Differential pulse polarography of germanium(IV), tin(IV), arsenic(V), antimony(V), selenium(IV) and tellurium(VI) at the static mercury drop electrode in catechol—perchlorate media

The differential pulse polarography of Ge(IV), Sn(IV), As(V), Sb(V), Se(IV) and Te(VI) has been investigated in perchlorate media containing catechol using a static mercury drop electrode. Under optimum conditions, Ge(IV), Sn(IV), As(V), and Sb(V) undergo reduction to yield well-defined peaks; detection limits of 82 ppb, 28 ppb, 4 ppm, and 25 ppb, respectively, have been calculated. Few electrolytes are known for which these ions exhibit a quantitatively useful polarographic response. While Se(IV) and Te(VI) may be detected at levels of 115 ppb and 17 ppb, respectively, addition of catechol does not enhance the peak current relative to that observed in simple perchlorate solutions, as was the case for the other ions studied. The determination of germanium, arsenic and antimony in samples is described.     

A novel catalytic adsorptive stripping voltammetric method for the determination of germanium ultratraces in the presence of chloranilic acid and the V(IV)·HEDTA complex

A novel, sensitive catalytic adsorptive stripping voltammetric procedure which can be used to determine trace amounts of germanium is described. The method is based on the interfacial accumulation of the complex formed by Ge(IV) and the product of the reduction of chloranilic acid on the hanging mercury drop electrode or the renewable silver amalgam film electrode, and its subsequent reduction from the adsorbed state followed by the catalytic action of the V(IV)·HEDTA complex. The presence of V(IV)·HEDTA greatly enhances the adsorptive stripping response of Ge. The reduction of the Ge(IV) in the presence of chloranilic acid and V(IV)·HEDTA was investigated in detail and the effects of pH, electrolyte composition, and instrumental parameters were studied. Under optimal conditions, the catalytic peak current of germanium exhibited good linearity for Ge(IV) concentrations in the range of 0.75–60 nM (for 60 s of accumulation at −0.1 V, r² = 0.995) and a low limit of detection (LOD = 0.085 nM). The procedure was successfully applied to determine Ge in water samples.

     

Synthesis and structures of an unusual germanium(II) calix[4]arene complex and the first germanium(II) calix[8]arene complex and their reactivity with diiron nonacarbonyl

The protonolysis reaction of the germanium(II) amide Ge[N(SiMe3)2]2 with calix[4]arene and calix[8]arene furnishes the two germanium(II) calixarene complexes {calix[4]}Ge2 and {calix[8]}Ge4, respectively, which have been crystallographically characterized. The calix[4]arene complex contains a Ge2O2 rhombus at the center of the molecule and is one of the only four germanium(II) calix[4]arenes that have been structurally characterized. The calix[8]arene species is the first reported germanium calix[8]arene complex, and it exhibits an overall bowl-shaped structure which contains two Ge2O2 fragments. The latter complex reacts with Fe2(CO)9 to yield an octairon compound, which has also been structurally characterized and contains four GeFe2 triangles arranged around the macrocyclic ring. The germanium(II) centers are oxidized to germanium(IV) in this process, with concomitant reduction of the neutral diiron species to Fe2(CO)(8)2- anions.     

Spectrophotometric determination of germanium with Catechol Violet and cetyltrimethylammonium bromide

A ternary complex between germanium, Catechol Violet (CV) and cetyltrimethylanunoniuni bromide is proposed for the determination of germanium. The stoichiometric ratio Ge:CV is 1:2. Beer's law is obeyed from 0.1 to 1.0 ppm of Ge. The method is highly selective. Interference from Sn(IV), Fe(III), Bi(III), Cr(VI), Mo(VI), V(V) and Sb(III) in mg amounts is eliminated by extracting the germanium into carbon tetrachloride from 9M HC1 and then stripping into water before the photometric determination.     

Germanium(II)-mediated reductive cross-aldol reaction of bromoaldehydes with aldehydes: NMR studies and ab initio calculations

A highly practical reductive cross-aldol reaction of alpha-bromoaldehydes with various aldehydes has been developed using Ge(II)Cl 2 to produce aldehyde germanium(IV) aldolates, which were directly transformed to various multifunctionalized compounds. A remarkable change in stereoselectivity depended on the alpha-bromoaldehydes employed; secondary alpha-bromoaldehydes gave syn selectivities, while tertiary alpha-bromoaldehydes accomplished the synthesis of anti-selective aldol products with a quaternary carbon center. NMR studies and X-ray analysis strongly suggested the formation of germanium enolate in the reaction of alpha-bromoaldehyde 2h with GeCl 2-dioxane. Detailed mechanistic studies, including NMR analysis and ab initio calculations, revealed the generation of stable germanium aldolates, which was due to the remarkably low Lewis acidity of the germanium(IV).     

Two Different Products Observed in the Reaction of a Bis(germylene) with Molybdenum Hydride [Mo(H)Cp(CO)3]

The reaction of the dimeric bis(germylene) [Ge{3,5‐(CF₃)₂pz}₂]₂ ( 2 ) with protic molybdenum hydride [Mo(H)Cp(CO)₃] yielded two different products. In diethyl ether the divalent germylene readily inserts into the Mo–H σ‐bond and the product of the oxidative addition, [Ge(H){Mo}(pz)₂] ( 4 ) (with pz = 3,5‐disubstituted pyrazole, 3,5‐(CF₃)₂pz; {Mo} = [MoCp(CO)₃]), was isolated featuring a germanium(IV) hydride moiety. In toluene an interesting “cascade” reaction takes place furnishing a bis‐metal substituted digermane [{Mo}(H)(pz)Ge–Ge(pz)₂{Mo}]. Although the detailed mechanism of the reaction remains the subject of speculation it seems likely that a germylene, [Ge^II(pz){Mo}], inserts into the germanium(IV) hydrogen bond of [Ge(H){Mo}(pz)₂] under formation of a germanium‐germanium bond, which is a rare reaction behaviour.     

Use of 73Ge NMR spectroscopy for the study of electronic interactions

The lack of understanding of the structural and electronic factors that affect the often difficult to observe germanium resonance has been a major deterrent to studies of bonding interactions at germanium. We utilized the symmetrical system GeR 4 to determine what structural factors inherent in the R group affect the shape and position of the (73)Ge resonance. The (73)Ge resonances of symmetrical tetrakis germanium compounds of the type GeR 4 (R = alkyl, aryl), GeX 4 (X = F, Cl, Br, I), Ge(OR) 4 (R = alkyl, methoxyalkyl, dimethylaminoalkyl), Ge(NR 2) 4 (R = alkyl), and Ge(SR) 4 (R = alkyl, dimethylaminoalkyl) were examined for evidence of intramolecular coordination. Although many of these compounds have sharp resonances due to idealized tetrahedral symmetry with relatively long relaxation times, others have broad or no observable resonances due to fast quadrupolar relaxation. We hypothesize that the perturbation of symmetry by even weak Lewis interactions or conformational changes causes broadening of the resonance before the interaction can become sufficiently strong to cause the significant low-frequency shift generally associated with hypercoordination in most nuclei. Intermolecular coordination to GeCl 4 is believed to be responsible for the low-frequency shifts in (73)Ge resonances and the associated changes in peak widths in mixtures with bases such as tributylphosphine oxide (TBPO) and triethylphosphine oxide (TEPO). Adduct formation with these bases is confirmed by broad (31)P resonances that are resolved into five peaks at -40 degrees C. The exchange-broadened resonances due to the 1:1 and 1:2 TEPO adducts are also observed at -40 degrees C in the (73)Ge spectrum. Thus, relatively strong bonding to the germanium in GeCl 4 results in both low-frequency shifts and broadening of the resonance. The broad (73)Ge resonances that occur in some compounds may be in part due to exchange as well as quadrupolar relaxation.     

Synthesis of Five Coordinate Spirocyclic Germanium(IV) Complexes Containing Diethanol Amine

Reaction of dihydroxo(2,2′-iminodiethanolato-AWO′) germanium(IV) (A) or dihydroxo(2,2′-methyliminodiethanolato-N,O.O′) germanium(IV) (B) with bidentate ligands, e.g. diol, α-hydroxy acid, oxalic acid, 2,6-pyridinedicarboxylic acid, or 2-aminophenol in a mixture of ethanol and xylene mixture yielded a series of unsymmetrical spiro-germanium complexes 1-6. These complexes were characterized by NMR, IR, mass spectra and elementary analysis. The ¹H NMR spectrums of all these compounds show the existence of an intramolecular N – Ge bond. X-ray analysis of compound 6 shows a short N–Ge bond (2.08 Å).     

Voltammetric and chronoamperometric investigation of germanium amalgams: Part I. Properties of the homogenous amalgam

Using cyclic voltammetry and chronoamperometry with several anodic steps the deposition and particularly the oxidation of germanium from a HMDE was investigated within pH range 4–12 at Ge (IV) concentrations ranging from 4×10^?7M to 1×10^?4M in the absence of ligands capable to form the complex compounds with Ge(IV) in a solution. It was found that the initially formed product of electrodeposition is a homogeneous, usually supersaturated amalgam. Germanium from this amalgam oxidizes at about 1 V (vs. mercury sulphate reference electrode) or after some induction period, the length of which depends on concentration of Ge(0) in mercury, it begins to crystallize forming heterogenous germanium amalgam. Germanium from this heterogenous amalgam oxidizes in a separate voltammetric peak at more positive potentials. The solubility of germanium in mercury was evaluated on the basis of the oxidation current of homogenous amalgam and the value obtained is equal to (2±0.5)×10^?7M i.e. (1.1±0.3)×10^?7 wt. %. Applying the Stevens and Shain method the diffusion coefficient of germanium in mercury was found to be (1.32±0.1)×10^?5 cm² s^?1.     

Square-wave voltammetry of the o-catechol-Ge(IV) catalytic system after adsorptive preconcentration at a hanging mercury drop electrode

Square-wave (SW) voltammetry in connection with a hanging mercury drop electrode has been applied for studying the reduction of Ge(IV) catalyzed by o-catechol after adsorptive preconcentration. Acetate buffer solutions with low and high analytical concentrations of o-catechol [with respect to that of Ge(IV)] have been used. Dependences of SW catalytic peaks on accumulation conditions have been attributed to the formation of the catalytic complexes via a direct-adsorption mechanism. The nature of the electrocatalytic process (involving an apparently quasi-reversible electrode reaction with an adsorbed reactant and a diffusing product) allows us to explain complex dependences of catalytic peaks on SW-parameters. Adequate conditions for determination of o-catechol and Ge(IV) by means of SW catalytic adsorptive voltammetry have been established.     

Effect of dicitrato- and dimalatogermanic acids on polycondensation of maleic anhydride with ethylene glycol

The catalytic activity of citric (H₄Citr) and malic (H₃Mal) acids, their coordination compounds with germanium(IV) H₂[Ge(HCit)₂] and H₂[Ge(Mal)₂], and germanium dioxide GeO₂ in polycondensation of maleic anhydride and ethylene glycol at various temperatures was studied (catalyst: ethylene glycol molar ratio 0.01: 1). The process kinetics was evaluated and the time of its completion was determined. The copolymerization kinetics of some of the prepared oligoesters with triethylene glycol dimethacrylate was studied, and the copolymer properties were determined.     

Determination of germanium by potentiometric stripping analysis and adsorption potentiometric stripping analysis

Potentiometric stripping analysis was applied to determination of germanium(IV) in 0.2M NH₃-NH₄Cl (pH 8.4) buffer solution at −1.8 V (vs. Ag/AgCl), with dissolved oxygen or Hg(II) as oxidant. The sensitivity was 8.5 × 10⁻⁹M in the presence of 2.0 × 10⁻⁵M Hg(II) with plating for 15 min after deaeration for 20 min. Cyclic voltammetry revealed that GE(IV) å Ge at the surface of the mercury-film electrode in a one-step irreversible reduction reaction, and the Ge at the electrode was oxidized by dissolved oxygen in the solution. The presence of complexing agents such as Alizarin Red (ARS), which forms a Ge(IV) complex adsorbed at the electrode, improved the sensitivity by one order of magnitude. The presence of adsorption was revealed by the temperature coefficient, the electrocapillary curve and cyclic voltammetry. Ge-containing samples were analysed by the proposed methods and agreement with the results obtained by other methods was excellent.     

High-resolution solid-state MAS 73Ge NMR spectra of some organogermanes

High-resolution solid-state magic angle spinning (73)Ge NMR spectra of some organogermanium compounds were measured. Most tetrasubstituted germanes with identical substituents exhibited signals except for one case. Tetrasubstituted germanes with two kinds of different but somewhat similar substituents exhibited broad peaks. Trisubstituted germanes failed to show signals, indicating the importance of symmetry around germanium.     

Ge8R6: the ligands define the bonding situation within the cluster core

The disproportionation reaction of Ge(i) halides open up a way to cluster compounds with an average oxidation state of the germanium atoms inside the cluster core in between 0 and 1. Simultaneously compounds with germanium in an oxidation state greater than i are formed. During the reaction of Ge(i) bromide with one equivalent of LiR (R = 2,6-(tBuO)(2)C(6)H(3)) the cluster compound Ge(8)R(6) and the molecular Ge(iv) compound R(3)GeBr were isolated, representing the reduction and the oxidation product of the disproportionation reaction, respectively. The molecular structure of the Ge(8) cluster compound shows a highly different arrangement of the eight germanium atoms in the cluster core with respect to the only other Ge(8)R(6) cluster compound where amido ligands are bound to the germanium atoms. Quantum-chemical calculations reveal that the distinct arrangement of the germanium atoms can be traced back to a different bonding situation inside the cluster frameworks, which is induced by the different ligands attached to the germanium atoms. These experimental and theoretical results show that the ligands are not only necessary for protecting the cluster core against the exterior but also have a strong influence on the bonding situation and therefore on the electronic situation inside the cluster core. Hence, the ligand influences the electronic properties and consequently the physical properties which is now seen, for the first time, in metalloid germanium cluster compounds.     

Density Functional Theory Calculations Revealing Metal‐like Band Structures for Ultrathin Germanium (111) and (211) Surface Layers

To find out if germanium possesses facet‐dependent electrical‐conductivity properties, surface‐state density functional theory (DFT) calculations were performed on one to six layers of germanium (100), (110), (111), and (211) planes. Tunable Ge(100) and Ge(110) planes always present the same semiconducting band structure with a band gap of 0.67 eV expected of bulk germanium. In contrast, one, two, four, and five layers of Ge(111) and Ge(211) plane models show metal‐like band structures with continuous density of states (DOS) throughout the entire band. For three and six layers of Ge(111) and Ge(211) plane models, the normal semiconducting band structure was obtained. The plane layers with metal‐like band structures also show Ge−Ge bond‐length deviations and bond distortions, as well as significantly different 4s and 4p frontier‐orbital electron counts and relative percentages integrated over the valence and conduction bands from those of the semiconducting state. These differences should contribute to strikingly dissimilar band structures. The calculation results suggest the observation of facet‐dependent electrical‐conductivity properties of germanium materials; when making transistors from germanium, the facet effects with shrinking dimensions approaching 3 nm may also need to be considered.     

Un réactif spécifique du germanium: la phénylfluorone

Based on the action of methyl fluorone on Ge(IV) the use of this reagent for the detection of germanium is described. It is necessary to treat with 6N HCl to make this reaction specific.However, another derivative of fluorone, namely phenyl fluorone, is still better for identifying Ge(IV). By placing a drop of the solution under test, previously strongly acidified (3 N to 6N in HCl), on a phenyl fluorone reagent paper and adding 2 or 3 drops of 6 N HNO₃, a. sensitive and specific reaction for germanium is obtained.The only interfering ions are those of strong oxidising agents (Ce⁺⁴, Cr⁺⁶, Mn⁺⁷, etc.) which destroy the reagents and must be eliminated in the first place.Other ions and ions of the group of the sulphides soluble in alkalisulfides do not interfere, even in the proportion of 100 parts by weight, to 1 of Ge. The limit of dilution is about 10^-5.5.     

Ge4Br4[Mn(CO)5]4 and Ge6Br2[Mn(CO)5]6: first germanium cluster compounds containing Mn(CO)5 ligands

Cluster compounds of germanium exhibiting germanium-germanium bonds, where the germanium atoms are additionally bound to transition metal ligands, are rare. Here a synthetic pathway to such cluster compounds is described, starting from metastable Ge I halide solutions leading to the two cluster compounds Ge4Br4[Mn(CO)5]4 and Ge6Br2[Mn(CO)5]6, being the first examples of germanium cluster compounds bearing Mn(CO)5 ligands. The Ge6 compound exhibits a novel arrangement of germanium atoms that has not been previously observed in ligand stabilized cluster compounds of germanium, neither with organic nor with transition metal ligands. The bonding situation inside the cluster compounds is discussed, together with a possible reaction pathway that opens the way to metalloid cluster compounds of germanium exhibiting Mn(CO)5 ligands.     

High-resolution solid-state 73Ge NMR spectra of hexacoordinated germanium compounds

High-resolution solid-state magic angle spinning 73Ge NMR spectra of hexavalent germanium compounds, i.e. diiodogermylene (1a) and bis(1-pyrrolyl)(meso-tetraphenylporphyrinato)germanium (3a), were determined. To the best of our knowledge, this is the first example of high-resolution solid-state 73Ge NMR spectra of hexacoordinated germanium nuclei. The symmetry requirement for observation of high-resolution solid-state 73Ge NMR spectra is discussed.     

Germanium carboxylates: the first X‐ray diffraction study of germanium(II) dicarboxylate and germanium(IV) tetracarboxylate

Germanium(II) dipropionate (1) has been synthesized and its crystal structure, as well as that of germanium(IV) tetrapropionate (2), has been determined. By contrast to monomeric 2 with monodentate propionate ligands, compound 1 is associated, forming a cyclotetramer [Ge(O₂CEt)₂]₄ (1a) via intermolecular dative C?O → Ge interactions. Copyright © 2005 John Wiley & Sons, Ltd.     

A theoretical study on growth patterns of Ni-doped germanium clusters

Ni-doped germanium clusters have been systematically investigated by using the density functional approach. The growth-pattern behaviors, stabilities, charge transfer, and polarities of these clusters are discussed in detail. Obviously different growth patterns appear between small-sized Ni-doped germanium clusters and middle- or larger-sized Ni-doped germanium clusters. The Ni-convex or substituted Ge(n) frames for small-sized clusters as well as Ni-concaved or encapsulated Ge(n) frames for middle- or large-sized clusters are dominant growth patterns. The calculated fragmentation energies manifest that the magic numbers of stabilities are 5, 8, 10, and 13 for Ni-doped germanium clusters; the obtained relative stabilities exhibit that the Ni-encapsulated Ge(10) cluster is the most stable species of all different-sized clusters, which is in good agreement with available experimental observations of CoGe(10)(-). Natural population analysis shows that different charge-transfer phenomena depend on the sizes of the Ni-doped Ge(n) clusters. Additionally, the properties of frontier orbitals and the polarities of Ni-doped Ge(n) clusters are also discussed.