Search

Germaaluminocenes are formed by salt metathesis reactions of dipotassium germacyclopentadienediides with pentamethylcyclopentadienylaluminum dichloride. The reactivity pattern of these sandwich complexes is determined by the electrophilic central aluminum atom and by the nucleophilic dicoordinated germanium center. Surprisingly, the products formed by reactions with Lewis acids, Lewis bases, amphiphiles and compounds with polar double bonds are those expected from the reaction of a hypothetical aluminagermapentafulvene with these types of reagents. This suggests that germaaluminocenes are synthetic equivalents to these pentafulvenes. [ABSTRACT FROM AUTHOR]

The synthesis of the germacalicene 7 from the reaction of the dipotassium germole dianion K2[6] with 1,2‐bis‐diisopropylamino‐3‐chlorocyclopropenyl perchlorate is reported. Based on the crystal structure analysis and the results of DFT calculations, the germacalicene 7 can be viewed as a cyclopropenium germacyclopentadienide ylide that is isoelectronic to α‐cationic phosphanes. First reactivity studies revealed its nucleophilic character and resulted in the isolation of the air‐ and moisture‐stable carbonyl iron complex 15 and the cationic silver complex 20. One‐electron oxidation of the germacalicene 7 was achieved by its reaction with [Ph3C][B(C6F5)4] and the bis‐cationic Ge−Ge‐bonded dimer 22 was isolated. Ylidic reactivity: Germacalicene is, in contrast to calicene, a non‐planar compound and is best described as a germanium/carbon ylide (see figure). Its reactivity is dominated by the lone pair at the germanium center. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis of two η5‐aminoborole complexes of germanium(II) from the reaction of a germole dianion with aminoboron dichlorides is reported. This reaction constitutes a remarkable example of a germole‐to‐borole transformation. The two aminoborole complexes of germanium(II) were fully characterized by multinuclear NMR spectroscopy, IR spectroscopy, HRMS, and, in one case, by X‐ray crystallography. The results of quantum‐mechanical calculations favor the electronic structure of a half‐sandwich complex of GeII over an ionic representation with a germanium dication stabilized by an aromatic aminoborole dianion. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Silylated germylene-PMe3 adducts exchange their phosphane moiety smoothly for an N-heterocyclic carbene or isocyanide species to form their respective base adducts. Reaction of the silylated germylene-PMe3 adducts with monosubstituted alkynes produce germylene adducts with the alkyne inserted into a Ge−Si bond. A computational study of this process provides evidence for the initial formation of a germirene, which rearranges to a vinylgermylene species. The thermodynamic driving force for this reaction is provided by subsequent adduct formation with PMe3. Reaction of the PMe3 adduct of bis[(trimethylsilyl)silyl]germylene with disubstituted alkynes leads to the formation of stable germirenes, which can be isomerized further to silagermetes. [ABSTRACT FROM AUTHOR]

The ionization of 1,1-dihydridocyclopentasilane 7 has been found to yield the cyclic polysilanylsilyl cation 8 instead of the expected hydrogen-substituted silylium ion 6. The silyl cation 8 is stabilized by the formation of an intramolecular Si-H-Si bridge, which also provides the thermodynamic driving force for its formation. In general, the preference for the formation of Si-H-Si bridges can be used to scavenge and identify transient intermediates in the Lewis acid induced rearrangement of polysilanes. The validity of this concept has been demonstrated for one central step in this chemistry, the ring-contraction reaction of cyclohexasilanes to form silylcyclopentasilanes. [ABSTRACT FROM AUTHOR]

Silylated germylene-PMe3 adducts exchange their phosphane moiety smoothly for an N-heterocyclic carbene or isocyanide species to form their respective base adducts. Reaction of the silylated germylene-PMe3 adducts with monosubstituted alkynes produce germylene adducts with the alkyne inserted into a Ge−Si bond. A computational study of this process provides evidence for the initial formation of a germirene, which rearranges to a vinylgermylene species. The thermodynamic driving force for this reaction is provided by subsequent adduct formation with PMe3. Reaction of the PMe3 adduct of bis[(trimethylsilyl)silyl]germylene with disubstituted alkynes leads to the formation of stable germirenes, which can be isomerized further to silagermetes. [ABSTRACT FROM AUTHOR]

Germaaluminocenes are formed by salt metathesis reactions of dipotassium germacyclopentadienediides with pentamethylcyclopentadienylaluminum dichloride. The reactivity pattern of these sandwich complexes is determined by the electrophilic central aluminum atom and by the nucleophilic dicoordinated germanium center. Surprisingly, the products formed by reactions with Lewis acids, Lewis bases, amphiphiles and compounds with polar double bonds are those expected from the reaction of a hypothetical aluminagermapentafulvene with these types of reagents. This suggests that germaaluminocenes are synthetic equivalents to these pentafulvenes., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The salt metathesis reaction of dipotassium germacyclopentadienediide with aluminum(III) dichlorides provides either half-sandwich alumole complexes of germanium(II) or aluminylene germole complexes. Their molecular structure and the delocalized bonding situation, revealed by density functional theory (DFT) calculations, are equally described as isomeric aluminagerma[5]pyramidanes with either the germanium or the aluminum atom in the apical position of the pentagonal pyramid. The product formation and the selectivity of the reaction depends on the third substituent of the aluminum dichloride. Aryl-substituents favor the formation of alumole complexes and Cp*-substituents that of the isomeric germole complexes. With amino-substituents at the aluminum atom mixtures of both isomers are formed and the positional exchange of the two heteroatoms is shown by NMR spectroscopy. The alumole complexes of germanium(II) undergo facile reductive elimination of germanium and form the corresponding alumoles., (© 2024 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Efforts to prepare an elusive donor-free phosphenium ion, [R 2 P] + , led us to synthesize functionalized fluorophosphonium cations of the type [R 2 P(F)X] + (X=SiEt 3 , H, F), which were obtained from the related neutral fluorophosphines R 2 PF and R 2 PF 3 upon protonation and reaction with solvated [Et 3 Si] + ions (R=2,6-Mes 2 C 6 H 3 ). The hypothetical reductive elimination of [R 2 P(F)SiEt 3 ] + and [R 2 P(F)H] + affording [R 2 P] + , Et 3 SiF and HF, respectively, was calculated to be endothermic by 40.1 and 190.6 kJ mol -1 ., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The synthesis of two η 5 -aminoborole complexes of germanium(II) from the reaction of a germole dianion with aminoboron dichlorides is reported. This reaction constitutes a remarkable example of a germole-to-borole transformation. The two aminoborole complexes of germanium(II) were fully characterized by multinuclear NMR spectroscopy, IR spectroscopy, HRMS, and, in one case, by X-ray crystallography. The results of quantum-mechanical calculations favor the electronic structure of a half-sandwich complex of Ge II over an ionic representation with a germanium dication stabilized by an aromatic aminoborole dianion., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Silylated germylene-PMe 3 adducts exchange their phosphane moiety smoothly for an N-heterocyclic carbene or isocyanide species to form their respective base adducts. Reaction of the silylated germylene-PMe 3 adducts with monosubstituted alkynes produce germylene adducts with the alkyne inserted into a Ge-Si bond. A computational study of this process provides evidence for the initial formation of a germirene, which rearranges to a vinylgermylene species. The thermodynamic driving force for this reaction is provided by subsequent adduct formation with PMe 3 . Reaction of the PMe 3 adduct of bis[(trimethylsilyl)silyl]germylene with disubstituted alkynes leads to the formation of stable germirenes, which can be isomerized further to silagermetes., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In the presence of PMe3 or N-heterocyclic carbenes, the reaction of oligosilanylene dianions with GeCl2⋅dioxane gives germylene-base adducts. After base abstraction, the free germylenes can dimerize by formation of a digermene. An electrochemical and theoretical study of a bicyclic tetrasilylated digermene revealed formation of a comparably stable radical anion and a more reactive radical cation, which were characterized further by UV/Vis and ESR spectroscopy., (© 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.)