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The quasibinary section of the intermetallic phases MAl4 and MGa4 with M=Sr and Ba have been characterised by means of X-ray diffraction (XRD) studies and differential thermal analysis. The binary phases show complete miscibility and form solid solutions M(Al1− xGa x)4 with M=Sr and Ba. These structures crystallise in the BaAl4 structure type with four- and five-bonded Al and/or Ga atoms (denoted as Al(4b), Al(5b), Ga(4b), and Ga(5b), respectively) that form a polyanionic Al/Ga sublattice. Solid state 27Al NMR spectroscopic analysis and quantum mechanical (QM) calculations were applied to study the bonding of the Al centres and the influence of Al/Ga substitution, especially in the regimes with low degrees of substitution. M(Al1− xGa x)4 with M=Sr and Ba and 0.925≤ x≤0.975 can be described as a matrix of the binary majority compound in which a low amount of the Ga atoms has been substituted by Al atoms. In good agreement with the QM calculations, 27Al NMR investigations and single crystal XRD studies prove a preferred occupancy of Al(4b) for these substitution regimes. Furthermore, two different local Al environments were found, namely isolated Al(4b1) atoms and Al(4b2), due to the formation of Al(4b)-Al(4b) pairs besides isolated Al(4b) atoms within the polyanionic sublattice. QM calculations of the electric field gradient (EFG) using superlattice structures under periodic boundary conditions are in good agreement with the NMR spectroscopic results. [ABSTRACT FROM AUTHOR]

In tyrosinium polyiodide hydrate, cations and anions aggregate in layers. The cation layers are stabilized by classical hydrogen bonds. The anionic part of the structure consists of parallel infinite polyiodide strands; the distance pattern along these chains suggests the presence of smaller subunits I3−, I2 and I−. Comparative calculations for small fragments and longer chains in frozen geometries indicate that this unexpected arrangement is favoured by local stabilizing anion…anion interactions and partial charge transfer between the subunits. The topological analyses of the electron density ρ, its negative Laplacian L = −蜑2ρ and the electrostatic potential φ functions have been used to study the intrachain I–I and I…I interactions. Thorough analysis carried out with L indicates the successive arrangement of generalized charge concentration and charge depletion sites (for either L ＞ 0 or L ＜ 0 regions) along bond paths, and permits to distinguish iodides from iodine atoms even when they are involved in intermediate situations where interatomic distances and net charges are not conclusive. [ABSTRACT FROM AUTHOR]

Polymorphism and an unexpected reconstructive phase transition in [Cu(trop)(μ-OMe)]2 (trop = tropolonate) were studied by single crystal and powder X-ray diffraction; the phase transition is associated with a huge hysteresis of ca. 200 °C. In the readily reproducible crystal form, the methoxide-bridged dinuclear subunits aggregate to infinite chains by longer bonds in the Jahn-Teller distorted coordination sphere. Analogous alkoxide-bridged derivatives with the substituted ligand hinokitiol (hino), [Cu(hino)(μ-O R)]2 ( R = Me, Et, iPr) form pairs of dinuclear complexes and aggregate to discrete tetranuclear molecules. The inter-cation distance patterns are reflected in the magnetic properties of these two structure types: Strong antiferromagnetic coupling within the dinuclear subunits is observed in either case, but susceptibility measurements confirm differences in exchange coupling between neighboring central CuII atoms. [ABSTRACT FROM AUTHOR]

We report the first complete characterization of metallycryptates encapsulating Ag(i) cations: carboxylato ligands derived from l-proline and l-alanine chelate and bridge six Cu(ii) centres arranged in a slightly distorted octahedral fashion. Eight oxygen atoms of these ligands are disposed in square-prismatic geometry and coordinate the monovalent cation. Two alternative metallacryptates based on alanine have been identified which differ with respect to aggregation: a solid in which pairs of encapsulating sites are formed competes with an infinite chain of M(i) coordinating sites. In contrast, the individual encrypting moieties are arranged as overall neutral and isolated molecular species in the proline-based metallacryptate. This proline derivative can accomodate Ag(i) and Na(i) cations and form a solid solution. Susceptibility measurements confirm ferromagnetic interactions between the Cu(ii) within the hexanuclear proline cryptate and thus underline the similarity between solids accommodating Na(i) and Ag(i). Spectroscopic results suggest that these metallacryptates hardly dissociate in methanol solution. [ABSTRACT FROM AUTHOR]

Complete miscibility of the intermetallic phases (IPs) SrGa2 and BaGa2 forming the solid solution Sr1− xBa xGa2 is shown by means of X-ray diffraction, thermoanalytical and metallographic studies. Regarding the distances of Sr/Ba sites versus substitution degree, a model of isolated substitution centres (ISC) for up to 10 % cation substitution is explored to study the influence on the Ga bonding situation. A combined application of NMR spectroscopy and quantum mechanical (QM) calculations proves the electric field gradient (EFG) to be a sensitive measure of different bonding situations. The experimental resolution is boosted by orientation-dependent NMR on magnetically aligned powder samples, revealing in first approximation two different Ga species in the ISC regimes. EFG calculations using superlattice structures within periodic boundary conditions are in fair agreement with the NMR spectroscopy data and are discussed in detail regarding their application on disordered IPs. [ABSTRACT FROM AUTHOR]

Five coordination polymers with the stoichiometry CaX2(valine)2(H2O)2 (X = Cl, Br) were obtained from the corresponding calcium halides and either racemic and enantiopure valine. In all cases the zwitterionic amino acid is exclusively O coordinated and the halides act as counteranions for the resulting one-dimensional cationic chains. The enantiopure chloride shows dimorphism; both forms differ in connectivity from the bromide. In contrast to this structural variability for L-valine, the derivatives of the racemic amino acid are isomorphous. [ABSTRACT FROM AUTHOR]

In catena-poly[copper(II)-di-μ-chlorido-μ-proline-κ2 O: O′], [CuCl2(C5H9NO2)] n, two symmetry-independent metal cations adopt distorted octahedral coordination, typical for d9 Jahn-Teller systems. Each chloride bridge is involved in both a short and a very long interaction with a CuII centre. The centrosymmetric crystal structure contains homochiral chains of opposite handedness which extend along the shortest lattice parameter ( i.e. a). The O: O′-bridging coordination mode of proline, although a common motif for such complexes in general, is remarkable for CuII; the vast majority of amino acid derivatives of this cation are characterized by N, O-chelation. [ABSTRACT FROM AUTHOR]

Reactions of calcium bromide with enantiopure and racemic proline in aqueous solution lead to two solids in which the zwitterionic amino acid acts as a bridging ligand between neighbouring cations. Depending on the chirality of the amino acid, topologically very different products are obtained. With racemic proline, bromide acts as a simple uncoordinated counter-anion for the cationic heterochiral chains in catena-poly[[aquacalcium(II)]-μ-aqua-μ3-DL-proline-μ2-DL-proline], {[Ca(C5H9NO2)2(H2O)2]Br2} n. In agreement with chemical intuition, only carboxylate and aqua O atoms coordinate the alkaline earth cation in a low-symmetry arrangement. In contrast, L-proline affords the two-dimensional network poly[dibromidobis(μ2-L-proline)calcium(II)], [CaBr2(C5H9NO2)2] n, with an unexpected CaBr2 unit in a more regular coordination sphere. [ABSTRACT FROM AUTHOR]

In catena-poly[copper(II)-di-μ-chlorido-μ-proline-κ2 O: O′], [CuCl2(C5H9NO2)] n, two symmetry-independent metal cations adopt distorted octahedral coordination, typical for d9 Jahn-Teller systems. Each chloride bridge is involved in both a short and a very long interaction with a CuII centre. The centrosymmetric crystal structure contains homochiral chains of opposite handedness which extend along the shortest lattice parameter ( i.e. a). The O: O′-bridging coordination mode of proline, although a common motif for such complexes in general, is remarkable for CuII; the vast majority of amino acid derivatives of this cation are characterized by N, O-chelation. [ABSTRACT FROM AUTHOR]

Under accelerated and controlled evaporation, chain polymers crystallize from aqueous solutions of CaII and MnII halides with enantiopure L-alanine or racemic DL-alanine. In all ten solids thus obtained zwitterionic amino acid ligands bridge neighbouring cations. The exclusively O-donor-based coordination sphere around the metal cations is completed by aqua ligands; the halides remain uncoordinated and act as counter-anions for the cationic strands. Despite the differences in ionic radii and electronic structure between the main group and the transition metal cation, their derivatives with L-alanine share a common structure type. In contrast, the solids derived from DL-alanine differ and adopt structures depending on the metal cation and the halide. Homochiral chains of either chirality or heterochiral chains with different arrangements of crystallographic inversion centres along the polymer strands are encountered. On average, the six-coordinated CaII cations, devoid of any ligand field effect, show more pronounced deviation from idealized octahedral geometry than the d-block cation MnII. [ABSTRACT FROM AUTHOR]

Alkali metal triphenylsilyls [Li(12-crown-4)SiPh3]·(thf)0.5 (2), [Na(15-crown-5)SiPh3]·(thf)0.5 (3) and [K(18- crown-6)SiPh3(thf)] (4) were synthesized using 1,1,1-trimethyl-2,2,2-triphenyldisilane (Ph3SiSiMe3) and isolated in high yields. Solid state structures were determined by single crystal X-ray diffraction. These alkali metal silyls catalyzed the regioselective hydrosilylation of 1,1-diphenylethylene to give the anti-Markovnikov product. The presence of crown ethers enhanced the reactivity of the metal silyls in hydrosilylation catalysis. [ABSTRACT FROM AUTHOR]

Four new structures based on CaCl2 and proline are reported, all with an unusual Cl-Ca-Cl moiety. Depending on the stoichiometry and the chirality of the amino acid, this metal dihalide fragment represents the core of a mononuclear Ca complex or may be linked by the carboxylate to form extended structures. A cisoid coordination of the halide atoms at the calcium cation is encountered in a chain polymer. In the 2D structures, CaCl2 dumbbells act as nodes and are crosslinked by either enantiomerically pure or racemic proline to form square lattice nets. Extensive database searches and topology tests prove that this structure type is rare for MCl2 dumbbells in general and unprecedented for Ca compounds. [ABSTRACT FROM AUTHOR]

Reactions of manganese(II) chloride, bromide and iodide with proline as an enantiopure and racemic ligand result in six crystalline solids for which diffraction experiments have been performed at 100 K. For two of these compounds, crystal structures at ambient temperature had been reported previously. The most surprising outcome of our systematic comparison lies in the role of chirality: with enantiopure proline three different coordination polymers have been obtained, whereas racemic proline yields isomorphous mononuclear complexes under the same reaction conditions. [ABSTRACT FROM AUTHOR]

The chain polymer [{Cd(μ-X)2py2}g1/∞ ] (X = Cl, Br; py = pyridine) undergoes a fully reversible phase transition between a monoclinic low-temperature and an orthorhombic high-temperature phase. The transformation can be directly monitored in single crystals and can be confirmed for the bulk by powder diffraction. The transition temperature can be adjusted by tuning the composition of the mixed-halide phase: Transition temperatures between 175 K up to the decomposition of the material at ca. 350 K are accessible. Elemental analysis, ion chromatography and site occupancy refinements from single-crystal X-ray diffraction agree with respect to the stoichiometric composition of the samples. [ABSTRACT FROM AUTHOR]

A multifunctional coupler with an ethylene carbonate- and a thiolactone ring was synthesized. As proof of principle the coupler was reacted with four low-molecular weight building blocks to form a multifunctional molecule. The reactivity/selectivity of the coupler towards amines, acrylates and acyl halides was evaluated. [ABSTRACT FROM AUTHOR]