σ-Aromaticity in an Unsaturated Ring: Osmapentalene Derivatives Containing a Metallacyclopropene Unit

In general, aromaticity can be clarified as π- and σ-aromaticity according to the type of electrons with major contributions. The traditional π-aromaticity generally describes the π-conjugation in fully unsaturated rings whereas σ-aromaticity may stabilize fully saturated rings with delocalization caused by σ-electron conjugation. Reported herein is an example of σ-aromaticity in an unsaturated three-membered ring (3 MR), which is supported by experimental observations and theoretical calculations.

Why Does Activation of the Weaker C═S Bond in CS2 by P/N-Based Frustrated Lewis Pairs Require More Energy Than That of the C═O Bond in CO2? A DFT Study

The sequestration of carbon disulfide (CS2), a common pollutant in environmental systems, is of great importance due to its physical harm to human beings. Compared with CO2 capture, that of CS2 is much less developed. The use of P/N-based frustrated Lewis pairs (FLPs) has been proven, both experimentally and theoretically, to be an alternative strategy to efficiently sequestrate CO2. Therefore, we pose the question of whether the analogue CS2 could also be sequestrated by the same FLPs, given that the C═S bond in CS2 is weaker than the C═O bond in CO2.

Unexpected 1,2-Migration in Metallasilabenzenes: Theoretical Evidence for Reluctance of Silicon to Participate in π Bonding

Density functional theory (DFT) calculations were carried out to investigate the 1,2-migration in metallasilabenzenes. The results suggested that the chloride migration of metallabenzenes is unfavorable due to the loss of aromaticity in the nonaromatic analogues. In sharp contrast, such a migration in metallasilabenzenes is favorable due to the reluctance of silicon to participate in π bonding. The migration of hydride and methyl group from the metal center to the silicon atom in metallasilabenzenes is computed to be also feasible.

Interconversion between Ruthenacyclohexadiene and Ruthenabenzene: A Combined Experimental and Theoretical Study

Treatment of ruthenabenzene [(C9H6NO)Ru{CC(PPh3)CHC(PPh3)CH}(C9H6NO)(PPh3)]Cl2 (1) with NaBH4 produces the first ruthenacyclohexa-1,4-diene [(C9H6NO)Ru{CC(PPh3)CH2C(PPh3)CH}(C9H6NO)(PPh3)]Cl (2), which was fully characterized. Under an oxygen atmosphere, complex 2 can easily convert to complex 1. DFT calculations were carried out to rationalize the high regioselectivity in the reaction of the ruthenabenene 1 with NaBH4 and the interconversion between 1 and 2.

Theoretical study on the interconversion of silabenzenes and their monocyclic non-aromatic isomers via the [1,3]-substituent shift: Interplay of aromaticity and Bent's rule

Density functional theory (DFT) calculations were performed to examine the substituent effects on the interconversion of silabenzenes and their monocyclic non-aromatic isomers. A previous study suggested that aromaticity is the driving force for this process. Interestingly, our systematic calculations reveal that the contribution from aromaticity can be evaluated quantitatively (ca. 30 kcal mol-1). Thus it is the interplay of aromaticity and Bent's rule that determine their relative stabilities.

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