Hydrogermolysis Reaction Research Articles

Preparation, absorption spectra, and electrochemsitry of the trigermanes R3GeGePh2GeR3 (R3 = ButMe2, PhMe2, Bun3) and tetragermanes R3Ge(GePh2)2GeR3 (R3 = Et3, Bun3)

The trigermanes ButMe2GeGePh2GeMe2But and PhMe2GeGePh2GeMe2Ph and the tetragermanes Et3Ge(GePh2)2GeEt3 and Bun3Ge(GePh2)2GeBun3 were synthesized via the hydrogermolysis reaction. These species were characterized by UV/visible spectroscopy, cyclic voltammetry, and differential pulse voltammetry. The properties of the two trigermanes were also compared with those of Bun3GeGePh2GeBun3, and the UV/visible absorption maxima of these three trigermanes fall in the narrow range of 246 – 249 nm while their oxidation potentials differ by 233 mV. Both ButMe2GeGePh2GeMe2But and Bun3GeGePh2GeBun3 exhibit two irreversible oxidation waves in their CVs and DPVs. The absorption maxima for the two tetragermanes are similar and their oxidation potentials differ by only 58 mV. The CV and DPV of Et3Ge(GePh2)2GeEt3 exhibits three irreversible oxidation waves while that of Bun3Ge(GePh2)2GeBun3 contains only one. The X-ray crystal structure of Et3Ge(GePh2)2GeEt3 was determined and this represents a rare example of a tetragermane with alkyl substituents at the terminal germanium atoms.

Donor-acceptor molecular oligogermanes: Novel properties and structural aspects

The linear oligogermyl amide 2, Ph3GeGeMe2NMe2, was obtained by reacting Ph3GeLi with 1, Me2Ge(Cl)NMe2. The amide 2 was used for the synthesis of molecular oligogermanes 3, Ph3GeGeMe2Ge(C6F5)3, and 4, [Ph3GeGeMe2]2Ge(C6F5)2, containing electron donor (Me, Ph) and acceptor (C6F5) groups, by using a hydrogermolysis reaction in n-hexane. The molecular structures of 3 and 4 were studied by XRD. It was shown that in a crystal 3 forms wide channels, in which the solvated nonpolar n-hexane molecule is present. The NMR (1H, 13C and 19F), optical (UV/vis absorption, luminescence) and electrochemical (cyclic voltammetry) properties of both compounds were also studied. The impact of the substitution type by the electron withdrawing groups (at the terminal position, such as in 3, or within the compound, such as in 5), on the physical properties was also studied.

Structure/property relationships in branched oligogermanes. Preparation of (Me3Ge)3GePh, (Me2ButGe)3GePh, and (Me2PhGe)3GePh and investigation of their properties by spectroscopic, spectrometric and electrochemical methods

The three branched oligogermanes (Me3Ge)3GePh, (Me2ButGe)3GePh, and (Me2PhGe)3GePh were synthesized via the hydrogermolysis reaction and were characterized by NMR (1H, 13C, and 73Ge) spectroscopy. In addition, these three compounds and (Bun3Ge)3GePh were analyzed using high resolution accurate mass mass spectrometry (HRAM-MS), which represents the first HRAM-MS investigation of branched oligogermanes. The effects of varying the substituent pattern on the peripheral R3Ge- groups on the electronic properties of these oligogermanes were investigated using cyclic and differential pulse voltammetry (CV and DPV), UV/visible spectroscopy, and 73Ge NMR spectroscopy. The CV, DPV, and 73Ge NMR data were compared to several previously reported branched oligogermanes, including (Bun3Ge)3GePh, (Ph3Ge)3GePh, (Ph3Ge)3GeH, and (Me3Ge)4Ge.

A Series of Isopropyl-Substituted Oligogermanes Pri3Ge(GePh2)nGePri3 (n = 0–3) Featuring a Luminescent and Dichroic Pentagermane Pri3Ge(GePh2)3GePri3

The series of oligogermanes Pri3Ge(GePh2)nGePri3 (n = 0, 2; n = 1, 3; n = 2, 4; n = 3, 5) were prepared by the hydrogermolysis reaction. All four species were characterized by NMR (1H and 13C) and UV/visible spectroscopy as well by cyclic voltammetry and differential pulse voltammetry. The oligogermanes exhibited a successive red shift in their absorbance maxima as the length of the Ge–Ge chain was increased, and these molecules also became easier to oxidize as the chain length was increased. The X-ray crystal structures of 4 and 5 as well as the trigermane HPh2GeGePh2GePh2H (6) were determined. The pentagermane 5 was shown to be dichroic in the solid state due to the packing of the individual molecules in a columnar fashion in the crystal. Pentagermane 5 is also luminescent in solution, exhibiting an emission maximum at 380 nm. The physical properties of 5, like the hexagermane Pri3Ge(GePh)4GePri3, mimic the properties of the larger polygermane systems.

Synthesis, structure, and properties of the hexagermane Pri3Ge(GePh2)4GePri3

The synthesis of the hexagermane Pri3Ge(GePh2)4GePri3 was achieved starting from the cyclotetragermane (Ph2Ge)4. Ring-opening of (Ph2Ge)4 with Br2 yielded Br(GePh2)4Br that was converted to H(GePh2)4H, and this material was treated with two equiv. of Pri3GeNMe2 to furnish Pri3Ge(GePh2)4GePri3 via the hydrogermolysis reaction. The X-ray crystal structures of (Ph2Ge)4, Br(GePh2)4Br and Pri3Ge(GePh2)4GePri3 were determined. The hexagermane Pri3Ge(GePh2)4GePri3 represents the longest structurally characterized linear oligogermane reported to date and exhibits physical properties that resemble those of the larger polygermane systems. The hexagermane is luminescent and interacts with polarized light, appearing pale yellow under one orientation of polarized light and deep blue under the opposite orientation. The electrochemistry of Pri3Ge(GePh2)4GePri3 was also explored, and this species exhibits the expected five irreversible oxidation waves.

Substituent Effects in Digermanes: Electrochemical, Theoretical, and Structural Investigations

The digermanes R3GeGePh3 (R3 = Bui3, Hexn3, (C18H37)3, or ButMe2) were synthesized using the hydrogermolysis reaction, and the X-ray crystal structures of Bui3GeGePh3and ButMe2GeGePh3 were determined. The isobutyl-substituted digermane contains two independent molecules in the unit cell with Ge–Ge bond distances of 2.4410(5) and 2.4409(5) Å, and ButMe2GeGePh3 has a Ge–Ge bond distance of 2.4255(3) Å. These four digermanes and the four additional digermanes R3GeGePh3 (R3 = Me3, Bun3, Bus3, or PhMe2) were characterized by cyclic voltammetry, differential pulse voltammetry, and linear sweep voltammetry in order to determine the effects of varying substituent patterns on the oxidation potential of these systems. Digermanes having more inductively donating substituents exhibit more negative oxidation potentials than those having less inductively donating substituents. Density functional theory calculations were also performed on these eight systems, and the energies of their frontier orbitals were determined. The energy of the HOMO and LUMO in these systems was shown to depend on the electron-donating ability of the organic substituents.

Synthetic, Structural, and Physical Investigations of the Large Linear and Branched Oligogermanes Ph3GeGePh2GePh2GePh2H, Ge5Ph12, and (Ph3Ge)4Ge

The syntheses of two linear oligogermanes, Ph3GeGePh2GePh2GePh2H and Ge5Ph12, were achieved using a hydrogermolysis reaction starting with HPh2GeGePh2GePh2H. The preparation of the hydride-terminated tetragermane indicates that selectivity is possible using the hydrogermolysis reaction, which had not been observed previously. The structures of both of these compounds were determined, and they were also characterized by UV/visible spectroscopy and electrochemical methods (CV and DPV). The pentagermane Ge5Ph12 exhibits four irreversible oxidation waves in both its CV and DPV, as was observed for other aryl-substituted oligogermanes. The successful synthesis of the neopentane analogue (Ph3Ge)4Ge was also achieved by starting from GeH4 and Ph3GeCH2CN. This material was structurally characterized; the structure of (Ph3Ge)4Ge is highly sterically congested and contains long Ge–Ge single-bond distances that average 2.497(6) A and exhibits an nearly idealized tetrahedral geometry at the central germanium atom wit...

ChemInform Abstract: Synthetic, Structural, and Physical Aspects of Organo‐Oligogermanes

AbstractReview: 97 refs.

Reactivity of α-germyl nitriles with acetonitrile: Synthesis, structures, and generation of Ph 3Ge[NHC(CH 3)CHCN] and 2,6-dimethyl-4-(triphenylgermylamino)pyrimidine from Ph 3GeCH 2CN

The formation of 3-aminocrotononitrile and 4-amino-2,6-dimethylaminopyrimidine has been observed during the course of the hydrogermolysis reaction between a germanium amide and a germanium hydride, either as the free amines or bound to germanium as ligands consisting of their conjugate bases. These species arise from the dimerization or trimerization of acetonitrile, and have only been detected when germanium amides having substantial steric bulk at the germanium center are employed in the reaction. The isolation of germanium-bound 3-aminocrotononitrile compounds suggests that α-germyl nitrile species R 3GeCH 2CN that result from the reaction of the germanium amides R 3GeNMe 2 with CH 3CN solvent also can further react with CH 3CN to generate the 3-aminocrotononitrile and 4-amido-2,6-dimethylaminopyrimidine species. The two germanes Ph 3Ge[NHC(CH 3) CHCN] and 2,6-dimethyl-4-(triphenylgermylamino)pyrimidine have been prepared and structurally characterized, and the conversion of Ph 3GeCH 2CN to Ph 3Ge[NHC(CH 3) CHCN] and 2,6-dimethylamino-4-(triphenylgermylamino)pyrimidine as well as the conversion of Ph 3Ge[NHC(CH 3) CHCN] to 2,6-dimethyl-4-(triphenylgermylamino)pyrimidine in acetonitrile solvent has been observed using 1H NMR spectroscopy.

Synthesis, Structures, and Properties of Branched Oligogermanes

We have employed the hydrogermolysis reaction for the preparation of rare branched oligogermanes, and have obtained for the first time the X-ray crystal structures of several branched tetragermanes, including (Ph3Ge)3GePh, (Ph3Ge)3GeH, and (Ph3Ge)3GeX (X = Cl or Br). We also have at our disposal branched tetragermanes having the formula (EtOCH2CH2Bu n 2Ge)3GePh, where the ethoxyethyl substituent serves as a protecting group for a germanium–hydride active site. These reagents have been employed for the stepwise synthesis of higher branched systems having up to 13 bonded germanium atoms in the oligomer backbone. The synthesis, structures, and physical characteristics of these systems are described. GRAPHICAL ABSTRACT

SYNTHETIC, STRUCTURAL, AND PHYSICAL ASPECTS OF ORGANO-OLIGOGERMANES

The hydrogermolysis reaction has been used to prepare a variety of linear and branched oligogermanes that have been fully characterized. The combination of a germanium hydride protection/deprotection strategy with the hydrogermolysis reaction allows for the addition of one or two germanium atoms to the Ge – Ge chain at a time in linear systems, or three germanium atoms at a time in the case of branched systems. The physical properties of both types of oligogermanes have been probed using UV/visible spectroscopy and cyclic voltammetry, and several of the experimental results have been complimented with theoretical investigations. The syntheses, structures, and properties of these oligogermanes are the foci of this review.

Syntheses, Structures, and Electronic Properties of the Branched Oligogermanes (Ph3Ge)3GeH and (Ph3Ge)3GeX (X = Cl, Br, I)

The branched oligogermanium hydride (Ph3Ge)3GeH was synthesized via a hydrogermolysis reaction from GeH4 and Ph3GeNMe2 and was converted to the halide series of compounds (Ph3Ge)3GeX (X = Cl, Br, I) upon reaction with [Ph3C][PF6] in CH2X2 solvent (X = Cl, Br, I). These species were fully characterized by NMR (1H and 13C) and UV/visible spectroscopy, cyclic voltammetry, and elemental analysis. In addition, (Ph3Ge)3GeH was analyzed by 73Ge NMR spectroscopy and exhibits two resonances at δ −56 and −311 ppm. A Ge−H coupling constant of 191 Hz was observed in the proton-coupled 73Ge NMR spectrum of (Ph3Ge)3GeH. The X-ray crystal structures of (Ph3Ge)3GeH and (Ph3Ge)3GeX (X = Cl, Br, I) were obtained and represent the first examples of branched oligogermane hydrides or halides to be characterized in this fashion. The Ge−Ge bond distances in (Ph3Ge)3GeH are short (average value 2.4310(5) Å), while those in the halide compounds (Ph3Ge)3GeX are similar to one another and range from 2.4626(7) to 2.4699(5) Å. The UV/visible and cyclic voltammetry data for these species have been correlated with DFT computations, and excellent agreement was found between the experimental and theoretical data.

Structural, spectral, and electrochemical investigations of para-tolyl-substituted oligogermanes

The synthesis of four new oligogermanes containing para-tolyl-substituents has been achieved via the hydrogermolysis reaction, including the digermane Tol 3GeGePh 3, the trigermanes Tol 3GeGePh 2GeTol 3 and Tol 3GeGeTol 2GeTol 3, and the tetragermane Tol 3GeGePh 2GePh 2GeTol 3 (Tol = p-CH 3C 6H 4). These four oligogermanes have been structurally characterized and their structures have been compared with those of their per-phenyl-substituted analogs. The digermane Tol 3GeGePh 3 exhibits an unusually short Ge–Ge bond distance of 2.408(1) Å. The four para-tolyl-substituted oligogermanes have also been characterized by UV/visible spectroscopy and cyclic voltammetry. The expected red shift in the absorbance maximum with increasing catenation was observed for this series of compounds. Their cyclic voltammograms each contain n − 1 irreversible oxidation waves ( n = the number of Ge atoms), which is atypical since oligogermanes generally exhibit only one irreversible oxidation wave regardless of the degree of catenation.

Syntheses, structures and properties of linear and branched oligogermanes

This Perspective surveys recent developments in the synthesis and characterization of discrete oligogermanes. The use of the hydrogermolysis reaction, combined with a protection/deprotection strategy for a Ge-H moiety, has resulted in the synthesis of a variety of oligogermanes where the number of catenated atoms and the identity of the organic substituents can be readily controlled. Relationships between the composition of these oligomers and their optical and electronic properties have also been established.

Preparation, Structure, and Reactivity of Discrete Branched Oligogermanes

The hydrogermolysis reaction of PhGeH3 serves in the synthesis of discrete branched oligogermanes. Treatment of PhGeH3 with 3 equiv of the α-germyl nitriles R3GeCH2CN (R3 = Ph3 or Bu2CH2CH2OEt), which are generated in situ from the corresponding amides R3GeNMe2 and CH3CN, furnishes the tetragermanes PhGe(GePh3)3 and PhGe(GeBu2CH2CH2OEt)3 in excellent yield. The crystal structure of PhGe(GePh3)3 was determined. This compound is the first branched oligogermane to be structurally characterized. Reaction of the tetragermane PhGe(GeBu2CH2CH2OEt)3 with Bui2AlH generated the intermediate hydride PhGe(GeBu2H)3. Subsequent treatment of PhGe(GeBu2H)3 with the synthons R2Ge(NMe2)CH2CH2OEt (R = Bu, Et, Ph) in CH3CN solution furnished the heptagermanes PhGe(GeBu2GeR2CH2CH2OEt)3 (R = Bu, Et, Ph). The latter process also proceeds through the in situ formation of the α-germyl nitriles R2Ge(CH2CN)CH2CH2OEt.

Preparation of Oligogermanes via the Hydrogermolysis Reaction

The hydrogermolysis reaction has been shown to be useful for the formation of germanium−germanium bonds. The Ge−Ge bond forming reaction involves a germanium amide and a germanium hydride and requires the use of acetonitrile as the solvent. A key factor in the formation of the Ge−Ge bond involves reaction of the germanium amide R3GeNMe2 with acetonitrile solvent to furnish an α-germylated nitrile R3GeCH2CN which contains a labile Ge−C bond. This species undergoes subsequent reaction with a germanium hydride R3GeH to form the Ge−Ge bond. Using this method, the digermanes Bun3GeGePh3 and Et3GeGePh3 have been obtained and their X-ray crystal structures have been determined. The preparation of three synthons for stepwise oligogermane chain buildup, R2Ge(NMe2)CH2CH2OEt (R = Et, Bu, Ph), has also been achieved. These synthons react with Ph3GeH in CH3CN to afford the corresponding digermanes, which in the case of R = Et and Bu undergo subsequent reaction with DIBAL-H to generate a digermane hydride. The ethyl and n-butyl digermane hydrides then are subsequently reacted with an additional equivalent of the appropriate synthon to produce the corresponding trigermanes, and repetition of these two steps furnishes the tetragermanes Ph3GeGe(R2)Ge(R2)Ge(R2)CH2CH2OEt (R = Et, Bu). Thus, in this study two new series of oligomeric organogermanium species have been prepared and fully characterized.

Trimésitylgermyllithium: Synthèse et réactivité

Abstract The new organogermyllithium Mes 3 GeLi has been prepared in good yield by hydrogermolysis reaction of t-butyllithium in THF. The bulky group favours stabilization in the form of the THF complex. Mes 3 GeLi has been characterized by alkylation reaction with MeI. Some metalation reactions are reported. They lead to the formation of unsymmetrical or symmetrical organogermylmercuric compounds and also of new dissymetrical digermanes by a classic nucleophilic reaction. In contrast, the reaction of Mes 3 GeLi with benzoyl chloride is more complex and apparently proceeds by a single electron transfer process.