Germanium Species Research Articles

XB2Bi2 (X = Si, Ge, Sn, Pb): Penta-Atomic Planar Tetracoordinate Si/Ge/Sn/Pb Clusters with 20 Valence Electrons.

Planar tetracoordinate silicon, germanium, tin, and lead (ptSi/Ge/Sn/Pb) species are scarce and exotic. Here, we report a series of penta-atomic ptSi/Ge/Sn/Pb XB2Bi2 (X = Si, Ge, Sn, Pb) clusters with 20 valence electrons (VEs). Ternary XB2Bi2 (X = Si, Ge, Sn, Pb) clusters possess beautiful fan-shaped structures, with a Bi-B-B-Bi chain surrounding the central X core. The unbiased density functional theory (DFT) searches and high-level CCSD(T) calculations reveal that these ptSi/Ge/Sn/Pb species are the global minima on their potential energy surfaces. Born-Oppenheimer molecular dynamics (BOMD) simulations indicate that XB2Bi2 (X = Si, Ge, Sn, Pb) clusters are robust. Bonding analyses indicate that 20 VEs are perfect for the ptX XB2Bi2 (X = Si, Ge, Sn, Pb): two lone pairs of Bi atoms; one 5c-2e π, and three σ bonds (two Bi-X 2c-2e and one B-X-B 3c-2e bonds) between the ligands and X atom; three 2c-2e σ bonds and one delocalized 4c-2e π bond between the ligands. The ptSi/Ge/Sn/Pb XB2Bi2 (X = Si, Ge, Sn, Pb) clusters possess 2π/2σ double aromaticity, according to the (4n + 2) Hückel rule.

Redox‐chemistry of Pyramidanes: A DFT Study

AbstractBased on previous experimental findings, a DFT study on the redox‐induced rearrangement of a series of germa‐, phospha‐ and borapyramidanes is presented. Upon stepwise two‐electron reduction, these 5‐vertex nido‐clusters are predicted to form their respective monocyclic derivatives (germole diides, (tri)phospholides and borole diides) which are formally related to the cyclopentadienide anion. Hence, it is likely that these rearrangements are a common reactivity of pyramidanes. Based on the calculations, the oxidation of these monocyclic derivatives is expected to result in the formation of meta‐stable dimers for germanium and phosphorus species, and monomeric borole derivatives for boron species. Consequently, investigating the redox chemistry of pyramidanes presents an exciting opportunity to discover new and unique main‐group species.

Design of an Organic Template for Synthesizing ITR Zeolites under Ge-Free Conditions.

Germanosilicate zeolites with various structures have been extensively synthesized, but the syntheses of corresponding zeolite structures in the absence of germanium species remain a challenge. One such example is an ITR zeolite structure, which is a twin of the ITH zeolite structure. Through the modification of a classic organic template for synthesizing ITH zeolites and thus designing a new organic template with high compatibility to ITR zeolite assisted by theoretical simulation, we, for the first time, show the Ge-free synthesis of an ITR structure including pure silica, aluminosilicate, and borosilicate ITR zeolites. These materials have high crystallinity, corresponding to an ITR content of more than 95%. In the methanol-to-propylene (MTP) reaction, the obtained aluminosilicate ITR zeolite exhibits excellent propylene selectivity and a long lifetime compared with conventional aluminosilicate ZSM-5 zeolite. The strategy for the design of organic templates might offer a new opportunity for rational syntheses of novel zeolites and, thus, the development of highly efficient zeolite catalysts in the future.

Impact of network topology on the thermal and mechanical properties of lithium germanate glasses

AbstractIn this work, we study the structure–topology–property relations of a series of melt‐quenched lithium germanate glasses. These glasses exhibit the so‐called germanate anomaly, that is, the germanium atoms feature a distribution of four‐coordinated and higher coordinated germanium species, manifesting itself as anomalies in several material properties. Here, we couple variations in the number of atomic bond constraints with measured variations in thermal and mechanical properties, including thermal conductivity, Vickers hardness, and fracture toughness. For thermal conductivity, a strong correlation is found with sound velocity as well as with the volumetric constraint density. For hardness, a good correlation with volumetric constraint density is found, whereas, for fracture toughness, variations in network topology alone are insufficient to explain the composition–property relation. To account for this, we apply a recent model which incorporates knowledge of local structure, mechanical properties, and fracture patterns to predict the fracture toughness, showing a good qualitative agreement with the experimental data.

Acyl metalloids: conformity and deviation from carbonyl reactivity.

Once considered as mere curiosities, acyl metalloids are now recognized for their utility in enabling chemical synthesis. This perspective considers the reactivity displayed by acylboron, -silicon, -germanium, and tellurium species. By highlighting the role of these species in various transformations, we demonstrate how differences between the comprising elements result in varied reaction outcomes. While acylboron compounds are primarily used in polar transformations, germanium and tellurium species have found utility as radical precursors. Applications of acylsilanes are comparatively more diverse, owing to the possibility to access both radical and polar chemistry.

Speciation of germanium in environmental water reference materials by hydride generation and cryotrapping in combination with ICP-MS/MS

A method for the speciation analysis of the three main species of germanium in environmental waters, namely inorganic germanium (iGe), monomethyl germanium (MMGe) and dimethyl germanium (DMGe), has been developed. Germanium species were volatilized by hydride generation (HG) prior to their preconcentration/separation in a semi-automated cryogenic trap (cryotrapping, CT) and detection by ICP-MS/MS. A procedure to minimize the iGe blanks from the chemicals and water is reported. One mL of water can be analyzed without any pretreatment. After application of this procedure, and the careful optimization of all experimental variables, limits of detection (LOD) of 0.015, 0.005 and 0.003 ng L−1 have been obtained for iGe, MMGe and DMGe, respectively. Standard addition experiments did not show any significant matrix effect, and, therefore, external calibration was used for sample analysis. In the Tris-HCl + L-Cysteine reaction media, additional experiments did not reveal any significant demethylation of MMGe to iGe in the process of HG-CT, which could affect the accuracy of the analysis in seawater. The method has been applied to the analysis of iGe, MMGe and DMGe in certified reference materials of unspiked natural waters: CASS-4, CASS-5 and CASS-6 (nearshore seawater); NASS-5 and NASS-7 (seawater); SLRS-4, SLRS-5 and SLRS-6 (river water).

Recovery of pure germanium oxide from Zener diodes using a recyclable ionic liquid Cyphos IL 104

A novel process is developed for the recovery of germanium from the leach liquor of Zener diodes using solvent extraction. Extraction is carried out using a phosphonium ionic liquid, Cyphos IL 104, as an extractant. Preliminary investigations carried out on Ge(IV) extraction using Cyphos IL 104 include influence of various parameters like temperature, equilibration time, and concentration of extractant, chloride ion, and acid on the distribution of Ge(IV). NMR spectrum of Ge(IV)-extractant complex was analyzed to support the proposed extracting species of germanium. Quantitative extraction of germanium is achieved from 7 mol/L HCl onwards using 0.1 mol/L Cyphos IL 104. Optimum conditions for quantitative extraction of Ge from leach liquor of Zener diodes were developed. McCabe-Thiele plots were constructed for the extraction and stripping of Ge(IV) from leach liquor to determine the number of stages required at a particular aqueous/organic phase ratio. Separation of germanium from copper, mercury and iron has been achieved by selective stripping of these metal ions. Germanium is recovered as germanium oxide from the strip solution using NaOH as a precipitating agent. The synthesized germanium oxide is characterized by XRD, FE-SEM and EDX techniques.

Synthesis of α-Alkenyl α,β-Unsaturated Ketones via Dehydrogermylation of Oxagermacycles with Regeneration of the Germanium(II) Species.

The synthesis of α-alkenyl α,β-unsaturated ketones using germanium(II) salts is reported. Oxagermacycles derived from α,β-unsaturated ketones with germanium(II) salts and aldehydes can be transformed into α-alkenyl α,β-unsaturated ketones. Ammonium salts promoted the elimination of Ge(II) species to afford the two classes of α-alkenyl α,β-unsaturated ketones in good yields. The α-alkenyl α,β-unsaturated ketones are precursors for multisubstituted heterocycles.

Selective separation of Germanium(IV) from simulated industrial leachates containing heavy metals by non-dispersive ionic extraction

Ge(IV) can be found in industrial leachates of coal gasification fly ashes (CGFA) or zinc resources. In this research, the selective separation of germanium from simulated water leach liquors of CGFA containing Zn(II), Ni(II), Cd(II), and Co(II) was carried out using flat sheet (FSSLM) and hollow fiber supported ionic liquid membrane (HFSLM) systems containing Aliquat 336 as an ionic liquid carrier. As a result, Aliquat 336 was found to be an effective carrier for the selective transport of Ge(IV) from these types of solutions. In addition, the selective transport of germanium was performed from a simulated acidic zinc leach liquor using an FSSLM system. According to the results obtained, sulfuric acid in zinc leach liquors has not an insignificant effect on the transport of germanium in comparison to a water medium consisting of CGFA leach liquors. The germanium transport from both types of solutions was selective and its efficiency reached >98%. Finally, the facilitated transport of germanium was conducted in an HFSLM under the same condition obtained using the FSSLM system. It was observed that this system could transport the maximum amounts of germanium species in the first 30 min, showing its faster transport than that of the FSSLM system.

A multiply functionalized base-coordinated Ge(II) compound and its reversible dimerization to the digermene.

Stable compounds with a GeGe bond are usually prepared under relatively harsh reaction conditions that are incompatible with many functional groups. In particular, unsaturated functionalities are not tolerated owing to their facile reaction with low-coordinate germanium compounds. We now report the synthesis of an imino-functionalized germanium(II) species, stabilized by coordination of an N-heterocyclic carbene (NHC), by reaction of an isonitrile with a heavier NHC-coordinated vinylidene. Removal of the NHC by a Lewis acid results in dimerization to the corresponding digermene with a GeGe bond. The reversibility of this process is demonstrated by addition of two equivalents of NHC to the isolated digermene.

Anionic access to silylated and germylated binuclear heterocycles.

A simple access to silylated and germylated binuclear heterocycles, based on an original anionic rearrangement, is described. A set of electron-rich and electron-poor silylated aromatic and heteroaromatic substrates were tested to understand the mechanism and the factors controlling this rearrangement, in particular its regioselectivity. This parameter was shown to follow the rules proposed before from a few examples. Then, the effect of the substituents borne by the silicon itself, in particular the selectivity of the ligand transfer, was studied. Additionally, this chemistry was extended to germylated substrates. A hypervalent germanium species, comparable to the putative intermediate proposed with silicon, seems to be involved. However, a pathway implicating the elimination of LiCH2Cl was observed for the first time with this element, leading to unexpected products of the benzo-oxa (or benzo-aza) germol-type.

Mixed Network Former Effects in Oxide Glasses: Spectroscopic Studies in the System (M2O)1/3[(Ge2O4)x(P2O5)1–x]2/3

The structure of mixed-network former glasses in the system (M2O)0.33[(Ge2O4)x(P2O5)1–x]0.67.(M = Na, K) has been studied by 31P and 23Na high-resolution and dipolar solid state nuclear magnetic resonance (NMR) techniques, O-1s X-ray photoelectron spectroscopy, and Raman spectroscopy. Using an iterative fitting procedure, a quantitative structural model has been developed that is consistent with all of the experimental data and which provides a detailed description of network connectivities, network modification processes, and spatial cation distributions. Formation of heteroatomic P–O–Ge linkages is generally preferred over homoatomic P–O–P and Ge–O–Ge linkages, as shown by a detailed comparison with a random linkage model. An exception occurs in glasses with low germanium contents (x = 0.2) where a pronounced nonlinear dependence of the glass transition temperature on x can be related to a cross-linking of the sodium ultraphosphate network by fully polymerized germanium species, possibly including also 5- and 6-fold coordination states. At higher x values, the Ge component is modified as well, however, the fraction of anionic nonbridging oxygen atoms bound to germanium is always lower than expected for proportional modifier sharing between both network formers. Rather, the phosphate component is preferentially modified by the cations, leading to the formation of P(1) units at high x values. Consequently, the local coordination of the cations is dominated by phosphorus, as is clearly evident from the 23Na{31P} rotational echo double resonance (REDOR) results. This preferred association, combined with the formation of P(1) units, results in partially clustered cation distributions, which can be detected by 23Na spin echo decay spectroscopy. Finally, the joint interpretation of all of the data from NMR, Raman, XPS, and thermal analysis measurements offers indirect evidence for the formation of higher germanium coordination states in this glass system.

Replacing Tin in Lactide Polymerization: Design of Highly Active Germanium‐Based Catalysts

Most germane: Hexacoordinate germanium(IV) species exhibit unprecedented activities, yet controlled behavior, as initiators for the ring-opening polymerization of rac-lactide to form polylactide polymers.

Titanium–Germoxy Precursor Route to Germanium-Modified Epoxidation Catalysts with Enhanced Activity

The complex Ti[OGeiPr3]4 (1), prepared via the reaction of Ti(OiPr)4 with iPr3GeOH, represents a useful structural and spectroscopic model for titanium–germanium species dispersed onto silica. This precursor was used to introduce site-isolated Ti(IV) centers onto the surface of a mesoporous SBA15 support via the thermolytic molecular precursor method. The local environments of the supported materials (TiGe3SBA15 and calcined TiGe3SBA15-O2) were studied by various spectroscopic methods, including X-ray absorption spectroscopy. These materials are active catalysts for the epoxidation of cyclic and terminal olefins with alkyl hydroperoxides under anhydrous conditions. Compared to catalysts synthesized from siloxide-only precursors, the new catalysts produce 2–3 times more product after 9 h under identical reaction conditions for the epoxidations of cyclohexene and 1-octene. The new materials did not significantly leach under reaction conditions.

Effect of HF concentration on the composition and distribution of Ge species in the framework of ITQ-13 and ITQ-17 zeolites

Two germanosilicates with zeolitic structures, namely ITQ-13 and ITQ-17, have been synthesized from gels containing various amounts of hydrofluoric acid. Although both zeolites possess similar compositions, they differ not only by their pore size and framework topology but also by the nature of the cavities surrounding fluoride species in the structure. For ITQ-17, in which fluoride is almost exclusively located in D4R units, a decrease in HF concentration in the gel has no influence on the fluoride content in the zeolite. However, it favors the incorporation of germanium species in the framework, particularly in D4R units. Zeolites obtained at low HF concentrations are characterized by high Ge contents and Si/Ge atomic ratios close to 1 in D4R units. In the case of ITQ-13, the possibility for fluoride to reside not only in D4R units but also in the larger [415262] cages minimizes the influence of the HF concentration on the zeolite framework composition. Reducing the HF concentration in the gel has no effect on the Si/Ge ratio in the final zeolite but it decreases the fluoride content in the structure. At low HF concentration, fluoride is absent from [415262] cages and is almost exclusively present in all-silica D4R units. As the concentration increases, fluoride starts to occupy Ge-rich D4R and [415262] cages, as clearly evidenced by 19F NMR. By contrast to ITQ-17, the amount of HF in the gel does not influence the distribution of Ge species in the framework.

Selective recovery of germanium with N-methylglucamine functional resin from sulfate solutions

Growing demand of germanium and uncertainties in supply create a need for research into efficient separation methods. Ion exchange recovery of germanium from sulfate solutions was studied with equilibrium experiments, column experiments, and modeling. Based on screening of four commercial resins by equilibrium experiments, a bifunctional N-methylglucamine resin was selected for dynamic adsorption studies and modeling. The adsorption of germanium onto the resin depended strongly on pH. The first pKa value of germanic acid, Ge(OH)4, is 9 and its anionic dissociation products (oxoanions) were adsorbed to the nitrogen containing groups by anion exchange mechanism. The germanium species were all adsorbed to glucose sites. Other metal ions in the studied multimetal feeds decreased the Ge adsorption directly by competition, and indirectly by acting as buffers to prevent pH increase and the dissociation of germanic acid. Iron was found to have a particularly detrimental effect on the adsorption.A competitive adsorption model was used to describe the sorption equilibrium of germanic acid and its dissociation products to glucose sites and to amine groups. A transport-dispersive model with a solid film linear driving force model was employed for the dynamic modeling. Authentic and simulated feed solutions were used to study the effect of competing metals. The feed solutions contained 63–490mg/L Ge and metal sulfates so that ionic strengths were between 0.58 and 5.82mol/L. The constructed simulation model predicted the equilibrium isotherms and the breakthrough curves of germanium well.

G73e Nuclear Magnetic Resonance Spectroscopy of Germanium Compounds

The field of G73e NMR spectroscopy is reviewed in this paper, from early developments in the 1950s to present day research. Specific attention is paid to recent investigations, including the observation of fluxional behavior of hypervalent germanium species having five or six attached ligands by 73Ge NMR spectroscopy, the spectral properties of linear and branched oligogermanes that contain single germanium-germanium bonds, and the relatively new field of solid-state germanium-73 NMR.

Quantification of Short and Medium Range Order in Mixed Network Former Glasses of the System GeO2–NaPO3: A Combined NMR and X-ray Photoelectron Spectroscopy Study

Glasses in the system xGeO2–(1–x)NaPO3 (0 ≤ x ≤ 0.50) were prepared by conventional melting–quenching and characterized by thermal analysis, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and 31P nuclear magnetic resonance (MAS NMR) techniques. The deconvolution of the latter spectra was aided by homonuclear J-resolved and refocused INADEQUATE techniques. The combined analyses of 31P MAS NMR and O-1s XPS lineshapes, taking charge and mass balance considerations into account, yield the detailed quantitative speciations of the phosphorus, germanium, and oxygen atoms and their respective connectivities. An internally consistent description is possible without invoking the formation of higher-coordinated germanium species in these glasses, in agreement with experimental evidence in the literature. The structure can be regarded, to a first approximation, as a network consisting of P(2) and P(3) tetrahedra linked via four-coordinate germanium. As implied by the appearance of P(3) units, there is a moderate extent of network modifier sharing between phosphate and germanate network formers, as expressed by the formal melt reaction P(2) + Ge(4) → P(3) + Ge(3). The equilibrium constant of this reaction is estimated as K = 0.52 ± 0.11, indicating a preferential attraction of network modifier by the phosphorus component. These conclusions are qualitatively supported by Raman spectroscopy as well as 31P{23Na} and 31P{23Na} rotational echo double resonance (REDOR) NMR results. The combined interpretation of O-1s XPS and 31P MAS NMR spectra shows further that there are clear deviations from a random connectivity scenario: heteroatomic P–O–Ge linkages are favored over homoatomic P–O–P and Ge–O–Ge linkages.

Designing bis(phosphaalkenyl)germylenes and their tungsten complexes – A theoretical study

A theoretical investigation of bis(phosphaalkenyl)germanium(II) species of the type Ge(CR 2 = PR 1) 2 (R 1 = H, Me, Ph, Mes; R 2 = H, Me, Ph, Cl, F, SiMe 3) was performed in order to evaluate the singlet–triplet gap for the considered germylenes and the effect of groups in β and γ positions relative to the germanium atom. Optimized geometrical parameters are presented. The coordination ability of these species towards the W(CO) 5 moiety was also investigated; calculations indicate a predilection for the coordination through the germanium atom.

Supramolecular assemblies of germanium(ii) halides with O-, S- and Se-donor macrocycles – the effects of donor atom type upon structure

Reaction of [GeCl(2)(dioxane)] with [18]aneS(6) (1,4,7,10,13,16-hexathiacyclooctadecane) gives the neutral [GeCl(2)([18]aneS(6))] which forms a supramolecular sheet network involving exocyclic coordination, with the macrocycles bridging Ge atoms which are in a pseudo-trigonal bipyramidal environment from two Cl and two S atoms (saw-horse), with one lone pair assumed to occupy the remaining equatorial void. Conversely, using the mixed S/O macrocycles [18]aneS(3)O(3) (1,4,7-trithia-10,13,16-trioxacyclooctadecane) and [15]aneS(2)O(3) (1,4-dithia-7,10,13-trioxacyclopentadecane) (L) leads to the monocationic pentagonal pyramidal [GeCl(L)](+) whose structures show endocyclic Ge coordination, and displacement of one Cl. The Ge-S and Ge-O bond lengths are surprisingly disparate in these two complexes, and in the former the coordinated Cl is axial, while in the latter it occupies the pentagonal plane (with an S atom axial). Cyclic selenoethers form one-dimensional or two-dimensional supramolecular assemblies with Ge(ii) halides, including [GeCl(2)([8]aneSe(2))] ([8]aneSe(2) = 1,5-diselenacyclooctane), [(GeCl(2))(2)([16]aneSe(4))] ([16]aneSe(4) = 1,5,9,13-tetraselenacyclohexadecane), [GeBr(2)([16]aneSe(4))] and [(GeI(2))(2)([16]aneSe(4))]·GeI(4)- these represent the first germanium species with selenoether ligation. Structural studies on each of these show exocyclic GeX(2) coordination, giving networks based upon Se(2)X(2) coordination at Ge(ii) with a distorted pseudo-trigonal bipyramidal environment in which the Ge-based lone pair is assumed to occupy the vacant equatorial vertex. Further weak GeX contacts are also evident in some cases. The weak, secondary GeS/Se and GeX interactions that pervade these systems may be regarded as a further type of supramolecular interaction allowing assembly of new network structures, and the long II contacts evident between the GeI(2) and GeI(4) units in [(GeI(2))(2)([16]aneSe(4))]·GeI(4) probably provide a small thermodynamic contribution leading to co-crystallisation of ordered GeI(4) molecules within the network.