Synthesis and Oxidation of a Paddlewheel-Shaped Rhodium/Antimony Complex Featuring Pyridine-2-Thiolate Ligands.

The paddlewheel-shaped complex [Sb(µ-pyS)4 Rh]2 (1) (pyS- = 2-S-C5 H4 N- ) was synthesized from [Rh(pyS)(cod)]2 (cod=1,5-cyclooctadiene) and Sb(pyS)3 . Upon oxidation with ONMe3 , the complex [(µ-O)Sb(µ-pyS)3 Rh(κ2 -pyS)]2 (2) is formed. Both 1 and 2 form dimers and feature short Rh-Sb bonds and bridging pyS ligands. 121 Sb Mössbauer spectro- scopy and computational studies were employed to elucidate the Rh-Sb bonding in 1 and 2. Both covalent (Rh-Sb, X-type Sb ligand) and dative (Rh→Sb, Z-type; Rh←Sb L-type Sb ligand) interactions have to be considered for the description of their bonding situations.

Redox-Active N-Heterocyclic Germylenes and Stannylenes with a Ferrocene-1,1'-diyl Backbone.

We describe ferrocene-based N-heterocyclic germylenes and stannylenes of the type [Fe{(η5 -C5 H4 )NR}2 E:] (1 RE; E=Ge, Sn; R=neopentyl (Np), mesityl (Mes), trimethylsilyl (TMS)), which constitute the first examples of redox-functionalised N-heterocyclic tetrylenes (NHTs). These compounds are thermally stable and were structurally characterised by means of X-ray diffraction studies, except for the neopentyl-substituted stannylene 1 NpSn, the decomposition of which afforded the aminoiminoferrocene [fc(NHCH2 tBu)(N=CHtBu)] (2) and the spiro tin(IV) compound (1 Np)2 Sn (3). DFT calculations show that the HOMO of the NHTs of our study is localised on the ferrocenylene backbone. A one-electron oxidation process affords ions of the type 1 RE+. . In contrast to the NHC system 1 RC, the localised ferrocenium-type nature of the oxidised form does not compromise the fundamental tetrylene character of 1 RE+. .

Tin(IV) Compounds with 2-C6F4PPh2 Substituents and Their Reactivity toward Palladium(0): Formation of Tin-Palladium Complexes via Oxidative Addition.

The tin(IV) compounds MexSn(2-C6F4PPh2)4-x (1, x = 1; 2, x = 2) and ClSn(2-C6F4PPh2)3 (3) were obtained from the reactions of 2-LiC6F4PPh2 with MeSnCl3 (3:1), Me2SnCl2 (2:1), or SnCl4 (3:1), respectively. The reactions of 2-LiC6F4PPh2 with SnCl4 in different stoichiometric ratios (4:1-1:1) gave 3 as the main product. Compound Cl2Sn(2-C6F4PPh2)2 (4) was formed in the transmetalation reaction of 3 and [AuCl(tht)] but could not be isolated. 1 and 2 react with palladium(0) sources {[Pd(PPh3)4] and [Pd(allyl)Cp]} by the oxidative addition of one of their Sn-CAryl bonds to palladium(0) with formation of the heterobimetallic complexes [MeSn(µ-2-C6F4PPh2)2Pd(κC-2-C6F4PPh2)] (5) and [Me2Sn(µ-2-C6F4PPh2)Pd(κ2-2-C6F4PPh2)] (6) featuring Sn-Pd bonds. The reaction of 3 with palladium(0) proceeds via the oxidative addition of the Sn-Cl bond to palladium(0), thus furnishing the complex [Sn(µ-2-C6F4PPh2)3PdCl] (7) featuring a Sn-Pd bond and a pentacoordinate Pd atom. Transmetalation of MexSn(2-C6F4PPh2)4-x (x = 1-3) with [Pd(allyl)Cl]2 gave MexClSn(2-C6F4PPh2)3-x and [Pd(allyl)(µ-2-C6F4PPh2)]2. For x = 1, the compound MeClSn(2-C6F4PPh2)2 (generated in situ) reacted with another 1 equiv of [Pd(allyl)Cl]2 by the oxidative addition of the Sn-Cl bond to palladium(0) and the reductive elimination of allyl chloride, thus leading to [MeSn(µ-2-C6F4PPh2)2PdCl] (8). The reductive elimination of allyl chloride was also observed in the reaction of 3 with [Pd(allyl)Cl]2, giving [Sn(µ-2-C6F4PPh2)3PdCl] (7). All compounds have been characterized by means of multinuclear NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and selected compounds by 119Sn Mössbauer spectroscopy. Computational analyses (natural localized molecular orbital calculations) have provided insight into the Sn-Pd bonding of 5-8.

Unusual Mixed Valence of Eu in Two Materials-EuSr2Bi2S4F4 and Eu2SrBi2S4F4: Mössbauer and X-ray Photoemission Spectroscopy Investigations.

We have synthesized two new Eu-based compounds, EuSr2Bi2S4F4 and Eu2SrBi2S4F4, which are derivatives of Eu3Bi2S4F4, an intrinsic superconductor with Tc = 1.5 K. They belong to a tetragonal structure (SG: I4/mmm, Z = 2), similar to the parent compound Eu3Bi2S4F4. Our structural and 151Eu Mössbauer spectroscopy studies show that, in EuSr2Bi2S4F4, Eu-atoms exclusively occupy the crystallographic 2a-sites. In Eu2SrBi2S4F4, 2a-sites are fully occupied by Eu-atoms and the other half of Eu-atoms and Sr-atoms together fully occupy 4e-sites in a statistical distribution. In both compounds Eu atoms occupying the crystallographic 2a-sites are in a homogeneous mixed valent state ∼2.6-2.7. From our magnetization studies in an applied H ≤ 9 T, we infer that the valence of Eu-atoms in Eu2SrBi2S4F4 at the 2a-sites exhibits a shift toward 2+. Our XPS studies corroborate the occurrence of valence fluctuations of Eu and after Ar-ion sputtering show evidence of enhanced population of Eu2+-states. Resistivity measurements, down to 2 K, suggest a semimetallic nature for both compounds.

EuAu3Al2: Crystal and Electronic Structures and Spectroscopic, Magnetic, and Magnetocaloric Properties.

The intermetallic compound EuAu3Al2 has been prepared by reaction of the elements in tantalum ampules. The structure was refined from single-crystal data, indicating that the title compound crystallizes in the orthorhombic crystal system (a = 1310.36(4), b = 547.87(1), c = 681.26(2) pm) with space group Pnma (wR2 = 0.0266, 1038 F(2) values, 35 parameters) and is isostructural to SrAu3Al2 (LT-SrZn5 type). Full ordering of the gold and aluminum atoms was observed. Theoretical calculations confirm that the title compound can be described as a polar intermetallic phase containing a polyanionic [Au3Al2](δ-) network featuring interconnected strands of edge-sharing [AlAu4] tetrahedra. Magnetic measurements and (151)Eu Mössbauer spectroscopic investigations confirmed the divalent character of the europium atoms. Ferromagnetic ordering below TC = 16.5(1) K was observed. Heat capacity measurements showed a λ-type anomaly at T = 15.7(1) K, in line with the ordering temperature from the susceptibility measurements. The magnetocaloric properties of EuAu3Al2 were determined, and a magnetic entropy of ΔSM = -4.8 J kg(-1) K(-1) for a field change of 0 to 50 kOe was determined. Band structure calculations found that the f-bands of Eu present at the Fermi level of non-spin-polarized calculations are responsible for the ferromagnetic ordering in this phase, whereas COHP chemical bonding coupled with Bader charge analysis confirmed the description of the structure as covalently bonded polyanionic [Au3Al2](δ-) network interacting ionically with Eu(δ+).

Understanding the anomalous behavior of Vegard's law in Ce1-xMxO2 (M = Sn and Ti; 0 < x ≤ 0.5) solid solutions.

The dependence of the lattice parameter on dopant concentration in Ce1-xMxO2 (M = Sn and Ti) solid solutions is not linear. A change towards a steeper slope is observed around x ∼ 0.35, though the fluorite structure (space group Fm3m) is preserved up to x = 0.5. This phenomenon has not been observed for Ce1-xZrxO2 solid solutions showing a perfectly linear decrease of the lattice parameter up to x = 0.5. In order to understand this behavior, the oxidation state of the metal ions, the disorder in the oxygen substructure and the nature of metal-oxygen bonds have been analyzed by XPS, (119)Sn Mössbauer spectroscopy and X-ray absorption spectroscopy. It is observed that the first Sn-O coordination shell in Ce1-xSnxO2 is more compact and less flexible than that of Ce-O. The Sn coordination remains symmetric with eight equivalent, shorter Sn-O bonds, while Ce-O coordination gradually splits into a range of eight non-equivalent bonds compensating for the difference in the ionic radii of Ce(4+) and Sn(4+). Thus, a long-range effect of Sn doping is hardly extended throughout the lattice in Ce1-xSnxO2. In contrast, for Ce1-xZrxO2 solid solutions, both Ce and Zr have similar local coordination creating similar rearrangement of the oxygen substructure and showing a linear lattice parameter decrease up to 50% Zr substitution. We suggest that the localized effect of Sn substitution due to its higher electronegativity may be responsible for the deviation from Vegard's law in Ce1-xSnxO2 solid solutions.

Intricate short-range ordering and strongly anisotropic transport properties of Li(1-x)Sn(2+x)As2.

A new ternary compound, Li(1-x)Sn(2+x)As2, 0.2 < x < 0.4, was synthesized via solid-state reaction of elements. The compound crystallizes in a layered structure in the R3̅m space group (No. 166) with Sn-As layers separated by layers of jointly occupied Li/Sn atoms. The Sn-As layers are comprised of Sn3As3 puckered hexagons in a chair conformation that share all edges. Li/Sn atoms in the interlayer space are surrounded by a regular As6 octahedron. Thorough investigation by synchrotron X-ray and neutron powder diffraction indicate no long-range Li/Sn ordering. In contrast, the local Li/Sn ordering was revealed by synergistic investigations via solid-state (6,7)Li NMR spectroscopy, HRTEM, STEM, and neutron and X-ray pair distribution function analyses. Due to their different chemical natures, Li and Sn atoms tend to segregate into Li-rich and Sn-rich regions, creating substantial inhomogeneity on the nanoscale. The inhomogeneous local structure has a high impact on the physical properties of the synthesized compounds: the local Li/Sn ordering and multiple nanoscale interfaces result in unexpectedly low thermal conductivity and highly anisotropic resistivity in Li(1-x)Sn(2+x)As2.

Reactions with a Metalloid Tin Cluster {Sn10[Si(SiMe3)3]4}(2-): Ligand Elimination versus Coordination Chemistry.

Chemistry that uses metalloid tin clusters as a starting material is of fundamental interest towards understanding the reactivity of such compounds. Since we identified {Sn10[Si(SiMe3)3]4}(2-) 7 as an ideal candidate for such reactions, we present a further step in the understanding of metalloid tin cluster chemistry. In contrast to germanium chemistry, ligand elimination seems to be a major reaction channel, which leads to the more open metalloid cluster {Sn10[Si(SiMe3)3]3}(-) 9, in which the Sn core is only shielded by three Si(SiMe3)3 ligands. Compound 9 is obtained through different routes and is crystallised together with two different countercations. Besides the structural characterisation of this novel metalloid tin cluster, the electronic structure is analysed by (119)Sn Mössbauer spectroscopy. Additionally, possible reaction pathways are discussed. The presented first step into the chemistry of metalloid tin clusters thus indicates that, with respect to metalloid germanium clusters, more reaction channels are accessible, thereby leading to a more complex reaction system.

Chemistry of stannylene-based Lewis pairs: dynamic tin coordination switching between donor and acceptor character.

The coordination chemistry of cyclic stannylene-based intramolecular Lewis pairs is presented. The P→Sn adducts were treated with [Ni(COD)2] and [Pd(PCy3)2] (COD = 1,5-cyclooctadiene, PCy3 = tricyclohexylphosphine). In the isolated coordination compounds the stannylene moiety acts either as an acceptor or a donor ligand. Examples of a dynamic switch between these two coordination modes of the P-Sn ligand are illustrated and the structures in the solid state together with heteronuclear NMR spectroscopic findings are discussed. In the case of a Ni(0) complex, (119)Sn Mössbauer spectroscopy of the uncoordinated and coordinated phosphastannirane ligand is presented.

Ferrocenyl-functionalized Sn/Se and Sn/Te complexes: synthesis, reactivity, optical, and electronic properties.

An adamantane-shaped, ferrocenyl-substituted tin selenide complex, [(FcSn)4Se6] (1; Fc = ferrocenyl), and a ferrocenyl-substituted tin telluride five-membered ring, [(Fc2Sn)3Te2] (2), were obtained upon treatment of FcSnCl3 with K2E (E = Se, Te). Complex 1 further reacts with Na2S·9H2O and [Cu(PPh3)3Cl] to form a ternary complex, [(CuPPh3)6(S/Se)6(SnFc)2] (3). We discuss structures, optical and electrochemical properties as well as Mössbauer spectra.

The role of 2,6-diaminopyridine ligands in the isolation of an unprecedented, low-valent tin complex.

Stabilization of the central atom in an oxidation state of zero through coordination of neutral ligands is a common bonding motif in transition-metal chemistry. However, the stabilization of main-group elements in an oxidation state of zero by neutral ligands is rare. Herein, we report that the transamination reaction of the DAMPY ligand system (DAMPY=2,6-[ArNH-CH2 ]2 (NC5 H3 ) (Ar=C6 H3 -2,6-iPr2 )) with Sn[N(SiMe3 )2 ]2 produces the DIMPYSn complex (DIMPY=(2,6-[ArNCH]2 (NC5 H3 )) with the Sn atom in a formal oxidation state of zero. This is the first example of a tin compound stabilized in a formal oxidation state of zero by only one donor molecule. Furthermore, three related low-valent Sn(II) complexes, including a [DIMPYSn(II) Cl](+) [SnCl3 ](-) ion pair, a bisstannylene DAMPY{Sn(II) [N(SiMe3 )2 ]2 }2 , and the enamine complex MeDIMPYSn(II) , were isolated. Experimental results and the conclusions drawn are also supported by theoretical studies at the density functional level of theory and (119) Sn Mössbauer spectroscopy.

Generation of nanopores down to 10 nm for use in deep-nulling interferometry.

Scanning electron microscope images show that it is easy to generate nanopores on polycarbonate membranes with well-defined pore diameters by ion-track perforation and subsequent magnetron sputtering with metal. The size reduction of the nanopores during sputtering with gold is a linear function of time. Images of different angles and from the bottom side of the membrane show that the channels are the smallest very close to the surface of the metal layer, have a conelike shape, and reach about half as much into the polymer membranes as the metal-layer thickness. This topographical pore shape is ideal for use as optically coherent near-field sources in deep-nulling microscopy. We present the first results of significantly improved nulling stabilization in the presence (<2 nm optical pathway difference) and the absence (<0.6 nm optical pathway difference) of the nanoapertures in the focal region of a deep-nulling microscope.

Group 10-group 14 metal complexes [E-TM](IV): the role of the group 14 site as an L, X and Z-type ligand.

A series of new complexes of a general motif [R2E(µ-N,S)2TM-L] (E: metalloid group 14 element; TM: group 10 metal; R: Cl, Ph, pyS, OH, (N,N,O)-chelating ligands; N,S: 1-methylimidazole-2-thiolate (methimazolyl, mt(-)), pyridine-2-thiolate (pyS(-)); L: PPh3, PCy3, pyS) was synthesised and characterised by single-crystal X-ray diffraction, multi-nuclear NMR spectroscopy ((1)H, (13)C, (31)P, (119)Sn), (119)Sn Mössbauer spectroscopy and quantum chemical calculations. The E-TM bonding situation in these compounds can be described with various resonance structures which comprise E(ii)→TM(ii), E(iii)-TM(i) and E(iv)←TM(0) features. Thus, in these complexes the atoms of the group 14 based ligand sites reveal L-, X- and Z-type ligand characteristics. A systematic comparison between structural and spectroscopic parameters as well as the results from NLMO analyses of structurally related compounds provided information about the differences in the E-TM bonding situation upon alteration of the metal atoms or ligand patterns. Under investigation are the structurally related compounds [Cl2Sn(µ-pyS)2TM-PPh3] (1: TM = Pd; 2: TM = Ni; 3: TM = Pt), [Cl2Ge(µ-pyS)2Pd-PPh3] (4) and, for in silico analysis, [Cl2Si(µ-pyS)2Pd-PPh3] (5), which indicate a pronounced shift of the E-TM bond electron pair towards TM for TM = Pt. Further complexes serve as representatives of these compounds with different bridging ligands {[Cl2Sn(µ-mt)2Pd-PPh3] (8)}, different trans-E-TM-bound ligands {[Cl2Sn(µ-pyS)2Pd-PCy3] (9), [Cl2Sn(µ-pyS)2Pd]4 (10)} and with different substituents at Sn (including penta- and hexacoordinated tin compounds), i.e., [R2Sn(µ-pyS)2Pd-PPh3] with R = Ph (6) and pyS (7), [(O,N,N)Sn(µ-pyS)2Pd-PPh3] (11) and (12) having two different (O,N,N) tridentate ligands, and [(µ-OH)ClSn(µ-pyS)2Pd-PPh3]2 (13). The latter series indicates a shift of the E-TM (= Sn-Pd) bond electron pair towards Pd upon transition from penta- to hexacoordinated tin compounds.

Inorganic Double Helices in Semiconducting SnIP.

SnIP is the first atomic-scale double helical semiconductor featuring a 1.86 eV bandgap, high structural and mechanical flexibility, and reasonable thermal stability up to 600 K. It is accessible on a gram scale and consists of a racemic mixture of right- and left-handed double helices composed by [SnI] and [P] helices. SnIP nanorods <20 nm in diameter can be accessed mechanically and chemically within minutes.

New quaternary arsenide oxides with square planar coordination of gold(I) - structure, (197)Au Mössbauer spectroscopic, XANES and XPS characterization of Nd10Au3As8O10 and Sm10Au3As8O10.

The quaternary gold(I) arsenide oxides Nd10Au3As8O10 and Sm10Au3As8O10 were synthesized in sealed quartz ampoules from the rare earth (RE) elements, their appropriate sesquioxides, arsenic, arsenic(III) oxide and finely dispersed gold at maximum annealing temperatures of 1223 K. Both structures were refined from X-ray single crystal diffractometer data at room temperature and at 90 K. Nd10Au3As8O10 and Sm10Au3As8O10 crystallize with a new structure type that derives from the BaAl4 structure through distortions and formation of ordered vacancies. The structures consist of stacked polycationic [RE10O10](10+) layers with oxygen in tetrahedral rare earth coordination and polyanionic [Au(I)3(As2)4](10-) layers with gold in square planar or rectangular planar coordination of four arsenic dumbbells (255 pm As1-As2). In contrast to the well known ionic rare earth oxide layers, the gold arsenide layers rather show covalent bonding and account for the metallic nature of these two new arsenide oxides. This is confirmed by electronic structure calculations and resistivity measurements. The oxidation state of gold was investigated by (197)Au Mössbauer, X-ray absorption near edge structure (XANES) and photoelectron (XPS) spectroscopy. Due to missing comparative gold arsenide compounds, the monovalent gold phosphide oxides RE2AuP2O were measured for comparison. The XANES measurements additionally comprise monovalent gold arsenides REAuAs2. The XPS study contains BaAuAs as reference compound instead. Combination of all data clearly indicates Au(I), which was not observed in square planar coordination up to now. Temperature dependent magnetic susceptibility data show Curie-Weiss paramagnetism for Nd10Au3As8O10 and no magnetic ordering down to 2.5 K. Sm10Au3As8O10 shows the typical Van Vleck type paramagnetism for samarium compounds along with a transition to an antiferromagnetically ordered state at TN = 8.6 K.

Pyridine-2-thiolate bridged tin-palladium complexes with Sn(PdN2Cl2), Sn(PdN2S2), Sn(PdN2C2) and Sn(Pd2N4) skeletons.

Reactions of tin(IV) complexes of the type Sn(PyS)2X2 (X = Cl, PyS, Ph; PyS = pyridine-2-thiolate) with Pd(PPh3)4 provide easy access to novel heterometallic complexes with Pd-Sn bonds. Electronic characteristics of this connection were analysed by X-ray crystallography, (119)Sn Mössbauer spectroscopy and quantum chemical analyses.