Oligoorganogermanes: interplay between aryl and trimethylsilyl substituents

Derivatives of main group elements containing element–element bonds are characterized by unique properties due to -conjugation, which is an attractive subject for investigation. A novel series of digermanes, Ar3Ge-Ge(SiMe3)3, containing aryl (Ar = p-C6H4Me (1), p-C6H4F (2), C6F5 (3)) and trimethylsilyl substituents, was synthesized by the reaction of germyl potassium salt, [(Me3Si)3GeK*THF], with triarylchlorogermanes, Ar3GeCl. The optical and electronic properties of such substituted oligoorganogermanes were investigated spectroscopically by UV/vis absorption spectroscopy and theoretically by DFT calculations. The molecular structures of compounds 1 and 2 were studied by XRD analysis. Conjugation between all structural fragments (Ge-Ge, Ge-Si, Ge-Ar, where Ar is an electron-donating or withdrawing group) was found to affect the properties

Aryl oligogermanes as ligands for transition metal complexes

The ligand properties of a series of aryl oligogermanes R3Ge‐GeAr3, 3‐7 (Me3Ge‐GePh3 (3), Me3Ge‐Ge(pTol)3 (4), Ph3Ge‐GePh3 (5), (C6F5)3Ge‐GePh3 (6), Ph3Ge‐GeMe2GePh3 (7)), for the synthesis of transition metal carbonyl complexes such as R3Ge‐GeAr2(R’C6H4‐η6)M(CO)3 (M = Cr, 3a‐7a; M = Mo, 3b; M = W, 3c) were investigated. The target complexes were obtained in moderate yields using several different synthetic approaches. The physicochemical properties of these new derivatives were investigated by IR, UV/vis, NMR spectroscopy, electrochemistry and DFT calculations. The molecular structures of 3c, 4a and 5a were studied by single crystal X‐ray diffraction analysis. A comparative analysis of donor‐ and acceptor properties of aryl oligogermanes as ligands for transition metal carbonyl complexes is reported

Oligoorganogermanes: Interplay between Aryl and Trimethylsilyl Substituents

Derivatives of main group elements containing element–element bonds are characterized by unique properties due to σ-conjugation, which is an attractive subject for investigation. A novel series of digermanes, Ar3Ge-Ge(SiMe3)3, containing aryl (Ar = p-C6H4Me (1), p-C6H4F (2), C6F5 (3)) and trimethylsilyl substituents, was synthesized by the reaction of germyl potassium salt, [(Me3Si)3GeK*THF], with triarylchlorogermanes, Ar3GeCl. The optical and electronic properties of such substituted oligoorganogermanes were investigated spectroscopically by UV/vis absorption spectroscopy and theoretically by DFT calculations. The molecular structures of compounds 1 and 2 were studied by XRD analysis. Conjugation between all structural fragments (Ge-Ge, Ge-Si, Ge-Ar, where Ar is an electron-donating or withdrawing group) was found to affect the properties

Ethylene glycol oxidation over Ag-containing catalysts: A theoretical study

A theoretical interpretation of the mechanism of ethylene glycol oxidation to glyoxal over Ag-containing catalysts is considered. A model system, reflecting the interaction of Ag cluster with process adsorbates and/or intermediates, is proposed. Both partial oxidation of ethylene glycol to glyoxal and CO2 formation routes are reconstructed, and the corresponding reaction profiles are represented. The roles played by the most important reaction intermediates participating in the process under consideration are discussed

Germanium Complexes with <i>O<u>N</u>O</i> Tridentate Ligands: O-H Bond Activation Control According to DFT Calculations

Polydentate ligands are used for thermodynamic stabilization of tetrylenes—low-valent derivatives of Group 14 elements (E = Si, Ge, Sn, Pb). This work shows by DFT calculations how the structure (the presence or absence of substituents) and type (alcoholic, Alk, or phenolic, Ar) of tridentate ligands 2,6-pyridinobis(1,2-ethanols) [AlkONOR]H2 and 2,6-pyridinobis(1,2-phenols) [ArONOR]H2 (R = H, Me) may affect the reactivity or stabilization of tetrylene, indicating the unprecedented behavior of Main Group elements. This enables the unique control of the type of the occurring reaction. We found that unhindered [ONOH]H2 ligands predominantly led to hypercoordinated bis-liganded {[ONOH]}2Ge complexes, where an E(+2) intermediate was inserted into the ArO-H bond with subsequent H2 evolution. In contrast, substituted [ONOMe]H2 ligands gave [ONOMe]Ge: germylenes, which may be regarded as kinetic stabilized products; their transformation into E(+4) species is also thermodynamically favorable. The latter reaction is more probable for phenolic [ArONO]H2 ligands than for alcoholic [AlkONO]H2. The thermodynamics and possible intermediates of the reactions were also investigated

Ethylene glycol oxidation over Ag-containing catalysts: A theoretical study

A theoretical interpretation of the mechanism of ethylene glycol oxidation to glyoxal over Ag-containing catalysts is considered. A model system, reflecting the interaction of Ag cluster with process adsorbates and/or intermediates, is proposed. Both partial oxidation of ethylene glycol to glyoxal and CO2 formation routes are reconstructed, and the corresponding reaction profiles are represented. The roles played by the most important reaction intermediates participating in the process under consideration are discussed

Theoretical analysis of glyoxal condensation with ammonia in aqueous solution

The reactions of glyoxal with ammonia, ammonium salts, and amines cause the formation of the secondary organic aerosol (SOA) components (imidazole and its derivatives) in the atmosphere. The interaction of glyoxal and ammonia in aqueous solution is a primary reaction for these processes, and the explanation of its mechanism will allow developing the methods to control the formation of the SOA components. A detailed mechanism for the formation of key intermediates, namely, ethanediimine, diaminoethanediol, and aminoethanetriol, required for the imidazole ring cyclization, is proposed, and its potential energy surface (PES) has been constructed. This mechanism includes the experimentally identified intermediate compounds and takes into account the conformational and hydration equilibria of glyoxal. The schemes are proposed for further conversion of the key intermediates to the products of condensation between glyoxal and ammonia in the aqueous solution, C–N cyclic oligomers, that were identified. The products are shown to correspond to low positions on the PES in terms of Gibbs free energy, from −30.8 to −68.3 kcal mol−1, which confirms the high probability of their formation. The preferable thermodynamic pathway for formation of the imidazole products does not comprise the conversion of the diimine intermediate with the participation of the proton, but rather the interaction of either the diaminoalcohol with glyoxal monohydrate or two monoamine derivatives between themeselves (aminoethantriol and aminohydroxyacetaldehyde)

Acetaldehyde-ammonia interaction: a DFT study of reaction mechanism and product identification

The product of acetaldehyde and ammonia reaction, namely, 2,4,6-trimethyl-1,3,5-hexahydrotriazine trihydrate, was synthesized and identified using a combination of experimental (NMR spectroscopy, IR spectroscopy, melting point determination) and DFT-based theoretical approaches. A reaction mechanism was proposed. The reaction was shown to proceed via the formation of aminoalcohol, imine, and geminal diamine intermediates accompanied by cyclization of these species. The calculation results allowed us to build a potential energy surface of the acetaldehyde and ammonia interaction and determine the most energetically favorable pathway to yield acetaldehyde ammonia trimer. The reaction product was found in an energy minimum (-53.5 kcal/mol)