Reactivity of germanones: far removed from ketones – a computational study

Abstract

The recently isolated heavy ketone (X 2 E]O; E ¼ Ge) shows interesting reactivity towards simple addition reactions that are unknown for the organic (E]C) ketones. Density Functional Theory (DFT) calculations elucidate the role of the central atom and the substituent effects on the addition of acetone, carbon dioxide and water to formaldehyde, acetone, 2,4-dimethyl-3-pentanone, diphenyl ketone and their heavier (Si, Ge) analogs. NBO analysis reveals a large charge separation for heavier analogs, thereby increasing their reactivity. The activation barriers are reduced by as much as $30.0 to 40.0 kcal mol À1 for the nucleophilic addition to the heavy ketones as (E ¼ Si and Ge) compared to those of an organic ketone. Comparably lower stability of the reactants and higher stability of the transition state lowers the barriers of addition reactions for the heavier ketones. Apart from a smaller barrier, the nucleophilic addition reactions which are unfavorable for ketones are favored by 20-40 kcal mol À1 for their silicon and germanium counterparts. Calculations predict that similar addition reactions must be feasible for silanones (X 2 Si]O) as well.

Dynamic/Thermochemical Balance Drives Unusual Alkyl/F Exchange Reactions in Siloxides and Analogs

“…This would not be expected for the siloxides or germanoxides because of the low stability of silanones and germanones. 52,53 This set of observations reinforces our earlier conclusions that the Me/F exchange reaction only takes place in very specific systems where the energetic and dynamic behavior meet the right criteria.…”

“…Although for Me 3 SiO – the TS3 shows that the F – reattacks the N atom of NF 3 and promotes the O–N bond break to yield the fluoro siloxides, our calculations show that for Me 3 CO – , the F – reattack would yield acetone and cleavage of the C–F bond. This would not be expected for the siloxides or germanoxides because of the low stability of silanones and germanones. , …”

Structures and Electronic Properties of Heavier Congeners of Disk-Like Molecules: (Si, Ge) Sulflower and (Si, Ge) Olympicene

“…The barrier heights for such addition reactions to germanones have been calculated to be about 20− 30 kcal/mol lower than that for the organic ketones. 20 In a remarkable experimental accomplishment, Weinert and coworkers recently synthesized the linear-chain oligomeric Ge analogue of n-hexane, namely, hexagermane (Ge 6 ). 21 Bulky ligands like the isopropyl and the phenyl groups along the linear Ge 6 chain protected the linear chain from self-cyclization as well as atmospheric oxidation.…”

Theoretical Study of the Heterolytic σ Bond Cleavage on the Ge═O Bond of Germanone. An Insight into the Driving Force from Both Electronic and Dynamical Aspects

“…On the basis of the experimental results of the reactivity of germanone reported by Tamao and co-workers, Jissy and co-workers have investigated the nucleophilic addition of water and CO 2 to germanones by the DFT method. 39 However, the detail of the reaction mechanism of the cleavage of the chemical bond on the GeO double bond has not been clarified, although the property and the reactivity of the germanon have been examined. In this study, we therefore examine the mechanism of the σ bond cleavage on the GeO bond of germanone by means of both quantum mechanical (QM) and molecular dynamics (MD) methods.…”

“…Acetone, phenylsilane, and CO 2 also react with the GeO to form the (hydroxyl)­germyl enolate, the hydrosilylation product and the cyclic carbonate, respectively. On the basis of the experimental results of the reactivity of germanone reported by Tamao and co-workers, Jissy and co-workers have investigated the nucleophilic addition of water and CO 2 to germanones by the DFT method . However, the detail of the reaction mechanism of the cleavage of the chemical bond on the GeO double bond has not been clarified, although the property and the reactivity of the germanon have been examined.…”