Sn(20.5) square(3.5)As(22)I(8): a largely disordered cationic clathrate with a new type of superstructure and abnormally low thermal conductivity

Sn(20.5)As(22)I(8), a new cationic clathrate, has been prepared by using an ampoule technique. According to the X-ray powder diffraction data, it crystallizes in the face-centered cubic space group F23 or Fm(-)3 with a unit-cell parameter of a=22.1837(4) A. Single-crystal X-ray data allowed solution of the crystal structure in the subcell with a unit-cell parameter of a(0)=11.092(1) A and the space group Pm(-)3n (R=5.7 %). Sn(20.5)As(22)I(8) (or Sn(20.5) square(3.5)As(22)I(8), accounting for the vacancies in the framework) possesses the clathrate-I type crystal structure, with iodine atoms occupying the cages of the cationic framework composed of tin and arsenic atoms. The crystal structure is strongly disordered. The main features are a random distribution of vacancies, and shifts of the tin and arsenic atoms away from their ideal positions. The coordination of the tin atoms has been confirmed by using (119)Sn M?ssbauer spectroscopy. Electron diffraction and high-resolution electron microscopy (HREM) analyses have confirmed the presence of the superstructure ordering, which results in a doubling of the unit-cell parameter and a change of the space group from Pm(-)3n to either F23 or Fm(-)3. Analysis of the crystal structure has led to the construction of four ordering models for the superstructure, which have been corroborated by HREM, and has also led to the identification of disordered regions originating from overlap of the different types of ordered domains. Sn(20.5)As(22)I(8) is a diamagnetic semiconductor with an estimated band gap of 0.45 eV; it displays abnormally low thermal conductivity, with the room temperature value being just 0.5 W m(-1) K(-1).     

Unusually high chemical compressibility of normally rigid type-I clathrate framework: synthesis and structural study of Sn(24)P(19.3)Br(x)I(8)(-)(x) solid solution, the prospective thermoelectric material

A novel tin phosphide bromide, Sn(24)P(19.3(2))Br(8), and Sn(24)P(19.3(2))Br(x)()I(8)(-)(x) (x = 0-8) solid solution have been prepared and structurally characterized. All compounds crystallize with the type-I clathrate structure in the cubic space group Pmn (No. 223). The clathrate framework of the title solid solution shows a remarkable chemical compressibility: the unit cell parameter drops from 10.954(1) to 10.820(1) A on going from x = 0 to x = 8, a feature that has never been observed for normally rigid clathrate frameworks. The chemical compressibility as well as non-Vegard dependence of the unit cell parameter upon the bromine content is attributed to the nonuniform distribution of the guest halogen atoms in the polyhedral cavities of the clathrate framework. The temperature-dependent structural study performed on Sn(24)P(19.3(2))Br(8) has shown that, in contrast to the chemical compressibility, the thermal compressibility (linear contraction) of the phase is similar to that observed for the Group 14 anionic clathrates. The tin phosphide bromide does not undergo phase transition down to 90 K, and the atomic displacement parameters for all atoms decrease linearly upon lowering the temperature. These linear dependencies have been used to assess such physical constants as Debye temperature, 220 K, and the lattice part of thermal conductivity, 0.7 W/(m K). Principal differences between the title compounds and the group 14 anionic clathrates are highlighted, and the prospects of creating new thermoelectric materials based on cationic clathrates are briefly discussed.     

Unfolding Tin–Cobalt Interactions in Oxide‐Based Composite Electrodes for Li‐Ion Batteries by Mössbauer Spectroscopy

With a view to the development of new composite electrodes for lithium-ion batteries with electroactive tin and cobalt, Co-doped tin dioxide samples are studied. The role played by oxygen and cobalt atoms in the electrochemical behavior of tin-based electrodes for Li-ion batteries is examined by the powerful and selective (119)Sn M?ssbauer spectroscopy. For the discharged electrodes, the oxygen atoms in the lithia matrix tend to destabilize the Sn(0) atoms. In contrast, the presence of cobalt atoms helps to form a matrix that stabilizes the reduced tin atoms. Cobalt-tin interactions in electrochemical reduced Co(x)Sn(1-x)O(2) electrodes are deduced from the electrochemical and M?ssbauer results.     

Cationic cryptand complexes of tin(II)

A series of cationic cryptand complexes of tin(II), [Cryptand[2.2.2]SnX][SnX(3)] (10, X = Cl; 11, X = Br; 12, X = I) and [Cryptand[2.2.2]Sn][OTf](2) (13), were synthesized by the addition of cryptand[2.2.2] to a solution of either tin(II) chloride, iodide, or trifluoromethanesulfonate. The complexes could also be synthesized by the addition of the appropriate trimethylsilyl halide (or pseudohalide) reagent to a solution of tin(II) chloride and cryptand[2.2.2]. The complexes were characterized using a variety of techniques including NMR, Raman, and temperature-dependent M?ssbauer spectroscopy, mass spectrometry, and X-ray diffraction.     

Synthesis and spectroscopic and X-ray structural characterization of R2Sn(IV)-oxydiacetate and -iminodiacetate complexes

Seven novel R2Sn(IV)-oxydiacetate (oda) and -iminodiacetate (ida) compounds of the form [R2Sn(oda)(H2O)]2 (R = Me, nBu, and Ph) (1-3), [(R2SnCl)2(oda)(H2O)2]n (R = Et, iBu, and tBu) (4-6), and [Me2Sn(ida)(MeOH)]2 (7) have been synthesized and characterized by IR, 1H, 13C, and 119Sn NMR (solution), solid-state 119Sn CPMAS NMR, and (119m)Sn M?ssbauer spectroscopy. The crystal structure of [Me2Sn(oda)(H2O)]2, 1, shows it to be dinuclear (centrosymmetric), with two seven-coordinated tin atoms, bridged by one arm of the carboxylate group from each oda. By contrast, the crystal structure of [(Et2SnCl)2(oda)(H2O)2]n, 4, comprises a zigzag polymeric assembly containing a pair of different alternating subunits, {Et2SnCl(H2O)} and {Et2SnCl(H2O)(oda)}, which are connected by way of bridging oda carboxylates, thus giving seven-coordinate tin centers in both components. Finally, the structure of [Me2Sn(ida)(MeOH)]2, 7, also centrosymmetric dinuclear, is comprised of a pair of mononuclear units with seven-coordinate tin. The 119Sn solid-state CPMAS NMR and (119m)Sn Mossbauer suggest the presence of seven-coordinate Sn metal atoms in some derivatives and the existence of two different tin sites in the [(R2SnCl)2(oda)(H2O)2]n compounds.     

New stannide ScAgSn: determination of the superstructure via two-dimensional 45Sc solid state NMR

The new stannide ScAgSn was synthesized by induction melting of the elements in a sealed tantalum tube and subsequent annealing. ScAgSn crystallizes with a pronounced subcell structure: ZrNiAl type, P2m, a = 708.2(2) pm, c = 433.9(1) pm, wR2 = 0.1264, 321 F2 values, and 14 variables. The Guinier powder pattern reveals weak superstructure reflections pointing to a TiFeSi-type structural arrangement: I2cm, a = 708.1(1) pm, b = 1225.2(2) pm, c = 869.9(1) pm, wR2 = 0.0787, 5556 F2 values, and 49 variables. So far the growth of high-quality single crystals failed. Determination of the superstructure was partly based on merohedral triplet X-ray data augmented by 119Sn M?ssbauer spectroscopy and 119Sn and 45Sc solid-state NMR data. In particular, the observation of three crystallographically inequivalent sites in 45Sc NMR triple quantum magic-angle spinning (TQ-MAS) NMR spectra provided unambiguous proof of the superstructure proposed. The ScAgSn structure consists of a three-dimensional [AgSn] network (with Ag-Sn distances between 273 and 280 pm) in which the scandium atoms are located in distorted hexagonal channels, each having five tin and two silver nearest neighbors. Both crystallographically independent tin sites have a tricapped trigonal prismatic coordination, that is, [Sn1Sc6Ag3] and [Sn2Ag6Sc3] environments, which are well distinguished in the 119Sn NMR and M?ssbauer spectra because of their different site symmetries.     

Methyl-Dichlorophosphate von Zinn und Blei

Methyl Dichlorophosphates of Tin and Lead The compounds (CH₃)₃M(O₂PCl₂) (I), (M = Sn, Pb) and (CH₃)₂Sn(O₂PCl₂)₂ (II), formed by the reaction of the corresponding methyltin and methylleadchlorides with P₂O₃Cl₄ are described. The IR and Mössbauer spectra suggest that the tin compounds are polymerized through O? P? O bridges, whereby (I) and (II) contain metal atoms with coordination numbers five (D_3h) and six (D_4h), respectively.     

The unexpected motional isotropy of the tin atom in a tricoordinate stannylium cation

The dynamics of the metal atom in the recently isolated tricoordinate tin complex tris(2,4,6-triisopropylphenyl)stannylium tetrakis(pentafluorophenyl)borate was examined by temperature-dependent (119)Sn M?ssbauer spectroscopy over the temperature range 90 K < T < 170 K. Contrary to expectation, the metal atom motion in this temperature range is isotropic within experimental error of the M?ssbauer data, and is only moderately anisotropic, even at 293 K, as evidenced by single crystal X-ray diffraction data. The hyperfine parameters at 90 K are completely consistent with trigonal coordination involving sp(2) hybridization of the 5s5p bonding orbitals of tin.     

Trapping of tin(II) and lead(II) homologues of carbon monoxide by a benzannulated lutidine-bridged bisstannylene

The reaction of the benzannulated bisstannylene ligand 2 with Sn O or Pb O generated in situ gave the pincer complexes 3 and 4. Both complexes have been characterized by X-ray diffraction and multinuclear NMR spectroscopy. A divalent state has been found by M?ssbauer spectroscopy for the tin atoms in complexes 3 and 4.     

Iodination of stanna-closo-dodecaborate

The dianionic stannaborate [SnB11H11]2- oxidatively adds iodine at the tin vertex to give the iodinated cluster [I2SnB11H11]2- which maintains a closo structure, albeit having a nido electron count. The iodo-stannaborate [I2SnB11H11]2- is unstable at room temperature, but its structure was elucidated via single-crystal X-ray diffraction at low temperatures. The low-temperature 11B NMR spectrum exhibits a 5:1:5 signal pattern, and the 119Sn NMR shows a resonance at -1039 ppm. Iodination of the zwitterionic stannaborate iron complex Fe(SnB11H11)(triphos) leads to the formation of the corresponding iodo-stannaborate iron complex Fe(I2SnB11H11)(triphos) which features an iodinated stannaborate moiety that has a structure analogous to that of [I2SnB11H11]2-. The zwitterionic iodo-stannaborate complex is stable at room temperature, and the crystal structure and the 1H, 11B, 31P, and 119Sn NMR parameters were determined. 119Sn M?ssbauer spectroscopy supports the assignment of a tin oxidation state of +II for Fe(SnB11H11)(triphos) (delta = 2.71 mm s-1) and +IV for Fe(I2SnB11H11)(triphos) (delta = 1.22 mm s-1). Additional 57Fe M?ssbauer spectra confirm the iron oxidation state +II for both compounds.     

{Sn(9)[Si(SiMe(3))(3)](2)}(2-): A Metalloid Tin Cluster Compound With a Sn(9) Core of Oxidation State Zero

The disproportionation reaction of the subvalent metastable halide SnCl proved to be a powerful synthetic method for the synthesis of metalloid cluster compounds of tin. Now we present the synthesis and structural characterization of the anionic metalloid cluster compound [Sn(9)[Si(SiMe(3))(3)](2)](2-)3 where the oxidation state of the tin atoms is zero. Quantum chemical calculations as well as M?ssbauer spectroscopic investigations show that three different kinds of tin atoms are present within the cluster core. Compound 3 is highly reactive as shown by NMR investigations, thus being a good starting material for further ongoing research on the reactivity of such partly shielded metalloid cluster compounds.     

119mSn-Mössbauer-spektren von funktionell substituierten stannylenen und ihren stannio-komplexen mit chrom,molybdän- und wolfram-carbonyl-acceptoren

^119mSn Mössbauer data for a series of base-stabilized, intermolecularly associated tin(II) compounds ith O, Cl, P and As atoms bonded to tin are compared with isomer shifts (IS) and quadrupole splittings (QS) of their stannio complex derivatives with Cr, Mo and W carbonyls. Coordination at the tin lone-pair atom decreases IS to ca. 2.1 ± 0.2 mm s^?1 and increases the QS. QS values reflect the highly associated nature of the complexes (CO)₅MSn(Cl)E(t-Bu)₂ (M Cr, W; E  P, As) which are bridged through μ-E(t-Bu)₂ groups.     

Stable copper-tin cluster compositions from high-temperature annealing

Copper-doped tin clusters can be thermally annealed to much more stable compositions with a substantially higher copper/tin ratio. The annealed clusters are only prominent over a narrow range of compositions: CuSn(10-15)+, Cu2Sn(12-18)+, Cu3Sn(15-21)+, Cu4Sn(18-(24)+, and Cu5Sn(21-(27)+. These compositions are close to those found for W(m)Si(n)+ clusters, raising the possibility that the Cu(m)Sn(n)+ clusters have core-shell geometries like those proposed for the W(m)Si(n)+ clusters. Increasing the number of copper atoms causes a change in the dissociation pattern from the fission processes that are characteristic of semiconductor clusters to the expulsion of individual atoms, which usually occurs for metal clusters. The change in the fragmentation pattern may result because the clusters rich in copper melt before they dissociate, while the pure tin clusters dissociate directly from a solidlike phase.     

Mössbauer study of LaNiSn and NdNiSn compounds and their deuterides

Summary LaNiSn and NdNiSn compounds and their deuterides have been studied by variable temperature ¹¹⁹Sn M?ssbauer spectroscopy. The hyperfine parameters obtained experimentally are in good agreement with those derived from first principle calculations. The enlargement of quadrupole splitting observed for LaNiSn after deuteration confirms the lower symmetry of electron density around tin atoms indicated by the calculation of partial Sn-p density of states (DOS). Magnetic ordering is observed at low temperature in deuterided NdNiSn.     

Formation of Metal Clusters or Nitrogen-Bridged Adducts by Reaction of a Bis(amino)stannylene with Halides of Two-Valent Transition Metals

When the cyclic bis(amino)stannylene Me(2)Si(NtBu)(2)Sn is allowed to react with metal halides MX(2) (M = Cr, Fe, Co, Zn; X = Cl, Br [Zn]) adducts of the general formula [Me(2)Si(NtBu)(2)Sn.MX(2)](n) are obtained. The compounds are generally dimeric (n = 2) except the ZnBr(2) adduct, which is monomeric in benzene. The crystal structures of [Me(2)Si(NtBu)(2)Sn.CoCl(2)](2) (triclinic, space group &Pmacr;1; a = 8.620(9) ?, b = 9.160(9) ?, c = 12.280(9) ?, alpha = 101.2(1) degrees, beta = 97.6(1) degrees, gamma = 105.9(1) degrees, Z = 1) and of [Me(2)Si(NtBu)(2)Sn.ZnCl(2)](2) (monoclinic, space group P2(1)/c; a = 8.156(9) ?, b = 16.835(12) ?, c = 13.206(9) ?, beta = 94.27(6) degrees, Z = 2) were determined by X-ray diffraction techniques. The two compounds form similar polycyclic, centrosymmetrical assemblies of metal atoms bridged by chlorine or nitrogen atoms. While in the case of the cobalt compound Co is pentacoordinated by three chlorine and two nitrogen atoms, in the zinc derivative Zn is almost tetrahedrally coordinated by three chlorine atoms and one nitrogen atom. The iron derivative [Me(2)Si(NtBu)(2)Sn.FeCl(2)](2) seems to be isostructural with the cobalt compound as can be deduced from the crystal data (triclinic, a = 8.622(7) ?, b = 9.158(8) ?, c = 12.353(8) ?, alpha = 101.8(1) degrees, beta = 96.9(1) degrees, gamma = 105.9(1) degrees, Z = 1). If NiBr(2), PdCl(2), or PtCl(2) is combined with the stannylene, the reaction product is totally different: 4 equiv of the stannylene are coordinating per metal halide, forming the molecular compound [Me(2)Si(NtBu)(2)Sn](4)MX(2), which crystallizes with half a mole of benzene per molecular formula. The crystal structures of [Me(2)Si(NtBu)(2)Sn](4).NiBr(2).(1)/(2)C(6)H(6) (tetragonal, space group I4(1)/a, a = b = 43.86(4) ?, c = 14.32(2) ?, Z = 16) and [Me(2)Si(NtBu)(2)Sn](4).PdCl(2).(1)/(2)C(6)H(6) (tetragonal, space group I4(1)/a, a = b = 43.99(4) ?, c = 14.318(14) ?, Z = 16) reveal the two compounds to be isostructural. The molecules have an inner Sn(4)M pentametallic core (mean distances: Sn-Ni 2.463 ?, Sn-Pd 2.544 ?) with the transition metal in the center of a slightly distorted square formed by the four tin atoms, the distortion from planarity resulting in a weak paramagnetism of 0.2 &mgr;(B) for the nickel compound. The halogen atoms form bridges between two of the tin atoms and have no bonding interaction with the transition metal. The nickel compound has also been prepared by direct interaction of Br(2) or NR(4)Br(3) with [Me(2)Si(NtBu)(2)Sn](4)Ni as a minor product, the main products being Me(2)Si(NtBu)(2)Sn(NtBu)(2)SiMe(2,) Me(2)Si(NtBu)(2)SnBr(2), NiBr(2) and SnBr(2). Other metal clusters have been obtained by the reaction of Me(2)Si(NtBu)(2)Sn with tetrakis(triphenyphosphine)palladium or by the reaction of Me(2)Si(NtBu)(2)Ge with RhCl(PPh(3))(3). In the first case Ph(3)PPd[Sn(NtBu)(2)SiMe(2)](3)PdPPh(3) (rhombohedral, space group R3c, a = b = 21.397(12) ?, c = 57.01(5) ?, alpha = beta = 90 degrees, gamma = 120 degrees, Z = 12) is formed and is characterized by X-ray techniques to be composed of a central PdSn(3)Pd trigonal bipyramid with the tin atoms occupying the equatorial positions (Pd-Sn = 2.702(5) ?). In the second reaction all the triphenylphosphine ligands are replaced from rhodium and Rh[Ge(NtBu)(2)SiMe(2)](4)Cl is formed (monoclinic, space group P2(1)/n, a = 12.164(2) ?, b = 23.625(5) ?, c = 24.128(5) ?, beta = 102.74(3) degrees, Z = 4). The central core of this molecule is made up of a rhodium atom which is almost square planarly coordinated by the germanium atoms, two of which are bridged by chlorine (mean Ge-Rh = 2.355 ?).     

DFT calculations of the electric field gradient at the tin nucleus as a support of structural interpretation by 119Sn Mössbauer spectroscopy

DFT calculations, using an all-electron basis set and with full geometry optimization, were performed on 34 Sn(II) and Sn(IV) compounds of known structure and (119)Sn M?ssbauer parameters, to obtain the theoretical values of the electric field gradient components, V(xx), V(yy), and V(zz), at the tin nucleus. These were used to determine the quantity V = V(zz)[1+ 1/3((V(xx) - V(yy))/((V(zz))(2)](1/2), for each investigated compound, which is related to the quadrupole splitting (DeltaE) parameter according to DeltaE = 1/2eQV, where e is the electronic charge and Q is the quadrupole moment of the tin nucleus. The linear fitting of the correlation plot of the experimental DeltaE, versus the corresponding calculated V values, produced a slope that is equal to 0.93 +/- 0.03 and a correlation coefficient R = 0.982. The value of Q obtained, 15.2 +/- 4.4 fm(2), is in agreement with that previously experimentally determined or calculated by analogous procedures. The calculation method is able to establish the sign of the electric field gradient component V(zz), in agreement with the sign of DeltaE determined experimentally by M?ssbauer-Zeeman spectroscopy. The calculated structural parameters are in good agreement with the corresponding experimental data, determined by X-ray crystallography in the solid state, with average structural deviations of about 3 % for bond lengths and angles in the tin environment. Calculated values of DeltaE were obtained from the calibration fitting constant and from the values of V. By comparing experimental and calculated DeltaE parameters, the structure assignment of configurational isomers was successful in two test cases, in agreement with the experimental X-ray crystallographic structures. These results indicate that the method can be used as a tool to support the routine structure interpretation of tin compounds by (119)Sn M?ssbauer spectroscopy.     

Bis(triazacyclohexane) sandwich complexes of (Cu(I))(2), Cu(II) and Zn(II): complexes with cuprophilic attraction between two cationic copper(I) leading to unusual reactivity with dioxygen

As the first 1st-row transition metal complexes having six tertiary amine donor groups, bis(triazacyclohexane) sandwich complexes [L2M](BF4)2 (L = benzyl- or p-fluorobenzyl-triazacyclohexane, M = Cu or Zn) have been obtained by the protonolysis of Et2Zn in the presence of L or by reaction of [Cu(MeCN)4](BF4) with L in CH2Cl2 and subsequent air oxidation via an unprecedented Cu(I)(2) sandwich complex containing a short Cu-Cu contact.     

Reactivity of a tin(II) (iminophosphinoyl)(thiophosphinoyl)methanediide complex toward sulfur: synthesis and 119Sn Mössbauer spectroscopic studies of [{(μ-S)SnC(PPh2═NSiMe3)(PPh2═S)}3Sn(μ3-S)

Reaction of [(PPh(2)═NSiMe(3))(PPh(2)═S)CSn:](2) (1) with elemental sulfur in toluene afforded [{(μ-S)Sn(IV)C(PPh(2)═NSiMe(3))(PPh(2)═S)}(3)Sn(II)(μ(3)-S)] (2) and [CH(2)(PPh(2)═NSiMe(3))(PPh(2)═S)] (3). Compound 2 comprises a Sn(II)S moiety coordinated with the Sn(IV) and S atoms of a trimeric 2-stannathiomethendiide {(PPh(2)═NSiMe(3))(PPh(2)═S)CSn(μ-S)}(3). Compound 2 has been characterized by NMR spectroscopy, (119)Sn M?ssbauer studies, X-ray crystallography, and theoretical studies. (119)Sn NMR spectroscopy and M?ssbauer studies show the presence of Sn(IV) and Sn(II) atoms in 2. X-ray crystallography suggests that the Sn(II)S moiety does not have multiple bond character. Theoretical studies illustrate that the C(methanediide)-Sn bonds comprise a lone pair orbital on each C(methanediide) atom and an C-Sn occupied σ orbital.     

两种杂原子复配对Y型分子筛结晶性能的影响

分子筛作为催化剂或催化剂的载体材料广泛应用于各种催化反应过程中,将杂原子引人分子筛骨架中形成杂原子分子筛,可在较大的范围内调节分子筛表面的酸性中心和氧化还原催化活性中心.