Germyl Anions Research Articles

Front Cover: A Mixed‐Anion System Consisting of a Germyl Anion and Anions Delocalized on Conjugated Carbon Ring Skeletons (Chem. Eur. J. 25/2019)

Front Cover: A Mixed‐Anion System Consisting of a Germyl Anion and Anions Delocalized on Conjugated Carbon Ring Skeletons (Chem. Eur. J. 25/2019)

Stable Germenolates and Germenes with Exocyclic Structures

The first germenolates with exocyclic structures [(Me3Si)2Ge(Si2Me4)2GeC(R)O]−K+ (5a: R = Mes; 5b: o-Tol; 5c: 1-Ad) were synthesized by the reaction of the corresponding cyclic acylgermanes with KOtBu. 5a–c could be isolated by crystallization. The remarkable thermal stability of 5a–c even at room temperature allowed full characterization by NMR and UV–vis spectroscopy and by single-crystal X-ray crystallography. Spectroscopic and structural features in combination with DFT quantum mechanical calculations indicated that 5a–c are best described as acyl germyl anions in solution and in the solid state as well. The reactivity of 5a–c versus chlorosilanes parallels that observed for the structurally related silenolates. The aryl-substituted compounds 5a,b, thus, reacted with ClSiMe3 to give the exocyclic germenes (Me3Si)2Ge(Si2Me4)2Ge═C(OSiMe3)R (6a: R = Mes; 6b: o-Tol), while the alkyl-substituted species 5c afforded the Ge-silylated cyclic acylgermane. TDDFT calculations were used to assign the UV–vis absorption spectra and to gain more insight into the electronic nature of 5a–c and 6a.

ChemInform Abstract: UV and NMR Studies of Alkyl-Substituted Germyl Anions.

Abstract Several (trialkylgermyl)alkali metals (M = Li, Na, K) were investigated by UV, 1 H and 13 C NMR spectroscopic methods to clarify the nature of a germanium-(alkali metal) bond. On conversion of a trialkylgermane to the corresponding germylalkali metals, the bathochromic shift of UV absorption maxima, upfield shift of the 1 H NMR signals and downfield shift of the 13 C NMR signal are observed.

ChemInform Abstract: Facile Cleavage of Ge-C Bonds of N-(Germylmethyl)benzylamine Derivatives. Generation of Germyl Anions.

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Isolable silyl and germyl radicals lacking conjugation with pi-bonds: synthesis, characterization, and reactivity.

The one-electron oxidation reaction of tris[di-tert-butyl(methyl)silyl]silyl and -germyl anions with dichlorogermylene-dioxane complex results in the formation of stable tris[di-tert-butyl(methyl)silyl]silyl and -germyl radicals 1 and 2, representing the first isolable radical species of heavier Group 14 elements lacking stabilization by conjugation with pi-bonds. The crystal structures of both silyl and germyl radicals 1 and 2 showed a completely planar geometry around the radical centers. The ESR spectra of 1 and 2 showed strong signals with characteristic satellites due to the coupling with the 29Si and 73Ge nuclei. The small values of the hyperfine coupling constants a(29Si) and a(73Ge) clearly indicate the pi-character of both radicals, corresponding to a planar geometry and sp2 hybridization of the radical centers. Both 1 and 2 easily undergo halogenation reactions with carbon tetrachloride, 1,2-dibromoethane, and benzyl bromide to form the corresponding halosilanes and halogermanes.

Electron affinity of XnGe(OMe)3−n radicals (X = H, F; n = 0–2) and the Ge–H bond dissociation energy

The recent observation of a number of gas-phase germyl anions of the type XnGe(OMe)3 − n− (X = H, F; n = 0–2), suggests that these species are very stable and relatively unreactive in ion/molecule reactions. We report the electron affinity of the corresponding XnGe(OME)3−n radicals calculated at the QCISD(T) level using basis sets developed by the generator coordinate method and adapted to effective core potentials. These calculations show the electron affinity increasing in the order GeH3 (1.55 eV) < H2GeOMe (1.75 eV) < HGe(OMe)2 (1.95 eV) < Ge(OMe)3 (2.32 eV) < FGe(OMe)2 (2.67 eV) < F2GeOMe (3.12 eV), and are estimated to be within 0.10–0.15 eV (for the radicals at the upper end) of the true adiabatic values. Ge–H bond energies have also been calculated for some of the simpler systems and the 81.1 kcal mol−1 BDE0 K calculated for H3Ge–H is in very good agreement with the recommended experimental value of 82 ± 2 kcal mol−1.

Gas-phase nucleophilic reactions of Ge(OCH 3) 4: experimental and computational characterization of pentacoordinated Ge anions

The gas-phase ion/molecule reactions of F − and CH 3O − with Ge(OCH 3) 4 have been investigated by Fourier transform ion cyclotron mass spectrometry. Both nucleophiles react preferentially by an addition mechanism to yield XGe(OCH 3) 4 − (X = F, OCH 3) complexes that are identified as typical pentacoordinated Ge species. Pentacoordinated Ge adducts formed with excess internal energy can undergo elimination of formaldehyde to yield HGe(OCH 3) 4 −, or further elimination processes that result in the formation of germyl anions like Ge(OCH 3) 3 −. Other minor product ions are also observed which can be attributed to the intermediacy of a pentacoordinated adduct. Dissociation of the XGe(OCH 3) 4 − anions induced by infrared multiphoton excitation leads to sequential losses of formaldehyde and gives rise to different germyl anions like Ge(OCH 3) 3 −, HGe(OCH 3) 2 −, and H 2GeOCH 3 −. The XGe(OCH 3) 4 − and germyl anions react readily with BF 3 through successive methoxide-fluoride exchange and this reaction provides a gas-phase synthetic pathway for multiply fluorinated Ge anions. Ab initio calculations performed on model pentacoordinated species F n+1 Ge(OH) 4− n − (n = 0–4) reveal that addition of a fluoride ion on hydroxygermanes occurs preferentially in the apical position of a trigonal bipyramid. The fluoride affinity of the prototype molecule Ge(OH) 4 is calculated to be 60.9 kcal mol −1, and fluoride affinity increases monotonically with increasing fluorine substitution. The fluoride affinity of GeF 4 is calculated to be 79 kcal mol −1. Similar calculations also predict an unusually high hydride affinity (60 kcal mol −1) for Ge(OH) 4 with the hydride occupying an equatorial position.

Generation and reactions of metal-free trialkylgermyl anions from silylgermane and digermane

Metal-free trimethylgermyl anions were prepared by cleavage of the GeSi bond of (trimethylsily)trimethylgermane and the GeGe bond of hexamethyldigermane with tetrabutylammonium fluoride (TBAF) in hexamethylphosphoric triamide (HMPA). The reactions of metal-free germyl anions produced by a catalytic or one-equivalent amount of TBAF with organic halides carbonyl compounds, and α,β-unsaturated ketones were examined.

Electrochemical Generation of Germyl Anions from Digermanes

Electrochemical Generation of Germyl Anions from Digermanes

Addition of germyl anions to aliphatic ketones and α,β-unsaturated ketones

Trimethylgermyllithium reacts with aliphatic ketones and α,β-unsaturated ketones to give the corresponding trimethylgermylcarbinols stereoselectively and enolates of 3-germyl ketones regioselectively.

Facile Cleavage of Ge–C Bonds of N-(Germylmethyl)benzylamine Derivatives. Generation of Germyl Anions

Abstract The reactions of N-(germylmethyl)benzylamine derivatives with butyllithium were carried out. Facile cleavages of Ge–C bonds of the N-benzylgermylmethylamine derivatives giving the corresponding germyl anions and N-pentylbenzylamine were observed. The reaction mechanism of the Ge–C bond cleavage was discussed.

UV and NMR studies of alkyl-substituted germyl anions

Several (trialkylgermyl)alkali metals (M = Li, Na, K) were investigated by UV, 1H and 13C NMR spectroscopic methods to clarify the nature of a germanium-(alkali metal) bond. On conversion of a trialkylgermane to the corresponding germylalkali metals, the bathochromic shift of UV absorption maxima, upfield shift of the 1H NMR signals and downfield shift of the 13C NMR signal are observed.

ChemInform Abstract: Laser‐Photolysis Study of Ary1‐Substituted Germyl Anions.

Chemischer InformationsdienstVolume 17, Issue 20 Preparative Organic Chemistry ChemInform Abstract: Laser-Photolysis Study of Ary1-Substituted Germyl Anions. K. MOCHIDA, K. MOCHIDASearch for more papers by this authorM. WAKASA, M. WAKASASearch for more papers by this authorS. ISHIZAKA, S. ISHIZAKASearch for more papers by this authorM. KOTANI, M. KOTANISearch for more papers by this authorY. SAKAGUCHI, Y. SAKAGUCHISearch for more papers by this authorH. HAYASHI, H. HAYASHISearch for more papers by this author K. MOCHIDA, K. MOCHIDASearch for more papers by this authorM. WAKASA, M. WAKASASearch for more papers by this authorS. ISHIZAKA, S. ISHIZAKASearch for more papers by this authorM. KOTANI, M. KOTANISearch for more papers by this authorY. SAKAGUCHI, Y. SAKAGUCHISearch for more papers by this authorH. HAYASHI, H. HAYASHISearch for more papers by this author First published: May 20, 1986 https://doi.org/10.1002/chin.198620105AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume17, Issue20May 20, 1986 RelatedInformation

CIDEP STUDY OF THE FORMATION OF ARYL-SUBSTITUTED GERMYL RADICALS IN DIRECT PHOTOEJECTION OF THE GERMYL ANIONS

Abstract Photolysis of aryl-substituted germyl anions was studied by CIDEP at 77 K. The emmision pattern of the spectra detected after pulsed excitation revealed a contribution of the triplet mechanism.

LASER-PHOTOLYSIS STUDY OF ARYL-SUBSTITUTED GERMYL ANIONS

Abstract Photochemical primary processes of aryl-substituted germyl anions were studied at room temperature. The germyl radicals generated were observed directly by laser-photolysis.

Introduction of optically active triorganogermyl ligands into transition metal complexes. Synthesis of carbene complexes, crystal structure and absolute configuration of cis- S(-)(methylphenyl-1-naphthylgermyl)-(methylethoxycarbene) tetracarbonylmanganese

The attachment of triorganogermyl ligands to transition metals by displacement of a CO ligand is described. The optical stability of the germyl anions has been used to prepare a nickel-germanium complex by displacement of chloride (this reaction representing a limiting case) and more generally in the synthesis of germanium-transition metal bonds by displacement of CO (the transition metal being Cr, Mo, W, Mn, Fe, or Co). Optically active germyl anions are used in the synthesis of carbene complexes by insertion of CO ligands into a carbon-transition metal sigma bond. A crystallographic study of the complex MePh-(1-Np)Ge(CO) 4MnC(OEt)Me reveals that the carbene unit is cis to the germanium and that the germyllithium has reacted with retention of configuration.

Photodetachment of electrons from Group IVa binary hydride anions: The electron affinities of the SiH3 and GeH3 radicals

Relative photodetachment cross sections have been determined for the silyl and germyl anions (SiH3−, GeH3−) in the wavelength ranges 400.0–870.0 nm (3.10–1.43 eV) and 400.0–720.0 nm (3.10–1.72 eV), respectively. An ion cyclotron resonance spectrometer was used to generate, trap, and detect the negative ions, and a 1000 W xenon arc lamp with a grating monochromator was employed as the light source. Both ions exhibited cross sections behaving sigmoidally over the wavelength ranges studied. These experiments afford the following electron affinities: E.A. (SiH3·) ≤1.44±0.03 eV and E.A. (GeH3·) ≤ 1.74±0.04 eV. From estimates of proton transfer equilibrium constants, bond energies are approximated for silane and germane.

Infrared spectra of the germyl and silyl anions

The i.r. spectra of the germyl ion and its deuteriated analogue have been observed and a normal co-ordinate analysis has been performed which predicts a bond angle of ca. 93°. Attempts to observe the spectrum of the silyl ion failed because of interference of solvent absorptions (hexamethylphosphoramide) or failure of the preparation (dimethoxyethane solutions).