Bioactive versatile azomethine complexes of organotin(IV) and organosilicon(IV)

Diorganotin(IV) and diorganosilicon(IV) derivatives of the types R₂MCl(TSCZ) and R₂M(TSCZ)₂ (where TSCZ is the anion of a thiosemicarbazone ligand, R=Ph or Me and M=Sn or Si) have been synthesized and characterized by elemental analyses, molecular weight determinations and conductivity measurements. The mode of bonding has been established on the basis of IR and ¹H, ¹³C ²⁹Si and ¹¹⁹Sn NMR spectroscopic studies. Some of the representative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria in vivoas well as in vitro.The results of these investigations are reported. © 1998 John Wiley & Sons, Ltd.     

Diorganotin(IV) and triorganotin(IV) derivatives of diphenic acid

The diorganotin(IV) and triorganotin(IV) derivatives R₂SnA (R = Me, n-Pr, n-Bu, n-Oct) and (R₃Sn)₂A [R = Me, Ph, cyclohexyl (Cyh); A = an anion of diphenic acid] have been prepared and characterized by elemental analysis, IR, ¹H and ¹³C NMR spectroscopies. Tetrahedral tin forms a part of a diphenate cyclic ring in the diorganotin complexes with unidentate carboxylates, which have further been used for the synthesis of cyclic acid anhydrides. The soluble dinuclear triorganotin complexes (Me, Ph) possess symmetrically bonded carboxylates while the less soluble compound (Cyh₃Sn)₂A has two asymmetrically bonded carboxylates. All have a trigonal bipyramidal structure with R₃Sn units remote from each other.     

Two-phase reactions of tin(IV)–tetraphenylporphine complexes as carrier of anion selective electrodes

Two-phase reactions of [Sn(OH)₂(tpp)] with lipophilic anions and inorganic acids were studied and compared with those of [Zr(OH)₂(tpp)] having the same oxidation state of the central metal ion but different structural characteristics. The reaction with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate formed a 2:1 cationic dimer and 1:1 and 1:2 ion-pairs, while the reaction with dodecyl sulfate formed 1:1 and 1:2 ion-pairs. The 1:1 and 1:2 species formed concomitantly in the reaction with HCl and CH₃COOH having higher coordination abilities, while forming in stepwise manner in the reaction with HClO₄ and HNO₃ having lower coordination abilities. The 2:1 cationic dimer of Sn(IV) had significantly lower stability than that of Zr(IV). The affinity of Sn(IV) for Cl⁻ relative to OH⁻ was much higher, compared with Zr(IV). Except in extremely acidic media, [SnCl₂(tpp)] working as a carrier in PVC membranes hydrolyzed to give [Sn(OH)Cl(tpp)] or [Sn(OH)₂(tpp)], which showed stronger but less-selective potential responses at lower pH and weaker but more-selective responses to salicylate at higher pH. The affinities and responses of Sn(IV) complexes to oxygen-containing anions were weaker than those of Zr(IV) complexes.     

Structure and properties of double‐C,N‐chelated tri‐ and diorganotin(IV) halides

Tri‐ and di‐organotin(IV) compounds containing one or two 2‐(dimethylaminomethyl)phenyl‐ (L^CN) groups as chelating ligands were prepared by reactions of lithium compound L^CNLi with an appropriate amount of (organo)tin halide. The geometry of tin in 1 ((L^CN)₂SnPhCl) is on the boundary between octahedral and trigonal bipyramidal. The diorganotin compounds 2–4 ((L^CN)₂SnX₂, where X = Cl, Br, I) have a distorted octahedral geometry in the solid state and show dynamic processes in solution with a lowering of activation energy of the dynamic process going from diiodide to dichloride derivative. Compound 5 (L^CNSnPhCl₂) has a trigonal bipyramidal structure with non‐equivalent chlorine atoms. Copyright © 2005 John Wiley & Sons, Ltd.     

Highly efficient protection of alcohols and phenols catalysed by tin porphyrin supported on MIL‐101

The catalytic activity of 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrinatotin(IV) trifluoromethanesulfonate, [Sn^IV(TNH₂PP)(OTf)₂], supported on chloromethylated MIL‐101, was investigated in the trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) and also their tetrahydropyranylation with 3,4‐dihydro‐2H‐pyran. Excellent yields, mild reaction conditions, short reaction times and reusability of the catalyst without significant decrease in its initial activity are noteworthy advantages of this supported catalyst. Copyright © 2015 John Wiley & Sons, Ltd.     

Organosilicon(IV) and organotin(IV) complexes as biocides and nematicides: synthetic,spectroscopic and biological studies of N∩N donor sulfonamide imine and its chelates

A brief account is given of the synthesis and stereochemistry and the antibacterial, antifungal, nematicidal and insecticidal behaviour of organosilicon(IV) and organotin(IV) complexes of a biologically potent ligand, 2‐acetylfuransulfaguanidine. The unimolar and bimolar substitution products have been characterized by elemental analyses, conductance measurements, molecular weight determinations, and spectral studies, viz. IR, ¹H NMR, ¹³C NMR, UV, ²⁹Si NMR and ¹¹⁹Sn NMR spectra. The data support the binding of the nitrogen atom to the metal atom in R₃M(N^∩N), [R₂M(N^∩N)₂ and R₂M(N^∩N)Cl [(R = Me/Ph and M = Si(IV) and Sn(IV)] types of complex. Based on these studies, with coordination number five and six a trigonal bipyramidal and an octahedral geometry have been proposed for the resulting derivatives. The free ligand (N^∩NH) and its respective metal complexes were tested in vitro against a number of microorganisms to assess their antimicrobial properties. The results are indeed positive. In addition to these studies, the complexes also show good nematicidal and insecticidal properties. The results of these findings have been discussed in detail. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis and characterization of tin(IV)/organotin(IV) complexes with 2-benzoylpyridine-N(4)-cyclohexylthiosemicarbazone [HBPCT]: X-ray crystal structure of [SnCl3(BPCT)]

Four new tin(IV)/organotin(IV) complexes, [SnCl₃(BPCT)] (2), [MeSnCl₂(BPCT)] (3), [Me₂SnCl(BPCT)] (4), and [Ph₂SnCl(BPCT)] (5), have been synthesized by the direct reaction of 2-benzoylpyridine-N(4)-cyclohexylthiosemicarbazone [HBPCT, (1)] and stannic chloride/organotin(IV) chloride(s) in absolute methanol under purified nitrogen. HBPCT and its tin(IV)/organotin(IV) complexes (2–5) were characterized by CHN analyses, molar conductivity, UV-Vis, FT-IR, and ¹H NMR spectral studies. In all the complexes, tin(IV) was coordinated via pyridine-N, azomethine-N, and thiolato-S from 1. The molecular structure of 2 has been determined by X-ray single-crystal diffraction analysis. Complex 2 is a monomer and the central tin(IV) is six-coordinate in a distorted octahedral geometry. The crystal system of 2 is monoclinic with space group P121/n1 and the unit cell dimensions are a?=?8.3564(3)?Å, b?=?23.1321(8)?Å, c?=?11.9984(4)?Å.     

Rapid,highly efficient and chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by reusable electron‐deficient tin(IV)porphyrin

In this paper, rapid and highly efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) in the presence of catalytic amounts of high‐valent [Sn^IV(TPP)(OTf)₂] is reported. This catalytic system catalyzes trimethylsilylation of primary, secondary and tertiary alcohols as well as phenols, and the corresponding TMS‐ethers were obtained in high yields and short reaction times at room temperature. It is noteworthy that this method can be used for chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times without loss of its catalytic activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Interaction of methyltin(IV) compounds with carboxylate ligands. Part 1: formation and stability of methyltin(IV)–carboxylate complexes and their relevance in speciation studies of natural waters

Quantitative data on the stability of mono‐, di‐ and trimethyltin(IV)‐carboxylate complexes (acetate, malonate, succinate, malate, oxydiacetate, diethylenetrioxydiacetate, tricarballylate, citrate, butanetetracarboxylate and mellitate) are reported at t = 25 °C and I→ 0 mol l^?1. Several mononuclear, mixed proton, mixed hydroxo and polynuclear species are formed in these systems. As expected, the stability trend is mono‐ > di‐ > trimethyltin(IV) and mono < di < tri < tetra < hexa for the organotin moieties and carboxylate ligands investigated, respectively. Moreover, ligands containing, in addition to carboxylic,? O? and? OH groups show a significantly higher stability with respect to analogous ligands with the same number of carboxylic binding sites. The results obtained from all the systems investigated allowed us to formulate the following empirical predictive equation for correlation between complex stability and some simple structural parameters, (1) where n_carb and n_OH are the number of carboxylic and alcoholic groups in the ligand, respectively, r is the stoichiometric coefficient of H⁺ (positive) or OH^? (negative) and z_cat is the methyltin cation charge (CH₃)_xSn^z+ (z⁺ = 4 ? x). Distribution diagrams for some representative systems are also reported and are discussed in the light of speciation studies in natural waters. A literature data comparison is made with carboxylate complexes of other metal ions with the same charge as the organotin cations investigated here. Copyright © 2005 John Wiley & Sons, Ltd.     

π–π stacking motifs in dialkylbis{5‐[(E)‐2‐aryldiazen‐1‐yl]‐2‐hydroxybenzoato}tin(IV) complexes

The diorganotin(IV) complexes of 5‐[(E)‐2‐aryldiazen‐1‐yl]‐2‐hydroxybenzoic acid are of interest because of their structural diversity in the crystalline state and their interesting biological activity. The structures of dimethylbis{2‐hydroxy‐5‐[(E)‐2‐(4‐methylphenyl)diazen‐1‐yl]benzoato}tin(IV), [Sn(CH₃)₂(C₁₄H₁₁N₂O₃)₂], and di‐n‐butylbis{2‐hydroxy‐5‐[(E)‐2‐(4‐methylphenyl)diazen‐1‐yl]benzoato}tin(IV) benzene hemisolvate, [Sn(C₄H₉)₂(C₁₄H₁₁N₂O₃)₂]·0.5C₆H₆, exhibit the usual skew‐trapezoidal bipyramidal coordination geometry observed for related complexes of this class. Each structure has two independent molecules of the Sn^IV complex in the asymmetric unit. In the dimethyltin structure, intermolecular O—H…O hydrogen bonds and a very weak Sn…O interaction link the independent molecules into dimers. The planar carboxylate ligands lend themselves to π–π stacking interactions and the diversity of supramolecular structural motifs formed by these interactions has been examined in detail for these two structures and four closely related analogues. While there are some recurring basic motifs amongst the observed stacking arrangements, such as dimers and step‐like chains, variations through longitudinal slipping and inversion of the direction of the overlay add complexity. The π–π stacking motifs in the two title complexes are combinations of some of those observed in the other structures and are the most complex of the structures examined.     

Olefin polymerization by cyclopentadienyltris(dimethylamido)titanium(IV) complexes

Several titanium(IV) complexes of the type Cp′Ti(NMe₂)₃ [Cp′ = cyclopentadienyl ( 1 ), (dimethylaminoethyl)cyclopentadienyl ( 2 ), indenyl ( 3 ), and pentamethylcyclopentadienyl ( 4 )] were prepared, and their catalytic properties in the polymerization of α‐olefins were examined. Complexes 1 and 2 catalyzed the polymerization of ethylene in the presence of methylaluminoxane with a much higher activity than 3 or 4 . Complexes 3 and 4 polymerized ethylene with an activity similar to that of CpTiCl₃ ( 6 ). The preactivation of 2 , 3 , or 4 with trimethylaluminum (TMA) resulted in an increase in ethylene polymerization activities. Also, 1 and 2 were successfully used as ethylene/1‐hexene copolymerization catalysts, producing polymers with various amounts of 1‐hexene incorporation, depending on the amount of 1‐hexene in the feed mixture. Complex 1 likewise effectively polymerized styrene with a higher activity and higher syndiospecificity than the other three catalysts. Complexes 3 and 4 polymerized styrene with low syndiospecificity, whereas 2 produced only atactic polystyrene. The preactivation of 3 or 4 with TMA resulted in an increase in styrene polymerization activities and increased the syndiotacticity percentage of the polymers produced. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 313–319, 2001     

Synthesis and characterization of pentagonal bipyramidal organotin(IV) complexes of 2,6-diacetylpyridine Schiff bases of S-alkyl- and aryldithiocarbazates

New organotin(IV) complexes with empirical formula Sn(SNNNS)R₂, where SNNNS is the dianionic form of 2,6-diacetylpyridine Schiff bases of S-methyldithiocarbazate (H₂dapsme) or S-benzyldithiocarbazate (H₂dapsbz) and R = Ph or Me, have been prepared and characterized by IR, UV-Vis, NMR and Mössbauer spectroscopic techniques and conductance measurements. The molecular structures of the Sn(dapsme)R₂ (R = Ph and Me) have been determined by single crystal X-ray diffraction techniques. Both complexes have a distorted pentagonal-bipyramidal geometry in which the tin is coordinated by a dinegatively charged pentadentate chelating agent via pyridine nitrogen, two azomethine nitrogens, and two thiolate sulfurs. The five donors (N₃S₂) provided by the Schiff base occupy the equatorial plane close to a pentagonal planar array while the carbanion ligands occupy axial sites.     

Preparation and in vitro investigations of triphenyl[ω‐(tetrahydro‐2H‐pyran‐2‐yloxy)alkyl]tin(IV) compounds

The reaction of SnPh₃Li with X(CH₂)_n O–THP (THP = tetrahydro‐2H ‐pyran‐2‐yl; n  = 3, 4, 6, 8, 11; X = Cl, Br) afforded organotin(IV) compounds with the general formula Ph₃Sn(CH₂)_n O–THP ( 1 – 5 ). The tetraorganotin(IV) compounds were characterized using multinuclear NMR and infrared spectroscopies and high‐resolution mass spectrometry. Anticancer activity of the synthesized compounds was tested in vitro against the A2780 (ovarian), A549 (lung), HeLa (adenocarcinoma) and SW480 (colon) tumour cell lines with SRB assay. The in vitro investigations revealed that when a shorter chain was present a higher activity was achieved; however compounds 1 – 5 were found to be less active than cisplatin. In addition, the most active compound, 1 , enters A2780 cells and causes apoptosis by triggering both intrinsic and extrinsic caspase pathways.     

Anion exchange in trimethyl‐ and triphenyltin complexes with chromogenic ligands: solution equilibria and colorimetric anion sensing

A series of organotin(IV) compounds R₃Sn(A) where R = Me or Ph and A is a chromogenic nitrophenolate ligand were prepared and studied as possible colorimetric sensors for anions (F⁻, Cl⁻, Br⁻, AcO⁻, H₂PO₄⁻). Equilibrium constants for a complete set of reactions between R₃Sn(A) with A = 2‐amino‐4‐nitrophenolate (ANP) or 4‐nitrophenolate and anions (X⁻) involving formation of complexes R₃Sn(A)(X)⁻ and substitution products R₃Sn(X) and R₃Sn(X)₂⁻ were determined by UV‐vis and ¹H NMR titrations in MeCN and DMSO. The binding selectivity was AcO⁻ > F⁻ > H₂PO₄⁻ > Cl⁻ ≫ Br⁻ in both solvents and both for R = Me and Ph with higher affinity for R = Ph. Compounds with A = ANP were found to have the optimum properties as anion sensors allowing optical detection of F⁻, AcO⁻ and H₂PO₄⁻ anions in the 5–100 µM range by appearance of an intense absorption band of free ANP resulting from its substitution with the analyte. Selectivity and affinity of anion interactions with R₃Sn(ANP) are similar to those for thiourea receptors, but the organotin receptor produces a much larger naked eye detected optical signal, operates equally well in nonpolar and polar solvents and tolerates the presence of up to 20% vol. of water in DMSO. Copyright © 2011 John Wiley & Sons, Ltd.     

S,N‐Chelated organotin(IV) compounds containing 6‐phenylpyridazine‐3‐thiolate ligand—structural,antibacterial and antifungal study

A series of tri‐ and diorganotin(IV) compounds containing potentially chelating S,N‐ligand(s) (L^SN, where L^SN is 6‐phenylpyridazine‐3‐thiolate) were prepared and structurally characterized by multinuclear NMR spectroscopy. X‐ray diffraction techniques were used for determination of the structure of compounds containing one [(L^SN)Ph₂SnCl], two [(n‐Bu)₂Sn(L^SN)₂] and the combination of two L^SN and one L^CN [(L^CN)(n‐Bu)Sn(L^SN)₂] (where L^CN is {2‐[(CH₃)₂NCH₂]C₆H₄}‐) ligands. The coordination number of the tin atom varies from five to seven and is dependent on the number of chelating ligands present. The formation of the five‐membered azastanna heterocycle is favored over the formation of four‐membered azastannathia heterocycle in compounds containing both types of ligands. The di‐n‐butyl‐substituted compounds are the most efficient ones in inhibition of growth of yeasts, molds and G⁺ bacteria strains. Copyright © 2011 John Wiley & Sons, Ltd.     

Antimicorbial effects of newly synthesized organotin(IV) and organolead(IV) derivatives

Triorganotin(IV) and triorganolead(IV) derivatives of the types Me₃Sn(SCZ) and Ph₃Pb(SCZ) (where SCZ^? is the anion of a semicarbanzone ligand) have been synthesized by substitution reactions of trimethyltin chloride and triphenyl-lead chloride with semicarbazones derived from heterocyclic ketones. The resulting complexes have been characterized by elemental analyses, molecualr weight determinations and conductivity measurements. The mode of bonding has been established on the basis of infrared and ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopic studies. Some respresentative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria; the results of these investigations have been reported in the present paper.     

Hydrolysis of C,N‐chelated diorganotin(IV) chlorides and catalysis of transesterification reactions

Diorganotin(IV) dichlorides of formula L^CNRSnCl₂ (where R is nBu or Ph) containing one L^CN chelating ligand were hydrolyzed with aqueous sodium hydroxide in benzene. The composition of the products is strongly dependent on the amount of hydroxide. The partially hydrolyzed compounds of composition (L^CNRSnCl)₂(µ‐O) were isolated as crystalline products. A hydrolysis where more than one molar equivalent of NaOH is employed gave only a mixture of unidentifiable products. The structure of (L^CNPhSnCl)₂(µ‐O) was determined by X‐ray diffraction techniques in the solid state. In solution there was a mixture of diastereoisomers found, where the tin atoms serve as a stereogenic centers. The catalytic activity of starting dichlorides as well as (L^CNPhSnCl)₂(µ‐O) in various transesterification processes was investigated. The activity is very low in the case of starting dichlorides. When two molar equivalents of NaH are added or (L^CNPhSnCl)₂(µ‐O) is employed in the catalytic experiments, the activity is comparable to the literature data. Copyright © 2009 John Wiley & Sons, Ltd.     

Organometallic complexes with biological molecules. XIV. Biological activity of dialkyl and trialkyltin(IV) [meso‐tetra(4‐carboxy‐ phenyl)porphinate] derivatives

The effects of several organotin(IV) meso‐tetra(4‐carboxyphenyl)porphinate] derivatives with the general formula (R₂Sn)₂TPPC and (R₃Sn)₄TPPC (R = Me, Bu, Ph) were tested in vivo on ascidian embryonic development. Embryos at the two‐cell stage were incubated in 1 × 10⁻⁵ or 1 × 10⁻⁷ M solutions of various compounds. The ligand, [meso‐tetra(4‐carboxyphenyl)porphine] (H₄TPPC) was toxic at 1 × 10⁻⁵ M , because development was blocked at an early gastrula stage, whereas 1 × 10⁻⁷ M H₄TPPC allowed the eggs to develop up to the larva stage. The most toxic among the tested compounds was tributyltin(IV) [meso‐tetra(4‐carboxyphenyl)porphinate], (Bu₃Sn)₄TPPC, since the fertilized eggs were unable to divide into two cells, even at a concentration of 1 × 10⁻⁷ M . To correlate this embryonic arrest with the metabolic pathway, and especially to understand why cellular organelles first underwent chemical damage, 10⁻⁵ and 10⁻⁷ M (Bu₃Sn)₄TPPC‐cultured fertilized eggs were tested for DNA, RNA, protein, glucose, lipid and ATP contents, comparing the values obtained with those of control culture fertilized egg contents. The higher concentration (1 × 10⁻⁵ M ) reduced the content of all the tested compounds, but the lower one (1 × 10⁻⁷ M ), even if still unable to allow cleavage, reduced only the lipids and the ATP contents. A hypothesis concerning initial damage to mitochondrial membrane is proposed. Copyright © 2000 John Wiley & Sons, Ltd.     

Dioxobridged complexes of molybdenum (IV) and tungsten (IV) with N-alkylphenothiazines and their interactions with L-cysteine and L-histidine

Six new dioxobridged complexes of molybdenum (IV) and tungsten (IV) with N-alkylphenothiazines having the general formula M₂O₄(L)₂(H₂O)₂ [where M = molybdenum or tungsten and L = N-alkylphenothiazines] have been synthesised. The complexes have been characterised on the basis of analytical, molar conductance, magnetic susceptibility, spectral data, TGA and DTA. The low magnetic moments for the complexes are due to spin-spin interaction or metal-metal bonding. The interactions of these complexes with some biologically important amino acids have been studied.