Modellbetrachtungen zum Verständnis unerwarteter Eigenschaften der metalloiden Clusterverbindung [Ga84(N(SiMe3)2)20][Li6Br2(THF)20]·2Toluol

Towards the Understanding of the Unexpected Properties of the Metalloid Cluster Compound [Ga₈₄(N(SiMe₃)₂)₂₀][Li₆Br₂(THF)₂₀]·2Toluol In several short communications we have recently reported on the electrical and superconducting properties of the crystalline title compound 1 which contains anionic Ga₈₄R₂₀‐moieties. Here we present a collection of these results, complemented and interpreted by using DFT‐calculations on model clusters (Ga₈₄(NH₂)₂₀^?). These calculations allow a) a first insight into the dynamics of the Ga₈₄‐moieties (e.g. a rotation of the central Ga₂‐dumbbell) and thus an explanation of the temperature‐dependent Ga‐NMR‐spectra described recently, and b) estimations on the lattice energy of 1 and its resulting unexpected energetic stabilization compared to metallic gallium. A possible contribution of the cations in the electrical conduction mechanism of 1 can also be made feasible with model calculations. The basis for all the results presented is to be found in the “perfect” arrangement of nanoscopic Ga₈₄‐clusters in the crystal. This theoretically predicted condition for superconductivity in a “chain” of identical metal cluster molecules is a requirement which can hardly be realized by means of physical fabrication methods. Therefore, on the one hand the results presented here make for some disillusionment in the field of nanoscience, but on the other hand, especially in the field of synthetic chemistry, they present rewarding challenges for fundamental work in the future.     

Recent developments in homogeneous and dispersive liquid-liquid extraction for inorganic elements determination. A review

This review aims to provide an overview of homogeneous liquid-liquid extraction (HLLE) and dispersive liquid-liquid microextraction (DLLME) methods and their potential use in inorganic analysis. Relevant applications to the determination of metal ions, metalloids and organometals are included. The phase separation mechanisms of these unconventional solvent extraction techniques are discussed. The new trends in the field of miniaturization and automation are presented, while proposing future trends and potential new areas for their application.     

Der erste molekulare quadratisch‐antiprismatische Ga8‐Cluster mit closo‐Struktur

The First Molecular Square Antiprismatic Ga₈ Cluster exhibiting a closo Structure Ga₈(C₁₃H₉)₈^2– has been synthesized as a lithium salt from a reaction of fluorenyllithium with a metastable Ga^IBr solution. It is characterized by X‐ray structure analysis and DFT calculations. The eight Ga atoms form a square antiprismatic core and each Ga atom is σ‐bonded to a fluorenyl ligand. The Ga₈ entity of the cluster is described as a closo compound in contrast to the earlier presented species Ga₁₂(C₁₃H₉)₁₀^2–. This interpretation is based on DFT calculations for Ga₈H₈^2– and B₈H₈^2–.     

[Ge9{Si(SiMe3)3}2{Ge(SiMe3)3}]–: The Mixed Substituted Metalloid Germanium Cluster and the Intermetalloid Cluster [ZnGe18{Si(SiMe3)3}4{Ge(SiMe3)3}2]

The novel metalloid germanium cluster [Ge₉(Hyp)₂Hyp^Ge]^– ( 1 ) was synthesized, exhibiting two different bulky groups [Hyp = Si(SiMe₃)₃; Hyp^Ge = Ge(SiMe₃)₃]. Further reaction of 1 with ZnCl₂ gives the derivative [ZnGe₁₈(Hyp)₄(Hyp^Ge)₂] ( 2 ) in good yield, showing that the substitution of Si(SiMe₃)₃ by Ge(SiMe₃)₃ within a metalloid Ge₉R₃^– compound leads to a comparable reactivity. 1 and 2 are characterized by NMR spectroscopy, mass spectrometry ( 1 ) and single crystal structure analyses ( 2 ). 1 and 2 are the first metalloid germanium clusters bearing germyl groups.     

Sn(I) halides: Novel binary compounds of tin and their application in synthetic chemistry

Metalloid cluster compounds are ideal model compounds for the area between the molecular and solid state, i.e. the nanometer regime. For the synthesis of metalloid cluster compounds, the disproportionation reaction of a metastable subhalide is a fruitful synthetic route. In the case of tin, monohalides are needed for this synthetic route as tin(II) halides are too stable to be used. Due to thermodynamic data, gaseous SnBr should be formed at 1370 °C, and by applying a co-condensation technique it can be trapped at −196 °C and prepared in synthetic scale. Herein first analyses of SnBr are presented, showing that SnBr is more reactive than the corresponding GeBr, already disproportionating quantitatively to elemental tin and SnBr₂ on heating to room temperature. By applying nitrogen-based donor molecules like NnBu₃ or pyridine, the reactivity can be moderated and the solubility is enhanced leading e.g. to an SnBr emulsion, which can be used for the synthesis of metalloid cluster compounds of tin.     

FT/ICR–mass spectrometry in nanotechnology: the investigation of metalloid clusters

The particularity of metalloid clusters as a special kind of metal atom cluster is described. For the first time such metalloid clusters are investigated in the gas phase by means of FT/ICR–mass spectrometry, the results of which show that metalloid clusters represent a bridge between the bulk metal and metal compounds that can be found in solution after oxidation of the bulk metal. The metalloid clusters presented herein are [Ga₁₉R₆]^– (R=C(SiMe₃)₃), and SiAl₁₄Cp*₆ and the precursor Al₄Cp*₄ (Cp*= ⁵-C₅Me₅).     

Application of flowing-stream techniques to water analysis Part II. General quality parameters and anionic compounds: halogenated, sulphur and metalloid species

In the first part of this review [Talanta 60 (2000) 867], flowing-stream methods (namely, segmented flow analysis (SFA), continuous-flow analysis (CFA), flow-injection analysis (FIA), sequential-injection analysis (SIA), multicommuted flow-injection analysis (MCFIA) and multisyringe flow-injection analysis (MSFIA)) were presented as powerful analytical tools for nutrient determination in water samples when coupled to photometric/fluorimetric detection, flow-through ion-selective electrodes or amperometric sensors.In the present paper, relevant flow methods applied to the monitoring of anionic species as well as to the determination of general parameters for water quality evaluation (such as pH, alkalinity, chemical and biochemical oxygen demand, conductivity and total ionic content) are reviewed, and their background, detection technique and noteworthy analytical features are detailed. Furthermore, other techniques, such as flow systems connected to hydride-generation atomic absorption spectrometry, should be highlighted as practical approaches for metalloid determination since a series of speciation schemes are demonstrated to be readily adaptable.     

CE-ICP-MS for studying interactions between metals and biomolecules

Metal-biomolecule interactions comprise an important research area in metallomics, and are significant for biology, medicine, pharmacy, nutrition, metabolism, and environmental science. Hybrid techniques are preferred for studying interactions between metals and biomolecules. Of all the separation techniques, capillary electrophoresis (CE) exhibits high resolution, minimal sample and reagent consumption, and rapid and efficient separations with minor disturbance of the existing equilibrium between the metal species and their biomolecular complexes. Inductively coupled plasma mass spectrometry (ICP-MS) presents high sensitivity to most of elements and offers multi-element detection.This article provides an overview of CE-ICP-MS for the study of metal-biomolecule interactions. We discuss applications of CE-ICP-MS to the study of interactions between metals or metalloids and natural ligands, such as humic substances or fulvic acids, and the interchange of metal complexes with metal species in metalloproteins.     

AlCl3-catalyzed oxidation of alcohol

The metalloid salt AlCl₃, applied as catalyst for the oxidation of alcohol was presented. In water media, variety of alcohols, including inactive aliphatic alcohols, could be converted into corresponding carbonyl compounds with excellent conversion and selectivity. Especially, this green reaction system also exemplifies advances toward the domino synthesis alkenes in good yields (>52%) and perfect purity (>99%), and the reaction gave preferentially the E-isomer. The obvious advantages of the present protocol include green reaction media, wide functional group tolerance, convenient product isolation, as well as grams reaction scale.