and 5, by X-ray crystallography. The structural analyses of 1, 2 and 4 reveal them to be tetranuclear, possessing two different ladder-like structures. Complexes 5 is also a ladder-like structure, but the essential difference from 1 to 4 is that complex 5 is a hexanuclear complex containing mixed tri- and dimethyltin units, where the central tetranuclear Sn4O4 motif is bridged by two μ-OSn(Me)3 groups. A series of O–H⋯O, O–H⋯N and C–H⋯Cl intermolecular hydrogen bonds in these complexes play an important function in the supramolecular aggregation, and 2D network structures are formed by these interactions.