Carboxysilanes and -germanes. III. Ionization constants of triorganosilane- and triorganogermanecarboxylic acids in ethanol-water and dimethyl sulfoxide media

Steward, Omar W.; Dziedzic, Joseph E.; Johnson, James S.; Frohliger, John O.

doi:10.1021/jo00822a002

Cited by 14 publications

(5 citation statements)

References 1 publication

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“…The 5- exo cyclization rate constants of the aromatic acylgermanes correlate roughly linearly with the p K a value of the acids (XC 6 H 4 ) 3 GeCOOH as well as with the Hammett constant σ para . Plots of the cyclization rate constants against the 13 C NMR chemical shifts of the respective carbonyl carbon are also nearly linear (graphs shown in the Supporting Information).…”

Section: Resultsmentioning

confidence: 81%

Radical Cyclizations of Acylgermanes. New Reagent Equivalents of the Carbonyl Radical Acceptor Synthon

1997

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An in depth study of the capability of acylgermanes to function as acceptors in radical cyclizations is reported. Radicals add to acylgermanes, and rapid fragmentation of the resulting α-germylalkoxy radicals provides ketones and germyl radicals. The germyl radicals in turn propagate the chain by addition or abstraction, so the reaction occurs by a unimolecular chain transfer (UMCT) process. In contrast, acylsilanes also function as radical acceptors, but they do not participate in UMCT processes because a “radical-Brook” rearrangement intervenes. Cyclizations in 5-exo and 6-exo modes show good to excellent scope, and rate constants for cyclization can be varied over 2 orders of magnitude by changing the germanium substituents. Acyltriarylgermanes are among the best radical acceptors yet identified, and this quality makes them superior reagent equivalents of the carbonyl radical acceptor synthon. Parent cyclizations in the 4-exo and 7-exo modes fail. Attempted 3-exo cyclization results in a 1,2-acyl shift, which can be conducted alone or in tandem with a subsequent cyclization to the rearranged acylgermane. The results provide a foundation for future synthetic applications of radical cyclizations to acylgermanes.

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Section: Resultsmentioning

confidence: 81%

Radical Cyclizations of Acylgermanes. New Reagent Equivalents of the Carbonyl Radical Acceptor Synthon

1997

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“…The driving force for the TBP deformation of the copper(II) triphenylacetate dimer may be the intermolecular nonbonded repulsions of the bulky triphenylmethyl groups. The cage structure of this complex is expected to be more flexible than that of the acetates, because of the greater acidity of Ph3CCOOH compared with CH3COOH (pKa values of Ph3CCOOH and CH3COOH in dimethyl sulfoxide solutions are 9.29 and 11.41, respectively; Steward, Dziedzic, Johnson & Frohliger, 1971). Thus, the bulkiness of the substituent groups on the bridges and the weak- only structural data with R values less than 0.06 are presented.…”

Section: Molecular Structurementioning

confidence: 99%

Magneto-structural corrections of dimeric copper(II) trichloroacetates

Uekusa¹,

Ohba²,

Tokii³

et al. 1992

Acta Crystallogr Sect B

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Sixteen crystal structures of dimeric copper(II) trichloroacetates, (I)-(XVI), have been determined by single-crystal X-ray diffraction. In crystals of the compounds which have small -2J values, less than 200 cm-1, the coordination geometry around the Cu atom is deformed from square pyramidal (SP) to trigonal bipyramidal (TBP), and the Cu...Cu interatomic distance is elongated. The longer the Cu.--Cu distance, the smaller the -2J value, indicating that the spin super exchange interaction is weaker in the TBP than in the SP structure. The magnetic orbitals in the TBP structure may consist mainly of copper dz, orbitals (z along the axial direction of the TBP), which are perpendicular to each other at the two Cu atoms, and overlap only slightly with each other on

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“…Silacarboxylic acids have been experimentally found to be efficient carbon monoxide-releasing molecules and used, for instance, in the synthesis of bioactive molecules . In this regard, silacarboxylic and germacarboxylic acids have been previously reported. , It has also been indicated that silacarboxylic acids are demonstrated to be easy to handle, air-stable, and efficient carbon monoxide precursors . This has been demonstrated in the synthesis of important bioactive compounds such as HIV-1 inhibitor .…”

Section: Resultsmentioning

confidence: 98%

Mechanistic Studies of the Catalytic Reduction of CO₂ to CO: Efficient CO-Releasing Si- and Ge-Based Catalysts

Demissie

Kessete

2022

ACS Omega

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Besides its significant challenges, efficient catalytic conversion of CO2 to value-added chemicals is highly desired. Herein, we report efficient silicon- and germanium-based catalysts for CO2 activation and its reduction to CO studied using B3LYP-GD3/6-31++G(d,p)/tetrahydrofuran (THF) and M06-2X/6-311++g(d,p)/THF density functional theory methods. The catalysts were systematically designed based on the previously reported silicon- and germanium-based compounds. The germanium-based catalysts are reported for the first time in this study. The calculated transition state energy barriers (5.7–15.8 kcal/mol) indicate that all the catalysts can easily activate CO2. Among all the B3LYP-GD3-calculated transition-state energy barriers, the highest energy barrier found (27.2–28.3 kcal/mol) is for the protonation of the carboxylic acid group of the silacarboxylic and germacarboxylic acids. Once the silacarboxylic and germacarboxylic acids are protonated, the water molecule can easily dehydrate and leave the catalysts with CO. The electrochemical reduction of the M–CO (M = Si and Ge) complexes further enhances the complexes to easily release CO, with all transition state energy barriers being lower than 10 kcal/mol. The results show that both CO2 activation and its reduction to CO using the studied catalysts are thermodynamically and kinetically favorable. This work provides an important insight for CO2 activation and its reduction to CO using earth-abundant and nontoxic main group element-based catalysts.

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Carboxysilanes and -germanes. III. Ionization constants of triorganosilane- and triorganogermanecarboxylic acids in ethanol-water and dimethyl sulfoxide media

Cited by 14 publications

References 1 publication

Radical Cyclizations of Acylgermanes. New Reagent Equivalents of the Carbonyl Radical Acceptor Synthon

Radical Cyclizations of Acylgermanes. New Reagent Equivalents of the Carbonyl Radical Acceptor Synthon

Magneto-structural corrections of dimeric copper(II) trichloroacetates

Mechanistic Studies of the Catalytic Reduction of CO₂ to CO: Efficient CO-Releasing Si- and Ge-Based Catalysts

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Carboxysilanes and -germanes. III. Ionization constants of triorganosilane- and triorganogermanecarboxylic acids in ethanol-water and dimethyl sulfoxide media

Cited by 14 publications

References 1 publication

Radical Cyclizations of Acylgermanes. New Reagent Equivalents of the Carbonyl Radical Acceptor Synthon

Radical Cyclizations of Acylgermanes. New Reagent Equivalents of the Carbonyl Radical Acceptor Synthon

Magneto-structural corrections of dimeric copper(II) trichloroacetates

Mechanistic Studies of the Catalytic Reduction of CO2 to CO: Efficient CO-Releasing Si- and Ge-Based Catalysts

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Mechanistic Studies of the Catalytic Reduction of CO₂ to CO: Efficient CO-Releasing Si- and Ge-Based Catalysts