Germanium Center Research Articles

ChemInform Abstract: (Tris(trimethylsilyl)methyl)- and (2,4,6-Tri-tert-butylphenyl)( pentamethylcyclopentadienyl)germylene: Synthesis and Structure.

(Pentamethylcyclopentadienyl)germanium chloride (1) reacts with (tris(trimethylsilyl)methyl)lithium to give (pentamethylcyclopentadienyl)(tris(trimethylsilyl)methyl)germylene (3) and with (2,4,6-tri-tert-butylphenyl)lithium to yield (pentamethylcyclopentadienyl)(2,4,6-tri-tert-butylphenyl)germylene (4). Both germylenes (3 and 4) are monomeric with a fluxional eta-2 bonding between the germanium center and the Me5C5 ring. Compound 3 crystallizes in the monoclinic space group P2(1)/c with unit cell dimensions a = 9.954 (1) angstrom, b = 8.759 (2), angstrom, c = 29.416 (6) angstrom, beta = 95.05 (2)-degrees, and Z = 4. Complex 4 crystallizes in the monoclinic space group P2(1)/n with unit cell dimensions a = 10.404 (5) angstrom, b = 13.519 (6) angstrom, c = 19.203 (10) angstrom, beta = 103.62 (4)-degrees, and Z = 4.

Raman spectroscopy of glasses and melts of the Na2O-GeO2 system

Glasses and melts of the system X mol % Na2O · GeO2 (X = 0, 10, 20, 30) are investigated using high-temperature Raman spectroscopy. Addition of an oxide modifier is shown to bring about an increase in the coordination number of central germanium atoms along with the depolarization of the three-dimensional GeO2 network. The glass-melt transition in germanate systems with a low oxide-modifier content is accompanied by the transition of six-coordinated germanium atoms into four-coordinated (with oxygen) ones and a simultaneous formation of nonbridge oxygen atoms.

Halogermanium(II) Complexes Having Phenylamidinate As Supporting Ligands: Syntheses, Characterizations, and Reactivities

Novel germylenes [{Me3SiNC(Ph)NSiMe3}GeX] (X = Cl, Br, I) and [{Me3SiNC(Ph)NSiMe3}2Ge] with the bidentate phenylamidinato ligand have been synthesized in high yields by a salt metathesis reaction between Cl2Ge·dioxane or I2Ge and the lithium salt of the ligand. They were characterized by 1H and 13C NMR and mass spectrometry and single-crystal X-ray structure analyses, which confirmed N-chelation and a three-coordinate germanium center. The cycloaddition reactions with o-quinone led to cycloadducts, whose structures were determined by X-ray analyses. The chelation of the ligand to the metal center was conserved, affording penta- and hexacoordinated germanium(IV) atoms. Complexation reactions with [codW(CO)4] and [nbdMo(CO)4] resulted in trinuclear bis(germanium(II)) transition-metal complexes in “trans” octahedral geometry.

Glacial geomorphology and glacial history of the Muzart River valley, Tianshan Range, China

The Muzart River originates on the southeastern slope of Tumur Peak, the largest center of modern glaciation in the Tianshan Range. Glacial landforms and sediments indicate that there are four major Quaternary glaciations in this drainage. The glacial landforms contain considerable information about the changes of the ancient glaciers. Dating the landforms allows the temporal and spatial variations of the ancient glaciers in this valley to be understood and provides essential information in reconstructing the paleoenvironment in this region. Electron spin resonance (ESR) dating of a well-exposed section, the multiple end moraines of the Pochengzi glaciation (the third set of moraines), and the local outwash and fluvial sediments on the Kezibulake glacial plain (the fourth set of moraines) was carried out using germanium (Ge) centers in the glacial quartz grains, which are sensitive to both sunlight and grinding. Eleven depositional ages have been determined. Based on the dating results, the principle of superposition and the glaciations pattern reported in the adjacent valley, the Pochengzi end moraines were determined to be deposited during the major glacial intervals that are equivalent in age to marine oxygen isotope stages (MIS) 2, mid-MIS 3 and MIS 4 and the Kezibulake glacial deposits were determined to be equivalent in age to MIS 6. Furthermore, the Tugaibieliqi end moraine (the second set of moraines) was deposited during the Neoglaciation (a cold period between 3 and 4 ka) and the 3–4 end moraines located at the terminuses of the modern glacier were deposited during the Little Ice Age. The ages of the Pochengzi glacial deposits can be subdivided into three clusters, they are 13.6–25.3 ka, 39.5–40.4 ka and 64.2–71.7 ka, respectively. The largest local last glacial maximum (LGM L) occurred during MIS 4 rather than the global Last Glacial Maximum (LGM G) of MIS 2. Furthermore, a glacier that is slightly larger than that of MIS 2 developed in this drainage during mid-MIS 3. The ancient Muzart glaciers were compound valley glaciers during the Neoglaciation, MIS 2 and mid-MIS 3, and piedmont glaciers during MIS 4 and MIS 6.

On the Bonding in N-Heterocyclic Carbene Complexes of Germanium(II)

A series of N-heterocyclic carbene (NHC) complexes of Ge(II) were synthesized and structurally characterized. Unlike previous observations, the carbenic carbon−germanium bond length does not vary systematically with the electronic demands of the substituents on the germanium center. Computational analysis of the energetic and structural metrics of model compounds is consistent with a lack of a substituent effect on the carbenic carbon−germanium bond length.

Ionic nature of Ge(ii)-centered dications: a germanium K-edge X-ray absorption near edge structures study

Measurement of the ionic nature of [Ge(cryptand[2.2.2])](2+) by XANES has provided direct experimental evidence that the germanium center is best described as a nearly-naked dication encased within an electron rich cryptand cage.

Activation of Tellurium with Zintl Ions: 1/∞{[Ge5Te10]4−}, An Inorganic Polymer with Germanium in Three Different Oxidation States

The solvothermal reaction among tellurium, manganese, and the Zintl compound K(4)Ge(9) has led to the formation of a polymeric mixed-valent complex {[Mn(en)(3)](2)(Ge(5)Te(10))}(n) (1; en = ethylenediamine). The most interesting structural feature of this material is the presence of three different oxidation states of germanium centers and the formation of Ge-Ge bonds in the infinite polymeric chains (1)/(infinity){[Ge(5)Te(10)](4-)}. X-ray photoelectron spectroscopy characterization confirms the different oxidation states of germanium.

Cationic Crown Ether Complexes of Germanium(II)

Fit for a king: Cationic complexes of Ge(II) can be prepared by using crown ethers to stabilize and protect the germanium center. Three different crown ethers were employed: [12]crown-4 (see structure, Ge teal, O red, C gray), [15]crown-5, and [18]crown-6. The structures of the cationic complexes depend on the cavity size of the crown ether and on the substituent on germanium.

Structure, Bonding, and Hyperconjugation of Germaallene: A Theoretical Study

A theoretical study on germaallene molecules, including monogermaallenes, digermaallenes, and trigermaallene, was performed based on B3LYP and ab initio methods. The following results were observed: (a) symmetric 1,3-digermaallene has a linear allenic-type structure and 1,2-digermaallene is bent at the central germanium atom with a GeGeC bond angle of 142.2°. (b) Only 2-germaallene, 1,2-digermaallene, and trigermaallene have cyclic isomers. The germacyclopropylidene and digermacyclopropylidene are the global minima on their bending potential energy surfaces, and the high-energy cyclic isomer of trigermaallene is unstable. (c) The deviation of the germaallenic skeleton from linearity is strengthened with increasing Ge═Ge bonds. NPA and WBI analyses reveal that there are double bonds between the terminal and central Ge or C atom for monogermaallenes and digermaallenes, the central Ge atom of trigermaallene does not adopt the orbital hybridization, and a partial bond exists between two terminal Ge atoms for the interaction of their p orbitals. The π−σ hyperconjugation strengths of germaallenes were estimated on the basis of the total NBO second-order perturbation energy. The hyperconjugation strengths of monogermaallenes and digermaallenes follow in the order 1-germaallene > 1,3-digermaallene > 2-germaallene > 1,2-digermaallene.

Stable Compounds of Composition LGe(II)R (R = OH, PhO, C6F5O, PhCO2) Prepared by Nucleophilic Addition Reactions

The stable β-diketiminate germanium(II) compounds LGeR [L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3] (R = OTf, OH, PhO, C6F5O, PhCO2) are described. LGeOTf (2) is synthesized by salt metathesis reaction of LGeCl (1) with AgOTf and can be isolated as colorless crystals in 90% yield. Compound L′Ge (3) (L′ = CH{(C═CH2)(CMe)(2,6-iPr2C6H3N)2}) was obtained by treatment of LGeOTf (2) with 1 equiv of 1,3-di-tert-butylimidazol-2-ylidene (NHC) in toluene. Reaction of 3 with H2O, PhOH, C6F5OH, and PhCO2H, respectively, in toluene provided the germanium(II) compounds 4−7 in high yield. Compounds 2−7 were characterized by microanalysis and multinuclear NMR spectroscopy. Furthermore compounds 5, 6, and 7 are confirmed by X-ray structural analysis with the result that compounds 5, 6, and 7 are monomeric and the germanium center resides in a trigonal-pyramidal environment.

Synthesis of the germanium(II) calixarene [formula omitted]Ge 4 and its reaction with Fe 2(CO) 9: Generation of the germanium(II)/iron(0) complex [formula omitted]Ge 4[Fe(CO) 4] 2

An uncommon germanium(II) calixarene species { p - Bu 8 t calix [ 8 ] arene } Ge 4 ( 1) was synthesized from Ge[N(SiMe 3) 2] 2 and p - Bu 8 t calix[8]arene in 94% yield. Complex 1 reacts with Fe 2(CO) 9 to yield the germanium(II) macrocyclic complex { p - Bu 8 t calix [ 8 ] arene } Ge 4[Fe(CO) 4] 2 ( 2), which contains two neutral Fe(CO) 4 fragments, in 77% yield. The X-ray crystal structures of 1 and 2 were determined and each species contain two Ge 2O 2 rhombi having two germanium(II) centers and bridging aryloxide ligands from the calix[8]arene framework. The Ge 2O 2 rhombi are also connected to the calix[8]arene framework by terminal germanium–aryloxide bonds. Complexes 1 and 2 were also characterized by NMR spectroscopy and their 1H NMR spectra have been correlated with their solid state structures.

A Cryptand-Encapsulated Germanium(II) Dication

Unlike cations of metals such as sodium or calcium, oxidized silicon and germanium centers generally require strongly bound covalent ligands. We report the synthesis and characterization of a germanium(II) dication in the form of the salt (Ge.cryptand[2.2.2])(O3SCF3)2. The salt is isolated in 88% yield from the reaction of cryptand [2.2.2] and an N-heterocyclic carbene complex of GeCl(O3SCF3) as an air-sensitive, white solid. The crystal structure of the salt shows minimal interaction between the cryptand-encapsulated germanium(II) ion and the two -O3SCF3 counterions. These results suggest a widely expanded role of cryptands and related molecules in stabilizing nonmetallic cations.

Three branch polyunsaturated organosilicon and organogermanium dendrimers

3-Branch dendrimers of the first generation possessing at the focal point, the silicon atom, a trimethylsilylvinyl or trimethylsilylethynyl group, and at the central germanium atom an isopropyl group have been synthesized using a combined approach or a convergent reaction scheme. NMR spectra of all synthesized compounds are studied, and their molecular masses are calculated and experimentally determined. The key parameters of new dendrimers are given.

Two-electron germanium centers with a negative correlation energy in lead chalcogenides

It is shown that the charge state of the 73Ge antisite defect that arises in anionic sublattices of PbS, PbSe, and PbTe after radioactive transformation of 73As does not depend on the position of the Fermi level, whereas the 73Ge center in cationic sublattices of PbS and PbSe represents a two-electron donor with the negative correlation energy: the Mossbauer spectrum for the n-type samples corresponds to the neutral state of the donor center (Ge2+), while this spectrum corresponds to the doubly ionized state (Ge4+) of the center in the p-type samples. In partially compensated PbSe samples, a fast electron exchange between the neutral and ionized donor centers is realized. It is shown by the method of Mossbauer spectroscopy for the 119Sn isotope that the germanium-related energy levels are located higher than the levels formed in the band gap of these semiconductors by the impurity tin atoms.

A Germanium(II)-Centered Dication

The dicationic 42+ complex with three N-heterocyclic carbenes coordinated to a germanium center is reported. The complex was characterized by 1H NMR and FT Raman spectroscopy, and the structure was determined by single-crystal X-ray diffraction. Electronic structure calculations reveal a partial positive charge at germanium and that the germanium lone pair shows no evidence for π bonding.

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.

Study on the electronic effect on coordinating donors in heptacoordinate trichlorogermanes

Trichloro[tris(2,5-dimethoxyphenyl)methyl]germane ( 1a), trichloro[tris(3-fluoro-6-methoxyphenyl)methyl]germane ( 1b), and trichloro[tris(2-methoxy-5-trifluoromethylphenyl)methyl]germane ( 1c) were synthesized. X-ray crystallographic analyses of 1a– c revealed their heptacoordinate geometries around the germanium atoms. The interatomic distances between the oxygen atoms and the central germanium atoms in the crystalline state were not significantly affected by change of functional groups on the benzene rings, while the optimized structures by theoretical calculations and Atoms in Molecules (AIM) analysis indicated linear relationship between the donating ability of functional groups and the O⋯Ge interatomic interactions.

Dianionic amidinates at silicon and germanium centers: Four-, six- and eight-membered rings

At variance to an earlier finding, the reaction of Me 2SiCl 2 with Li[(Me)N–C(Ph)–NH] ( 1a), in the presence of a base, gives a six-membered ring molecule μ-[(Ph)(MeN)C–N][–SiMe 2–N–C(Ph)–N(Ph)–SiMe 2–] ( s3a ), whereas with Li[ i PrN–C(Ph)–NH] ( 1b), a four-membered ring molecule μ-[ i PrN(Ph)C–N] 2(SiMe 2) 2 ( s4b ) was formed. In contrast, with Li[ t BuN–C(Ph)–NH] ( 1c), no such reaction occurred. Obviously, a delicate influence of steric effects has to be taken into account. In fact, the latter amidinate reacts with GeCl 2 to form an eight-membered ring molecule [ t BuN–C(Ph)–N–Ge] 4 ( 5c) without adding an additional base. The compounds are fully characterized and their structures determined by X-ray diffraction. DFT calculations confirm the dependence on steric influences. The relative energies of ground and transition states give a rationalization the ease of transformations of the various rings via pathways with penta- and hexacoordinate silicon centers, which in turn relates to the experimental results on penta- and hexacoordinate silicon amidinates and their fluctional behavior in solution.

Structural and Configurational Properties of Ethene, Silaethene, Germaethene, and Stannaethene: A Density Functional Theory Study and Natural Bond Orbital Analysis

B3LYP/6-31G*-B3LYP/3-21G,* and B3LYP/LANL2DZ**-based density functional theory (DFT) methods were used to investigate the ground-state structural and configurational properties of ethene (1), silaethene (2), germaethene (3), and stannaethene (4). All three methods showed that the ground-state structure of compounds 1–4 is planar. The results confirmed that the π bond energies (rotational barriers) are decreased from compound 1 to 4. The double-bond rotation energy profiles show the existence of plane symmetrical intermediates, due to the pyramidalization at the silicon, germanium, and tin center in compounds 2–4 , respectively. Based on the B3LYP/6-31G*, B3LYP/3-21G* and B3LYP/LANL2DZ** optimized ground state geometries, the Natural Bond Orbital (NBO) analysis of donor-acceptor (bond-antibond) interactions revealed that the stabilization energies associated with the electronic delocalization from σ M−H bonding orbitals to π * C = M antibonding orbitals increase from compounds 1 to 4. Also, the donor-acceptor interactions, as obtained from NBO analysis, could fairly explain the decrease of occupancies of σ M − H bonding orbital and the increase of occupancies of π * C = M antibonding orbitals from compounds 1 to 4. Also, the NBO results showed that by increase of π C = M → σ * M − H resonance energy in compounds 1–4, the π C = M bonding orbital occupancies decrease, while the σ * M − H antibonding orbital occupancies increase. The results confirmed that by increase of σ M − H → π * C = M and also π C = M → σ * M − H resonance energies, the π bond energies (rotational barriers) decrease from compounds 1 to 4. It has to be noted that the energy gap between π C = M bonding and π * C = M antibonding orbitals decreased from compounds 1 to 4.

Syntheses, Structures, and Reactions of Heptacoordinate Trihalogermanes Bearing a Triarylmethyl-Type Tetradentate Ligand

Trichloro[tris(3-tert-butyl-6-methoxyphenyl)methyl]germane (3), containing a tetradentate ligand with three methoxy groups as coordinating sites, was synthesized by the reaction of the corresponding (triarylmethyl)lithium species with tetrachlorogermane. In contrast to the case for the previously reported trichlorosilane analogue, 3 slowly decomposed during column chromatography on silica gel, although it was quite stable against moisture. The corresponding trifluoro-, tribromo-, and triiodogermanes 4−6 were prepared from the trichlorogermane 3. X-ray crystallographic analyses of 3−6 showed heptacoordinate structures with interatomic distances between the oxygen atom and the central germanium atom shorter than the sum of van der Waals radii. By systematic comparisons of these intramolecular interactions based on the interatomic distances, it was found that they strongly depend on the Lewis acidity of the trihalogenated germanium atom. An Atoms-in-Molecules (AIM) analysis of the model compound 4‘, in which three tert-butyl groups of trifluorogermane 4 were omitted, showed the existence of weak and ionic bonding between oxygen and germanium atoms. Reactions of these trihalogermanes with aqueous NaOH, LiAlH4, and BX3 were also investigated. Alkaline hydrolysis of trihalogermanes resulted in the cleavage of the carbon−germanium bond. LiAlH4 also caused the same kind of bond cleavage, together with nucleophilic attack on the germanium atom, giving the trihydrogermane 8. Reaction of the trihalogermanes with trihaloboranes was found to be an efficient procedure to give other trihalogermanes through a halogen exchange reaction.