GeCl4 Research Articles

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).

Cycloaddition on Ge(100) of the Lewis Acid AlCl3

The adsorption and decomposition of AlCl3 on Ge(100) was studied using scanning tunneling microscopy (STM) and high-resolution core-level photoemission spectroscopy (HRCLPES). Through the analysis of the STM image and Ge 3d and Cl 2p core-level spectra of AlCl3 on Ge(100), we found that an AlCl3 molecule reacts with two Ge atoms via a cycloaddition reaction, which forms Cl−Ge and AlCl2−Ge without breaking AlCl3. Additionally, by considering valence shell electron pair repulsion (VSEPR) arguments, the effect of molecular structure on the surface chemistry was explained. To our knowledge, the adsorption of Lewis acid molecules on a semiconductor surface has not been studied in detail. These are the first results for the adsorption structures of Lewis acid molecule on Ge(100).

Synthesis, characterisation and reactivity of germanium(ii) amidinate and guanidinate complexes

Reactions of lithium salts of the bulky guanidinate ligands, [ArNC(NR2)NAr](-) (NR2 = N(C6H11)2 (Giso-) and cis-NC5H8Me2-2,6 (Pipiso-); Ar = C6H3Pri2-2,6), with GeCl2.dioxane afforded the heteroleptic germylenes, [(Giso)GeCl] and [(Pipiso)GeCl], the former of which was structurally characterised. The further reactivity of these and the related complexes, [(Piso)GeCl] and [(Priso)GeCl] (Piso- = [ArNC(Bu(t))NAr]-, Priso- = [ArNC(NPri2)NAr]-) has been investigated. Salt elimination reactions have yielded the new monomeric complexes, [(Piso)Ge(NPri2)] and [(Piso)GeFeCp(CO)2], whilst a ligand displacement reaction afforded the heterometallic species, [(Piso)Ge(Cl)(W(CO)5)]. Chloride abstraction from [(Priso)GeCl] with GaCl3 has given the structurally characterised contact ion pair, [(Priso)Ge][GaCl4]. In addition, the inconclusive outcome of a number of attempts to reduce the germanium halide complexes are discussed.

Reaction of germanium tetrachloride with oxygen under MCVD fiber preform fabrication conditions

The GeO2 yield in the reaction between GeCl4 and oxygen has been determined as a function of the reaction time under typical MCVD fiber preform fabrication conditions. It is shown that the yield increases steadily over time and may attain 100%. In the case of the cooxidation of germanium and silicon tetrachlorides under the same conditions, there is an optimal reaction time corresponding to a maximum in GeO2 yield. The temperature profile along the reaction zone has been optimized in terms of germania yield.

Nonthermal plasma synthesis of size-controlled, monodisperse, freestanding germanium nanocrystals

Germanium nanocrystals may be of interest for a variety of electronic and optoelectronic applications including photovoltaics, primarily due to the tunability of their band gap from the infrared into the visible range of the spectrum. This letter discusses the synthesis of monodisperse germanium nanocrystals via a nonthermal plasma approach which allows for precise control of the nanocrystal size. Germanium crystals are synthesized from germanium tetrachloride and hydrogen entrained in an argon background gas. The crystal size can be varied between 4 and 50nm by changing the residence times of crystals in the plasma between ∼30 and 440ms. Adjusting the plasma power enables one to synthesize fully amorphous or fully crystalline particles with otherwise similar properties.

Ab initio study of spectroscopic constants and anharmonic force field of Ge74Cl2

The equilibrium structure, spectroscopy constants, and anharmonic force field of germanium dichloride have been calculated at MP2, B3LYP, and CCSD(T) levels of theory employing two basis sets, cc-pVDZ and cc-pVTZ, respectively. The computed geometries, rotational constants, and vibration-rotation interaction constants, and quartic centrifugal distortion constants are compared with the available experimental data. The harmonic frequencies, anharmonic constants, and cubic and quartic force constants are predicted. The calculated results show that the MP2 results are in excellent agreement with experiment and represent a substantial improvement over the results obtained from B3LYP. The CCSD(T) method is also an advisable choice to study anharmonic force field of molecules.

Thermal and Mechanical Properties of Silicon Tetrachloride (SiCl4) and Germanium Tetrachloride (GeCl4) in Their Vapor and Liquid Phases

The most‐common physical properties of the precursor species SiCl4 and GeCl4 in their vapor and liquid phases are compiled from several sources in the literature. General expressions over a large range of temperature are proposed either by the use of referenced expressions or by the use of suitable empirical models.

New stable germylenes, stannylenes, and related compounds 7. Synthesis and structures of compounds Hal—Sn—OCH2CH2NMe2 (Hal = Cl or F)

New stable divalent tin derivatives containing no bulky substituents at the metal atom, Hal—Sn— OCH2CH2NMe2 (Hal = Cl or F), were synthesized, and their crystal structures were studied by X-ray diffraction. Unlike the analogous monomeric divalent germanium derivative Cl—Ge—OCH2CH2NMe2, the new compounds are centrosymmetric dimers formed via two intermolecular Sn←CO coordination bonds.

Safer alternative liquid germanium precursors for relaxed graded SiGe layers and strained silicon by MOVPE

Commercial strategy to graded SiGe buffer layers and “strained silicon” involves passing germane (GeH 4) gas or germanium tetrachloride (GeCl 4) vapors as the preferred germanium sources, along with a silicon source over a heated substrate. Today, one of the major limitations impacting the commercialization of SiGe technology is the lack of a commercially viable and safer process that eliminates hazards associated with GeH 4 and the excessively higher thermal budget associated with GeCl 4. The key to growing successful SiGe structures is thus a strategic deposition process that employs safer alternative germanium sources, and allows a wide growth temperature window without degrading the film properties and jeopardizing the environment, health and safety (EHS) aspects of overall operation. In this paper, we report on the development of safer alternative liquid germanium precursors along with the first successful use of a new organo germanium precursor, iso-butyl germane (IBGe) for the growth of high purity Ge and SiGe films. We also detail our strategy to identify the most appropriate candidates from a large number of organo germanium compounds along with initial results on SiGe films and high-quality epitaxial Ge films deposited using IBGe.

The synthesis and characterization of germanium dichloride and dimethyl aluminium chloride derivatives of the 2,2-dipyridylamine ligand

The reactions of germanium dichloride and dimethyl aluminium chloride with 2,2-dipyridylamine (dpa) affords germanium and organo-aluminium complexes. Structural characterization reveals that the preferential coordination site of both germanium and aluminium is within the sterically protected pyridyl, (pyridyl = C5H5N = py), pocket. Py2NGeCl, compound (1), crystallizes in the triclinic space group, P-1, with cell coordinates; a=8.2956(11), b=9.9938(13), c=12.6517(17), α=92.033(2)°, β=92.834(2)°, γ=91.685(2)°. The aluminium complex, Py2NAlMe2·Al(Me)Cl, (2), crystallizes in the orthorhombic space group, Pna2(1), with cell parameters: a=13.3707(10), b=10.8706(8), c=16.1306(12). The X-ray analysis of the side products of these reactions, the lithium halide adducts are also reported.

The transannular interaction germanium–nitrogen in germocanes: The influence of substituents

The reaction of RN(CH 2CH 2OH)CHR 1CR 2R 3OH ( 1– 8) with a stoichiometric amount of tetrachloro(bromo)germane leads to the corresponding RN(CH 2CH 2O)(CHR 1CR 2R 3O)GeHal 2 ( 9– 21). Difluorenylgermocane 22 was prepared by treatment of diethoxydifluorenylgermane with N-methyldiethanolamine. Different dialkanolamines were found to be successive precursors of dimethylgermocanes, RN(CH 2CH 2O)(CHR 1CR 2R 3O)GeMe 2 ( 23– 26). The chemical properties of simple and easy to access germocanes RN(CH 2CH 2O) 2GeX 2 [X = OH, Br ( 28), Cl ( 29)] were studied and the difluoro ( 27), haloalkoxy ( 30– 32), and dialkoxy ( 33, 34) derivatives were prepared. The structures of the compounds 16, 20– 22, and 26 were confirmed by X-ray diffraction and the structural features in solution of 23 and 26 were studied by NMR spectroscopy (NOEs). The relationship between the nature of substituents at different positions of the germocane skeleton and the strength of the intramolecular Ge ← N bond is discussed.

Dispersed fluorescence spectroscopy of the GeCl2 ÖX̃ transition

The laser-induced fluorescence excitation spectrum of the GeCl(2) A-X transition at ultraviolet wavelengths (300-320 nm) was recorded in a direct current discharge supersonic free jet expansion. The excitation spectrum contains several sharp peaks and a congested diffuse structure. Dispersed fluorescence spectra following the excitation of these GeCl(2) ultraviolet bands were successfully acquired for the first time. The analysis of the dispersed fluorescence spectra reveals the detailed vibrational structure of the X (1)A(1) state. We have assigned the vibrational structures corresponding to different isotopomers (Ge(35)Cl(2), Ge(35)Cl(37)Cl, and Ge(37)Cl(2)). The vibrational fundamental frequencies were determined: 409 cm(-1) (symmetric stretch), 159 cm(-1) (bend), and 352 cm(-1) (antisymmetric stretch) for the X (1)A(1) state of GeCl(2). Vibrational parameters of the ground electronic state including vibrational frequencies, anharmonicity, and bend-stretch coupling constant were determined. Our dispersed fluorescence spectra also clarify the vibrational assignments of the hot bands and provide more experimental data for unraveling the nature of the congested diffuse structure at shorter wavelengths in the excitation spectrum.

Preparation of Monodisperse GeO2 Nanocubes in a Reverse Micelle System

We report here a synthesis method for single-crystal monodisperse GeO2 nanocubes in a reverse micelle system. Hydrolysis of germanium tetrachloride (GeCl4) in a micelle system produces GeO2 nanocub...

Internal dynamics in organometallic molecules: Rotational spectrum of (CH3)3GeCl

The microwave spectra of (CH(3))(3)(74)Ge(35)Cl and its isotopologues (CH(3))(3)(72)Ge(35)Cl and (CH(3))(3)(74)Ge(37)Cl have been studied in the frequency range from 3-24 GHz revealing the complex internal dynamics of this organometallic molecule with three internal rotors. The assignment of the complex spectrum has been facilitated by permutation-inversion theory and ab initio calculations. The V(3) barrier to internal rotation is determined to be 372.359(47) cm(-1). Furthermore, an analysis of the chlorine quadrupole coupling yields the description of the Ge-Cl bonding character which is estimated to be dominated by covalent contributions (46.5%) together with 37.6% ionic and 15.9% pi-bonding character. From isotopic substitution the Ge-Cl bond distance could be determined as 2.15198(97) Angstroms.

Reaction of Germanium Tetrachloride with Chloro(phenyl)silanes in the Presence of Aluminum Chloride

The effect of the quantity of aluminum chloride on the direction and depth of reaction of germanium tetrachloride with chloro(phenyl)silanes of the general formula PhnSiCl4−n (n = 1 – 3) was studied to show that radical exchange between germanium and silicon is initiated only if the mixture contains no less than 2.5–5 wt % of aluminum chloride. With trichloro(phenyl)silane, the radical exchange is initiated at 5 wt % of aluminum chloride and results in exclusive formation of trichloro(phenyl)germane. The reactions of GeCl4 with dichlorodiphenylsilane and chlorotriphenylsilane in the presence of 2.5–7.5 wt % of aluminum chloride give dichlorodiphenylgermane as the major product, and at AlCl3 concentrations of above 10 wt % the major product becomes to be trichloro(phenyl)germane.

Synthesis and Structure of a Germylene Bearing a 1,8-Dimethoxyanthracene Ligand

Abstract A novel chlorogermylene compound, (1,8-dimethoxy-9-anthracenyl)chlorogermylene, has been synthesized by the reaction of GeCl2·dioxane and 9-lithio-1,8-dimethoxyanthracene. X-ray crystallographic study of the germylene revealed the bis-coordination of the oxygen atoms at the 1,8-positions to the germanium(II) center and the elongation of the Ge–Cl bond caused by the coordination.

Crystal structure of germanium(II) dichloride solvated by tetrahydrofuran

AbstractThe thermally highly unstable tetrahydrofuran solvate of germanium(II) dichloride (GeCl2 · 2THF) was crystallized, and its crystal structure was determined. It consists of a chain of GeCl2 units connected by secondary Cl···Ge contacts [3.846(2) Å] in which each Ge atom is coordinated to two molecules of THF. Two weak hydrogen bonds of the CH ··· ClGe type in GeCl2 · 2THF were also detected both with lengths of 2.90(3) Å. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:361–363, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20105

Divalent Germanium Compound with a Radical-Anionic Ligand: Molecular Structures of (dpp-BIAN)•-GeCl and Its Hydrochloration Products [(dpp-BIAN)(H)2]•+[GeCl3]- and [{(dpp-BIAN)(H)2•+}2(Cl-)]+[GeCl3]- (dpp-BIAN = 1,2-Bis{(2,6-diisopropylphenyl)imino}acenaphthene)

The germanium(II) compound (dpp-BIAN)GeCl (1), which contains the radical anion of dpp-BIAN can be prepared either by reacting free dpp-BIAN ligand with 2 equiv of GeCl2(1,4-dioxane) in Et2O or by metathetical reaction of the sodium salt of dpp-BIAN with germanium dichloride in Et2O or benzene. The reaction of benzene solutions of 1 with 2 or 3 equiv of HCl led to protonation of the dpp-BIAN ligand affording [(dpp-BIAN)(H)2]*+[GeCl3]- (2) and [[(dpp-BIAN)(H)2*+]2(Cl-)]+ [GeCl3]- (3), which incorporate the radical cation of the protonated ligand. Compounds 1-3 have been characterized by elemental analysis, IR, UV-vis, and electron spin resonance (ESR) spectroscopy. Molecular structures of 1-3 were determined by single-crystal X-ray diffraction. In molecule 1, the Ge atom is positioned at the apex of the slightly distorted trigonal pyramid. The Ge-N bond lengths in 1 are 2.0058(19) and 2.004(2) A. The molecular structure of 2 consists of contact ions [(dpp-BIAN)(H)2]+ and [GeCl3]-. In the molecular structure of 3, two radical cations of [(dpp-BIAN)(H)2]+ are "coordinated" by the chlorine anion. The ESR signal of 1 indicates the presence of a dpp-BIAN radical anion and shows a hyperfine structure due to the coupling of an unpaired electron to 14N, 73Ge, 35Cl, 37Cl, and 1H nuclei (AN=0.48 (2 N), AGe=0.96, ACl=0.78 (35Cl), ACl=0.65 (37Cl), AH=0.11 (4 H) mT, g=2.0014). Both 2 and 3 reveal ESR signals of radical cation [(dpp-BIAN)(H)2]*+ (septet, AN=0.53, AH=0.48 mT, g=2.0031).

A computational investigation on GenCl− and GenCl (n=1–6) clusters by density functional methods

Abstract Geometry optimizations of GenCl− and GenCl (n = 1–6) clusters are performed at the (U)B3LYP/6-31++G(d,p) level. Subsequently, electronic and bonding features of the resulting equilibrium structures are systematically calculated and discussed. The emphasis of this study is placed on electron affinity (EA), fragmentation energy, HOMO–LUMO gap, Ge–Cl bond length as well as stability. More specifically, the impact on internal electron transfer between the Ge n − ( Ge n ) subsystem and Cl atom in GenCl− (GenCl) clusters is discussed. In addition, theoretical results of EAs for GenCl (n = 4–6) clusters are in good agreement with experimental results available.

Synthesis, characterization and enantioselective free radical reductions of (1 R,2 S,5 R)-menthyldiphenylgermane and its enantiomer

(1 R,2 S,5 R)-Menthyldiphenylgermane and its enantiomer have been prepared in a few steps from germanium tetrachloride. The initial step in this sequence, namely the reaction between germanium tetrachloride and menthylmagnesium chloride, produces menthylgermanium trichloride, which is the exclusive product of this Grignard reaction, presumably due to the bulk of the menthyl group. When used at a low temperature (−78 °C) and in conjunction with Lewis acids, such as magnesium salts, these chiral germanes are capable of reducing ester functionalized radicals in high enantioselectivity, but in low-moderate yield. For example, ( R)-naproxen ethyl ester was obtained in 15% yield and 99% ee by reaction in toluene of 2-bromonaproxen ethyl ester with (1 R,2 S,5 R)-menthyldiphenylgermane in toluene at −78 °C in the presence of magnesium bromide. At 80 °C, (1 R,2 S,5 R)-menthyldiphenylgermane reacted with primary alkyl radicals with a rate constant of 1.02 × 10 6 M −1 s −1. Kinetic studies reveal the Arrhenius expression for this reaction to be: log(k/M −1 s −1) = (11.1 ± 0.4) − (34.6 ± 3.1)/ θ where θ=2.3 RT kJ mol −1.