Short Sn Research Articles

The First Planar, Not Twisted, Distannene - A Structural Alkene Analog. Synthesis, Isolation and X-ray Crystallography Characterization.

The tetrasilyl-substituted distannene, (tBu2 HSi)2 Sn=Sn(SiHtBu2 )2 6, was synthesized by mild thermolysis (70 °C in hexane) of tris(di-tert-butyl-hydridosilyl)stannane 4. The X-ray crystallography structure of 6 reveals the following unusual structural properties: a planar geometry around both Sn atoms (Σ∡Sn=359.87°), a non-twisted Sn=Sn double bond, and the shortest Sn=Sn double bond of 2.599 Å among all acyclic distannenes. Thus, compound 6 is the first reported distannene having a structure closely analogous to a classic alkene. Reactions of 6 with CCl4 or with 2,3-dimethylbuta-1,3-diene to produce 1,2-dichlorodistannane 9 and the [2+4] cycloadduct 10, respectively, are characteristic for a Sn=Sn double bond.

The Imino Stannylene SnNH Incorporated in a Molecular Tin‐Nitrogen Cage and other Tin(II)‐Nitrogen Derivatives

The iminostannylene HNSn was successfully incorporated in a molecular cage of composition (Me2RSi–NSn)3(HNSn) with group R either being a methyl (1) or vinyl (2) substituent. An X‐ray structure analysis reveals that 2 consists of a distorted Sn4N4 cube. The Sn–N(H) bond lengths [2.189(2) Å] are in the range for Sn4N4 hetero cubanes. When stored in a toluene solution the clusters 1 and 2 decompose slowly into the symmetric cubanes (Me2RSi–NSn)4 [R = Me (3), CHCH2 (4)] and an amorphous and insoluble powder of composition HNSn. The decomposition follows a first order rate law as established for 2 with a half life time t1/2 = 320 d at 20 °C. The compounds 1 and 2 can thus be regarded as a result of interaction between three entities {Me2RSi–NSn} and one entity {HNSn}. We also isolated the twistane‐like Me2Si(NtBu)2Sn2NtBu (5) in a crystalline form. The central structure of this molecule, which has almost C2v symmetry, has a trigonal bipyramid Sn2N3 unit with the nitrogen atoms occupying the equatorial plane. Each nitrogen atom has a tert‐butyl ligand and two of the N atoms are further connected by the dimethylsilyl group. There is one nitrogen atom in an almost planar environment (only bonding to tert‐butyl and two tin atoms) with a remarkable short Sn–N bond length of 2.048(5) Å. Both tin atoms in cage 5 can bond to Cr(CO)5 to form [Me2Si(NtBu)2Sn2NtBu][Cr(CO)5]2 (6) with an almost linear Cr–Sn···Sn–Cr arrangement and Sn–Cr bond lengths of 2.581(1) Å (X‐ray diffraction).

Antioxidative vs cytotoxic activities of organotin complexes bearing 2,6‐di‐tert‐butylphenol moieties

Two series of organotin(IV) complexes with Sn–S bonds on the base of 2,6‐di‐tert‐butyl‐4‐mercaptophenol (L1SH) of formulae Me2Sn(L1S)2 (1); Et2Sn(L1S)2 (2); Bu2Sn(L1S)2 (3); Ph2Sn(L1S)2 (4); (L1)2Sn(L1S)2 (5); Me3Sn(L1S) (6); Ph3Sn(L1S) (7) (L1 = 3,5‐di‐tert‐butyl‐4‐hydroxyphenyl), together with the new ones [Me3SnCl(L2)] (8), [Me2SnCl2(L2)2] (9) (L2 = 2‐(N‐3′,5′‐di‐tert‐butyl‐4′‐hydroxyphenyl)‐iminomethylphenol) were used to study their antioxidant and cytotoxic activity. Novel complexes 8, 9 of MenSnCl4 − n (n = 3, 2) with Schiff base were synthesized and characterized by 1H, 13C NMR, IR and elemental analysis. The crystal structures of compounds 8 and 9 were determined by X‐ray diffraction analysis. The distorted tetrahedral geometry around the Sn center in the monocrystals of 8 was revealed, the Schiff base is coordinated to the tin(IV) atom by electrostatic interaction and formation of short contact Sn–O 2.805 Å. In the case of complex 9 the distorted octahedron coordination of Sn atom is formed. The antioxidant activity of compounds as radical scavengers and reducing agents was proved spectrophotometrically in tests with stable radical DPPH, reduction of Cu2+ (CUPRAC method) and interaction with superoxide radical‐anion. Moreover, compounds have been screened for in vitro cytotoxicity on eight human cancer cell lines. A high activity against all cell lines with IC50 values 60–160 nM was determined for the triphenyltin complex 7, while the introduction of Schiff base decreased the cytotoxicity of the complexes. The influence on mitochondrial potential and mitochondrial permeability for the compounds 8 and 9 has been studied. It is shown that studied complexes depolarize the mitochondria but don't influence the calcium‐induced mitochondrial permeability transition.

Tin···Oxygen Tetrel Bonding: A Combined Structural, Spectroscopic, and Computational Study

A series of R2Sn (R = Me, Ph) complexes of the Schiff’s base salicylaldehyde acyldihydrazone with a methylene spacer of variable length have been structurally characterized in order to explore the prevalence of Sn···O noncovalent interactions. Structural studies show that these can exist, with the shortest Sn···O distance of 3.480(2) A in this library of compounds, significantly shorter than the sum of the van der Waals radii (3.92 A). Crystallographic studies also show that steric effects are important, and these interactions are seen only for compounds with Me2Sn while they are not observed for Ph2Sn. However, this is not simply a steric effect, and C–H···O interactions can compete with these Sn···O interactions. A computational study, in combination with the quantum theory of atoms in molecules, shows that these interactions are mostly electrostatic in origin with little evidence of covalency.

Interfacial reaction of SnII on mackinawite (FeS)

The interaction of SnII with metastable, highly reactive mackinawite is a complex process due to transient changes of the mackinawite surface in the sorption process. In this work, we show that tin redox state and local structure as investigated by Sn–K X-ray absorption spectroscopy (XAS) change with pH. We observe at pH<7 that divalent Sn forms two short (2.38Å) Sn–S bonds to the S-terminated surface of mackinawite, and two longer (2.59Å) Sn–S bonds pointing most likely towards the solution phase, in line with a SnS4 innersphere sorption complex. Precipitation of SnS or formation of a solid solution with mackinawite could be excluded. At pH>9, SnII is completely oxidized to SnIV by an FeII/FeIII (hydr)oxide, most likely green rust, forming on the surface of mackinawite. Six O atoms at 2.04Å and 6 Fe atoms at 3.29Å indicate a structural incorporation by green rust, with SnIV substituting for Fe in the crystal structure. The transition between SnII and SnIV and between sulfur and oxygen coordination takes place at a pH of 7 to 8 and an Eh of −250mV, close to the thermodynamically predicted transitions from mackinawite to Fe (hydr)oxide and from sulfide to sulfate. The uptake processes of SnII by mackinawite are largely in line with the uptake processes of divalent cations with soft Lewis-acid character like Cd, Hg and Pb, and lead to a strong retention of Sn with logRd values from 5 to 7 across the investigated pH range of 5 to 11.

Flux Synthesis and Crystal Structure Determination of the Colored Skutterudite Ir2Sn3Se3

AbstractThe skutterudite (CoSb3) related crystal structure of Ir2Sn3Se3 = IrSn1.5Se1.5 is determined from single crystal data for the first time. High temperature solid state and flux reactions were applied to prepare powder and single crystals samples. Its crystal structure was refined from data of a fourfold twin crystal in space group R$\bar{3}$ (no. 148). It contains 24 formula units per unit cell [a = 12.6510(3) Å, c = 15.5236(6) Å, V = 2151.67(8) Å3] and represents the first single crystal determination of a colored skutterudite Ir2A3X3 = Ir(A, X)3 with heteroatomic [Sn2Se2] units and [Sn3Se3] coordination for Ir sites. The distorted Sn2Se2 rings show short and long Sn–Se distances. The obtained structure is isotypic to Ir2Sn3Te3 but differs from the cubic model estimated earlier for Ir2Sn3S3 (homoatomic Sn4 and S4 units). According to electronic band structure calculations Ir2Sn3Se3 is a low gap semiconductor (ΔE = 0.4 eV).

Metal‐Centered Zintl Ions Isolated by Direct Extraction from Endohedral Intermetallic Precursor: [Co1–x@Sn9]4– (x ≈ 0.32) and [Co2@Sn17]5–

AbstractTwo new compounds with Co‐centered Sn9 clusters were obtained by the extraction directly from the intermetallic precursor K4.79Co0.79Sn9 in ethylenediamine with addition of cryptand [2.2.2]. The anions [Co0.68@Sn9]4– in K[K([2.2.2]crypt)]3[Co0.68@Sn9] (1) consisting of overlaying [Co@Sn9]4– and [Sn9]4– cluster anions are connected by K atoms to form infinite $\rm^{1}_{\infty}$K[Co0.68@Sn9] chains. The anions [Co2@Sn17]5– in [K([2.2.2]crypt)]5[Co2@Sn17]·en·tol (2) are built from two [Co@Sn9] sharing one common Sn atom, with the same composition but a different conformation as in the previously reported [K([2.2.2]crypt)]5[Co2@Sn17]. Quantum chemical calculations for the different conformers of [Co2@Sn17]5– reveal that both conformers are rather close in energy and that the short intercluster Sn–Sn distance in 2 does not originate from attractive interactions.

N,N′-Fused Bisphosphole: Heteroaromatic Molecule with Two-Coordinate and Formally Divalent Phosphorus. Synthesis, Electronic Structure, and Chemical Properties

The reduction of 6,12-dichloro-1,2,3,4,7,8,9,10-octahydro-6H,12H-[1,2,3]benzodiazaphospholo[2,1-a][1,2,3]benzodiazaphosphole (3) by metallic magnesium in tetrahydrofuran (THF) affords the N,N'-fused bisphosphole 1 in 92% yield. The compound reveals a novel type of 10π-electron heteroaromatic system [NICS(0) = -11.4], containing a two-coordinate and formally divalent phosphorus atom. Compound 1 possesses a much higher coordination activity than many other diazaphospholes. This is caused by a novel type of complexation to a metal ion wherein the lone phosphorus pairs are not involved in metal coordination. Instead, the 10π-electron heteroaromatic system provides two electrons for P → M bond formation. Polarization of the ligand results in the formation of extended molecular associates or cluster compounds. Complexes of 1 with mercury dichloride [{(1)3HgCl}2(μ6-Cl)](+)Cl(-) (7) and tin dichlorides [1·SnCl2(PhMe solvate)] (8a) and [1·SnCl2] (8b) are, in fact, supramolecular in nature, containing multiple intermolecular short contacts. Crystals of complex 8a containing short Sn···Sn packing interactions were converted reversibly to metallic tin after workup with THF. The simple mixing of 1 and 3 (1:1) gave a P-P bridging dimeric species prone to easy dissociation. The addition of GeCl2(diox) to the equimolar mixture of 1 and 3 shifted the equilibrium to the formation of a poorly soluble salt-like dimer 6, which is, in fact, a stacked 18π-electron dication having a through-space delocalization of π electrons.

An Empirical Research on Consumers' Purchasing Behavior of Virtual Products in SNS

Based on the research of Social Networking Sites (for short SNS), the study involves the trading of virtual product development status, collates and summarizes the research results in China and abroad on consumers buying behavior of virtual products. The researchers attempt to explore factors influencing consumers to buy SNS virtual products by using questionnaires to collect personal information of SNS customers. In addition, the Theory of Planned Behavior (for short TPB) has been selected as theoretical model and the empirical analysis uses structural equation modeling method to analyze the factors affecting several different groups of users of SNS who will be the consumers or potential consumers of virtual products. The findings are as follows: (1) the passionate export-oriented consumer attitudes towards virtual product of SNS will clearly and directly affect the type of the Behavioral Intention (for short BI) of buyers of virtual products; the perceived behavioral control can even directly affect the final actual purchase behavior. (2) The Subjective Norm (for short SN) of traditional inward-oriented consumers has a significant impact on virtual product purchase behavior and will also directly affect the final purchase behavior. (3) The SNS under self-supporting consumers on virtual product attitudes and purchasing attitudes of virtual products mainly affected their BI.

Speciation and structure of tin(II) in hyper-alkaline aqueous solution.

The identity of the predominating tin(ii)-hydroxide complex formed in hyper-alkaline aqueous solutions (0.2 ≤CNaOH≤ 12 mol dm(-3)) is determined by potentiometric titrations, Raman, Mössbauer and XANES spectroscopy, supplemented by quantum chemical calculations. Thermodynamic studies using a H2/Pt electrode up to free hydroxide concentrations of 1 mol dm(-3) showed the presence of a single monomeric complex with a tin(II) : hydroxide ratio of 1 : 3. This observation together with Raman and Mössbauer spectroscopic measurements supplemented by quantum mechanical calculations proved that the predominating complex is [Sn(OH)3](-), and that the presence of the other possible complex, [SnO(OH)](-), could not be proven with either experiments or simulations. The structure of the trihydroxidostannate(II) complex, [Sn(OH)3](-), was determined by EXAFS and was found to be independent of the applied hydroxide and tin(II) concentrations. The mean Sn-O bond distance is short, 2.078 Å, and in very good agreement with the only structure reported in the solid state. It is also shown that at pH values above 13 the speciation of the predominant trihydroxidostannate(II) complex is not affected by the presence of high concentrations of chloride ions.

(O-Methyl dithiocarbonato-κS)triphenyltin(IV)

In the title compound, [Sn(C6H5)3(C2H3OS2)], the SnIV atom adopts a distorted SnC3S tetra­hedral coordination geometry. A short Sn⋯O contact [2.988 (4) Å] is also present. The phenyl rings are each disordered over two sets of sites with an occupancy ratio of 0.550 (8):0.450 (8). The crystal studied was found to be a racemic twin with a twin component ratio of 0.57 (18):0.43 (18).

Low-temperature redetermination of tribenzylchloridotin(IV)

Compared to the previous studies [Ng (1997 ▶). Acta Cryst. C53, 56–58; Yin et al. (2005 ▶). Huaxue Shiji, 27, 295–296], the redetermined structure of the title compound, [Sn(C7H7)3Cl], exhibits a doubled c unit-cell parameter. There are two mol­ecules in the asymmetric unit, with both Sn and both Cl atoms having 3 site symmetry. The Sn atoms have distorted SnClC3 tetra­hedral geometries and the mol­ecules inter­act by way of short Sn⋯Cl bridges [Sn⋯Cl = 3.418 (2) and 3.475 (2) Å], thereby forming chains propagating in c.

Octa-n-butyl-1κ2C,2κ2C,3κ2,4κ2C-bis(μ-2,3-dibromopropionato)-1:2κ2O:O′,3:4κ2O:O′-bis(2,3-dibromopropionato)-1κO,3κO-di-μ3-oxido-1:2:4κ3O:O:O,2:3:4κ3O:O:O-tetratin(IV)

In the centrosymmetric tetra­nuclear title complex, [Sn4(C4H9)8(C3H3Br2O2)4O2], one of the two independent Sn atoms is five-coordinated by one O atom of the carboxyl­ate anion, two bridging O atoms and two n-butyl groups in a C2SnO3 distorted trigonal bipyramidal geometry. The other Sn atom also has a distorted trigonal bipyramidal geometry, being coordinated by two O atoms of two carboxyl­ate anions, one bridging O atom and two butyl groups. An inter­esting feature of the crystal structure is the short Sn⋯O [2.756 (4) Å] and O⋯O [2.608 (3) Å] inter­actions. The –BrCH2—CHBr– segments of the two carboxyl­ate anions are disordered over two positions [site occupancies of 0.60 (1)/0.40 (1) and 0.53 (2)/0.47 (2)]. Weak non-directional C—H⋯O inter­actions lead to the formation of infinte chains along the a axis; other weak inter­molecular C—H⋯π inter­actions are also present.

2-(1,3-Dithiolan-2-ylidene)-5-(4-methylphenyl)-3-oxopent-4-enoato-κO]triphenyltin(IV)

In the title compound, [Sn(C6H5)3(C17H17O3S2)], the SnIV atom adopts a distorted tetra­hedral SnC3O geometry. A short intra­molecular Sn⋯O contact of 2.793 (2) Å also occurs.

Tetrakis(phenylethynyl)tin(IV)

The asymmetric unit of the crystal structure of the title compound, [Sn(C8H5)4], consists of one fourth of a discrete tin complex and one half of another which both possess nearly ideal tetrahedral symmetry; the site symmetries of the two Sn atoms are \overline4 and 2. The bond angles at all acetylide C atoms are almost linear. The Sn—C distances [2.076 (6) and 2.065 (6)–2.069 (6) Å in the two complexes) are short when compared to the sum of the covalent radii of C and Sn (2.177 Å), but consistent with another tetrakis(alkynyl)tin complex. The acetylenic bond distances [1.196 (7) and 1.183 (7)–1.207 (7) Å] are consistent with a triple C[triple-bond]C bond. Therefore, despite the short Sn—C distances, the ligands are mainly σ-bonded to the metal. In the solid state, these complexes form a three-dimensional network via agostic C—H interactions as a phenyl proton in the ortho position interacts with the acetylenic carbon in the α position to the tin center.

Crystal structure and chemical bonding in tin(II) acetate

Tin(II) acetate was prepared and its crystal structure was solved from X-ray powder diffraction data. Tin(II) acetate adopts a polymeric structure consisting of infinite Sn(CH 3COO) 2 chains running along the c-axis which are packed into groups of four. The acetate groups bridge the Sn atoms along the chains. The Sn atoms are asymmetrically surrounded by four oxygen atoms with two short Sn–O distances (2.170(6), 2.207(6) Å) and two longer ones (2.293(7), 2.372(8) Å). The coordination environment of the Sn atoms is completed up to a strongly distorted trigonal bipyramid SnO 4E by the sterically active lone electron pair E. The coordination environment of the Sn atoms is virtually identical for Sn(CH 3COO) 2 in the gaseous and solid phase: the two short Sn–O bonds and the lone electron pair are located in the equatorial plane of the trigonal bipyramid and the two longer Sn–O bonds are directed towards the apical vertexes. Localization of the lone electron pair on Sn(II) was confirmed by electron localization function (ELF) analysis. The polymeric nature of the tin(II) acetate crystal structure was confirmed by a MALDI-TOF experiment.

μ-Fumarato-κ2O:O′-bis[tris(2-methyl-2-phenylpropyl)tin(IV)

In the centrosymmetric title compound, [Sn2(C10H13)6(C4H2O4)], the Sn atom adopts a distorted tetra­hedral SnC3O geometry, with a mean Sn—C distance of 2.143 (3) Å and with Sn—O = 2.070 (2) Å. A short Sn⋯O contact of 3.072 (4) Å is also present.

Stress analysis of spontaneous Sn whisker growth

Spontaneous Sn whisker growth is a surface relief phenomenon of creep, driven by a compressive stress gradient. No externally applied stress is required for the growth, and the compressive stress is generated within, from the chemical reaction between Sn and Cu to form the intermetallic compound Cu6Sn5 at room temperature. To obtain the compressive stress gradient, a break of the protective oxide on the Sn surface is required because the free surface of the break is stress-free. Thus, spontaneous Sn whisker growth is unique that stress relaxation accompanies stress generation. One of the whisker challenging issues in understanding and in finding effective methods to prevent spontaneous Sn whisker growth is to develop accelerated tests of whisker growth. Use of electromigration on short Sn stripes can facilitate this. The stress distribution around the vicinity and the root of a whisker can be obtained by using the micro-beam X-ray diffraction utilizing synchrotron radiation. A discussion of how to prevent spontaneous Sn whisker growth by blocking both stress generation and stress relaxation is given.

Progress in the Understanding of Drug–Receptor Interactions, Part 1: Experimental Charge‐Density Study of an Angiotensin II Receptor Antagonist (C30H30N6O3S) atT=17 K

An experimental study of the electron-density distribution rho(r) in an angiotensin II receptor antagonist 1 has been made on the basis of single-crystal X-ray diffraction data collected at a low temperature. The crystal structure of 1 consists of infinite ribbons in which molecules are connected by an N-H...N hydrogen bond and several interactions of the C-H...O, C-H...N, and C-H...S type. The molecular conformation, characterized by the syn orientation of a tetrazole and a pyrimidinone ring with respect to a phenyl spacer group, is stabilized by two short SO and SN intramolecular contacts between a substituted thiophene fragment and the other two heterocycles of 1. The electrostatic nature of these interactions is documented. Furthermore, the Laplacian of rho(r) in the plane defined by the sulfur, oxygen, and nitrogen atoms involved in these interactions shows their strongly directional character as the regions of charge concentration on the valence shell of the nitrogen and oxygen atoms directly face the regions of charge depletion on the valence shell of the sulfur atom. All the chemical bonds and the relevant intra- and intermolecular interactions of 1 have been quantitatively described by the topological analysis of rho(r). Simple relationships between the bond path lengths (R(b)) and the values of rho at the bond critical points (rho(bcp)) have been obtained for the 28 C-C bonds, the seven N-C bonds, and the four O-C bonds. For the first two classes of bonds the relationship is in the form of a straight line, whose parameters, for the C-C bonds, agree, within experimental uncertainty, with those previously derived in our laboratory from a 19 K X-ray diffraction study of crystals of a different compound. Maps of the molecular electrostatic potential phi(r) derived from the experimental charge density display features that are important for the drug-receptor recognition of 1.

Triorganotin Fluoride Structures: A Ligand Close‐Packing Model with Predominantly Ionic Sn−F Bonds

AbstractThe synthesis and complete characterization by multinuclear NMR, infrared, and Mössbauer spectroscopy, by single crystal X‐ray analysis, as well as by electrospray mass spectrometry of the new soluble triorganotin fluoride Me2PhSnF (1) is reported. The crystal structure of 1 reveals a rod‐like polymeric structure in the solid state. Solutions of 1 in apolar solvents, such as toluene, contain mixtures of interconvertible oligomers. Ab initio MO calculations on model compounds H3SnF, [H3SnFSnH3]+, and [FH3SnFSnH3F]− indicate that the Sn−F bonds are substantially ionic in character, and suggest open‐chain species, rather than cyclic species. In donor solvents, such as pyridine, 1 forms complexes with the solvent, such as Me2PhSnF·pyridine. The solid‐state structure of (Me3SiCH2)3SnF (2) is reformulated as monomeric with a weak intermolecular Sn···F interaction that gives rise to a [4+1] coordination. The relative short Sn−Sn separation enables the fluorine atoms to oscillate (flip‐flop) between two neighboring (Me3SiCH2)3Sn− groups, which is expressed in the X‐ray experiment by a dynamic disorder. Ab initio MO calculations on a model compound, [H3SnFSnH3]+, suggest only a small energy barrier for the flip‐flop motion. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2003)